ongoing headache HELP!!!

[79tbik5]

1979 k5
tbi 5.7 (67,000 on engine)
700r4 with shift kit and tranny cooler
painless wiring​

ok so i moved to colorado bout 4 months ago for a job, and two days before i left my truck just decided it needed to have some major issues so i was forced to leave it and rent a car to get out here. so once i got some cash under my belt i called an old mechanic friend in my small town and told him to do what he needed to do to get it ready to drive to colorado (trying to help him out in this economy), so a grand and a month later i was told it was ready to go so i flew home on a weekend and as soon as i picked it up i knew it wasnt ready, but i went for it anyway, didnt really have a choice! it just stumbles at mid throttle and has a rough idle after driving for a minute or two at most. so i kept it held wide open and it runs great above 2500 rpm. he put in a new high pressure fuel pump, alternator, battery, fuel filter. so i checked timing, plugs, wires, they were good. stopped in vegas and put on a new tps and map sensor, still didnt fix the problem. reset the computer in utah, same thing. so once i got home i tore the tbi apart and cleaned it all, checked vaccum lines, went through the wires, still nothing. then i was driving it and it just decided its not gonna start at my buddies house, shot a lil ether down the throttlebody, would fire for a sec and then die, so its gotta be a fuel issue. get it towed home, get it off the truck and the damn thing fires! im lost, my next step is a full rebuild kit for the tbi cause im thinking the fuel pressure regulator at this point. i kinked the return line while it was running for just a few seconds and it didnt change the way it ran at all (heard that was a way to test it). any help would be greatly appreciated thanks!!​

 

[Fordum]

Sounds like the EGR valve.. Sticking open.

 

[Fordum]

Check out this thread. Might give you a clue.

http://coloradok5.com/forums/showthread.php?t=275167

 

[79tbik5]

ya, thanks i was considering that until it decided not to start at all. but ill definately be checking that tmro. could the egr cause it not to start at all? its really pissing me off cause its intermittent.

 

[Fordum]

Well, I know that if you open the EGR while it is idling, it will usually stall, so I would suspect that if it were stuck open it would not crank in the first place.

Never really tried though.

 

[79tbik5]

thanks i will deffinately be giving that a shot and getting back to you!

 

[4X4HIGH]

Sounds to me like a bad ignition module. When they fail they can either kill spark or make the fule pump not work. They are cheap and notorious for going bad so I would just replace it. If this fixes your problem then I would buy another one to keep in your "trail repair" box in case this happens again (trust me, it will) and you can swap it in less than 5 minutes and make for a happy day.

 

[79tbik5]

But I can hear my fuel pump coming on even when it won't start, so I don't think that's it

 

[79tbik5]

But if they are cheap than I might as well just replace it and rule it out if anything

 

[4X4HIGH]

But I can hear my fuel pump coming on even when it won't start, so I don't think that's it

The fuel pump coming on has nothing to do with the signal that the ignition module sends to the ECM to tell it to fire the injectors. If you think about it the fuel pump should cycle for 2 seconds when the key is turned to the run position and the engine hasn't even cranked yet.

 

[79tbik5]

ya very good point, i had to special order it, but it should be here friday so we will see!

 

[POORBOYK5]

A TBI ign module shouldnt be a special order part..... Standard #LX340 or LX340T BWD #CBE28 or CBE28Z. I work for Advance down in the springs and know those #'s off the top of my head. We stock plenty.