CJM: Ultimate 370z Fuel Pump Thread

[Jayhovah]

Originally Posted by phunk

Running without the venturi installed or running it with the extra hole in it has ruled out the venturi as the source of your pressure spike. Unfortunately Nissan does not sell the venturi jet, so the only way to replace it is to replace the entire fuel pump housing. It will need to be replaced or repaired since the additional hole will either entirely defeat the venturi system or render it too weak for standard use. The car will fuel starve from not being able to recover fuel on the driver side of the tank.

All the black gunk/debris in the fuel pump canister is normal. I dont know where it comes from but its in every stock 370z fuel pump I have ever opened. The strainer being darker probably isnt a big deal yet, looks pretty normal for a well used one. It wouldnt effect the fuel pressure spike anyway as the most it could ever effect, if it were completely clogged up, it would restrict the pumps intake resulting a pressure loss rather than pressure spike.

Since your fuel system is stock, the only possible way for fuel pressure to exceed the regulator setting is if the regulator cannot vent out well enough, or if the regulator itself is damaged/clogged. You have eliminated regulator venting from the equation, so there are only 2 possibilities left. Your regulator is bad or clogged up, or the fuel pressure gauge is reading high.

I would replace the fuel pump module with another one since this is inevitable at this point*, and then if the fuel pressure is still too high according to the gauge, i would either try another gauge or I would just ignore it and write it off as the gauge just reads a few psi high.

*: unless you can find a way to plug that extra hole up with something that will not dissolve in gasoline. Such as machining a custom plug on a lathe and pressing it in, or something.

Another thing you can try, is drilling out the outlet on the stock regulator. I have never had to do this but I do not generally use a stock fuel system. All the cars I work with are using return kits. But I believe that Stillen has their customers drill the outlet on the regulator so it itself can vent better. This might be worth a shot as it could not hurt anything so long as you do not drill too deep into it.

I'll dry drilling the regulator, seems like I don't have much to lose at this point and may as well experiment. As for plugging the hole on the opposite side of the venturi - JB weld makes a couple of epoxy putty products that they say can be submerged in gasoline.. might see if that does it. If I do manage to repair the damage, do you think I drilled out the venturi too much for the 255lph? If I did, what would the symptoms be? low idle pressure? or low pressure while driving? Could I then correct the problem by just upgrading to a 340lph?

Any recommendations on getting a new fuel pump assembly? Used units for the G37 seem to be much less expensive, but the part number is slightly different. Do you know if they use the same venturi piece or regulator?

Also, do I need the little venturi piece if I upgrade to a return system? A new assembly is $350..might be better put towards an upgrade.

Thanks for continuing to provide feedback. Really appreciate the advice! Hope the documentation of my experience in this thread will help someone else!