91 Sub burned 3 ign. modules no start again

[Leper]

I am buying a 91 Burban that has wasted 3 ignition modules in 3 weeks. The original one, a used one and a good one from O'reilleys. Any suggestions??? The cap, rotor, coil are all fairly new. One note, the first one went out after the tranny was removed and replaced. I will be checking for a pinched wire or a loose ground tomorrow, I couldn't see tonight. I'm thinking mabey the dist is bad, but I am not familiar with these ignition systems yet. I have heard that from a few people already. I am all ears. Please help.
TIA
Leper

 

[diesel4me]

not sure...

I've only played with older HEI's--but if they burn modules rapidly,usually its due to voltage spikes,or failure to apply the silicone heat transfer compund to the back side that rests on the distributor housing..after cleaning it off of course..

Voltage spikes or surges can be caused by loose connections to the module,coil,ignition switch,or any wires going into the distributor,excessive charging rate(bad regulator in the altenator), or loose ground wires...A faulty coil might do it too,though you'd likely notice skipping or poor performance if the coil secondary windings were shorted..pick up coil is a possibility too..most of the time its voltage surges that make them go "poof"...

I ran a separate ground wire from the distributor base to the battery - terminal on my 74 K20 after it blew 2 brand new modules in rapid succession--it never blew another one after that..I think the distributors dont ground well just poked into the block and all covered in oil sometimes..

I had several GM vehicles with points that ran lousy unless I ran a ground wire from the breaker plate out the "window" of the cap, and to ground...you could actually see arcing at the breaker plate while it was running until I added the extra ground wire!..My nailhead 401 Buick ran tits after I did that,and several other mechanics had given up on it!..

 

[Leper]

You mentioned the pick-up coil. Is that a seperate piece from the distributor or is it a internal part? Can it be replaced seperately?

 

[Leper]

Ttt

 

[Leper]

Heeeellllpppppp!!!!!

 

[90K5]

pick up coil is at the bottom of the dist, will need to pull it out to replace

 

[diesel4me]

yup--

In the older HEI's it sits where the points used to go on the point style distributors..I'm not familiar with later ones after 1986 or so,but I assume to change a pick up coil you have to still yank the distributor out,drive out the roll pin that holds the drive gear on (mark it first so you can put it back on in the same spot with a center punch),and remove the shaft from the distributor--
Then there is a snap ring you need to remove that holds the pick up coil on the base of the distributor..then it pulls off..again,this is the older HEI's..newer ones might not be set up the same--I'd look in a motor's manual or something first!..sometimes its easier to just drop in a used or rebuilt distributor!..might not be that expensive at Autozone...but first I'd check all the wiring--hate to have the rebuilt one pop its module if it is due to a bad connection or a wire shorting out somewhere..

 

[Leper]

Thanks for the reply.