94 chevy 350 No pulse at tbi injectors. Wont start.

[Feedmebeans]

I was driving down the street one day and the truck just shut off. I tried shutting it down and  turning it over again, but it just kept cranking. After some investigation I narrowed it down to fuel as the injectors were not spraying anything. Changed the fuel filter and it was fine and I can hear the fuel pump turn on when I try to start it. I connected a noid light to the injectors and didn't get any pulse. I tried popping the clutch and the engine spins but immediately shuts off when I push the clutch back down I did just change it over to a manual. Any help would be great as this is my daily driver and need it running again. I can't for the life of me figure it out.

[Jsdirt]

My memory is extremely fuzzy on these trucks, but if I remember right, pulse is controlled by something in the distributor. That is, so long as the wiring to the injectors is good (didn't get crushed / pinched somewhere during the swap - it happens).

[Feedmebeans]

I don't think anything got crushed. I've been driving it for months with the manual I thought it might be the ignition control module "it's under the distributor cap." I'm gonna change that today and see what happens.

[Jsdirt]

Don't just wing parts at it. If you have a wiring problem, you'll have wasted money on a part you didn't need.

 

I lost access to my free wiring diagrams - everyone wants their cut these days. Best thing to do is buy the online diagrams & service info, and figure out what you should be seeing on what wire, and where.

[Jsdirt]

I just came up with this in a quick search. Glancing at the diagram, it looks to be a ground-side switched circuit. YOu'll need to see if you have power on one side of the plug. If you do, you've either got a wiring problem, or the ECU isn't providing a ground signal to the injectors. This could be a computer power, ground, or input problem.

 

 

[Jsdirt]

EDIT to the above - you should see 12v on BOTH sides of that circuit all the way to the engine computer with that particular plug on the engine computer disconnected from it, key on engine off. That will confirm circuit integrity from the ignition switch, all the way to the computer. If you have 12v on both sides of the injector plug (key on, engine off), and pins A9 & A16 of the PCM (which you should see), you'll need to investigate an input problem.

 

I've forgotten what inputs can kill injector pulse - possibly if it thinks there's low oil pressure  (I know this will kill fuel pump control - not sure if pulse, too), or vehicle is in gear while attempting to start. Wish I had access to the service info. Lack of FREE info drives me friggin nuts ...

[Feedmebeans]

So I took out the ignition control module and had it tested. It failed so I replaced it thinking that if it was broken it might be the problem it wasn't. But it was broken anyways so whatever.