Fuel pressure and leakdown specs for CMFI systems is as follows: Key ON, engine OFF, fuel pump running: 55psi to 61psi. Pressure must remain above 50psi for at least 10 minutes after the pump shuts off. As mentioned, GM does not publish any engine running specs, all readings are taken with the engine off, and cold.

Checking fuel pressure and leakdown at the service port gives us an overall indication of the entire fuel delivery system. Your reading of regulated fuel pressure is 60psi, and the leakdown pressure is 30psi after 6 minutes. These results tell us that a problem exists somewhere in the fuel delivery system. They do not tell us what or where the problem is. The next step is to check maximum fuel pump output pressure and leakdown at the fuel filter. This will tell if the pump is able to build sufficient pressure, and hold it. The pressure tester must be modified so it will connect directly to the pressure line, (from the pump) at the fuel filter connection. All fuel pressure and flow must end at the tester. Make sure there are no external fuel leaks between the pump module connection and the fuel pressure tester. While the pump is running, pressure must be ~70psi to ~103psi, and it must remain above 50psi for at least 10 minutes after the pump shuts off. If it fails one or both tests, the problem is in the tank. If it passes both tests, the problem is in the plenum. Post your results.

 

Finally got to play with a it for a few minutes. Haven't checked the fuel pressure since I put the new pump in. Key on it went up very slow???
Stopped at about 52.

5 minutes later, 30lbs
10 minutes later 30lbs
20 minutes later 27ish…

Decided to test it again, purged the pressure.

Key on 0 lbs???
Huh?

Start it…. running…. 0 lbs.

So today all I learned was a need a new fuel pressure gauge.

Well, the gauge is fine, the f'ing ethanol gas eat up with rubber in the fitting, which allowed me to over tighten it, squashing the little teet that opens the schrader valve. Why it worked the first time and not the second, I do not know.

 

Okay…

At the fuel filter:


Key on then off was 90+ lbs. Hard to tell exactly, my cobbled together connection wouldn't hold the pressure and it visibly leaked gas.

It stopped leaking at 80lbs.
5 minute, 75lbs.
10 minutes, 70lbs
15 minutes, 68lbs
20 minutes 65lbs

I called it quits there.

On the rail:
60 key on.

Dropped to:
50lbs @ 1.30 minutes
40 @ 4.50 min
30 @ 10.00 min
25 @ 15.00 min
20 @ 35.00 min


Hmm. Last time I had the plenum off there was no sign of washing. Nut kit is 2 years old, looks good, no sign of leaks. Spider and FPR are both less than 11 months old.

Good grief I don't want to think about it being the spider after changing two in as many years. Can the FPR be bad and not visibly leaking? I don't have any fuel leaks that I'm aware of between the filter and the engine.

 

Digging around I found I have an new FPR. I have a vague recollection now, I think when I bought the first spider I wasn't sure if it was coming with an FPR or not so I bought one.
At least that solves my "what to try first" question.

 

Pump is fine. Provided there are no external line leaks, the excessive leakdown is in the plenum. Pull her off and activate the pump, look for leaks. Could be nut kit, regulator, (internal or external) or a leaky poppet valve or injector.

 

last time i bought a replacement regulator will be my last time, it was set wrong from the factory (90psi) and started leaking again in 1 month. It was a Dorman, it was also alittle too big around to fit in the housing

 

Ran home for lunch and pulled the plenum off. Looks like I have washing on the right side. Trying to figure out if it's coming from where the nut kit enters the spider, or the unit itself. M*^#%@$*#! I swear it wasn't there when I had it apart a month ago or so.

Luckily I have a set of O rings and will change them anyway.
I think I may change the FPR anyway.

Lord I hope it's not the spider itself, I can't keep doing this crap.

 

Pulled the spider. Looks like the tubes themselves might be leaking where they enter the body. I'm not happy. lol

Maybe I'll JB weld the F'ing things in.

 

I feel your pain Keep us posted.

 

Changed the nut kit O rings. Changed the FPR. Fiddled with the injector tubes some.

Key on 60... 50 off.

Took 30 minutes to drop to 40.


Running worse than ever. lol. Instead of stumbling when I hit the gas, it stumbles when it shifts (and sometimes when I hit the gas).

Unhooked the battery hoping things will reset. Double checked all my plugs and vaccume lines, don't see anything off.

Sort of reminds me what happened last year after I changed everything, it ran like crap but finally threw a code for the O2 sensor. Changed that and it was great for a year. I can't have my yearly tuneup including a fuel pump, spider and O2 sensor every time.

In a bit I'll reattach the battery and try it again.


ETA: Drove 10-12 miles or so. Got no better, threw no codes. Before I could at least drive it most of the time. Occasionally I'd have to pull over to the side of the road when it got real bad till it cleared up. but now it's half that bad, all the time. What makes the check engine light come on? If sputtering, coughing and backfiring, and not having enough power to do 30 mph isn't enough, what does it take? lmao Fixing things that are wrong makes it run worse. Okay…. um...