The Stovebolt Site Forums The Shop Area The Electrical Bay Bad ignition module symptoms?

Does anyone know the symptoms of a bad HEI ignition module? My truck is skipping and popping when I step on the gas. When I double checked the timing my light was missing a beat every 3 or 4 flashes. I ran a wire from the battery to make sure it wasn't my soddering job in the ignition switch and It ran the same. I have only had the hei for a couple of mounths and have hardly ran it.

That's not a symptem of a module. Sounds like cap or rotor or plug wires. Possibly carboned up plugs.

I've found that the module does only two things:It works or it doesn't, nothing in between

everything is about 3 months old with maybe 10 miles on it but I am going to check it all out again

That's a fact.

I think it is number one spark plug,did you check it ?

sounds like you may have bad wires or check your firing order 2 mixed up wires can play havic onya rick

6-cylinder or V8? Either way, try triggering the timing light from the #6 spark plug wire instead of #1. The timing mark will appear at the same place, just one turn of the crankshaft out of phase, and if it's a plug or wire problem, the triggering error will go away. A quick check on the HEI module can be done with a heat gun and a can of Freon refrigerant. Hit the distributor housing with a full-hot blast from the heat gun to stress the module, and if it dies or misses, hit it with a squirt of liquid refrigerant for a quick cool-down. A cold module will usually start working OK again for a short while. I've isolated modules that were on the verge of failing with that procedure several times.
Jerry

One thing I found years ago when the HEI was first being used was that the wires coming out of the pole piece would work loose and when things turned they would cut in and out. Take the cap off and then take off the rotor. Check the small wires coming out that go up to the module plugin. Make sure they are in and secure.

If the timing is correct and it runs good otherwise, I'd be inclined to check that the advance is working properly.

Bad ignition modules will first start giving problems like working when cold, and not working when warm. This will only be once or twice before it doesnt work.

Jerry covered the technique for checking it at the shop (vs out on the road using icecubes from the cooler)

Ok. I checked the wires inside the cap and the double checked that I had the firing order correct. I pulled two plugs and they looked ok. A little black because the truck is running to rich. I connected my light to the number 6 wire and had no flashes at all. I moved it around some and it started flashing but not as it should. I double checked the light on car to and it works fine. I don't have anything to freeze the module with but the truck runs the same hot or cold. the timing is set to 10 deg. btdc and the advance is moving freely. I dont know how to chech if the vacuum is advancing it properly. When I hook the line up the timing changes. Its a 61 with 283 and distributor, plugs, wires, cap and roter are all new. bad coil? not enough power to run it? I did have it running almost perfect after I put this in.

Pull a plug wire & stick a piece of metal in it or pull the boot back. Set it a short distance from the engine with insulated pliers. If this system is working right it should throw a spark like a bolt of lightning. Be careful it will bite. If the timing changes when you hook the vacuum line to it the vacuum advance is OK. If the timing advances as you run the engine faster then the mechanical advance is working. Set the initial timing with the vacuum hose off.

Check the voltage coming to the HEI from the ignition switch. If you haven't run a heavy-gauge wire all the way from the switch to the coil you're probably trying to run your HEI ignition system on about 9 volts. There will be a ceramic resistor, or a nickel-chrome wire from the ignition switch to the coil that drops the voltage to the original coil. That circuit MUST be bypassed for the HEI to work properly. Find the terminal at the back of the ignition switch that powers the coil in the run position, and install a #10 wire from there to the HEI coil input terminal. Just disconnect and tape off the power wire that went to the original coil.
Jerry

I did that when I installed the hei. I picked up that tip on here. I also ran a wire straight from the battery the other day to see if it made a difference and there was no change. I will try the spark test on monday night. thanks guys

It appears that you've been through most of it. I think I might give the pick up coil a check. It's more likely to act retarded off and on than the ign. module imo...

Ok, I did the spark test and it was a nice consistent spark at about 1/2 -3/4 of an inch away from the manifold as I eased back it would spart to look just like my timing light. It looks good to me but Im not sure how far it should jump. FYI make sure your pliers have real insilation. the first set had some kind of rubber but I guess wasn't good enough. Just enough zap for a good laugh though.

Will the plugs being fouled cause the timing light not to flash. I pulled one out again and cleaned it as best I could and the light worked like a charm for about 30 seconds and then went right back. When I pulled the plug again it was already powdery and black. I have been having trouble with the carb but i was trying to get everything else right so I tuned it in correctly. Im going to take them to work and sandblast them

It was the plugs. New doesn't always mean better. back to the carb.........

I had problems with my mallory electronic dist ( no points) on
my 52.....drove me crazy , sometimes it would go for months with no problem, crazy symptoms........even did the check Mallory required, showed to be ok .........I decided to change the module
and there the problem was..........no more problems after that..

here is a pix of it..

so I would say the module can be intermittent.....