At a loss......

[rubio9800]

Hello everyone,

I am ripping out my beard trying to figure this out (i'm no mechanic, my first g body)

Apologies for my memoir, here is the situation:

Symptom: Car turns off, could be at idling when first starting up or when accelerating, happens randomly.
High voltage when using a volt meter.


I've done a crap load of things to the car since i got it in Sept 2020, 81 grand prix, 265

• new battery (optima yellow top)
• Cleaned up ground cables/battery ones too
• new alternator (250amp,internal regulator, added a sound system) (most recent)
• Big 3 done, 0 gauge (most recent)
• new distributor cap
• new rotor
• new ignition control module (most recent)
• new ignition coil
• new fuel filter
• spark plug/wires new
• carburetor rebuild
  
  Didn't have any more ideas so i took it to a shop to get diagnosed. When mechanic measured the voltage going to the distributor it was reaching 15+volts
  Car would start and as the voltage climbed it would shut off as it approached 15v, highest i saw was 15.2 when was at the shop, highest he saw was 16v. Mechanic also told me he checked other things such as for vacuum leaks, loose carburetor, checked adjustments on carb.

Mechanic mentioned it could be the alternator and should have it tested. At that point maybe was thinking bad voltage regulator? So i went to Oreilly's and they ran the test multiple times, everything showed as Passed.

For fun, i purchased an alternator from them, 70amp stock and see if the behavior would be the same. Issue still occurs, highest reading i seen so far on a dvm has been 14.7v. Couple times as the engine came on, boom abruptly turned off.

The alternator that was in the car when i first purchased it, doesn't work anymore. But now that i think about it i did have these symptoms as well, but also had a carburetor that needed to be rebuilt.


I'm stuck! Could it be the distributor shaft?
Just getting to the shop was a nightmare with the times it would shut off on me. Fear of being rear ended!

I appreciate the time you may have taken to read my drama 🙂

Have a great weekend folks!

 

[88AZSS]

Could it be a fuel issue? Youve listed electronics and most things are new. Did tests to rule out some things. But spark is only one of the three things needed to get the engine going and stay going. Have you checked your fuel lines? Filter in carb? Once you rule out the electronic aspect move on to fuel and start from the simple stuff and move forward. Keep us posted.

 

[rubio9800]

Could it be a fuel issue? Youve listed electronics and most things are new. Did tests to rule out some things. But spark is only one of the three things needed to get the engine going and stay going. Have you checked your fuel lines? Filter in carb? Once you rule out the electronic aspect move on to fuel and start from the simple stuff and move forward. Keep us posted.

forgot to mention i also did change my fuel filter, thanks for reminding me.

No clue how i would start to check fuel lines? Any advice?, would have to do some research myself if its something a n00b can do. Is the 15v+ not a concern? Wouldn't that count as overcharging the system?

 

[64nailhead]

When the car isn't running do you have spark? And do you have power at the coil (what voltage if you know it)?


If you believe that you are having a voltage issue causing this, then with a charged battery either disconnect the alternator or remove the alternator belt and retest. The idea being that the car will run just fine on 12volts being supplied from a battery.

 

[fleming442]

Several things could be happening. First, check the battery connections, especially at the starter- those fusible links feed the ignition switch. Second, I wouldn't run the voltage that high. It might be good for amplifiers, but I'm betting the module in the base of the HEI probably doesn't like it too much. It could be heating up and losing spark. If you replace it, make sure to use the white paste on the base. Lastly, those are some fairly vague symptoms. You need to take better note of everything that goes on when it dies. Does it sputter first or run rough? Do the lights still work, or does all the power drop? It could literally be 100 different things. Just remember- fuel, air, spark. All 3 are needed to keep the engine running. I doubt it's air, so that leaves fuel and spark; go from there.

 

[OldsZZ383]

This is just a possibility: Check the fusible link connecting your engine to either the chassis or firewall. It's a special wire that's supposed to burn out to protect your car's electrical system... sometimes it gets overheated due to a high current surge and develops a crack. As the engine heats up the gap in the crack opens up the electric connections is lost and your engine dies!

 

[GP403]

The high voltage thing is puzzling. I'm not sure how the alternator would be able to put out 16V, I don't know what the internals of one is all about, but is that even possible? I'd think it would have a pretty low max it would physically be able to put out.

Just for fun I tried to search for the max V an alternator can put out and came across this thread:

Should an alternator ever run over 14.5V?

Bought a replacement alternator but I am sending it back as I measured and have seen it running over 16.5V. The manual says the regulator should keep it to a max of about 14.5V. I put a brand new ...

mechanics.stackexchange.com

This is just a possibility: Check the fusible link connecting your engine to either the chassis or firewall. It's a special wire that's supposed to burn out to protect your car's electrical system... sometimes it gets overheated due to a high current surge and develops a crack. As the engine heats up the gap in the crack opens up the electric connections is lost and your engine dies!

I was just about to say it almost sounds like an intermittent connection problem. Always fun to trace down. or there's something "half-way" (?) opening up or partially shorting out and presenting a very high load to the alternator, causing it to do that. not sure if that makes sense.

 

[rubio9800]

When the car isn't running do you have spark? And do you have power at the coil (what voltage if you know it)?


If you believe that you are having a voltage issue causing this, then with a charged battery either disconnect the alternator or remove the alternator belt and retest. The idea being that the car will run just fine on 12volts being supplied from a battery.

did not think of that , i will try over the weekend.

 

[OldsZZ383]

This is just a possibility: Check the fusible link connecting your engine to either the chassis or firewall. It's a special wire that's supposed to burn out to protect your car's electrical system... sometimes it gets overheated due to a high current surge and develops a crack. As the engine heats up the gap in the crack opens up the electric connections is lost and your engine dies!

Changing a fusible link is cheap... you can get one at any auto parts store... changing it may be a knuckle buster depending on where it is located on the firewall / engine... still the only way to eliminate the possibility that it is the culprit...

 

[rubio9800]

Several things could be happening. First, check the battery connections, especially at the starter- those fusible links feed the ignition switch. Second, I wouldn't run the voltage that high. It might be good for amplifiers, but I'm betting the module in the base of the HEI probably doesn't like it too much. It could be heating up and losing spark. If you replace it, make sure to use the white paste on the base. Lastly, those are some fairly vague symptoms. You need to take better note of everything that goes on when it dies. Does it sputter first or run rough? Do the lights still work, or does all the power drop? It could literally be 100 different things. Just remember- fuel, air, spark. All 3 are needed to keep the engine running. I doubt it's air, so that leaves fuel and spark; go from there.

sorry for the vagueness , this is the most i’ve done on a car lol, i’m more of a computer guy

the engine does not sputter when it dies, the lights work, stereo works.

i did replace the ignition module and applied the paste it came with. the paste was not white, was clear. don’t know how to tell if the ignition module could be bad?

when it starts i wouldn’t say it’s running rough, not too confident in being able to tell .