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Understanding the 370z Fuel System, Upgrades, and Diagnostics.

**This article is currently a work in progress**

Contents:
    -Intro
    -Fuel Tank Layout
    -Fuel Sending Unit
    -Plumbing
    -Fuel Rails and Injectors
    -Upgrades
    -Diagnostics

INTRO:

Overall, the 370z fuel delivery system is much alike the 350z system. So, this document's information really does cover both platforms. If you read our original introduction to the 370z fuel pump assembly tech document, you will find some redundancy. But, if you are performing work on the fuel pump assembly, we would recommend reading both documents as they have a slightly different focus.

The system is a pretty clean layout, and rather basic. There are just a few things going on that people have to keep in mind when dealing with this system. Many modern cars use nearly identical layouts, but the things that have changed in the way fuel systems are done over the last couple decades seem to have eluded or confused many.

Rather than explain the differences right now, lets just dive in and start from scratch with exactly how this fuel system works. I will try and cover some of the different ways things are done along the way.

FUEL TANK LAYOUT:

For superior balance and safety, the fuel tank is placed near the center of the car. It is between the seats and the hatch area, under the rear console. Below is a drawing of the tank from the Nissan service Manual. Notice that the shape of the floor has a large hump in it. This is the driveshaft pass through clearance. You can probably already begin to imagine how a tank of this shape is going to need some solutions to deal with.

{INSERT FUEL TANK DRAWING HERE ITEMS 1/2 for FPA and Sensor}

Item 1 in the photo is the fuel sending unit. This drops into the top of the passenger side of the fuel tank. The fuel sending unit is where most of the action takes place, and it also has a level sensor to read the fuel level on this half of the tank.

Item 2 is a level sensor for the other half of the tank. The flange on the tank is the same 6 bolt flange that is on the other side. Its also the same as a 350z or a 300ZX and most likely other Nissans.

The fuel fill tube comes into the passenger side of the tank where the fuel pump assembly is. This is of course a wise decision with a split gas tank. This means that if the car was completely out of fuel, and you only filled one gallon, that one gallon will land on the side of the tank that the fuel pump is on.

The last detail of the tank you need to know about is the transfer tube. Since the tank is split for the driveshaft to pass through, there has to be a way for the fuel pump to access the fuel on the drivers side of the tank. There is a small tube attached to the floor of the fuel tank that allows the fuel pump assembly to transfer fuel from the drivers side of the tank to the passenger side. More information on that coming up.

FUEL SENDING UNIT:

This is where most things on the delivery end of the fuel system take place. Here is what we are working with:

The first thing that stands out is the level sensor and float assembly. Its interesting how it attaches to the black spacer that raises it up. If you remove the spacer the level sensor does mount in the lower location directly on the white canister. Not that you would want to.

Then we have the white canister that surrounds all the action. I call this the swirl can. Its almost a form of a surge can. Its job is to hold some fuel around the fuel pump that is within it. The fuel tank has almost no baffles in this car. Without some type of surge protection, the car would constantly suffer fuel pressure drops as fuel sloshed around the tank, especially as the fuel level drops lower.

If you remove the canister with level sensor, you will find the guts of the fuel delivery system. What is left is the fuel filter housing. The fuel pump itself mounts to the fuel filter housing, right in the middle of it. The filter itself wraps partly around the pump. Observe this photo:

We are able to see the very top of the fuel pump, with a black nylon hose feed the fuel output into the inlet of the filter housing. Now as you would expect, the fuel has to pass through the filter element to the other end of the filter housing.

From there, there is another black nylon hose that takes the fuel to the flange that mounts to the tank, where it can exit and head to the engine. This hose is visable in the first photo of the fuel pump assembly. You can see it going up and out on the left hand side of the assembly in the photo.

Seems simple enough really. But there are some additional features going on here to control the fuel pressure, move fuel through the transfer tube in the tank, and help promote filling of the swirl canister.

These additional features are built into the filter housing and the white swirl canister. Examine this photo:

We are looking at the side of the filter housing. The fuel pump has been removed, and the nylon hose that goes from the pump to the filter inlet has been removed. As you can see there is still some thing going on here. The hose exiting the top left of the photo is again the nylon hose that is the fuel filter outlet to the top tank flange.

The silver metal piece is the fuel pressure regulator. All of its plumbing is happening underneath the exposed portion. The plastic above it is simply just to hold it in place. This regulator is fed around its side, and it is bleeding off fuel from the filter housing to regulate a static pressure. Its outlet orifice is on its bottom where the bled off fuel (considered the return fuel, even in a "returnless" system) continues to serve other purposes.

Lets focus on the regulator for a moment. Lets cut it out of there and show you some more.

I have removed enough plastic to take it out. Examine the following photograph. You can see the small channel on the side that feeds the inlet to the regulator, and you can see the outlet channel in the center on the bottom that it dumps the return fuel into.

Ignore the black oring in there, that was part of something else we were working on. One thing to note, is that the 370z fuel pressure regulator does not need any modifications to support larger fuel pumps like the 350z unit did. The outlet orifice on the regulator itself is already of adequate size, and even with an Aeromotive Stealth pump, it can maintain proper pressure control at idle.

