HEI Problem
 

I have sent a pic of the ?

Re: HEI Problem
 

Check the module bolts in the distributor below the rotor button.

Re: HEI Problem
 

Could be a bad battery or weak alt. What happens if you add jumper cables? dIrect wire the dizzy to the battery to make sure it ges a pull 12v and see what happens.

Re: HEI Problem
 

Hei needs full 12 volt power supply, you really need to run the pink wire from the ignition switch ( hot ) direct to the HEI, other issues that could be there, bad contacts at the coil on top of the distributor, and or bad module.

Re: HEI Problem
 

In order for HEI's to work/operate right they need a full 12 volts...I am not entirely sure on a direct 12 volt source that tunrs on and off....maybe somewhere in the ignition switch? I have my hei dizzy hooked the one of the starter solenoid studs and it performs fine...I am going to try an hook my new one up to a better source when I put it on. Yer coil could have gone out as well. Hope yer able to figure the issues out with ease.

Re: HEI Problem
 

The battery is new. I will run a wire from the battery to the dist. and see what it does.

Re: HEI Problem
 

the wire to the disturb tor needs to be I think 14 gaqe or bigger. if it was not changed and used the original wire it would not bring enough juice to the distributor.

Re: HEI Problem
 

I bought wires for the dist. today. They have the connectors on the ends that go into the dist. One for volts, and one for the tach. The volt wire is 12 gauge. I got them at NAPA. When I run the new wire to it should I put in a inline fuse? And, if so what amp?

Re: HEI Problem
 

No. do not put a fuse in the ign. system.

Re: HEI Problem
 

Thanks

Re: HEI Problem
 

If the truck was running fine and now it's not why would the wiring hook up be wrong. It has to be something that has failed or come loose. Pull a plug wire and check for spark first.

Re: HEI Problem
 

GRS original post said it was coming from the firewall plug, ( resistor wire....?, only getting 7 volts ) he needs direct from the ignition pink wire. Plus those plugs have always been a source of failure with resistance and corrosion.

Re: HEI Problem
 

The rotor my have a hole burned thru the middle of it. It will ground the coil to the top of the distributor shaft. It's a common problem when the plugs get warn.
In 1975, when the HEI became standard in everything (74 for Corvettes), the spark plug gap was .065. A GM service bulletin came out to change the gap to .045 because of holes burned thru rotors.

Re: HEI Problem
 

There are several things that could be wrong here, and the low voltage would be the most likely source. But simply re-wiring it may not cure the problem. The module or the coil could either one be burnt up from the low voltage source.
Another, often overlooked possibility would be the grounding. I have seen in in extremely rare instances where a ground wire needed to be added to the distributer, because for whatever reason, the distributer wasn't grounded good to the intake. I think this is really a long shot, but worth mentioning.

A lot of the auto parts stores can supposedly test modules and coils for you, unless you know how to yourself. I would thoroughly test the parts, before just replacing things.

Re: HEI Problem
 

When I crank the truck to start it. I get 7 t0 8 volts to the hei. When it is in run position with the key on it is 12 volts. I have replaced the module, cap, and rotor. I may just go ahead and replace the coil too before trying to start it. And I am going to run a 12 gauge wire from ing. switch , or fuse to the hei.

Re: HEI Problem
 

Check or replace the pickup coil. They are known to fail as the wires are constantly flexing as the vacuum advance works.

Re: HEI Problem
 

I wouldn't keep throwing parts at it until you get the voltage problem fixed. HEI will not operate on 7-8 volts and if it does, it won't for very long.
Diagnostic 101 will tell you to verify you have sufficient voltage and ground first, then test the components.

While cranking do you have a pulse to the coil from the pickup module?
is the coil ground strap good?
Do you have no spark at all, or just a very weak spark?

This is what you need to know before replacing parts-what's working and what is not.

Re: HEI Problem
 

Concur...get the right and steady voltage in an out of it first.

Re: HEI Problem
 

I will run a 12 gauge wire with 12 volts tomorrow. How can I check the module?

Re: HEI Problem
 

Check the ground strap at the coil, its a bent flat strip of metal under the cap. They have a tenadancy to corrode and fail. You can also OHM check the pick up coil by disconnecting the module and testing between the green and white wire at the right side of the module with an OHM meter. I have never trusted aftermarket modules in HEI dizzys and recently Ate crow when I broke down and had A GM module sitting at work. A 40 mile tow , a GM module install And a re wire of the bulkhead connector and I was on the road. Not saying it's the module, but there are millions of fAilures with the aftermarket ones.

Re: HEI Problem
 

I lost a starter [cranking and cranking to get it to fire] due to one of those hi perf crappy aftermarket modules made from china no doubt..

Re: HEI Problem
 

I just received my new HEI from SpeedMaster. 65K coil. I am thinking of running a 12 gauge wire from the battery to a 50 amp switch, then to the distributor. That should be enough voltage?

Re: HEI Problem
 

Are you talking about wiring your HEI thru a relay? If so, yes that should work. Just control the relay from your ignition switch.

Re: HEI Problem
 

Why would you not just wire it to the ignition switch?
The ignition system will not draw anywhere near 50 amps.

Those high power ( or advertised as such) ignition systems are really a wasted effort, unless you have the engine to really need it.

Re: HEI Problem
 

Ok...I'll try that. Yer talkin to someone who is electronically illiterate...well..maybe not That bad...but...lol! Thanks. :chevy: