HEI eats modules - Whats wrong? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

beaterC10 · 06-05-2004, 05:53 PM

I have replaced the module in my HEI two times since Easter. Both times the truck ran fine and then would not start after sitting. The truck is an 84, with an older 350. The original ESC has been unplugged and a non ESC HEI is installed.

It looks like all I need is the original power lead installed? There is another plug that piggybacks the power plug, but it goes to either the ESC connector or the 700r4 connector. The original 700r4 was replaced with a 350 before I bought the truck.

I have used this same dizzy in an 83 that had the ESC unplugged and had no problems. The first module was a made in Hong Kong "performance module" the last one was a made in USA stock replacement. Am I just unlucky or is there something I should look at?

I have seen postings on reworking the ESC wiring when a non-ESC HEI installed what is the purpose of that? Any ideas?

Dave

*1FaastC10* · 06-05-2004, 06:20 PM

i've got a buddy who is having problems with HEI modules as well, if he finds anything out, i'll be sure to let you know. until then, i'll be watching this thread for tips and tricks on how to locate the problem.

i guess, pretty much what i just said was "TTT"

NeCrOmAnCeR · 06-05-2004, 07:07 PM

Are you putting heat conductive grease under the module when you replace it? Excess heat really does those things in!

mychevyii20 · 06-05-2004, 07:34 PM

From experience, once a V8 HEI module goes, REPLACE THE COIL and rotor. Check the cap Why? Besides overheating which is rare, the thing that fries the module is high voltage getting to it. This is caused by a "leaking" coil letting spark voltage go back through the primary wires or a rotor that is letting spark ground to the shaft etc.

The V8 HEI, with the coil in the distributor cap, still work when they are going bad. It is too hard to explain how to check them visually, but for the price it is good, cheap insurance. I learned this lesson in the 70's when coils where $12 and the modules where $50.

**crossy** · 06-05-2004, 09:55 PM

I agree with both. if you are definitely using the grease then it could be one of the other two problems described.

beaterC10 · 06-05-2004, 10:03 PM

Thanks for the information.

I used dielectric grease each time. I replaced the coil in February when it would not start. The cap and rotor were replaced last summer when I installed the 350. Since February I have replaced the coil and two modules.

There is some tracking on the rotor, so maybe a new cap and rotor will solve the problem.

Dave

**kwmech** · 06-05-2004, 10:17 PM

How about the ground strap that goes from the coil to the harness?

beaterC10 · 06-05-2004, 10:39 PM

If you are talking about the lead in the cap that grounds to the frame of the coil, yes it is there.

jimfulco · 06-06-2004, 12:48 AM

Bad plug wires (too much resistance) can cause HEI modules to fail.

06-05-2004, 05:53 PM	#1
beaterC10 Senior Member Join Date: Jul 2003 Location: Indianapolis, IN Posts: 1,277	HEI eats modules - Whats wrong? I have replaced the module in my HEI two times since Easter. Both times the truck ran fine and then would not start after sitting. The truck is an 84, with an older 350. The original ESC has been unplugged and a non ESC HEI is installed. It looks like all I need is the original power lead installed? There is another plug that piggybacks the power plug, but it goes to either the ESC connector or the 700r4 connector. The original 700r4 was replaced with a 350 before I bought the truck. I have used this same dizzy in an 83 that had the ESC unplugged and had no problems. The first module was a made in Hong Kong "performance module" the last one was a made in USA stock replacement. Am I just unlucky or is there something I should look at? I have seen postings on reworking the ESC wiring when a non-ESC HEI installed what is the purpose of that? Any ideas? Dave

06-05-2004, 09:55 PM	#5
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	I agree with both. if you are definitely using the grease then it could be one of the other two problems described. __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

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06-05-2004, 06:20 PM	#2
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,400	i've got a buddy who is having problems with HEI modules as well, if he finds anything out, i'll be sure to let you know. until then, i'll be watching this thread for tips and tricks on how to locate the problem. i guess, pretty much what i just said was "TTT"

06-05-2004, 07:07 PM	#3
NeCrOmAnCeR Registered User Join Date: Feb 2004 Location: Hodgenville, Ky Posts: 735	Are you putting heat conductive grease under the module when you replace it? Excess heat really does those things in!

06-05-2004, 07:34 PM	#4
mychevyii20 Registered User Join Date: Mar 2004 Location: North Texas Posts: 4	From experience, once a V8 HEI module goes, REPLACE THE COIL and rotor. Check the cap Why? Besides overheating which is rare, the thing that fries the module is high voltage getting to it. This is caused by a "leaking" coil letting spark voltage go back through the primary wires or a rotor that is letting spark ground to the shaft etc. The V8 HEI, with the coil in the distributor cap, still work when they are going bad. It is too hard to explain how to check them visually, but for the price it is good, cheap insurance. I learned this lesson in the 70's when coils where $12 and the modules where $50.

06-05-2004, 10:03 PM	#6
beaterC10 Senior Member Join Date: Jul 2003 Location: Indianapolis, IN Posts: 1,277	Thanks for the information. I used dielectric grease each time. I replaced the coil in February when it would not start. The cap and rotor were replaced last summer when I installed the 350. Since February I have replaced the coil and two modules. There is some tracking on the rotor, so maybe a new cap and rotor will solve the problem. Dave

06-05-2004, 10:17 PM	#7
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,487	How about the ground strap that goes from the coil to the harness?

06-05-2004, 10:39 PM	#8
beaterC10 Senior Member Join Date: Jul 2003 Location: Indianapolis, IN Posts: 1,277	If you are talking about the lead in the cap that grounds to the frame of the coil, yes it is there.

06-06-2004, 12:48 AM	#9
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Bad plug wires (too much resistance) can cause HEI modules to fail.



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