HEI ingnition module failing HELP!!!!

[xjmtdew]

Hi guys I've been roaming this forum for a couple of months now admiring all handy work that has gone in to the trucks on this forum and its given me inspiration to start working on my 72 again.

Here's the deal I have a 72 C-20 with a 350/700R4. Its got a Holley 2D TBI kit as well as a GM HEI distributor. The problem is that the HEI module keeps burning up. I cant keep an ignition module alive in the truck for more that 20 miles? I've rewired the distributor, put a new coil in, new spark plugs, spark plug wires, many many HEI modules, added a second frame ground to the battery, and im still back to the same problem. My question is has any one else had this much hassle with the GM HEI module and if you did what did you do to solve it?
At this point I am ready to ditch the HEI module and go for an MSD ingnition that replaces the module like this one http://www.jegs.com/i/MSD/121/8500/10002/-1 does anyone have any experience with the MSD Super HEI kit ?

Thanks for the help!!!

[Stocker]

Welcome from NorCal!

Odd problem, they are usually very reliable... I put a used GM HEI in my '72 several years ago and no issues. My only guess would be the power source. Did you run a wire from the fuse block or did you tap into another hot lead somewhere?

[Brad]

You've got some other problem. The modules don't burn up that fast. Millions of cars out there have been running the factory original for years. You'll be throwing your money away and not fixing the real issues.

[ChevLoRay]

Based on your comments, I am assuming that you are using the dilectric grease on the bottom of the module before you install it, right? That stuff is supposed to insulate the module from the hot breaker plate onto which it is installed.

[68gmsee]

Three questions:

Do you have the HEI with the ground wire or is it ground to the block through the shaft?

Have you replaced/checked the coil pack and all the internal connections to make sure they're okay?

Do you have the exact 12VDC required to run the distributor?

[Brad]

Here's a tech article that might prove useful:
http://www.autozone.com/az/cds/en_us...rInfoPages.htm

[xjmtdew]

I have rewired the 12v lead from the fuse block, That didnt work. I just recently wired a 8ga wire directly from the battery to the distributor with a switch to control the ignition.

I have used the dielectric grease... same problem

I have the module that grounds through the distributor to the engine block.

14.1 volts to at the batt when running as well as at the module!

replaced the coil twice the last time i replaced the whole distributor thinking that it could be something else ???

any other ideas ?

[tractor1963]

Originally Posted by xjmtdew

I have rewired the 12v lead from the fuse block, That didnt work. I just recently wired a 8ga wire directly from the battery to the distributor with a switch to control the ignition.

I have used the dielectric grease... same problem

I have the module that grounds through the distributor to the engine block.

14.1 volts to at the batt when running as well as at the module!

replaced the coil twice the last time i replaced the whole distributor thinking that it could be something else ???

any other ideas ?

Where are you getting the modules from?I had a problem much like that when I was buying them Advance Auto,I switched auto parts stores,no more problems.Just my .02 cents.Also,do you have block to chassis ground?or to the body?If not add them,see if it helps.

[xjmtdew]

Originally Posted by Stocker

Welcome from NorCal!

Odd problem, they are usually very reliable... I put a used GM HEI in my '72 several years ago and no issues. My only guess would be the power source. Did you run a wire from the fuse block or did you tap into another hot lead somewhere?

Originally Posted by Brad

Here's a tech article that might prove useful:
http://www.autozone.com/az/cds/en_us...rInfoPages.htm

Thanks for the article Brad I will be reading this until my eyes bleed!!

[Wrenchbender Ret]

There is a ground strap or wire on some models that goes under the coil to the center term on the inside row of the cap. Sometimes when a cap is replaced they leave this connecter in the old cap. Check that. If its ok you may have a bad plug wire causing a charge back through the dist.

[xjmtdew]

Originally Posted by Wrenchbender Ret

There is a ground strap or wire on some models that goes under the coil to the center term on the inside row of the cap. Sometimes when a cap is replaced they leave this connecter in the old cap. Check that. If its ok you may have a bad plug wire causing a charge back through the dist.

I checked the ground strap and also replaced it when I installed the new coil. As for the wires they are all brand new, less than 100 miles on them.

Thanks for all the responses.

[Pont406]

I am just curious, what did you gap the plugs at?

[Gray Ghost]

Your problem might be the pole piece inside the distributor....have you rebuilt the innards yet?

[xjmtdew]

Originally Posted by Pont406

I am just curious, what did you gap the plugs at?

I didn't gap the plugs, but I never have before? Could that cause the module to fail?

Originally Posted by Gray Ghost

Your problem might be the pole piece inside the distributor....have you rebuilt the innards yet?

I have almost replaced every part in the distributor expect the condenser and the connections. That could be my problem? I'm thinking maybe at this point just getting a whole new distributor would be the best option could save me some money and headaches!

[cdowns]

have you ever cleaned up your ground wires from the engine block to the frame and from the frame to the battery?

