camaro1185

100% stock L98

I just finished doing my fuel pump, everything went together well, but now that everything is back together I am STUPID lean at idle. Its fine once I give it gas, but at idle in park its 160+ blms. This is all after the car has warmed up (i forget, is that closed loop), it will idle for about 1.5 minutes, then start running rough (hunting idle), then stall.

The weird thing is that if I pull the vac line to the regulator, the idle does NOT increase??

I did try 2 different BINS one was a modified 89 350 iron head bin (egr delete, vats delete etc. no change to fueling or spark), and no change. The second bin was an ARAP (no vats) just for the hell of it, and while it had the hunting idle, it didnt stall.

Here is how the problem started. I started the car and drove it around the neighborhood. It ran well, until it got into closed loop. I got on it about 75% throttle and once it got to the top of 1st, it just cut out, like no fuel was being injected, but it didn't stall out. I then pulled into my driveway, and went from a stop and gave it about 75% throttle and same thing, it started to idle hunt, but didn't stall.

I then pulled it into the garage turned it off, and about 5 mins later i started it, and just at idle it started to idle hunt. It was in park, and not in drive like before.

I ordered my FP from racetronics and I got their hotwire kit
My fuel pump primes at start up
I don't have any vac leaks (I checked before doing the pump)
I cant hear any exhaust leaks
The fuel pressure regulator is not ripped, but i guess it can still be bad
About 800 miles ago, I did new bosch 3 22lb injectors and fpr
Filter was done about 2k ago
Plugs, wires, cap, rotor about 1.5k miles ago

Any ideas?

Johnnygeek

Ive herd to unplug O2 sensor if that helps then injectors may have debris clogging them a bit.

camaro1185

Unplugged the o2, no change.

camaro1185

I did some working on it yesterday, and burned a chip that would keep the car in OPEN loop only. It still stalled. I then, added fuel to the section of the maf tables that makes it idle to take care of the lean problem, it still stalled. So that tells me that its something that is NOT controlled by the ECM that is creating this problem since in open, sensors such as IAC, O2, CTS etc are not being used.

Any ideas??

skibum2100

I know you said there are no vacuum leaks, but maybe it wouldn't hurt to check everything again. It sounds like a vacuum issue to me.

Hope this helps.

camaro1185

Ill check for vacuum leaks.

I did some more checking, everything from the tank forward (to the inlet of the fuel rails) check out. I took the feed line off and its pumping the fuel like no ones buisness, but some how from the feed line to the rails/injectors/fpr etc it looses a TON of pressure. If I press the scrader valve after priming the system, i get just a coueple spits out. I have done it before and it came out like a guizer.

What can that be that makes it loose the pressure from feed to injectors?

Its so little pressure, the fuel pressure tester gauge doesnt move.

camaro1185

Ok, did some more trouble shooting yesterday. I got fuel pressure and they are as follows:
Prime: 40psi
Idle:30Psi
Idle no vac: 35psi
Prime return blocked: 100psi
Also, the pressure dropped 15psi in about 1.5hrs (30 to 15psi)
It still stumbles like a SOB. What could the problem be?

With the 100 psi number I'm thinking I confirmed my pump is good, so what can it be? regulator? injectors? Both have only about 500 miles on them.

skibum2100

Hi guys,

Temperature, is your gas overheating. A new problem for us lately is overheating fuel. When the fuel gets too hot the pump can't draw it into the housing (because if boils at the impeller) and pressure drops.

The pump seams ok, the regulator works at first (so why would it stop), injectors only as a last resort, but it could be temperature related.

Hope this helps.

camaro1185

Nope, it isn't boiling. If i start the car cold it does it too. The injectors are new, maybe 500 miles on the bosch 3's.

skibum2100

Unreal...okay then. The last think I can think of is the "pulsator." This connects the fuel pump to the fuel pump hanger assembly. The original one looks like a small brake master cylinder. Did you replace this when you did the pump?

camaro1185

Yep, with a piece of fuel line.

skibum2100

Wow...how unfortunate.

Maybe you could monitor the fuel pump voltage/amps and see what it does when it starts to loose pressure. Hopefully some light can be shed on this problem, Perhaps the pressure regulator spring is tired (even though its new). Another fuel pressure regulator would only be ~$20 at AdvanceAutoParts.

camaro1185

Thanks, I appreciate it, I think its the regulator. I doubt a bad pump could provide a 100 psi.

I will check back. I hope to get a reg today and install it.