Strange Issue

[Resin]

I've got a weird one if you want to scratch your brain.
For all intents and purposes, I am working with an L03 89 Firebird. It's actually closer to an L05 now but that's beside the point.
I got it to start a couple of times, it was running super rough though. Timing was jumping around.
Then it quit sparking.

What I can't wrap my head around, is that the coil is sending power to the middle post of the distributor.
The injectors are firing.
But there is no spark at the plugs.
Where is the power from the coil going?

Plug wires are brand new all within ohm spec. 1.3k for the wire going to #1.
There is nothing flowing to the plug though.

I've seen plenty of other posts about similar issues, but they all don't have an injector pulse and/or no spark at the coil either.
Has anyone seen anything like this before?
Could it be an issue with the ECU?

Regards,
Resin

[Sledhead2]

If it is coming out of coil wire then look at your cap and rotor. spark should go right from rotor tap to cap post.

Look for carbon marks in the cap, they will look like little stress cracks.

Did button burn out on rotor.

[Resin]

I will take a close look at both of them later today. I have tried two entirely separate distributors and they both behave the same way. I have tried two separate coils as well. Thanks for the suggestion though, it's entirely possible they are both bad. I will report back.

Regards,
Resin

[Resin]

Well, I took a look at both of the distributors and I don't see any damage anywhere. Things have now gotten weirder though.
Now I can't get the car to crank. Fuses are all good from what I can tell. Lights on the dash come on with the key. I get 12v to the injectors.
The security light now stays on. I've tested the resistance of the key and it is still in spec. I tested the continuity of the wires to the ECU and they're not broken with 0 ohms. Tested the key side of the circuit too. I'm starting to think more and more that my ECU is dead. Does that track? Am I crazy?

[Fast355]

I've got a weird one if you want to scratch your brain.
For all intents and purposes, I am working with an L03 89 Firebird. It's actually closer to an L05 now but that's beside the point.
I got it to start a couple of times, it was running super rough though. Timing was jumping around.
Then it quit sparking.

What I can't wrap my head around, is that the coil is sending power to the middle post of the distributor.
The injectors are firing.
But there is no spark at the plugs.
Where is the power from the coil going?

Plug wires are brand new all within ohm spec. 1.3k for the wire going to #1.
There is nothing flowing to the plug though.

I've seen plenty of other posts about similar issues, but they all don't have an injector pulse and/or no spark at the coil either.
Has anyone seen anything like this before?
Could it be an issue with the ECU?

Regards,
Resin

How can it be closer to a L05? It either has a 305 or a 350.

That being said, cap and rotor, especially the rotor ar suspects. If the rotor has burned through, the spark is grounding out on the distributor shaft.

[Fast355]

Well, I took a look at both of the distributors and I don't see any damage anywhere. Things have now gotten weirder though.
Now I can't get the car to crank. Fuses are all good from what I can tell. Lights on the dash come on with the key. I get 12v to the injectors.
The security light now stays on. I've tested the resistance of the key and it is still in spec. I tested the continuity of the wires to the ECU and they're not broken with 0 ohms. Tested the key side of the circuit too. I'm starting to think more and more that my ECU is dead. Does that track? Am I crazy?

The ECU has nothing to do with the engine cranking over. That is a function of thr VATS module and starter relay.

[Resin]

I just jumped the outside two wires on the starter relay and it cranks again. Is the VATS not part of the ECU?
It's gone back to no spark at the plugs now though too.

[Resin]

It's a 1995 350 block with vortec heads and a custom burnt chip. Not exactly L05 but closer.

[Resin]

Let me check for resistance between the middle post and the shaft then. Would that be telling?

[Resin]

0 ohms from the distributor shaft to the intake manifold. Open loop from the coil post to the shaft.

[Resin]

19811
The starter solenoid looks like it us run through the ECU. Am I interpreting that wrong?

[dave w]

It appears to me that the starter solenoid sends a voltage to the computer that the engine is being started cranking.

[Resin]

Sounds good. That makes sense.
So I have two separate issues now.
Next thing that I'm going to verify is that the Rotor is actually spinning. It seems that would explain the issue better than the ECU not working.
I didn't think about it till I had already left the shop last night.
Thanks all for your input. I hadn't even thought about the voltage grounding through the distributor shaft but that prompted the idea that it isn't spinning at all, or at least intermittently.

[steveo]

a weak coil will sometimes have enough output to jump one gap but fail to jump the second one. takes quite a big spark to jump the distributor and the spark plug. seen it a few times.

[Resin]

A combination of a low battery and bad spark plug wire seems to have been the culprit on the spark issue. I think steveo was right. Now I have a different issue. The TBI is spitting fuel like a backfire and it actually caught the unit on fire. That is likely a valve issue right?

[1project2many]

So this is a tough situation to help with. It's tough b/c as an experienced mechanic I've gotten used to seeing and thinking of problems in ways that help diagnose the what's wrong. Your description may be right but it doesn't match up well with what I'm used to seeing.

Sucks that you had a fire. Hopefully it didn't result in other damage! I think a fuel pressure test might be a good idea. Low fuel pressure can cause hard star, no start, and backfire. I'm not sure what else to recommend at this point.

[Resin]

Can a vacuum leak possibly cause backfiring? I will throw my fuel pressure gauge on it tomorrow. No damage, I had a fire blanket at the ready and threw it over immediately.

[steveo]

no even a massive vac leak will not cause a fire. a fire in your throttle body could only be a severely leaking injector (unlikely) or a timing or valvetrain issue. is it possible that while messing around diagnosing the previous issue you have clocked the distributor improperly

[Resin]

It is certainly possible. Would the rotor being backwards cause that? I.E. pointing at wire 1 when #6 is at TDC?

[MO LS Noobie]

Ignition timing, improper firing order, to lean of fuel mixture, are some of the other issues that will cause backfiring through the intake.

[Resin]

Well I am both sad and delighted to report that she is now running. I found the problem. It was me. I am the problem. I installed the distributor backwards. Thank you everyone for your experience and assistance.

[steveo]

glad you beat it
its definitely something ive done before

[MO LS Noobie]

Those that never make a mistake are never doing anything. We've all been there, done that. The best lessons for me are the most painful, makes it kind of hard to forget. I worked with a guy once that when he stabbed a distributor 180° out he just modified the rotor to fit. Could not convince him otherwise. I did not envy the next person to have to change the distributor rotor, and try to figure out why it wouldn't run. Glad yours worked out

[TriumphR3]

Holy mackerel! I would have never thought to mode the rotor cap! I just reclocked the distributor. Silly me. Yes we have all done it. Hopefully you only make that mistake once.