fuel problem

[capowered240]

I took it out for a short test drive today and it felt fine. So I go back to my friends shop and turn it off. Well I look at the fuel pressure gauge and it is still around 26-28 psi. After about 4-5 minutes its back down to 0. Also where the fuel pressure regulator is I can hear like fuel is still running threw the rail. I pull the sparkies out when it cools off and #3 and #4 on top of the piston has gas on it. On the fuel pressure, is it suppose to go down to 0 when you turn it off?

[ca18det240hatch]

sounds like you got a few leaky injectors..

[rico05]

Odd. I have my Nismo FPR set at 36psi, and when I shut it off, it stays. I dunno if it is the gauge or the system. That seems odd.

[Sil40sK]

If you're fuel pressure is dropping like that and you're getting gas on your #3 and #4 cylinders then it sounds to me like you've got leaky #3 and #4 injectors bud. The gauge should stay at whatever base pressure you have it set at once you've turned the car off.

[capowered240]

Alright that does sound about right. Would sending them out to get them cleaned help? If not, I'll just get some more injectors. Thanks for helping.

[ca18datsun510]

while you are messing around there, pull the vacuum line off the fpr. see if it smells like gas. easiest way to check if the diaphragm inside is broken.

[capowered240]

I'll do that. I've got the nismo adjustable fpr. Also If anybody needs a stock fpr, I've got one for sale.

[float_6969]

ditto on the leaky injectors. Just send them off and have them rebuilt. They'll literally be like brand new and you'll be set for years to come.

The fuel pressure should hold for HOURS after you turn the car off. Sometimes my car will still have a few pounds of pressure on it in the morning if I drove it right before I went to bed.

If the NISMO unit is on the car and relatively new, I would doubt that it's bad.

[capowered240]

Alright, I just got the nismo unit about a month ago.

[ca18datsun510]

should have said that earlier......

[dattodude]

I've got a sard reg and walbro pump. It drops to zero within 5 seconds from running pressure. Both were new when I fitted them, and only a 10 hours of running time in age. Nothing wrong with my setup, fuel pressure is steady at 42psi at idle and 60psi @ 18psi boost and 7000rm :-)

Fuel on the pistons sounds like either a wiring problem, or more likely a stuck injector or two.

Just giving my two cents of experience.

[float_6969]

I think the SARD regulators don't work the same internally than the NISMO unit does. IIRC they have some sort of dampening device in them that helps to even out the fuel pulses from the pump.

Maybe that is the cause of your quick leak down compared to ours?

[dattodude]

Possibly. I remember the old nissan FPR kept fuel pressure for several hours, but I was using an external bosch pump then too. It's more likely to be pump related I would think. A regulator is not exactly rocket science in design, and I expect all are functionally the same internally.

I guess if others comment on their fuel pressure behaviour, we should be able to figure it out.

[float_6969]

I think you nailed it with the pump actually. Most of us are using Walbro intake pumps. I'll bet they have some sort of internal check valve that prevents the fuel from back flowing into the tank.

Are the Walbro pumps a diaphram or cintrifugal type pump? From the fluctuation I see in the needle on my fuel pressure gauge, I'm led to believe that they are a diphram type, which would mean that they wouldn't leak down like any other type of pump would.