TBI problems

[1987 GMC Jimmy]

As far as I know there is not polarity on the injectors and you can not install them backwards because there is a little pin on them that has to sit in a slot on the injector pods. Otherwise you crack the injector pod and get to search for a new throttle body...ask me how I know this.
The injector do click when they are pulsed with a 12 volt source. I actually have three sets (like I said ask me how I know that the parts of the throttle body crack easily). One isn't in great condition but the other two sets I have tested and as far as I can tell function as they should. Originally I was told that you could test the injectors with a 9 volt battery and I found out that it takes a 12 volt source to get them to cycle.
I have ordered an AC Delco ignition control module and I am going to try it out. The one I put on it was a house brand and I know that they can be picky about brands sometimes. I noticed that the voltage at the injectors was only around 5 volts, so I am wandering if the off brand icm isn't the issue. If this doesn't do it I guess she is going to sit until I can afford to pay someone to figure it out.

That may be worth looking into. The injector pulse and ignition aspect are controlled separately. You could also pull the ICM and have it tested just for kicks. I don't know. You've covered a lot of stuff. The only thing that comes to mind is when stuff gets funky in any computer controlled vehicle, the ECM may be on the fritz.

 

[chrispbrown27]

The AC Delco ICM arrived and is on and no change. Now she is going to sit until I can get it to a mechanic. Thanks to everyone for the help.

 

[87ChevyR10]

What about the pick up coil? I know when mine died, everything worked as expected, but the truck would not fire. I replaced everything ignition related. Once the dizzy was replaced, the truck worked just fine again. From my understanding, if the pickup coil fails, the computer prevents the tbi from spraying fuel. It'll even let the pump run as normal. This seems to be about the only other thing to rule out.

 

[Georgeb]

What about the pick up coil? I know when mine died, everything worked as expected, but the truck would not fire. I replaced everything ignition related. Once the dizzy was replaced, the truck worked just fine again. From my understanding, if the pickup coil fails, the computer prevents the tbi from spraying fuel. It'll even let the pump run as normal. This seems to be about the only other thing to rule out.

It's
Cheaper than a towing and shop bill too.

 

[87ChevyR10]

It's
Cheaper than a towing and shop bill too.

And it's not the middle of winter, either.

 

[chrispbrown27]

Ok, so I couldn't just let her sit. I decided to drop a new distributor in as a hail mary. When I dropped it in I noticed that the fuel pump primed as if I had turned the key to the on position (it was in the on position the entire time). So I got to investigating, thinking I had pinched a wire some place. While I was laying on top of the engine trying to see what was going on I noticed that every time I dropped the distributor in the coil wire would spark and the fuel pump would prime. This doesn't seem normal to me it kind of makes me think there is a short somewhere.....Any ideas?

 

[r67northern]

I think there's a big ground wire that is attached to the T-stat housing. Try cleaning that up really well and see what happens. I was chasing a TIB problem with my wagon earlier and that was one of the things I did. Of course, it didn't help because my problem really was the distributor.

It took a new fuel pump to figure that out though.

 

[chrispbrown27]

I have done the fuel pump thing...It seems like I have changed just about everything. I know it's got to be something simple that I am just missing. I got a recommendation for a good mechanic not too far up the road, so now I just have to get it up there.

 

[r67northern]

Good luck, the distributor on the wagon was the last shot before doing the same thing. Luckily it was the problem.

Strange that it fires ok with direct gas. But then I swear I was being lied to by my tbi which led me to the fuel pump first and then eventually back to the distributor

 

[Rusty Nail]

i swear i was being lied to by my tbi

lmao!

 

[Senck243]

Did you ever get this straightened out?


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[chrispbrown27]

Sorry it took me so long to respond. Yes, I ended up taking it to a mechanic. Took him two weeks but finally figured it out. Two issues.... broken power wire to ecm and bad injectors. He never did find where the wire broke so he just ran a new one. He ended up putting another throttle body on it and she is running fine now.

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