Now we can look at the rest of the work the return fuel has to do. Look again at this photograph:

Now lets remove the object of focus.

The red circle is where it press fit into right under the fuel pressure regulator. So the return fuel is entering this assembly at the red circle. You can see that it is a sort of T fitting.

Off the side of the T fitting we have a black nylon hose that is extending to the siphon venturi. The return fuel enters the siphon venturi from the top. It then travels down and out at the yellow circle. When it leaves at the yellow circle, it just sort of drains into the swirl canister. The green circle is the suction inlet of the venturi. The return fuel passing through the siphon venturi creates a suction at this green circle. If you recall, it was mentioned that the fuel tank has a transfer tube built into the floor of it. Well that tube, on the passenger side, has a long black nylon hose with a quick connector that plugs in right here at the green circle. So the suction generated at the green circle from the venturi is pulling fuel from the drivers side of the fuel tank, and its exiting through the yellow circle and into the swirl canister. Of course, the swirl canister just overflows in general to the passenger side of the tank. The passenger side of the tank also overflows right back to the drivers side of the tank and vice versa. So fuel is really just moving back and forth all over the place.

Looking at the last function inside the fuel pump sending unit, is its self-refilling venturi. I call this the swirl venturi, or the swirl jet for short. I call it this because it is venturi injecting the white canister with fuel from an angle that is going to sort of swirl the fuel back into the canister from an opening on the bottom. At very high tank levels, fuel will simply overflow into the canister all the time. But as the tank gets lower and fuel is sloshing around, its helpful to inject fuel that is passing by underneath the assembly as well.

Thats where the blue circle in the photo above comes into play. When you assemble the canister to the filter housing, that blue circled port interfaces with a port on the canister.

So when you assemble it, these 2 red circles connect one another and the return fuel coming from that portion of the T fitting ends up injecting the "swirl jet". That component is the little black toe on the white canister at the very bottom left.

It just injects the fuel back into the canister and pulls in surrounding fuel in the area.

Both the swirl venturi and the siphon venturi have very small orifices. A venturi depends on this small orifice to create the pressure differential that causes the entire venturi effect. So, you can say that they are definitely restrictive. The restriction that they create generates the pressure in the return fuel plumbing. If this pressure were to become too high, the regulator feeding them could no longer do its job, and fuel pressure at idle could raise. This is not a concern with a stock fuel pump, the system is balance well for that. But when upgrading the pump, it can cause a problem. We will cover that in the "upgrades" section.

One little bit of information, these cars run the fuel pump at full power full time. Some cars use resistor packs on a relay to reduce voltage to the fuel pump in order to curb its output when the engine is under low load, and then switch to full voltage under high load. This is more typical on return fuel system cars, most likely to reduce heat in the fuel and evaporative emmissions if I had to guess, not to mention probably increase the fuel pump's lifespan.

Posted by CJ Motorsports at 10/24/2011 3:14 PM | Add Comment

CJM S1 Fuel System Installation

This document is currently unfinished.

Note: Installation is intended for qualified individuals. This manual is not fully detailed, as some operations should be familiar for an experienced VQ35 Technician.

Note: No fittings come tightened from CJM. Properly torque every fitting in the entire system. Some fittings come preinstalled, but they are not torqued. Do not over-torque fittings as component damage can occur. Aluminum parts can strip out and be damaged by over-torqueing very easily.

NOTICE: CJ MOTORSPORTS IS NOT LIABLE FOR ANY DAMAGES TO THE VEHICLE THAT THIS SYSTEM IS INSTALLED ON. THIS IS A RACE ONLY KIT AND IS INTENDED FOR EXPERIENCED INSTALLATION AND MAINTANCE WITH FREQUENT CHECK-UPS AND INSPECTION. FUEL INJECTION SYSTEM FAILURE OR LEAKAGE MAY RESULT IN ENGINE DAMAGE OR ENGINE FIRES THAT CAN DESTROY THE VEHICLE OR RESULT IN DEATH. INSTALLER IS RESPONSIBLE FOR SECONDARY INSPECTION OF ALL COMPONENTS FOR MANUFACTURING FLAWS BEFORE INSTALLATION.

You may wish to purchase a new pump seal o-ring from the Nissan dealer, as they sometimes expand to become useless, therefore delaying reassembly.

If you find any missing steps, please let us know so that we can update this page and improve on it.

Step 1: Disassembly

Make sure that the car has less then 1/4 tank of fuel before starting the installation.

Leave the car sit for several hours before beginning installation. This is to reduce fuel pressure held in the system and allow for cooling of the engine.

Remove Strut Tower Bar.

Remove Engine Cover.

Remove Air Intake Tube that attaches to throttle body.

Disconnect Throttle Body electrical connector. Optionally remove throttle body.

Remove EVAP Purge Solenoid Vacuum Line.

Remove EVAP Purge Solenoid Mounting Bracket Bolt and Electrical Connector. Then thread the bracket bolt back into the plenum by itself so that you do not loose it.

