Electrical question - Truck dies while driving

[kxmotox247]

I am fully aware that this truck needs to be rewired. However, I can't afford that right now and need to find out what the problem is. I am stumped.
My 67' always fires right up. The problem only seems to happen once it's warmed up and is very inconsistant.
I can drive at 35mph or 65mph and the truck will die, make backfires (that sound like gunshots and scares the hell out of my girlfriend), the radio dies, the tach will go all the way around completely clockwise. Sometimes the truck will pick itself back up and keep running. Other times, it won't. So as soon as I feel the truck fall on it's face...I'll throw it into neutral and turn the key off.
It's got an HEI distributor. I thought maybe it was the ignition module so I grabbed one out of another old distributor. I noticed that the one in the truck didn't have any grease on it and pops said that it should...it needs the grease to actually held transfer heat out of it and into the dist. instead of cooking itself.
Anyway, the truck still has the same problem. It just seems to lose all electrical power. Sometimes it will come back on it's own, sometimes not. It always restarts. But it's definately taking the reliability/dependability away from driving the truck.
What's going on? Any ideas? Another bad ign. module? Bad Battery? Bad Ground? Ignition switch power problem?
Thanks!

[68haywagon]

With the HEI did you replace the power wire to the distributer? The original wire cuts the voltage to the distributer to help protect the points, which does not leave enough voltage for the HEI.

Just a thought.

Mike

[ChevLoRay]

Shades of my past....

I ultimately gave up on my HEI, and bought an ACCEL replacement HEI for my '69. In my case, I later determined that the wire from the pick-up coil, to the module, had broken. What I experienced was letting off of the gas, on occasions, would then be followed by the truck dying. It would then restart, like nothing was wrong. Finally, on New Years Day of '03, I was headed to get some hog jowl for my black eye peas (Southern thing, y'all) and it died. A woman pulled up behind me (I was at an intersection, waiting to turn left) and she started honking at me. I tried cranking it, but quickly smelled gas so I quit doin' that. She kept honking at me, through the second change of the lights. I went to her and told her that I'd be glad to honk her horn, if she would start my truck. While old enough to be married, she had her mom in there, too. She started sputtering and said something about me needing to buy a new truck. A policeman buddy came and pushed me into an adjacent parking lot and that was the end of that saga.

I had changed modules, twice, using the heat sink compound and was totally at odds as to why it was doing what it did. When I became convincedd that the distributor was the source of the problem, changing it was my immediate remedy and it worked. Fires hotter, now. I haven't had a fouled plug in the almost three years since it was installed.

Good luck.

[kxmotox247]

Originally Posted by 68haywagon

With the HEI did you replace the power wire to the distributer? The original wire cuts the voltage to the distributer to help protect the points, which does not leave enough voltage for the HEI.

Just a thought.

Mike

The previous owner installed the HEI. I've probably put 1500-2000 miles on it before this problem arose. I should probably check to see where the power is coming from either way. Maybe there is a break in the wiring somewhere.

Thanks...

[67ChevyRedneck]

There should be two ground wires in your distributor cap. One from the coil to the cap and another from the cap to where you plug the power and tach wires. Shifty had some good pics, but with the search down it may be difficult to find them. Mine was missing the latter wire and I fried two modules and a coil before I figured it out. My power wire had always been connected to the IGN UNFUSED slot, so that narrowed my options. Good luck with 'er.

[bejay]

if your losing the radio also when the problem occurs it has to be a power feed problem check the positive cable all the way to the starter closely for bare spots and check all connections such for loose connection at the power distribution block, make sure no wires are laying on exhuast manifold orto close to exhuast

[GasHog396]

If all the other suggestions don't help, try and disconnect the tack at the distributor. My (aftermarket) tack died a few years ago, and caused the truck to just die. No spark at the plugs at all. After messing around with it for a while, we tried unplugging the tack from the HEI dist, and it started right up. In your case, you may just have a momentary grounding problem in the tach.

[kxmotox247]

Originally Posted by GasHog396

If all the other suggestions don't help, try and disconnect the tack at the distributor. My (aftermarket) tack died a few years ago, and caused the truck to just die. No spark at the plugs at all. After messing around with it for a while, we tried unplugging the tack from the HEI dist, and it started right up. In your case, you may just have a momentary grounding problem in the tach.

Very Interesting...this is a repro factory tach. I'm going to start by checking out all my power wires.
It's so infrequent that I may not know right away. It's wierd how the tach does a full circle while the truck is backfiring. One of my dad's buddy's told him that's how tach's reset themselves...

[ChevLoRay]

On my note above, my problem began when I changed out the vacuum advance. Letting off of the gas, caused the breaker plate to move and that allowed the wire from the pickup coil to the module, to break.

I don't think that the problem I had, is necessarily what you are experiencing.

[shifty]

one other note that i haven't seen...heatsoak will cause HEI to fail. how hot is your engine running? how is your oil pressure? if your oil pressure is low or coolant is low/poor or you have blockage or hte thermostat is dying, these things will cause higher temps in the engine compartment and if your HEI gets too hot, it stops working. had this happen with one of my older engines. when i would get up in the 190-220 range sitting in traffic, HEI would give up the ghost. never foudn a way around it.

[long67]

replace your ignition switch. I had the exact same problem, blew up two mufflers before I found prblem. The back of the switch was separating from housing. Loss of power to everything.

[jlmtrout]

I blew up a pair of mufflers also, but my problem was the tach wire was shorting against the the wire to the ignition at the cap. I would turn a corner, give it some gas, lost power and the backfire occurred when the wires separated. I put male/female connectors about 6 inches from the cap because it was so difficult to connect the wires to the cap because of the blind angle, and that was where the wires were shorting. I covered the connection with tubing to prevent this from happening again. Just my .02 worth. Good luck and keep on truckin'........Jerry

[NPilot1975]

Didn't read through all the suggestions, but ensure you are not running the original ballister on the firewall with the HEI distributer. Points style ignition systems required it, your HEI does not. When they go bad you will get and loose power, plus it rduces the power to the distributer.

[kxmotox247]

I wasn't able to check on it last night but I'm pretty sure that the HEI power is not the power from the points system.
The wiring on this truck leaves a lot to be desired. I already had one near-miss fire incident and had to rewire the front light harness.
Thanks for the suggestions.

[kxmotox247]

Originally Posted by rick980

Fuel pump...when it warms up, I had that problem. Doesn't sound the same mine used to just die and then start then die then start......new fuel pump and voila.

Seems like a possibility but I don't see how the electrical cut-out occurs. I've got some diagnosin' to do.

Thanks for everyone's help!

[too much stuff]

Went through the same problem on my 69 recently. Was converted to hei before i bought it. No rhyme or reason, it would just die when it wanted to. Always started up again. Put a new ign switch and key in and had no problems since.

[walker]

Had the same problem with my '67. I finally found out that the spot in the fuse box I was using (ignition unfused 12v) had a bad conection on the back of the fuse box. I had taken off the body plug and cleaned that, as it had a lot of green corrosion in it, still no go. Then I pulled the fuse box apart, so you could see the part behind the fuses and there was rust galor! After an hour with a wire brush and WD-40, and a new female spade terminal, it is now giving me 12 volts all the time. i also now get a full 12v to my HEI. It is worth a look anyway.