Need Help! Engine shutting off

[Tuck73]

Posted a thread on here a few weeks that Bronco would just shutoff. Could restart and each time would run shorter and shorter time. Replaced coil, ignition switch and distributor. Didn’t fix anything. Dirt Donk told me to check voltage from alternator and it was generating 16 volts. Installed new alternator and drove it for over 30 minutes, no issues. Got home and realized I had not hooked up the alternator. Hooked it up and drove ten minutes and it shutoff again. Restarted dove a few minutes and shutoff again. Unhooked alternator and drove it home with no issues. Tested voltage on new alternator and it’s 13 - 14 volts. At this point, I’m at a complete loss. Seems as if the alternator is the problem but the new one is putting out the right voltage. Any help is appreciated.

 

[Speedrdr]

Just throwing this out there, may not help or you may have checked it. Do you have a good grounding surface between the alternator and alternator bracket and alternator bracket and engine? Not even sure it makes a difference, but… what year is your EB? Did you check the duraspark for connections or if unit is good? That is if you have a Duraspark ignition.

Randy

 

[Tuck73]

I should have good ground but I’m going to run a separate ground just to be sure. I’m running an electronic ignition system similar to the GM HEI. Not running a Duraspark system.

 

[DirtDonk]

Is it a DUI, or one of the less expensive brand alternatives?
Even though most of those have been running well for several years now, there was a rash of failures on the cheap ones in the beginning.
Because either the modules were insufficient for the heat generated, or the manufacture did not use proper or sufficient quantities of thermal transfer paste, between the module and the body of the distributor.
Inside, the GM modules require a thermally conductive paste (yes, just like the CPU in your computer) to keep them alive.
At this point, you could check that, or you could make sure that it’s actually a spark problem.

In the previous discussion, did you verify that there was no spark when the engine died?
Or could it be fuel?

At this point, it’s not apparent that it is your alternator.
The fact that you’re getting 13 to 14 V means it is working correctly. That’s assuming that it continues to do that.
If you can watch the voltmeter right up to the point that the engine dies to verify that the voltage stays stable, then I would venture a guess that it’s not the alternator.

 

[Tuck73]

Is it a DUI, or one of the less expensive brand alternatives?
Even though most of those have been running well for several years now, there was a rash of failures on the cheap ones in the beginning.
Because either the modules were insufficient for the heat generated, or the manufacture did not use proper or sufficient quantities of thermal transfer paste, between the module and the body of the distributor.
Inside, the GM modules require a thermally conductive paste (yes, just like the CPU in your computer) to keep them alive.
At this point, you could check that, or you could make sure that it’s actually a spark problem.

In the previous discussion, did you verify that there was no spark when the engine died?
Or could it be fuel?

At this point, it’s not apparent that it is your alternator.
The fact that you’re getting 13 to 14 V means it is working correctly. That’s assuming that it continues to do that.
If you can watch the voltmeter right up to the point that the engine dies to verify that the voltage stays stable, then I would venture a guess that it’s not the alternator.

It’s not fuel. It’s definitely spark. It’s a Jegs distributor. They tell me it comes from the same manufacturer as MSD. The distributor, ignition switch and alternator are brand new. I can unhook the alternator and it will run until the battery dies. Hook up the alternator and it will only run a few minutes then shutoff as if you turned the key off. I’m going to run a ground wire from the alternator to the battery and see if that does anything. If not, I’m going to get a new coil. I put a new coil in it but that was before I got the new alternator. I’m worried the old alternator messed up the new coil.

 

[67sport]

Is the alternator internally or externally regulated? If externally regulated, is it new and how is the wiring? Factory? In good shape?
It's acting a bit as is dirty voltage from the charging system is causing a glitch in the distributor electronics? What wiring is common to the two?

 

[Tuck73]

One wire internal regulator. The alternator is brand new. Old alternator was generating 16 volts. I think it ruined my distributor. Replaced distributor and alternator. Still having the same problem but the new alternator iss generating 13-14 bolts.