OK, Sorry for the book but here's my problem:

Big Red: 1988 GMC Sierra, Extended Cab 4x4, 350ci/5.7ltr TBI-model 220, w/Automatic Trans. 140K plus miles.

The truck sits more than it's been driven the last ten years. Before that is was driven out from Mich. to Phx. Driven all over the SW and Mexico. But other than a bad battery, it always started right up, even after sitting for 6 to 8 months.

Recently went out to make a Home Depot run in "Big Red". She fired right up as always. I pulled it from the back yard to the driveway and let it idle like I usually do after having it sit so long. Rinsed it off with a hose and it was running maybe 5- 10 minutes. Just as I was opening the door to turn on the wipers, it flat died. It died quickly like the spark was removed. no sputter, no nothing, it just quit.

So I grabbed my Haynes manual and started to troubleshoot. For ease of reading I will list the order of what I have done. Another thing is all of these parts are original. I have changed things like spark plugs, wires, cap, rotor, fuel filter, etc. at maintenance times, but the fuel system has been untouched. As one should, I tried to determine if it was spark or a fuel problem.

Confirmed the fuel pump fuse is good.

Confirmed the fuel pump relay was operating correctly.

Confirmed the fuel pump was running.

Removed the fuel feed line from the TBI and fired the fuel pump. Looks like a decent flow but at this point I have no way to check pressure. I am told I need an adaptor that goes inplace of the fuel filter.

Checked the fuel filter just to cover the bases, it's clean.

As a test, I pour some gas down the TBI. It fires on this gas until it is gone, then nothing.



This tells me it's a fuel problem and not a spark problem.



I checked for any error codes with my cheapy code reader, Code 12 (the all is well code) is all that it flashes out to me. no other codes.

After looking at wiring diagrams I 'jumped out' the "fuel pump oil pressure switch", (located behind & below the distributor). From reading and surfing forums I determined this will close once oil pressure has been achieved. From what I can tell this bypasses the ignition switch after the engine is running to keep the fuel pump running. It's a safety to kill the engine is oil pressure is lost. Am I correct?

Next was to inspect the TBI. I removed and rebuilt it. I sprayed all the parts down with carb cleaner, and blew out any orifice I could find. I took care to not submurge the injectors but I did spray and blow orifices on them too. They actually 'looked' fairly clean when I removed them. Re-assembled & re-installed but still no change. I did use the old "Fuel Pressure Regulator" spring, as the rebuild kit did not come with one.

I read that the 'Ignition Module' in the distributor sends a signal to the 'ECM' to pulse the injectors and the ignition coil. Now it would fire with gas poured down the TBI, so I didn't think this was the problem. In desperation I changed it out anyway, still no fire.

I ohmed out the injectors. The are at 0.9 ohms, (digital Fluke meter) I believe this is within range. When I checked for voltage at the injectors, my Fluke meter floats between 1.8 to 2.0 VDC. One injector connected and the other connector to the meter when cranking the engine. I am not sure what signal is being sent to the injectors, so I don't know what this reading is telling me.

I talked to a few more people and decided to try a new ECM. Switched the chips from the old ECM to the new, but still no change.

Now I am really running out of ideas. So I buy a new set of injectors and "try one". My thinking being if the new one does work, it will fire and run, but would be very rough. It still won't fire up.

Now I am reaching...

From what I read, the "idle Air Control" just allows air to bypass the throttle plates to control idle speed. But I am not ge

 

hmmm interesting, i had a car that did that once and after going through almost the same things you went through it turned out to be the ignition switch on the steering column. It would turn over the engine but wasn't sending any voltage to the rest of the electrical system. once I changed the switch I never had that problem again. Strange but true. Hopes this helps.

 

A friend of mine had a 96 chevy with a 350 that did a something very close. When you would try to start it, it would crank but would not fire. When we jump started it would start right up every time so we figured that problem must be in the electrical. We check everything including the fuel system and the fuel pressure which seemed to be ok. After messing with it for weeks we finally gave up and it went to the dealer. Turns out it was the fuel pump. I guess it just would not push enough fuel running off the battery alone.

 

Sorry for the long delay. I was side tracked with 'Life Responsibilities' and then lost my logon info. But now I can close the loop.

After not working on it for a month or so I went back at it and noticed I could hear fluid splashing in the gas tank when I turned the key to [On]. I also noticed my fuel flow to the TBI was much lower than before.

My new fuel presure gauge tells me [no fuel pressure]. Removing the fuel pump I find the hose from the pump, to the fuel line, finally ruptured. It was all FAT, Squishy and Expanded, and ripped. Replaced the pump and she started but ran very rough. I put the new injectors back in seeing as how I changed everything else out. Might as well include them too.

Now she purrs like a kitten.

 

Sorry for the long delay. I was side tracked with 'Life Responsibilities' and then lost my logon info. But now I can close the loop.

After not working on it for a month or so I went back at it and noticed I could hear fluid splashing in the gas tank when I turned the key to [On]. I also noticed my fuel flow to the TBI was much lower than before.

My new fuel presure gauge tells me [no fuel pressure]. Removing the fuel pump I find the hose from the pump, to the fuel line, finally ruptured. It was all FAT, Squishy and Expanded, and ripped. Replaced the pump and she started but ran very rough. I put the new injectors back in seeing as how I changed everything else out. Might as well include them too.

Now she purrs like a kitten.