Fuel Pump Pressure help

[rmahnovetsky]

I have been having idling troubles with my skyline R33 and Im trying to diagnose the problem. The main time I notice the problem is

1) When I put fuel in the car.

2) after the car is warmed up then I switch it off then I come back ~15 mins later and start it up.

I have cleaned all the contacts, sensors, AAC, AFM etc.. After doing all that I was begining to believe it was the fuel injectors so I got them cleaned. Still the same problem as the fuel injectors were 95% clean. So I got a inline fuel pressure guage and tested the fuel pressure. What I noticed is when I prime the fuel it goes up to 41 PSI once prime is finished it slowly drops back to 20 PSI. When the car is running it is aroud 36 PSI on idle it is about 34 PSI

Q1) After prime should the psi drop back to 20PSI or should it maintain ~ 41 PSI.

Q2) Is my PSI low?

Q2) any other suggestions.

[gtrken]

Factory pressure should be running at idle of around 38psi.

It shouldn't redally bleed off and this suggests a fuel line leak or a dead fuel regulator.

Try blocking the return line off with a pair of pliers while idling and the pressure should skyrocket and stay there, around 60-80 psi on a stock pump. If it bleeds back quickly then your pump is tired or dead.

There are better tests for this but it involves fuel flow meters which I doubt you would have in your shed

Cheers

ken

[rmahnovetsky]

Thanks for the info. Im gonna try that now!!! Will post up results.

[rmahnovetsky]

Well here are the results.

Clamping at clamp point the pressure rose up to ~60 and then fell back to 50 really quickly. So does this mean the pump is tired?

I noticed taking the lead off in the picture the pressure increased to 41.5 psi and idled well until warm then I had to put it back on for good idle. Though it was idling well with the lead on anyway. Actually adjusting the AAC value I notice the pressure increased/decreased so I guess the AAC value adjusts the pressure to the injectors... Cool!!

The second picture shows idle pressure ~750rpm

The third picture shows idle pressure at 1000rpm.

So does this mean my fuel pump is OK or tired? Am I ever going to solve this idle problem it driving me nuts.

[rmahnovetsky]

edited

[rmahnovetsky]

Anyone out there with fuel pump knowledge?