vengence99

i put one of those gm hei module's in my 75 van. it runs good with it in, but i am a little worried because i used a test light and i have power to both neg. and pos. coil post's. i'm no great mechanic but that does'nt seem right. a little help would be helpful.

440roadrunner

I BELIEVE that when an HEI is not firing (key on, engine off) it leaves the coil neg. "open." This would result in battery voltage being present on coil neg. If it runs OK I would not worry

One concern is that you have the dist. pickup coil hooked correctly. If there is any doubt, I can go look at mine, which also uses a Mopar (actually Accel) distributor and HEI module.

If you reverse the pickup, it "moves" the timing enough that the rotor and plug towers do not line up, otherwise known as "rotor phasing."

vengence99

thank's. i had a back-up module and pluged in. it didnt work. is there a way to check the module? i got these from the junk yard so who know's thier true condition. i just dont want to fry anything. i got alot of money and work into this thing. so far i've put on full lentgh headers, high-rise air-gap manifolr, 625 carter afb, new dist, alt. tranny kits, b&m shifter, race seat's, complete interior, all new tire's and more. fund's are running low now so i need to be careful. thank's for the reply.

440roadrunner

Can you detail how it's hooked up? What dist. are you using, IE stock Mopar breakerless, or what? If Mopar, have you set the reluctor gap?

One VERY important point is that the module MUST be grounded. The two mounting screws serve this function.

Here's one poorly drawn diagram, but it is accurate, from this page:

http://duster318.freeservers.com/tech/hei.html

You are looking at the top of the module (metal plate on back) as shown, "dished up"

Top left terminal goes to coil+ and switched ignition power from key

Bottom left goes to coil - and tach if used

Top right goes to pickup coil and REGARDLESS OF COLOR goes to the female shrouded terminal at the distributor

Bottom right goes to other pickup coil, and regardless of color goes to the male exposed terminal of the distributor.

IT IS IMPORTANT to hook both the original dark blue "ignition run" (ign 1) AND the brown "bypass" (ign2) which were originally hooked to opposite sides of the ballast.

"Ignition run" generally does NOT become hot when using the key to "crank." Only the brown bypass wire is hot during "crank."

vengence99

the web address you gave is the diagram i used. i'm using a stock elec. dist. i bypassed the ballest and ran a jumper wire, the other wire is running the volt. reg. both wire's are ran to the pos. side of the coil. i also grounded the module to the tranny bell housing

440roadrunner

You are aware, also, that you must mount the HEI module flat on a surface, with dielectric (heat conductive) grease to keep it cool?

Also, check your incoming voltage, key on, engine off. If it's somewhat lower than battery, I'd "hot wire" the coil pos with clip leads to the bat until you get the voltage drop sorted out.

Other than that, check the gap in the reluctor