Fuel Pressure Issue After Some Mods

[James_03]

Hey guys,

Car is a r32 gtr with rb30dett.

Have an issue atm. Basically I installed an 044 intank, tomei fpr, and a pressure gauge after the fuel filter.

What happens is when you turn the ign to the "on" position the pump will prime and you will see the pressure rise to 40psi, then go straight back down to 0 after prime. The car will start after 2-3 cranks then the idle pressure will sit at 40psi, revving will see it move slightly off 40psi but looks stable.

Now I used the existing factory gtr check vavle on the 044 so I don't see this as being the problem but it may be, it is around the right way and I was pretty careful when installing.

Am I right in assuming after switching to the ON position, it should prime then hold 40psi rail pressure waiting for crank yes? I am now going to chuck a factory r33 reg back on to see what happens.

Does anyone have suggestions?

Edited February 22, 2009 by James_03

[blind_elk]

At "ON", the FPR "sees" atmospheric pressure. At idle, the FPR "sees" vacuum, and the fuel pressure should be less than 40 psi. The FPR should adjust the fuel pressure so that the rail pressure is some constant value above manifold pressure.

It could be a faulty FPR. Or the check valve on the pump is faulty in some way.

[James_03]

At "ON", the FPR "sees" atmospheric pressure. At idle, the FPR "sees" vacuum, and the fuel pressure should be less than 40 psi. The FPR should adjust the fuel pressure so that the rail pressure is some constant value above manifold pressure.

It could be a faulty FPR. Or the check valve on the pump is faulty in some way.

Ok the thing I want to know most is when turning the key to "ON" and letting it prime for 5 sec, should the rail hold 40psi before starting? Because right before cranking its sitting at 0. I need to know if this is a problem.

I think I am incorrect in thinking this. Maybe its actually all OK. The factory GTR manual states it should be sitting at 40psi rail pressure on idle, which it is. But it's the prime I am concerned about.

I get what your saying but and thanks for the reply.

Edited February 22, 2009 by James_03

[rodger1]

It should hold pressure for start as other wise the pump has to build pressure before start , and easy way to check which side it's loosing pressure on is prime the pump and clamp the return line and if it drops it's on the feed side

[James_03]

Ok cool Ill give that a try, should be a good way of finding what the cause is.

Thanks mate.