Remove the final vacuum line connecting the EVAP Purge Solenoid to the metal pipe attached to the Fuel Pressure Damper Bracket.

Remove Brake Booster Vacuum Line from plenum top.

Remove Misc brackets from plenum collector and reinstall the bolts by themselves so that you do not misplace them. The bracket shown in the first picture will need to be unbolted from the timing chain cover as well.

With a rag in hand, remove the bolts attaching the fuel pressure damper and inlet hose from the fuel sub-tube. Be prepared for fuel leakage, as the system may still be under pressure. Pull the damper upward very slowly while surrounding the area with a rag to prevent fuel spray. Not a whole lot of fuel will come out, but it may come out under pressure and spray.

From underneath the vehicle, by the passenger side exhaust manifold, disconnect the fuel hose that leads to the damper you just removed. You will need to slide off the safty cap and then you can disconnect it. Fully remove and discard or store away the fuel feed hose with damper, it will no longer be used.

Remove all 18 bolts attaching the upper plenum. Follow REVERSE numerical order of this illustration.

Remove the first throttle coolant hose shown by the arrow in the illustration. You may wish to plug it with a bolt if it is leaking. Slowly lift the plenum off by the front and notice the final coolant hose on the bottom under the throttle. Remove that hose (and plug if needed) and place plenum aside. Be careful with the gasket, it cannot be taken off yet.

NOTE: From this point on, it is very important that you do not drop any hardware or tools. Should you drop something small into one of the intake ports, and the intake valves are open on that cylinder, you are at risk of losing something inside the engine that will not be retrievable without complete engine tear down.

Remove the PCV hose from the plenum collector as shown by the lower arrow. Then remove the 2 bolts holding the fuel pressure damper and tube bracket as shown by the 2 upper arrows.

Remove the bolts in the opposite order shown in the illustration. Set aside the gold PCV channel cover. Set aside the upper plenum gasket.

Lift the plenum collector off the engine carefully. Cover the 6 intake ports with tape to prevent anything from being dropped inside.

Remove all 4 bolts holding the fuel rails to the intake runners.

Carefully lift the fuel rails and injectors off the intake manifold. Look for any seals or o-rings that may have come off the bottom of the injectors and stuck into the 6 injector ports of the intake runners. If any came off, then place them back on their corresponding injectors.

Enter the interior of the vehicle. In a 350z, the fuel pump access panel is located in the large compartment behind the passenger seat. Remove the floor of the compartment by popping it up in the front and pulling it out. There will be a sheet of sound deadening material to set aside. In a G35, the pump access panel is located underneath the back seat on the passenger side.

When you reach the access panel, rotate the 4 clips 90 degress clock-wise.

Disconnect the harness connector and the fuel feed tube's quick connector. Have a towel ready to absorb some fuel from the connector when it is removed. If excessive fuel drips from the connector, it will remove the corrosion protection coating on the top of the gas tank. You can zip-zie a dry rag to the connector to collect remaining fuel as you push it aside to work in the fuel pump area.

Remove all 6 fuel pump assembly metal retainer bolts and set aside the metal retainer ring. Gently lift the pump assembly up an inch or so and get the black sealing o-ring out of there immediately. You can gently get the O-Ring over the top of the assembly with very little stretching by using care. The O-Ring will expand and be unusable if it contacts gasoline.

Gently navigate the assembly out of the fuel tank. Handle with care to prevent bending or damaging the fuel level sensor sending unit or float arm. Be aware of the fuel siphon hose that is connected to the fuel pump assembly on the side that faces the rear of the vehicle as you lift it out. When the assembly is a couple inches out, you can remove the siphon hose and drop it into the tank. If needed, you can rotate the assembly 90 degrees counter-clock-wise to ease removal of the siphon hose.

Place a towel under the pump assembly before carrying it away from the gas tank opening to prevent spilling gasoline in the vehicle interior.

With the pump assembly outside of the car, the dissassembly phase is complete.

Step 2: Fuel Pump Modification and Installation

Un-snap the black fuel temp sensor on the bottom of the can and unsecure its 2 wires from the canister. Remove the lower surge can off the assembly by releasing the snap lock and sliding them apart (pay attention to how it slides on/off to make reassembly easier). Take care not to damange the level sensor as there are 2 wires attached to it. You can pull the two terminals off the level sensor and set the entire can aside if you wish.

Drill a .430" diameter hole behind the electrical plug on the top of the assembly. While holding the assembly towards a bright source of light, you will be able to see through the plastic. You want to make sure that where you drill the hole will leave enough room on the underside for the bulkhead nut to thread without hitting anything while turning it.

Notice that on the underside of the assembly, around the hole that you drilled, you will need to use a dremel or other grinding tool to eliminate some support webbing. You need to remove enough so that the sealing washer can sit flush on the plastic and the bulkhead nut can spin freely with a socket on it.

Insert the bulkhead so that it will be facing the front of the vehicle when reinstalled (parallel with the back side of electrical plug) with a sealing washer on the top and bottom. Lubricate the rubber section of the washers so that they do not tear when tightening. Thread the bulkhead nut all the way down snug by hand. While holding the top of the bulkhead with a wrench, use a deep socket to tighten the nut.

