MarauderBob

Hello everyone, I am an exmechanic turned Plumber, back to mechanic thanks to the economy LOL. Anyways, I am currently working as a fleet mechanic for a small shop and I am having alot of issues with this truck.

It all started with sitting overnight in very cold climate and wouldn't start in the morning. Upon inspection I noticed the fuel pump was VERY loud, but engine was completely flooded, but at the same time a lean MIL on both banks was on (turns out it was on for atleast 2 months). I changed the plugs, noticed the wires arcing, so changed the wires/cap/rotor as well, found no vacuum leaks, and replaced the fuel filter as well (boy that pump sounded better! Super plugged) and she sounded better than ever and I drove it a couple hours running fine.

Later in the day it started to run very bad, sputtering and struggling and wouldn't hold idle. I checked the fuel pressure and it showed 64 PSI but dropped immediately to 25. I did a test with return blocked off and same results. Then I did a test right from the fuel line and my readings were 75/80 PSI with a drop to 70 or so MAX. I then pulled the intake and verified three leaking injectors and regulator, and one injector carboned shut. COOL. problem fixed! Replaced with MFI conversion, tested pressure and got 64 and holding TIGHT, buttoned her up and sent her out to plow snow. Truck ran BEAUTIFULL for two days, then started running crappy AGAIN! The driver dropped it off at the shop for me (outside) to fix in the morning. Once again no start and horribly flooded. I did not want to jump to conclusions on a bad MFI so I retested all the fuel pressures and this time the direct line from the pump is 30 PSI on first try, then 95 on the second try immediately following, then to ZERO in one second!!! I dropped the tank but not sure exactly where the check valve is? I went ahead and ordered up a replacement tank (rusty) and a new Delphi pump assembly.

I believe the start of all this mess is because of where the filler neck goes into the rubber hose for the tank was rusted completely in half 1/4" into the rubber! I also found a broken ground from the filler neck to the service body, but that did absolutely nothing for me.

Besides rust taking out everything on me, am I missing something here??? I am quite honestly scared to release this truck yet again! Not to mention this thing is REALLY making me look bad, but I believe I am attacking this on the right track?? I hope.. Any other ideas that would cause these symptoms?

I know these won't start if you do not have a minimum of 58 PSI holding pretty steady and I believe the flooding is from the guys moving the accelerator pedal in hopes of a start up.

Thanks guys.

Details:
1998 Silverado K2500 4x4 5.7
MFI conversion
Full tune up
Vacuum steady at 24
New IAC
Gas tank/FP assembly/filler neck arriving 2/8/11

Symptoms:
No MIL but pending I/M readiness
No start
Roating backwards upon key off sometimes
SOAKED intake and plugs, but no leaks in MFI.
Heavy rust inside filler hose
Scared employee

2wd-K5

yes i would say you are on the absolute right track the filler neck rusted out probly let all sorts of problems happen, ill bet theres water in the tank too, change the fuel filter again too, my guess is u have the problem solved, let us know how it turns out

RacerX

I would say you are on the right track. I would say that when you look in the tank look for debris that could clog the sock in the fuel pump pick-up. That could cause a problem. I ve seen many times the sugar in the tank. I have even seen a leaf in a tank one time.

Another thing is fuel pressure is supposed to be consistent. If you have the high pressure system then 55-65psi is your range. If you are getting 85 and 94 and 0 then you may not have replaced the fuel pressure regulator when you converted. FPR are to keep the pressure from getting too high not too low.

Pumping the pedal in any FI car doesnt flood the system. It does the opposite. It turns off the pump. When you crank the car(foot off pedal) on a FI the PCM turns the fuel pump on then sends gas to the injectors to aid in starting. It will only flood in this instance, if the injectors are leaky OR you have to crank repeatedly to start it.

Remember on an FI car flooding means nothing, fuel pressure is everything. It is possible that this thing had a bad fuel pump all the time. The check valve is IN the pump. These pumps are KNOWN to be doo-doo. A bad check valve makes it hard to build fuel pressure BUT a restricted sock makes it easy to give you high fuel pressure and the sputtering symptoms you experience. Another issue to contemplate which I would like to use to solidify my clogged pump theory is that when the guy fuels up the problem goes away for a while because the debris is randomly floating around the tank but when the fuel level drops the likelihood of the sock attracting the debris increases. And if the pump is clogged it will become very loud because it is basically working in vain.

What do you think?

MarauderBob

When I got the high readings then immediately 0, that was a test disconnected from the MFI. I thought these pumps pushed at near 100 PSI straight line pressure?

I agree on your theory 100%, hence why I ordered the stuff. The reason my pressure is so sparatic now is because the line is bleeding back to the tank immediately. After two seconds (pump shut off), the lines aren't even full enough to go over 30 PSi, hit the key right away and she fully pressureizes, but drops to zero all over again.

I thought that only WOT shut down the injectors and pumping allowed the flowing fuel to get sucked into the cylinders faster? Then the reverse rotation and smoke causes all the unburnt fuel to get pushed out the valves loading up the cats and intake? I figured this was the reasoning behind the intake being soaked again. I dried it all out and had a mirror in there and it stay dry for well over 20 KOEO cycles. The new injectors could be leaking down into the cylinders as I can't see to verify, but with the fuel line disconnected, my pressure remains the same with the immediate drop. So the pump is without a thought "done".

The regulator was part of the kit and it is the new design and dry as could be.

Thanks guys.

RacerX

100? Hahaha! Man, 7psi on a mechanical fp. 15psi on a low pressure system. 34psi on a high pressure system(GEN I). 60psi on a high pressure(GEN II).

But all in all FP should hold for at least a half hour. This is the purpose of the check valve, to keep the pump primed.

Any external manipulation of the pedal shuts off the injector signal. WOT shuts it all down and is best recommended to start a flooded engine.

Reverse rotation sounds like an timing set issue.