made in china

iTrader: (7)

I am having progressively harder starts on my Maxima. My car is a full 3.5 swap, and has a FPR set to static 51psi. When I turn my key off, the fuel pressure drops very quickly from 51 psi to 0 within 10 seconds or less. Seems to drop faster with hotter weather. When I turn key on, the fuel pressure will bump up to 51psi then quickly fall to 0psi if I don't start the car. Of course the ECU turns on the fuel pump only momentarily, and sometimes not at all if the car was running recently. I think that is normal, but my fuel pressure drop seems very bad. So, my car is very very difficult to start. Usually I don't let it crank and crank, I will crank for 3-4 secs, if it doesn't start I'll wait 5-7 secs and try again. It will usually fire up second time around, but the idle stumbles and the engine shakes badly. I have heard in other threads that this also tends to kill the motor mounts.

So, is it possible for a faulty fuel pump to allow bleed down of fuel pressure back thru the pump into the tank?

I reckon it could also be my Aeromotive FPR allowing the fuel pressure to bleed down suddenly, so I'll check that tonight.

When the fuel rail goes to 0 psi so quickly, does the fuel system lose prime and is this why my car starts so hard? I reckon at 0 psi even when the pressure comes back to 51psi there must be some air in the system.

I don't have any external fuel leaks, and my car currently gets 29+ MPGs, so whatever my prob is the fuel is being returned to the fuel tank.

Anybody have similar experience and get it resolved? I plan on testing it tonight by pinching off the fuel return line and then pinching off the fuel supply line to see which way the pressure is leaking back.

What do you guys think?

CMax03

iTrader: (3)

I would test the FP first to see if the dampner is open and letting the pressure drop! That or pressurize the fuel rail and clamp the pressure line and return line (if you have one) and see it the pressure bleeds off then you'll know it's an injector or seal!

MaxVQ5spd

iTrader: (1)

I am experiencing pinging on 93 octane this year (with the JWT ECU in) and have checked everything I can think of. My car is also hard to start at times requiring 3-4 second cranks and second start attempts (with or without the JWT ECU). My car does not run rough after a hard start though.

I ran a bottle of fuel injector cleaner through (on a long continuous trip like they recommend), changed the fuel filter, crank sensor, cam sensor, MAF sensor, and it still pings and is hard to start. It ran fine even when temps got up into the 90's last year. This year it will even ping some in the high 60's and low 70's.

Today I tested my fuel pump pressure. It was in spec with 34 psi at idle and peaking at 43 psi under throttle and when the switch is turned on. However, it drops immediately to zero when shut off. There was also an irregular clicking noise that seemed to be coming from an injector under the intake runners that sounded like one of them was not operating properly.

Given my problems I think it is more likely to be a single injector not operating correctly, which brings me to my question. Are the injectors supposed to hold pressure when the pump is off?

The way I figure it, if the pressure is bleeding back to the pump it would be hard to start, but I wouldn't have pinging (assuming it works as well as it did in my pressure test in real operating conditions). Made in china, your car's problem would probably have to be injector related too, using this same logic, or your car would not be running rough on startup. It is like you have an injector stuck open. Maybe we both do, but mine is stuck partially open and yours all the way?

NisTech

just put a fuel pump in. fuel is draining back into tank. 05-06 sentra has the same issue and they made a repair kit for them.
Not that many maximas with that issue but excessive cranking will result.

made in china

iTrader: (7)

That sounds plausible for my car. I reckon the original fuel pump has about 240K miles on it.