I just picked up an '86 Iroc with a TPI 305/700r4 that will start on starting fluid but die immediately. I'm getting spark but no injector pulse. My ECM has 2 distributor pulse inputs, a Lo and Hi. I'm using a multimeter to check these inputs to narrow down if my problem is the distributor or ECM, or possibly something else. I read somewhere to check the hz of the inputs, the Lo input gives me nothing, the Hi input gives me 14ish Hz while cranking the engine. Im leaning towards the ECM, but is there something else I should be checking. The pins for those inputs are B3 and B5 if that helps.

 

B5 is important to get injector pulse, could still be a icm even if you have spark or unplug all injectors and check for pulse with a noid. Shorted injectors can cause injector driver to shut off in the ecm.

 

All injectors showed a little over 15 ohms when I checked them, but I haven't tried a noid light yet. That's what I'll start with tomorrow when the journey to getting this jalopy running continues lol.

 

Ref Hi is the actual signal from the ICM. 14 Hz does sound about right, that is about 210 RPM (I hope I did that math right).

Ref Lo is a ground reference from the distributor. It is used for the DRP input circuitry within the ECM.

Check that the MEMCAL is the proper one for your car. The BCC on the small silver label on the PROM is what will define this. If it was swapped for another one where that MY car has VATS, the symptoms match...

RBob.

 

I'll check that this evening when I get off work. Will the label have my vehicle info to let me know it's the right one or is there a certain number I should be looking for? I'm also going to check that the tps voltage isn't too high, as I read that can also kill the injector pulse.

 

Post the chip letter, should be AUM or something similar. Correct on tps voltage it will go into clear flood mode.

 

But it has to be really high, like over 85% (above about 4.3 volts).

RBob.

 

I did some more digging and realized I hadn't ohmed the 9th injector when I did the others. Found it only had 4ish ohms, left it unplugged and now I have injector pulse. Still wouldn't start so I started making sure I still had spark to be sure. Checking the wires specifically with a screwdriver they all had strong spark. Started pulling plugs and the 2nd one I pulled was bad so I stopped right there until I can get new plugs. Will probably be this weekend before I get a chance to work on it some more so I will update y'all when I have the new plugs in.

New question, how will my car do in cold weather without the 9th injector? Will it start at all or will I just have to baby the throttle to keep it running intil it warms up?

 

Isn't the 9th injector completely separate from the ECM?

RBob.

 

Yes the timer switch gets power during cranking and not tied to ecm just starter solenoid power.
cold start will be hard if the ninth injector is delete or can update the tune to 89 $6e.