[Stocker]

Originally Posted by xjmtdew

I didn't gap the plugs, but I never have before? Could that cause the module to fail?

Shouldn't have any effect on your problem, no. But for the record, plugs should be gapped at .045" with HEI (vs .035" with points).

[Gray Ghost]

I had to do that last time. The rebuild didn't last very long, when we opened it up the windings were like a birds nest inside the dizzy....what a mess.

[1restorick]

Never use dielectric grease on the bottom of an HEI module. It will actually slow the transfer of heat. The heat conductive paste that comes with most new modules is the right stuff. Napa also sells it. It is white and very thick. The main ingredient is TiO2 or Titanium Dioxide. I will also say that I have seen many poor quality replacement modules. I test distributors often on my Sun Distributor Machine and find significant dwell variation with these generic modules. I have installed many MDS Capacitive Discharge boxes on GM HEI's with great results. It takes the module out completely and only uses the distributor to trigger the box. I also like the MDS replacement module the best, of all the performance versions that are offered. It's not cheap, but quality ignition parts never are. The orginal GM Modules are very high quality and typically live a long life. I would be sure to swap the small condensor with the module replacement because this could cause a potential path to ground. Best of luck.

Rick

[sweet70beast]

I always gap new plugs, you never know if they were dropped or rough handled before you got them.

[special-K]

I had a couple modules go up within a couple weeks.The second time I tore it out and replaced the pick ups,too,but it still fried.It was then I checked the two wires from the base to the in cap coil.I saw teeny breaks in the insulation and when bent saw green oxidized wires.I changed them and never had a problem.The wires I replaced them with came from a junk truck.The bad ones came on the recently bought rebuilt distributor that I paid good money for rather than use the junk one the wires came from.Yeah,ironic.

[68gmsee]

Hey, xjmtdew, any progress? I skimmed through most of the responses and looks like you have a lot of good suggestions.

On my previous post, I asked about the voltage (12VDC) but didn't elaborate. There are some instances where aftermarket modules don't have over volatage protection and can really give you grief.

Here's an excellent piece that helped me when I converted.
http://rmcavoy.freeshell.org/HEI.html

I especially noted this paragraph towards the bottom. I know you said you have a 72 but just wonder if it's possible you have too much voltage from the alternator.

Another important issue is the combination of voltage regulator and HEI module that you are using. If you have a mechanical regulator (stock on pre-71), you may have problems with burnt out HEI modules. I've heard that many replacement HEI modules (especially the inexpensive ones) do not have built-in over voltage protection. To prevent problems, either use GM (or other quality) HEI modules, or change to a solid state voltage regulator.

[ChevLoRay]

When I stated "dielectric grease" my intent was to indicate the usage of the correct compound as indicated in the post from 1restorick. NAPA has the stuff I use, and it comes in a box with 10 packages...and it ain't cheap.

[xjmtdew]

Originally Posted by special-K

I had a couple modules go up within a couple weeks.The second time I tore it out and replaced the pick ups,too,but it still fried.It was then I checked the two wires from the base to the in cap coil.I saw teeny breaks in the insulation and when bent saw green oxidized wires.I changed them and never had a problem.The wires I replaced them with came from a junk truck.The bad ones came on the recently bought rebuilt distributor that I paid good money for rather than use the junk one the wires came from.Yeah,ironic.

I took apart the dist. Yesterday and I did notice that the wires coming from the base of the dist. to the top of the cap were cracked a little inside the distibutor. These wires will be swapped out for new ones for sure.

Originally Posted by 68gmsee

Hey, xjmtdew, any progress? I skimmed through most of the responses and looks like you have a lot of good suggestions.

On my previous post, I asked about the voltage (12VDC) but didn't elaborate. There are some instances where aftermarket modules don't have over volatage protection and can really give you grief.

Here's an excellent piece that helped me when I converted.
http://rmcavoy.freeshell.org/HEI.html

I especially noted this paragraph towards the bottom. I know you said you have a 72 but just wonder if it's possible you have too much voltage from the alternator.

Another important issue is the combination of voltage regulator and HEI module that you are using. If you have a mechanical regulator (stock on pre-71), you may have problems with burnt out HEI modules. I've heard that many replacement HEI modules (especially the inexpensive ones) do not have built-in over voltage protection. To prevent problems, either use GM (or other quality) HEI modules, or change to a solid state voltage regulator.

I will have to check the voltage again when I am driving down the road. I really need to get some kind of datalogger for my laptop so I can see what the voltage is doing at the distributor. I have swapped out the old style alternator with a new GM unit so I'm not sure what type of voltage regulator that has built in, if any?



I went to the Checker near me and ordered an MSD Street Fire ignition module (early X-mas present) I figure that I will get all the parts on the distributor swapped out and then just get rid of the HEI module. I know that they are supposed to be reliable but so far in this truck I just havent seen it. The MSD should help with the fuel injection as well due to the multiple sparks. I will keep everyone updated on the progress.

Thanks everyone for the suggestions I will take all of them into consideration when I rebuild the distributor this week.