Fuel Problems!

[neilsteyn01]

I have a r33 gtst-has been running good for last 4 years. But recently i have been getting idle hunt issues once warmed up. i have cleaned the AAC, i have checked for vacuum leaks, cooler piping is on tight with no cracks/leaks.

Anyway while i have been trying to figure out why this idle is hunting to a point where the car stalls, the car now also feels like its surging around corners, still goes well in straight line, hits full boost. i thought it might be because of a low fuel tank, filled it up with 98 bp ultimate, like i always do. problem still evident. So i went on and removed the fuel pump, to see if maybe the sock was filled with anything, nothing!, tank looks clean inside, so no growth or anything that could hinder the pumps abilility to do its job.

I went on and carried out a fuel pressure test. i have never done one of these so hope i did it right. i connected the guage in the return line, right after i think its a regulator, where the ridgid line of the fuel rails ends. not sure if thats the right spot, but anyway i ended up getting 15 psi on idle and once car was of idle i got about 18-19 psi. im not sure how much it should be. but it sounds pretty low to me. I assume i have a stock fuel pump, but yet to find out, il post a pic up from when i took it out.

I also disconnected the down line, and primed the fuel into a bottle, and found it primed for 5 seconds. and in 15 seconds i ended up getting about 750 ml. so my pump was pumping about 3 l/m. However since the pump was only priming it would have only been at the lower pressure (15psi). Also not sure of what it should be pumping, in terms of volume?

i dont know what the standards are for the fuel pump and if its on its way out, always thought they either work or dont.

not sure what else i should look at. but its starting to drive me nuts.

any help would be appreciated.

[scotty nm35]

Pressure readings would need to be taken before the return line. Which brand pump is that? It looks exactly like the Tomei one I put in mine.

R33 gtr pumps have a built in reg of some sort so it should all be fine, I would be leaning towards the airflow sensor being dirty, have you cleaned that yet?

[neilsteyn01]

So where should I connect the gauge? After the fuel filter? I didn't start the car when I measured it. Just priming. How about the flow. Does 3l/m sound right?

[neilsteyn01]

Oh yes I have cleaned the afm with contact cleaner. Very carefully n it looks fairly clean anyway. Cleaned the plugs aswell. Just a question I read when u remove the two plugs on the tps that the car should still idle. Is this true. Because mine instantly dies when I remove the bottom one??

[tridentt150v]

walbro and others say 255 lp/h, I couldn't find the flow rate for a std unit, but that one you have pictured looks like a nismo/tomei unit [except for the fittings at the top?] like Scotty says.

And I can't remember but thought pressure was around 50psi....

[blind_elk]

Have you checked / cleaned the air filter? Have you replaced the fuel filter?

[neilsteyn01]

Yea airfilter is pretty clean and brand new fuel filter.