Still no fuel from injectors, no start

[rlsllc]

OK, this is making me mental. About a month ago, my van (1991 TBI 4.3) took to stalling. Then it would stall and not restart. I pulled the motor cover and breather, and saw that I was not getting any spray from the injectors. I knew that this van had a new pump and sending unit installed not long ago, and could clearly hear the fuel pump. I tapped on the regulator, and it started. OK, so I bought a regulator diaphram. Next time it stalled out, I replaced the diaphram. Still no start. Crap. I loosened the inlet line, hit the key, plenty of gas. removed the return and plugged it with my finger, and got it to start. I shut it off, reinstalled the line, it fired up, and I drove it home. The next day, it wouldn't start again.

I messed around with it, plugging the return, bleeding the pressure off, etc, until it started up. It ran ok, and I started to put the breather on, and it dies. Took the breather off, and it fired up. I moved it to where I work on stuff, and just as I put it in park, it died. No restart. Even with the relay jumpered. I used the pump to drain the tank into gas cans.

So, I changed the pump, pickup, filter, checked the harness and made a new, clean ground. after 2 tries, it started. It started 2 more times, and ran ok, I drove it around for like 15 minutes, and parked it for the night. I drove it around for a while today, parked it and put the motor cover and dash all the way back together, jumped in and hit the key, it fired for like 1 second, died, then wouldn't start again. (insert expletives here)

I've tried jumpering the relay, and can clearly hear the pump, I know it has 10 gallons of gas in it, and what feels like plenty of pressure when you plug the line with your finger. I wish it had a dang pressure test port: stupid GM. I now think it is either an injector, the ECM, or wiring, I don't know.

Anyone know how to check for injector signal, or how to actually check the injectors themselves? There is nothing in my book about it, and I've thrown enough wrong parts and work at it already (it was 20 freaking degrees yesterday when I was working on it outside).

Thanks.

Oh yeah,

[rlsllc]

OK, just a quick note...

I went out and screwed around with it for a while. I put a test light across the injector plug, cranked it, and nothing. I pulled the ecm and put a spare one in from an '86 that had a 5 speed, still nothing. I wasn't sure about it anyway, since it was a different year, but it plugged in. I hit the key again, and after about 1 or 2 seconds of cranking, it sprayed a fired up. I didn't drive it, since the ecm can't lock the converter being from a 5 speed van (I'm guessing here), but I did shut it off and replace the original ecm. It fired right up. ????? I checked the injector plug, and had a nice flickering light. I started and stopped it several times, and then after about 10 times it wouldn't start.

While it was running, I wiggled every wire and anything else that I could, from the ecm to the injectors, no change. Same with when it wouldn't spray, with or without the starter cranking.

An interesting note, you can unhook the oil pressure switch and it will continue to run. If you pull the relay, it will die. This is contrary to what I've read about these set ups before. Jumpering the relay will not get it to run. When it won't run there is no power (signal?) to the injectors. There is spark, though. This was with either ecm.

As of now, it decided not to start again. There is no real rhyme or reason to it. It didn't stall anymore, but did fail to restart after being shut down.


What tells the ecm to fire the injectors, and where can I find it???

[91AWDAstro]

Well I would check the inserts in the ecm connectors. I had one in mine that had backed out and not making connection.

I know that with OBD1 initial start timing is controlled by the distributer/ESC up to 400 rpm. I also believe the ECM looks for a signal from the pick up coil in the distributer to start injector firing. You could have a problem there. It sounds like a connection problem somewhere.

You can use a 12v test light accorss the injector to check for pulses. Best would be an oscilloscope.

[coolen]

i know that with my 94 tbi astro i had similar problems. It is definitly a connection problem. With my tbi i had to take the injector wires off and "rebend" them to fit tighter and never had a problem since. Yours seems so intermintent that it is unfit. Would it be as simple as a clogged injector that is sparatically spraying? I wish you the best of luck. I know that these sort of problems are absolutly NO FUN.

[v8famvan]

I would suspect your ignition control module - here is why.

Your ignition control module supplys the signal to the ECM to tell it to fire the injectors. It also supplys the ignition / spark signal. It can fault in the manner you have, as in spark is ok but has no injector drive.

How to test the injector control system.

Connect the aligator clip of a simple test light to a battery source.
Disconnect the larger (4) wire connector to the ignition control module.
Turn the ignition on.
Touch / release the test light tip to the purple/white wire in the 4 wire ignition control module.

What should happen is this:
The fuel pump prime will trigger - 2 seconds.
The injectors will pulse/spray fuel.

If you have no injector pulse/spray when cranking, but do have spark & it passes the above test - you have a faulty ignition control module.

[rlsllc]

I am going to do that test in the morning. Man I hope that is it, I admit that the distributor crossed my mind, but I had no idea about the modules, testing, or anything else.

That kind of test info is priceless. Many Thanks!

[rlsllc]

After following James' instructions, I now am quite sure that I have a bad ignition module. It reacted exactly as he described.

I plan to pick one up and replace it later today or tomorrow, today's the wife's B-day so I'll be playing it by ear.

I want to issue a GIANT THANK YOU!! to James. You Rock!

Later: OK I replaced it, and ran it through several starts, stops, short trips, and feel that all is well. Thanks to all who offered help!!!

[v8famvan]

Roy, glad to hear that you have resolved you issue & that I was able to assist you.

PS:I love a happy ending.

[canadavan]

Roy, glad to hear that you have resolved you issue & that I was able to assist you.

PS:I love a happy ending.

Ok, that's getting a little too personal...

[91AWDAstro]

Looks like the disease has hit my distributer. Been occasonally not starting except on starting fluid. No fuel from the injectors. Picked up the new module today.

[rlsllc]

I would have thought that a bad ignition module would cause "no spark", not "no fuel".

I admit that the pick-up in the distributor crossed my mind, as did the tach signal from the coil as a way of timing the squirt, but had not a clue of how it worked or how to test it.

I didn't suspect the ignition module since I had spark. (dunce)

I was lost, I admit. I guess I need some better shop manuals, and trash the Chiltons Joke Book.

I'm just glad it's fixed, running great, and hope this helps someone else trouble shooting. I'm so glad to have my 4x4 van back. Now if it would just snow.

This place rocks! James is my current Hero. (no offence, Petey)

[91AWDAstro]

We got the snow!, The factory service manual had a pretty good explination of how the sytem works. As mentioned initial spark is controlled by the ignition module up 400 rpm. After that the ECM takes over.

Glad you got yours running.

[AstroManiac]

Does my 97 AWD "W" engine have a Ignition Control Module???
Maybe that's why it won't start unless I give it a shot of starting fluid!!!
Where is it located???
My distributor only has a "Cam Position Sensor" in it!!!

[lockdoc]

I missed this thread when it first came up. Bummer. I found out all about how the module and injectors while converting my CPI to TBI for the V8 swap. Had the same problem. Unfortunately for me I had just rewired the van so I didn't know where to start! Thought I had screwed something up. Glad you found the problem.

[peter]

I also just stumbled onto this thread. Glad you found the problem, Rslic. Also glad that James came in handy for a change