Zenroth

Alright so this is turning into a bigger problem, and I find myself at a bit of a cross roads now.

Car was running fine, shut it off, next morning wouldn't start. No Spark/No Injector Pulse. (Confirmed with noid light)

What I've done:

Ignition/ECM fuses all check out okay.

Check for codes (Flashes 12, no other codes stored)

12 volts tested okay on each injector.

Fuel is arriving to the TBs fine. (Pump is on a switch, no relay/oil sensor needed.)

Went to replace the ignition module given the no spark condition, all the connectors inside broke. So I replaced the entire distributor. I now have spark (timing gun picks it up happily) but still no injector pulse..

Did an ohm test on the injectors.... 4 and 6 ohms.. I can't seem to find the spec for 84 injectors, but if they're the same as the rest of the years then they should be around 16 ohms. In which case this could be the problem. However, if I disconnect both injectors, and plug a noid light into one of them, I still get no pulses. Shouldn't I be seeing pulses?

So what I haven't tried is to get a AC reading on the #2 ECM connection that is the reference signal from the distributor. I'm still trying to figure out how in the world to fit under the passenger dash to even get the hush panel out of the way. Likewise I haven't swapped out the ECM.

Its just starting to seem very strange that my pickup coil or ignition module died in the distributor (no spark), my injectors (which were fully cleaned/serviced around 3-4 years ago) are reading 4-6 ohms, and I have no injector pulse, which kinda has me leaning towards a bad ECM.

For kicks I dug out a 10k ohm resistor, and tested it with the multi-meter to just make sure the meter hadn't gone crazy, and it came back correct.

I'll probably try an get an AC reading on the reference wire, by probing from the distributor to ecm connection, but I'm kinda left wondering what the hell, given the sudden massive amount of component failure when the car was running fine, and did around 300 miles hours before all this suddenly happened.

Zenroth

Right managed to drop the ECM, disconnect the black connector and probe #2 reference signal, 3volts AC when cranking so it seems thats fine. Ran some continuity tests from white side 8 and 9 back to the injector connectors, and those were fine.

Replacing the ECM, and maybe the injectors.. really not sure about that whole 4 and 6 ohms. Found reference to GM TBI injectors are suppose to be in the 1-2 ohm range, but that means mine are still way out of spec.

2thousand2

If your noid light is not flashing new injectors will not help. I cannot recall the sensor that can keep the ECM from creating a pulse, maybe someone else can chime in on that.

Good luck with it!

Zenroth

Thanks, and yeah seems like its the TPS that can cause that, but it checks out fine, and things don't work with it unplugged either.

Ordering a new computer, alas not very quickly it seems.

cudamax

Itsn't that the Ign Module and or Stator. I think the ECM needs to see pulses from the Ign module before it will start trigger-in fuel or it does it at the same time, but it starts there
Dist-less engines use the crank & cam triggers

cudamax

Still think it possibly ur new rebuilt dist/module I say atleast get another on, leave urs in the motor and plug ur module connections into the other dist and turn the key on and ground the housing on something and check to see if ur probe on the injector harness is pulsing/flashing. Also make sure the dist harness connectors aren't damaged, or
Stab harness just outside the dist with a clothes pin and check and trace the signal wire to the ecm that sends injector trigger.If u got it there then move on down the line and see if its coming out of the ecm but if ya dont go back to the dist

Zenroth

I'm getting the pulse from the distributor to the ecm, and getting spark. I think the ecm just crapped out as well, will know tuesday it seems.

Wires 8 & 9 to the injectors also have continuity so it seems that wire path isn't broken.

Zenroth

Right so to add a conclusion to this...

Replacement ECM restored the injector pulse, however I was still having a few problems.
At times one of the injectors would stop working and lose all voltage. Ends up for whatever reason the fuses despite testing good were seemingly flakey. Replacing those fixed that problem.

Then I was having an issue of the car randomly dying (at cruise or otherwise) and not wanting to restart. I was starting to suspect the ignition module in the new distributor was bad, but ultimately I decided to replace the ignition coil based upon the fact that every other part of the ignition and computer circuits seemed to have died or taken damage somehow. Replaced the coil and cover, and haven't had any problems since.