Remove the plastic cap for the OEM fuel pressure regulator housing (4). It is the white cap at the lowest point of the assembly, right next to the fuel pump cap. Pull the regulator out, but do not discard the large black o-ring (2) or white plastic spacer (3). Assemble the regulator bypass fitting as illustrated. Put the retaining clip (4) on the bottom of the bypass fitting, and then thread in the 90 degree fitting (5). When tightening, you may wish to hold the bypass fitting with pliers wrapped in electrical tape to prevent excessively damaging it. It does not need to be extremely tight.

Install the bypass plug assembly. Do not forget the o-ring that is supplied with the fuel system (1) or it will result in an internal pressure leak. Snapping in the cap will require effort as you compress the top o-ring. Make sure that both o-rings and the spacer do not fall off while assembling. Once it is snapped in, route the supplied hose as shown. You will need to hold the top of the bulkhead with a wrench while tightening the hose fitting to it. Use the supplied clamp to secure the hose to the 90 degree fitting.

Carefully replace the fuel surge can, level sensor wiring, temp sensor, and temp sensor wiring. When sliding the can on, it might have some resistence with the bypass hose. However, once the can is down all the way, it should freely slide up and down (it is self-height adjusting for multiple application use in different fuel tanks).

The final step is required only when using a Walbro 255lph fuel pump. The large amount of return fuel at idle will cause fuel pressure to spike due to restrictive internal plumbing of the pump assembly. This return pressure can be relieved by enlarging the swirl jet orifice. Remove the yellow swirl jet from the outside, bottom corner of the fuel can. It pops out downward. Do not break it, as it is NOT replaceable. Find the pinhole outlet and enlarge it to .070" - .100". Reinstall the part.

The fuel pump assembly can now be reinstalled just as it were removed. Do not forget to reconnect the siphon hose as you lower the unit into the tank. Take care in routing of the siphon hose as to prevent it from interfering with the fuel level sensor float arm. Reinstall or replace the tank sealing o-ring.

Step 3: Fuel Rail and Injector Installation

First install the injectors into the rails. Use a light coating of oil or other lubricant on the top injector o-ring to help insert it into the rail injector bosses. Be very careful to make sure the entire o-ring inserts and that it doesn't catch and get torn. When inserting the injector, position it so that the electrical clip is facing the flat side of the rail (which will face the valvecovers).

Be sure to have a lower o-ring installed into the intake manifold before installing the rail/injectors assembly. You may wish to lubricate the lower o-rings to assist. The longer rail fits on the passenger side of the engine with the flat side facing the valvecover. Use ONLY the included stainless bolts to hold down the rails. Torque sufficiently.

NOTE: Taller than factory injectors will require taller fuel rail spacers. RC Engineering includes .455" spacers with their injectors for the VQ35DE. The second picture here has an arrow pointing at the rail spacer to illustrate. If you are using OEM length injectors, be sure that the OEM rail spacers are installed.

Step 4: Fuel Pressure Regulator Installation

Install the regulator in the location shown. Before making installation permanent, set upper intake manifold parts on to make sure the regulator position is clear of the throttle body inlet neck and the EVAP solenoid. Also make sure there is enough clearance for any gauge or sensor you plan to use in the 1/8 NPT pressure port on the front of the regulator. Install included gauge now if desired.

Step 5: Hardpipe Adapter Installation

The hardpipe adapter is used to adapt the factory 5/16 hardpipe into an AN style connection. This allows you to install performance plumbing to the OEM hardpipe. The hardpipe adapter kit consists of 3 parts. Part #2 will be inside parts #1 and #3 in your package.

CAUTION: This step involves extra care to prevent injury or fire. When cutting the hardpipe, remember that there is still gasoline in there. Wear eye protection and do not generate any sparks while cutting.

Seperate the parts into 3 individual items. Installation requires you to cut the factory hardpipe. You want to cut it just before the bend that goes upward towards the headers. Cut it immediately before the bend to give yourself as much straight section as possible. The 2nd picture above shows where it will go (The arrow indicates location, but the photograph is taken of a Stage 2 system with upgraded hardpipe). DO NOT CUT THE WRONG PIPE, make sure your not cutting the EVAP pipe.

After cutting the pipe, you need to trim back about 1.5" of the plastic coating. This is most easily done with a razor blade. Use it as if peeling a carrot, starting at the cut edge and sliding down the pipe for the 1.5". After removing the coating, you need to prepare the pipe for use. Use a file to make the edge straight and perpendicular. Then use deburring tools or sand paper to deburr the end. Once properly deburred, part #2 should easily slide on and off.

Once deburred, begin installation by sliding item #1 down the pipe facing the direction illustrated in the first picture above. Then slide on part #2 facing the direction shown in the picture, with the externally tapered edge first.

With items #1 and #2 loose on the pipe, install item #3. It will thread into item #1. You want to firmly press item #3 up against the cut edge of the hardpipe while you tighten #1 against it. This will crush the compression fitting (#2) and create a seal. You need to make sure that you do not accidently compress item #2 while its not fully on the hardpipe.

