Question about fuel pressure

[Andy348]

Two questions.

1) Is the fuel pressure at the rail supposed to go lower when the revs go up? I go from about 40 psi down to approx 33 (maybe lower) when I rev the car up around 5000rpm.

2) Which hose do I test for the intank pump? I've attached a picture below. The hose that is angled up is what I attached the fuel pressure gauge to, and it came up with 0psi. The line with the T fitting on the end pumped out quite a bit of gas which I didn't think it was supposed to.

Thanks.

[jlevie]

The in-tank pumps is tested for flow not pressure. The rail pressure should go up when the throttle is opened, not down. The rail pressure going down at higher rfpm suggests a failed in-tank transfer pump, a clogged filter, or a dying high pressure pump. The FPR could also be bad.

Since an ETA car has a 2.5bar FPR and a 325i/is has a 3.0bar FPR, it would be good for you to say what car this is.

[Andy348]

Its an 86 325 with an is swap.

I've got a new high pressure pump and new filter, so I assume its the in tank pump.

Thanks for your help.