87 chevy 4.3 OT

[cat236]

A friend of the family's son has an 87 Chevy pickup with 4.3 engine. The problem is it keeps heating up module in distributor,then they fail.I showed him how to test voltage and ground.Ground was OK but had 16.2 VDC into Distributor at battery terminal. Tested alternator and showed same voltage at battery.Static battery voltage was 13.9. Had him take alternator off and took to my local rebuilder he tested and said it was good putting out 75amps at 14.5VDC. Installed alternator and inspected all grounds with no change. I am a disabled veteran and have limited funds.Have been a mechanic all of my life but mostly heavy equipment,ag and lawn and garden. The young man helps me out around the house and I try to teach him as much as I can to keep him out of trouble.I pay him a share of repair bills that he helps out with,I have also got him hooked up hauling scrap for some local shops to earn more money.He needs his truck to continue with the srap demands. I share all of this so you can see I am just trying to help this kid out. Through what I have seen of posts from Allen in Neb, Old, and so on, I got a feeling you fellas would do the same for a good kid. Thank you in advance. Wade

 

[MarkB_MI]

Before you do anything else, check the alternator output with a different meter. I think your meter is reading high. At any rate, I don't think 16 volts is going to blow the module; my guess is the problem is elsewhere.

 

[Allan in NE]

Hi Wade,

Yep, that was a common problem with those distributors after they got some age/mileage to ‘em.

There is a round, screened vent in the bottom of the housing which allows for air movement in and out of the distributor. They get plugged up with debris and then the distributor can't "breathe" and stay cool.

The vent is about the same diameter as your little finger.

Find it and clean out that accumulated, white residue with a shot or two of compressed air. It will help to clean all the white “tracking” residue from inside the cap and rotor also to prevent future plugging of the vent.

That'll cool 'er down and stop that module failure.

Allan

 

[Owen Aaland]

Mediun duty trucks had a diffrerent rotor with fan blades on the bottom to help move the air in the distributor. Using the new rotor cut way down on distributor problems on 6.0L engines. Maybe it would help here also.

 

[Allan in NE]

Sure couldn't hurt; those suckers really run hot.

Think there was a bulletin out on the problem when they were new if I remember right.

Allan

 

[Owen Aaland]

Fully charged battery voltage should be 12.6 volts after the surface charge has been drawn off. If the vehicle has just been run, turn the headlights on for five minutes and then test the voltage. If you are not close to 12.6 then your meter is probably off. If your meter is OK and you still have that high of alternator voltage you need to check the sensing wire going into the alternator. If that circut is open the alternator will go to full output all the time and your voltage will be too high but yet the alternator will bench test just fine.

 

[landlord7012]

Be sure to apply the silicone supplied with the module to clean surface. This ensure's proper heat sink.

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