This fitting takes a LOT of torque to seal. You are better off to start mildly tight, and if it leaks during pressure testing then you can torque it more. Pay lots of attention to this union for leaks during the pressure testing phase. If correctly installed, this adapter will be a leak free solution that will last forever. Be careful not to kink the pipe near the adapter, and do not ever open it later unless removing for good.

Step 6: Hose Installation

Step 7: Purge Debris and Pressure Test

It is highly recommended that you perform this step now, rather then after the car is running again.

To purge debris, you want to run your return line into a bucket and prime the fuel pump 4+ times to push any debris thru the system and into the bucket.

While doing this, you can also inspect all the lines in the engine bay. It is very important that you have absolutely zero leakage anywhere in the engine bay. Raise the regulator pressure to increase pressure in the system while checking for leaks. You need to check at every fitting and every crimp.

Step 8: Install Intake Manifold and EVAP Line

Step 9: Bleed Coolant

This step is really only required if you lost a lot of coolant when removing the throttle body coolant hoses, which doesnt typically happen.

Step 10: Set Pressure

Prime the fuel system and set the fuel pressure at the regulator. This is done by loosening the lock nut on the top, and turning the allen screw, and retightening the lock nut.

Step 11: Tune Vehicle

A RFS will completely alter the fuel pressure characteristics in your vehicle. A fresh tune is required after installation

Posted by CJ Motorsports at 5/24/2009 8:52 PM | View Comments (2) | Add Comment

CJM Twin Fuel Pump Installation Notes

This is not a complete installation guide, this is just some notes to help the installer.

Wiring Information
Terminal Installation
Plumbing Information

Wiring Information

You will need to cut the level sensor wires off of the factory assembly. Cut them as close as you can to the top to preserve as much length as possible. You will crimp one of the provided terminals to each wire, then insert them into the connector on the inside of the pump assembly.

The factory assembly has a temperature sensor. This is not used in the CJM assembly. To prevent a Service Engine Soon light, you will need to purchase a 2.4K Ohm resistor and wire it in-line (outside the tank) to replace the sensor.

Carefully route the slack on all wires inside the assembly. You do not want them in contact with any sharp edges that would wear away at the insulation, such as a hose clamp, as the vehicle vibrates.

You will need to use the factory fuel pump power wires to activate a pair of relays that you will use to power the twin pumps. This means running a decent gauge power wire from the battery to the relays and then to the pump connector.

IMPORTANT NOTE ON STAGING THE FUEL PUMPS; If you desire to stage the fuel pumps, that can be done. But it is important that you correctly wire which pump is the primary and which is the secondary. The primary pump MUST be the pump that is closer to the transfer siphon barb on the bottom of the canister. This pump runs the transfer siphon, which is why it needs to be in full time use. The other pump that has the hole in the can underneath it will be the secondary pump to engage under high load.

Summarized Recommended Wiring Parts List:

2.4K Ohm Resistor
(2) 12v Relays
Battery Power Wire
Misc Terminals for relays and battery

Terminal Installation

Note: Use a Volt Meter to make sure you are inserting terminals in the correct port of the plugs. You do not want to accidently reverse polarity of the pumps or send 12v to the level sensor.

CAUTION: While the plugs that go on the inside and the outside of the wiring bulkhead are identical, the one that goes inside the tank must be prepared. The rubber dust seal behind the terminals and the slider dust seal must be removed. If they are not removed, they will expand and extrude into chunks of rubber to clog your pump pickups. Please verify that the connector plug you are going to put on the inside of the bulkhead does not have any rubber inside or out. Also, the sliding safety lock needs to be removed from the connector that is being used inside the tank. This should have already been done for you, but please verify.

Remove the blue Terminal Lock by
pulling outward with needle-nose pliers.

This is what it looks like with the Terminal Lock removed.

Insert crimped terminals into the back of the connector as shown.
Either flat side can face up.

Slide the terminal in until you hear/feel the click.

These connectors feature a safty lock that prevents them from being pulled off.
This photograph shows the unlocked position.

This photograph shows the LOCKED position.
The connector cannot be removed in this position.

Plumbing Information

The twin pump assembly comes with no plumbing outside the tank. There are several ways to plumb this assembly based on the vehicle owners needs. We do offer a twin pump plumbing kit to adapt the twin pump assembly to our Stage 2 kits, creating the Stage 3 kit. Feel free to contact us about a Stage 3 plumbing upgrade.

To adapt the CJM Stage 1 or Stage 2 return fuel hose to the twin fuel pump assembly, you can use Earl's part number 921106ERL or a similar product.

The OEM fuel filter is located inside the OEM pump assembly. Since you are removing this OEM pump assembly, you may want to install an inline external fuel filter. We do with our Stage 3 upgrade.

The pump output fittings on the top of the twin pump assembly are -6 and facing straight up. Therefore you will need a pair of 90 degree -6 hose ends. Then you will need to run those 2 lines under the car and go from there. We would recommend running them into a Y fitting and using a single -8 or -10 up to the engine bay.

