(followup) 91' Chevy 2500 350CID Injector problem.?

Question

Fuel pump 7psi, good flow.
Relay changed (was good too)
Fuse good (tested)
Fuel filter was dirty (changed)
Full tank of gas
Starts every time runs two seconds, dies, THEN relay clicks off.
EGR not stuck.
Engine cold.

I've noticed, if I play with the throttle, I can keep it running.
TBI SEEMS to be delivering poor gas flow. When I play with the throttle, the pulses get stronger.

When it does die, the TBI delivers significant fuel just after it dies by the looks of it. Just not while running.
IDEAS?
Also, there is a device screwed into the rear left side of the TBI with a 4 wire connector. I disconnected that just for the hell of it, and it still did the EXACT same thing.

What was that I unplugged, and how often do they go out?

ANY help would be appreciated. Last time I had many good answers, and could only pick one as best answer. I wanted to pick four of them. Dodgeman, crud.....I can't think of the other ones. Sorry. I'll add to this as soon as I figure it out.

Answer 1

oil pressure switch??

Answer 2

Still fightin' it eh?
The fuel pressure seems a bit low (spec 9 - 13#), but it should run on that. It may not have much power, but it should run.
Have you checked for codes? It sounds like you have a pretty good idea of what you are doing, but you don't say.
Go here----->

http://autorepair.about.com/library/ts/obd-i/bl-dtcs-95.htm

...for a discussion of the procedure for retrieving the codes with a paperclip.
If you find any, refer to your manual for the proper diagnostics BEFORE repairs.
One other thing --- Have you INSPECTED the connections on the plugs of the ignition module inside the distributor? Where the distributor is located, it is prone to collect moisture inside the cap, and this will eventually lead to corrosion at the electrical connections.
Have you tried a 'Noid lite at the injectors?
They aren't all that expensive (< $10.00, AutoZone)
The truck WILL run with only one injector, so disconnect one and try the 'Noid lite, or if you must, a test light on the triger side. If the light stops flashing at the same time it BEGINS to die, you have found the system that is causing the problem.
I just left the ASE web site, and the repeated answer for a failure such as yours seems to be a failed pick-up coil in the distributor, or broken magnet, bad distributor shaft, and a bad ground for the distributor electronics, in addition to the little issue of corrosion on the connections.
Just a few more things to try.

Good Luck and Merry Christmas again.

Answer 3

1. If you have a voltometer; try checking the resistance on that injector. It should match or exceed voltage going into injector.
2. The MAP will give the puter wrong readings when it's too dirty also. Try taking the MAP out and spray it with something like starter fluid... Someone else may not recomend that but it works... If it's not dirty than check the resistance on the MAP too.
3. Are all of the vacuum lines correctly placed? The engine will die like that if there is a vacuum leak exceeding it's need to operate.
4. I've cleaned injectors with toothbrush bristles... They may just need to be cleaned...
5. Did you look for crimps in the fuel lines?
If this info doesn't help than take it to a master that has the technology to figure it out...

Answer 4

Does it run when it is warm?? It would seem that the only real possiblity you havent explored would be the fuel pressure regulator. Pull the vacuum hose that runs to it off and crank the engine for just a moment. If you get any gas out of that then you just found your problem. As far as what you unplugged I cant picture that part in my head but it could be idle air control maybe??? Or throttle position sensor??? Sorry not sure on that one but I doubt it has to do with the fuel issue. Hope this helps. Good Luck!!!