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If I’m to convince myself to keep my car I’d like to get it running as well as it was before I accidentally left the lights on for too long last week.
1976 L48 auto, HEI
Left the parking lights on for ~10 hours
Gauge lights lit up, no click from the starter solenoid
After a jump it starts, but runs rough
Half a mile down the road I lose all the gauges
Few miles later the car dies completely, needed to be towed home
I determined it to be a bad ignition module. Had the battery on the tender for a few days before it showed a full charge.
Took the distributor apart and went through it
Shaft endplay set to .020”
New ignition module, obviously
Aligned the dimple on the distributor gear with the metal part of the rotor when reinstalling
Got it all back together and started it
Turned over in short bursts at a time, like it still had low charge
When it finally started it ran very rough, very smoky out of the exhaust
Would die when put into gear, unless feathering the throttle
Alternator feels magnetic on the back when the car is running
Ignition timing set to 16 initial + 12 from the VA, confirmed to be 28
All cylinders firing, confirmed by timing light
New NGK BKR5E plugs, .045” gap
Needle confirmed to be operating freely and not bound up
I’m thinking some sort of wiring fault is preventing the alternator from actually charging the battery. I’ll check the voltage at the battery with the car on and off once I find my multimeter. If it’s not charging though where should I check? Also, despite replacing the blown gauge fuse they’re still not working (gauge lights are.) Where should I look for fixing that?
Last edited by Piersonpie; May 2, 2026 at 11:34 PM.
Had the battery on the tender for a few days before it showed a full charge.
Turned over in short bursts at a time, like it still had low charge
Sounds like your battery was damaged when it discharged so fully. (Have you checked it for electrolyte - can you remove the caps?)
Few miles later the car dies completely, needed to be towed home
Sounds like your alternator may not be charging correctly and the battery didn't have the juice to keep ignition going.
I think you have two first steps to take: fully charge the battery out of the car and have it load tested — replace if necessary; then test the alternator output voltage at the battery (should be right about 14v).
Aligned the dimple on the distributor gear with the metal part of the rotor when reinstalling
Is that the way it came off? Your setup may require it 180° from the standard rec.
When it finally started it ran very rough, very smoky out of the exhaust
What was the source for your replacement module?
Are you positive the distributor was dropped in correctly for firing order?
Battery reads 13 volts with engine off, 14.5 with it running. Interstate that was brand new as of February last year. No caps to remove.
I didn’t specifically check when I took it apart, but I don’t recall any reason why I would need the gear in backwards. New ignition module came from Blueprint Engines. Went back in with the rotor facing the exact same way it came out, but if I’m able to set my ignition timing correctly does it matter if it’s a tooth off in either direction?
I’ll double check the gear and pull the battery out to charge. Any idea what to check for the gauges?
(Edit: double checked, dimple is good.)
Last edited by Piersonpie; May 2, 2026 at 11:30 PM.
Definitely put a timing light on it and check your timing. Doesn't sound like you are a tooth off on the distributor. Wouldn't likely run that way.
None of your gauges work? How this can be from just leaving the parking lights on I do not understand.
Sounds like a bad ground. Or power wire to the gauges is defective.
Over the decades I’ve seen so many people blow the alternator diodes or other electronic components when they jump start their cars.
It only takes one spark.
Double check your resistance wire if you have one, look for any burnt, melted wiring, evidence of shorts, check the alternator and diodes, have a good load test done on the battery and not just a voltage check, everything in the ignition system.
Well it’s running better, but still not as well as it was before. Very slow acceleration like the timing is retarded. I’ve double checked it, but I’ll give it a triple check.
New cap & rotor. Now will barely fire off while cranking. Lots of black smoke. Also the headlights are coming up by themselves despite the switch being pushed in. Gauge fuse blew again.
Last edited by Piersonpie; May 3, 2026 at 05:00 PM.
Pulled the distributor and reinstalled, making sure the rotor is going in on compression of the #1 cylinder. It actually ran better, headlights went down. I noticed I had to give it a continuous little bit of throttle to keep it running, so I left the VA line unplugged. With this vacuum leak the engine would idle at ~750 RPMs.
It sounds like a timing and fuel mixture issue at this point. I replaced the gauge fuse again and it blew again. I’ll check the grounds.
Where did you apply the cables when jumping the car? Do you have an original alternator, with the original charge cable, or something else?
I'd absolutely check the dist voltage when running.
The last time I had to "give it a little gas" to keep it idling was when I didn't have my vacuum advance connected to manifold (it was on a ported vacuum port, so zero advance at idle).
Hopefully timing gets it! Though the gauge fuse is puzzling.
Jump came from a box (this one) and was put positive to positive then negative to negative.
12SI alternator with original charge wire. Reading 14.2 volts from the back of it with the car running, although it was a bit difficult to do with the engine shaking.
Reading at the distributor I’m getting between 8 and 14 volts. Not good I would assume.
New alternator arrives on Tuesday. I can change that out to see if it helps.
14.2 V at the alternator sounds good. If it goes up a lot when reving the engine that could be bad. Doubt your issue is with the alternator. Good clean voltage to the distributor is important however.
I run a power wire, (fused) directly from the battery positive post to a relay on the firewall. Relay is permanently grounded. Triggered by the wire that used to go to the positive terminal on the distributor. Then power out of said Relay directly to the positive terminal on the distributor. Giving me clean constant battery voltage to the distributor.
I've never burned out a module. My 50 year old wiring and switches have very, very little load on them. Car runs great.
Yes a bit of time to run wiring under car alongside the positive battery cable and up the firewall. But the cost is minimal. Results are worth the effort.
A quick and easy test. Take a couple yards of wire. Crimp a female 1/4" spade terminal on one end. Connect the other end to the positive terminal on the battery. Run wire out the window and to the distributor. Plug it into the positive terminal on the distributor.
Now the only way to shut down the engine will be to disconnect this wire.
Start engine.
How does it run now with constant 12 -14 volts?
A quick and easy test. Take a couple yards of wire. Crimp a female 1/4" spade terminal on one end. Connect the other end to the positive terminal on the battery. Run wire out the window and to the distributor. Plug it into the positive terminal on the distributor.
Now the only way to shut down the engine will be to disconnect this wire.
Start engine.
How does it run now with constant 12 -14 volts?
Runs with a consistent 14.2 volts at the distributor when set up like this. No issues being able to shut it down though. It still won’t idle without constant throttle.
That's strange. Hot wired like this will keep power to the coil. Turning off the key should have no effect.
Still won't idle? Ign. Timing? Vacuum advance timing?
Just turning up the idle speed screw?
OK, you have pulled the distributor out more than once reading this all over.
But you are not telling us how you are setting the timing.
Try about 14 degrees initial with the vac can disconnected and line plugged. Then hook up the vac can and see how much it is putting in.
Didn’t mess with the key, but I was able to let the engine die just by not applying any throttle. I’ve got the timing set to 16 initial plus 12 from the vacuum advance. When setting the timing when I would accidentally swing the distributor too far in either direction (too advanced/retarded) it still didn’t feel like it ever smoothed out. I’ll give it another shot tomorrow.
Rough running engine after dead battery