You will need a -6 return line to support the twin pumps.

Posted by CJ Motorsports at 2/24/2009 8:50 PM | Add Comment

A First Look: The 370z Fuel Pump Assembly

Section 1: A First Look
Section 2: Upgrading the Pump
Section 3: Return Fuel Conversion

Section 1: A First Look at the Nissan 370z Fuel Pump Assembly

The 370z fuel pump assembly is vastly different than the unit found in the 350z in terms of shape and packaging. However, it does perform all the same tasks in the same method, only with a couple upgrades in functionality. The first thing we noticed is that its TALL. The second thing we noticed, the swirl can is awfully limited in displacement, most of which is displaced by the pump housing and internal filter. This unit is a lot more obvious in its features unlike the 350z which takes a deeper look to figure out since most of the plumbing is internal.

Following the 350z theme, this unit pumps into an internal filter housing, and from the filter housing it exits the tank. The fuel pressure regulator bleeds pressure from the filter housing, and it dumps into channels that lead to a pair of venturis. One venturi to siphon fuel over the tank, and the other venturi firing into an inlet on the bottom of the swirl can to promote refill. Here you see a similar fuel temperature probe. The swirl venturi is in the black housing in the lower right of the photo.

The plumbing is mostly external on this assembly. Notice the fuel line that exits the fuel pump output and makes a u-turn directly into the fuel filter housing inlet. After the fuel flows thru the filter, it exits the filter housing via the teflon line leading off the left side of this photo, and goes straight out of the top of the assembly to head to the engine.

Here is where the secondary functions kick in. What you are looking at is a side view of the filter housing, notice the exit line leaving off the left of the photo. The metal object in the top center of the photo is the top of the fuel pressure regulator. It is similar in appearance to the 350z, but it is not the same, so our previous regulator pass-thru plugs will not fit this for return fuel conversion. Fuel bleeds out of the filter housing into the side of this regulator, which dumps downward (to the right in the photo). Notice that you cannot remove this regulator without modifications to the assembly which will require cutting off the part that holds it in place.

The 370z fuel pressure regulator outlet oriface (bottom) measures to about .090" compared to the 350z counterpart (top) that measures .065". This is a sign that its possible that the factory regulator will be able to support a fuel pump upgrade without modifications. The 350z regulator requires drilling the outlet to about .110 when putting in a 255LPH pump. The .110 may or may not be overkill, so its hard to determine at this time if the 370z regulator is going to be 255LPH friendly or if improvements will need to be made. The good news, is that you can actually get to the outlet oriface on the non-removeable regulator in the 370z should it need oversizing.

This part can be removed from the assembly. The location of the red circle is a press fit into the channel that the regulator dumps into. The blue circled region below it presses into the refill siphon that is mounted to the bottom of the can. So in effect, this is a T fitting that splits the return fuel to the venturis. The green circled barb is where the siphon hose connects. The yellow outlet is where the siphon venturi dumps.

Here you can see the assembly mounted to the filter housing, and with the T fitting pressed into the regulator outlet.

This photo is to illustrate how the bottom of the T fitting interfaces with the fill venturi. When you slide the filter housing into the canister, it will engage with the black inlet for the venturi.

The last thing of significant interest is this guy here. This is a return pressure relief valve. This will either help us out with upgrades, or make no difference at all. In the 350z, when you upgrade to a 255LPH fuel pump, return fuel or non-return fuel you still need to enlarge the opening of the fill venturi. This is because the quanity of fuel being dumped by the regulator at idle is significantly higher than with the stock pump, and the 2 venturis alone are too restrictive for the regulator to do its job since where it dumps is completely backed up with pressure. This valve will open when the pressure gets too high, so that the regulator can do its job. However, when it opens, it may relieve too much pressure and kill the venturis. If that is the case, we will have to open up the venturis anyway to keep the valve from opening as much as possible.

Section 2: Upgrading the 370z Fuel Pump
(Installing CJM Fuel Pump Installation Kit, For Walbro, DW, or Aeromotive Pumps)

Remove the retaining clip holding the top plate to the fuel pump assembly. It will require a pair of small tools to pry it outward on both sides.

Set aside the retaining clip, and the spring and spacer. Be careful not to misplace, they are important.

Remove the surge canister from the fuel pump assembly by spreading the pair of locks apart on either side of the assembly while gently pulling the canister off. It may require a little bit of rocking the canister while pulling on it. Be very careful not to break off the tabs for the locks.

Remove the blue and black wires powering the fuel pump from the top flange, and cut the hose leading from the fuel pump to the filter assembly.

Release the pump from the assembly by pressing the two tabs circled in red and rotating it free. It can now be dropped out the bottom of the filter housing.

Remove the remainder of the fuel pump hose by using a blade to split open the hose along the barbed output of the fuel filter inlet. Once its split open vertically along the entire barbed fitting it will come off easily.

This is what the assembly should look like now.

Inside the fuel pump bore, use a blade to cut the 3 attachment points for the OEM fuel pump retainer ring. Use a file to file the 3 areas smooth. The result should look like this picture.

