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will a hot alternator kill an engine

Angie

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I am scratching my head on this one... just started 3 days ago. when cold the truck starts easy, drives good. nothing out of the ordinary. After driving about 10 miles (15KMS) at a red light the truck will stall. I let it sit for a few minutes, then hit the key and the truck will start. if i don't let it sit and keep hitting key, the engine just turns over and won't fire. The truck so far hasn't died while moving. just at lights.

This has happened 4 times now. I have checked the Volts 14.8 running and 13 when not running so battery seems good. haven't checked volts when it dies. how can I check amps? and where should I take a temp of the alternator with IR? (i do have other alternators I can place in just wanted to ask this first to see if I am over looking something)

Doubt its a lack of fuel, but been known to be wrong before.

done all the basic checks, loose wires, connections and crap.

1990 - 4 Lt. auto
 


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fastpakr

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Is there a TFI module in this setup?
 

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Well after it dies, make sure you have spark... maybe your coil is getting weak, EDIS module failure maybe?

Doesn't sound like a bad alternator to me. Maybe it wouldn't hurt to have it tested, they do weird stuff, I had a bad one that would make my headlights flicker under load.

My fiance's '95 will occasionally just die too but it fires right back up like nothing happened, or it runs really rough for a few seconds and clears up. I haven't figured that out yet either.
 

Angie

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Is there a TFI module in this setup? I hate abbreviations... whats a TFI? I am guessing .... Fuel Injection?


shran ... would the coil pack act strange at only lower RPM?
 

fastpakr

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What brings up the 'lower RPM' question?


TFI is 'thick film ignition', it's Ford's older ignition module setup. I didn't remember it being used on 4.0's, but not sure. It was known for issues like you describe. Shran's also suggesting ignition module related issues. Definitely test for spark.
 

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TFI... Thick Film Integrated.

At least that is what I remember from my dyno lab days...
 

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That's probably right re integrated vs ignition.
 

Angie

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What brings up the 'lower RPM' question?

The engine will only stall out when I sit idle low RPM at a red light..... will a coil quit working at a low RPM and wouldn't it also die at high RPM?

where do I search for the 'thick film ignition', first i have ever heard of this... cheers and thanks
 

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Oh, interesting. I misread that the first time...

Confirming spark would be very helpful. If you've got spark, my next thought would be confirming that the IAC is functioning properly. Also that it's not a vacuum leak induced by the brake booster.
 

Angie

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Ya I checked for vac leak... but this can't be for it would die at all idles.... not just when engine is hot.

But you are missing the question... when engine is cold, or sits it fires no problem ... it is only after it has been driven that it dies. that is why i was asking if a faulty alternator would affect the amps being produced and drop the current to kill the engine when it is hot... as in faults in the stator / brushes. I am not sure how many amps the injectors and computer and such need to maintain to keep the engine/truck running.

IAC?? ahhh idle air control valve .... wouldn't that also act up when engine is cold? but do have a few extra of those kicking around too.... (have 2 more complete parts trucks with 4L)

cheers
 

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The injectors should fire all the way down to 9volts. All the electronics are tested to operate between 9 and 16 volts. If the truck will start after it sits for a minute I doubt it has anything to do with the alternator.

As for it being a vacuum leak... it is completely possible that you have a leak when at operating temp and not when cold.

Try popping it into neutral when at a light and see if the idle is stable.
 

Angie

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Confirming spark would be very helpful. If you've got spark, my next thought would be confirming that the IAC is functioning properly.

Head scratch... yes I fully agree spark and such, but hot or cold wouldn't affect spark. you have it or you don't ....

One other thing has entered my mind... would a torque converter act this way under any circumstances?
 

Angie

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As for it being a vacuum leak... it is completely possible that you have a leak when at operating temp and not when cold.

Try popping it into neutral when at a light and see if the idle is stable.

interesting.... hot engine vac leak....... if it will stay running ya i will try that....

i will go out now and let the truck run sitting to get to temp and then take it around the block and see if it dies.... I don't want to chance it during AM commutes to work as I have to drive over a mile long bridge... so taking wife's rig last 2 days...

cheers
 

Shran

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It does not have a TFI module. It does have an EDIS ignition module. My thought process was that either that or the coil itself is getting hot and perhaps is affected by really high or really low voltage from the alternator, or AC voltage leaking out... thus my suggestion to have it tested... but I just don't think the alternator is at fault.

Wonder if the crank position sensor could be flaky and not generating a signal sometimes.
 

Angie

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It does have an EDIS ignition module. My thought process was that either that or the coil itself is getting hot and perhaps is affected by really high or really low voltage from the alternator, or AC voltage leaking out... thus my suggestion to have it tested... but I just don't think the alternator is at fault.
How would I test those, (EDIS and coil) when hot vrs. cold? Can look into it. why I was thinking alternator is when they act up, it is usually at lower RPM's .... and they will/can kill your engine (stall out)

cheers and thanks.

Wonder if the crank position sensor could be flaky and not generating a signal sometimes.

as above, wouldn't that go wonky all the time and not just at low idle and after warmed up?
 

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