Install the OEM pump's pickup filter to the Walbro GSS342.

Install the Walbro GSS342 using the CJM Fuel Pump Installation kit by referencing the following series of pictures. 1. Install billet clamp by sliding it all the way down securing post and tightening post clamp allen screw. 2. Install length of hose into the billet clamp, but do not tighten. 3. Install length of hose onto the fuel filter inlet barb and tighten clamp. 4. Install U-Bend pipe to both hoses and tighten clamps.

5. Lubricate fuel pumps output barb, and slide into the assembly, engaging the fuel pumps output into the hose and billet clamp assembly. 6. Rotate the fuel pump until clocked properly and center in the assembly, and tighten the final clamp securing the hose to the fuel pump output barb.

The wiring pigtail supplied by Walbro will need to be used now. 2 spade connectors are to be crimped to the end of each wire and plugged back into the top flange.		NO PHOTOS AVAILABLE YET

Section 3: CJM Return Fuel Conversion for 370z

The factory fuel pressure regulator needs to be removed. In order to remove it, much plastic needs to be trimmed away. Much care needs to be taken to only remove the plastic required. Use the following photographs as reference.

You must not enter the fuel filter housing, or the assembly is ruined.



By this point the regulator may be removed.

Install the white spacer ring and o-ring from the factory regulator onto the CJM regulator fitting.

Install the CJM o-ring all the way down to the floor of the oriface where the regulator was.

Install the CJM Regulator Fitting with the factory regulators spacer and o-ring already installed. It will stop at about this height when it hits the CJM o-ring.

Install the CJM Regulator Fitting Clamp using the 2 supplied bolts. Make sure it is facing the correction direction. It will still fit when upside down. However, if not facing the correct direction, it will not leave the ears of the fitting in the correct location. Tighten the bolts gently and evenly.

This is what the assembly should currently look like.

Reinstall the canister and check for proper clearance by both of the bolt ears of the CJM Regulator Fitting. Clearance will be adequate all around here if the regulator fitting clamp was correctly installed.

Drill a hole directly in the center of the top flange. The diameter of the hole needs to be snug for the bulkhead fitting to seal correctly.

Install the bulkhead fitting with a washer on both sides of the plastic flange, and tighten the bulkhead nut.

Underside view of installed bulkhead fitting with washers and nut.

Reassemble the entire unit and connect the hose between the bulkhead and the CJM regulator fitting. Make sure that you can compress the spring loaded assembly about an inch without the blue hose becoming kinked.

Posted by CJ Motorsports at 2/21/2009 11:13 PM | Add Comment

Fuel Pump Upgrade Installation

Walbro GSS342 Installation (350z, G35, FX35, etc)

Note: Installation is intended for qualified individuals. This manual is not fully detailed, as some operations should be familiar for an experienced VQ35 Technician.

This is divided into 4 sections.

The Pump
Swirl Jet Modification
Regulator Modification
Final Assembly

Part 1: The Pump

Remove the 2 wires from the 3 clips so that they are loose. Pull up the locking tab on the right so that you can gently pull the unit apart. Be careful not to pull too hard on the wiring.

Place the 2 spings aside. The unit should look like this when seperated.

Use a screwdriver to pop the pump cap off the locks and remove the cap.

This is the unit with the cap removed.

Remove the electrical connector from the pump.

The pump is ready to slide out, downward.

Pump removed.

Walbro on the left, removed stock pump on the right.

Swap the top seal to the Walbro (Right arrow). Remove the sock by focusing on removing the round metal lock (left arrow).

Put the sock on the Walbro, and put the metal lock on the Walbro. Be careful, the metal lock is hard to get back on, and very easy to loose if it gets away on you.

Slide the Walbro back into the assembly. Make sure you feel the top seal slide into its position. Plug back in the electrical connector.

Use side-cutters to remove 3 of the 4 tabs on the bottom of the walbro (reference next picture for which 3 of the 4). Do not cut too deep or you will destroy the pump by opening a hole for it to leak. You want to cut them off almost flush. You are safer if you cut them high and file off the rest. Be cautious, the plastic cracks easily and if you crack it anywhere other than cracking the tabs off, the pump is ruined. You can even elect to file this all the way if you want to be extremely careful... filing it is messy so if you choose that route then take the pump back out so you dont get a mess of plastic everywhere and use compressed air to blow clean the sock.

Pump with 3 tabs removed.

Mark this part of the pump cap to file off. Notice the green marking.

Use a file like this and file off the area marked.

With some muscle, starting on the left and working your way to the right, reinstall the pump cap onto all the locks. It can be done at this point but if you feel that you just cannot get it to snap and lock SECURELY on, you can file other sections down to allow more room. Just be careful, if you file too much then the pump will fit loosely, you want it extremely snug and you want to make sure the cap is correctly seated so that it does not pop off. It should be flexing just a little to get on.

Pump installation is now complete, however, do NOT skip the following steps for pressure control.

Part 2: Swirl Jet Modification Procedure (REQUIRED FOR GSS342 or larger pumps)

If this step is skipped, your idle and low RPM/Load fuel pressure will be high and cause tuning grief. This will address the issue and is required WITH or WITHOUT a return fuel system.

Carefully remove the yellow swirl jet from the bottom of the can. Do not break it, its just cheap plastic.

Drill the outlet to .070". If you are using a larger pump like the DW or the Aeromotive, a .100" might be a better idea. Its very soft plastic and drills easy, be careful not to drill all the way through the entire part or it is ruined and not replaceable. Just drill until you can look into the large opening and see the drill has made it to the chamber.

Making sure the o-ring is still in place, snap the jet back into the can. This step is complete. Follow the next step if you DO NOT have a return fuel system.

Part 3: Regulator Modification

If you are installing a return fuel system, then skip this entire step and begin installing the return correction kit. This modification is only needed if the OEM regulator is going to remain in place. Return fuel systems eliminate the OEM regulator.

Remove the regulator cap. Remember, its just plastic, dont break it.

Remove the regulator. Just put a screwdriver under the lip and twist, it pops out easy.

Using a 7/64 drill bit, open the regulator outlet oriface. ONLY drill until you make it thru the sheet metal.

Blow the regulator off with compressed air. Making sure both o-rings and the plastic spacer are in place, reinsert the regulator into the housing and reinstall the regulator cap.

Part 4: Final Assembly

Reinstall the 2 assembly springs.

Reassemble the housing. It helps to use one hand to compress the filter sock. Dont pull out the wiring. Make sure you get it all back into place and when done properly the housing can be compressed by hand and it will naturally fully extend to its natural position when you let it go. Resecure the wires to the clips on the housing.

Posted by CJ Motorsports at 2/18/2008 8:30 PM | View Comments (1) | Add Comment

HKS vs OEM Headgaskets

This is a rather old comparison document. It was written when your only options for the DE were the OEM or the HKS gaskets. There are now more options available, including better OEM gaskets. We brought this over from the old site anyway.

Many VQ35DE builders have had issues sealing the original VQ35DE headgaskets beyond 500rwhp using OEM headgaskets and standard ARP head studs torqued to 70-80ft-lb. The CJM 350z experienced these issues starting at 14psi of boost and 575rwhp on the original build. Once the headgaskets were damaged, they started leaking at even 520rwhp @ 11psi of boost. Engine teardown is the only fix, as the the headgaskets cannot just be simply changed out on the VQ35DE. The labor is intensive enough to justify an entire rebuild.

CJM utilized the HKS headgaskets along with a 1/2" headstud modification for the second build. The torque on the headstuds was set to 95lb-ft. So far the combination has been a great success, with not even the slightest signs of any headgasket leakage at all. We would recommend that you contact your local HKS dealer for these headgaskets. The MSRP is $360.00, and they are worth every penny. **update 1/1/09, after a few years of use, the HKS headgaskets have still held strong at 14psi - 18psi of boost, a new engine build is taking place, hks headgaskets may be included in this build, or we may try the new HR series OEM gaskets which have been successful for many lately**

First lets go over some information provided by HKS, then I will show our comparison.

Text copied from HKS USA website: "HKS metal head gaskets are engineered to resist severe levels of heat that are generated by high-horsepower and high-boost applications. All HKS head gaskets are constructed with multiple layers of steel and coated with a special fluorine rubber to provide exceptional sealing. HKS head gaskets are designed to accommodate standard and certain oversized cylinder bores." (Source: http://www.hksusa.com/products/more.asp?id=732)

Text copied from HKS USA website: "The HKS Stopper-Type gasket consists of the maximum layers of plates possible and utilizes a molded stopper ring around each combustion chamber opening."
(Source: http://www.hksusa.com/products/more.asp?id=732)

Images from HKS USA website (click to enlarge):

The CJM Side-By-Side Comparison of the HKS VS OEM Headgaskets:
(CLICK ANY IMAGE IN COMPARISON TO ENLARGE)

NOTE: OEM Gasket is Silver/Black, HKS is all black.

Basic Side By Side Comparison. The HKS rubber coating is a little more "luxurious" and tacky feeling. I would feel confident in the HKS unit providing proper sealing without any copper spray. The OEM units I would probably end up giving a light coating of copper to. The HKS gasket is coated all over, while the OEM gasket is only coated in areas requiring sealing. The cooling and oil jackets appear indentical.

Thickness Comparison:

While HKS advertises a 10.3 C/R, we measured the OEM gasket to a 0.6mm
and the HKS to a 0.7mm. This will just barely reduce compression.

Embossing Comparison:

The OEM unit has double embossing around each combustion chamber on all 3 layers. The embossing around the cooling and oil jackets is not as aggressive.

The HKS gasket has half as much embossing around each chamber, but more aggressive embossing around the cooling and oil jackets

Middle Layer Comparison:

The Nissan OEM middle layer has embossing that matches the 2 outter layers.

The HKS unit's middle layer employs the HKS "Stopper" ring, which is a folding over of the layer. This will give extra sealing pressure precisely where needed.