HEI issues?

[zachste]

So driving yesterday was fine for about 10 minutes, came to a stop light slowing down, and truck shuts off like I turned the key off. Try to crank it back over and just cranks and cranks (sounds normal though). 1 minute later on the phone with the wife to come pick my boy up (he was riding with me), and I turn it over and it fires up.
Finish my trek a mile to Home Depot, return some lumber. Fires right and runs great when I'm leaving. Stop at the grocery store and fires right up leaving there as well as the rest of the way home.
Took it out again later that night to run a couple errands and ran like normal.
Did some poking around, no loose grounds, or hoses, or plug wires or anything. I am going to re-check the wiring and connectors on the distributor tonight, and maybe another look at the grounds.
After doing some searching I'm thinking maybe an HEI issue? ICM?

350/350 (thumpr cam, edelbrock carb, 2k stall converter and shift kit)

['68OrangeSunshine]

Module.

[truckster]

Originally Posted by '68OrangeSunshine

Module.

X2. I've chased an intermittent module for weeks before.

Make sure you use the heat transfer paste under it when you replace it.

[7tee]

Yep x3 on the module, been there...

[toolboxchev]

Also check the main power feed at the buss bar on your horn relay. Whether it be located under the dash or on the radiator support drivers side backside of the headlight.

[anew4961]

may be the pole piece has a broken wire gm. hei system were known for this. take the module out the two wires on the pole piece check with ohm meter move wire back and forth check to see if you loose resistance. if it does you need a new one

[zachste]

Originally Posted by '68OrangeSunshine

Module.

Originally Posted by truckster

X2. I've chased an intermittent module for weeks before.

Make sure you use the heat transfer paste under it when you replace it.

Originally Posted by 7tee

Yep x3 on the module, been there...

Thanks guys. Any brand or kit recommended over others?

Originally Posted by toolboxchev

Also check the main power feed at the buss bar on your horn relay. Whether it be located under the dash or on the radiator support drivers side backside of the headlight.

Originally Posted by anew4961

may be the pole piece has a broken wire gm. hei system were known for this. take the module out the two wires on the pole piece check with ohm meter move wire back and forth check to see if you loose resistance. if it does you need a new one

Thanks for the tips guys check these out as well.

[Steeveedee]

Someone has posted a complete troubleshooting flow chart around here somewhere. Don't just throw parts at it without actually diagnosing the problem. #1 problem I have seen with the HEI is the rotor has burned through. This doesn't cause an intermittent stalling scenario, your truck will just run badly. #2 is the module. That troubleshooting flow chart shows how to check that. In all my time, I've seen only one pickup fail.

[zachste]

Originally Posted by Steeveedee

Someone has posted a complete troubleshooting flow chart around here somewhere. Don't just throw parts at it without actually diagnosing the problem. #1 problem I have seen with the HEI is the rotor has burned through. This doesn't cause an intermittent stalling scenario, your truck will just run badly. #2 is the module. That troubleshooting flow chart shows how to check that. In all my time, I've seen only one pickup fail.

Oh nice, I'll do some searching and try to find the flow chart.

[geezer#99]

Do you have a dedicated 12v supply to your hei?

[RichardJ]

The starter is cranking the engine over, so it's getting 12 V to the ignition switch. If that circuit gets its 12 V by way of the horn relay as a junction block, wouldn't make any difference. The ignition switch needs to connect that 12 V to the Ignition circuit as well as starter solenoid.

The HEI modules are incredibly reliable. I'd check to see if you are getting the 12 V from that 50 year old ignition switch to the batt terminal on the HEI.

Unlike pertronix modules which have a reputation for intermittent problems, any HEI failure that I have ever heard of, including one of my own, when they die, they die.

[geezer#99]

If the resistance wire from the ignition switch to the distributor is still being used then he won't have 12v. Likely nearer 7v which causes undue heat in the module.

[zachste]

Originally Posted by geezer#99

Do you have a dedicated 12v supply to your hei?

Not sure, I'll have to do some testing/digging, as I didn't build the truck.

Originally Posted by RichardJ

The starter is cranking the engine over, so it's getting 12 V to the ignition switch. If that circuit gets its 12 V by way of the horn relay as a junction block, wouldn't make any difference. The ignition switch needs to connect that 12 V to the Ignition circuit as well as starter solenoid.

The HEI modules are incredibly reliable. I'd check to see if you are getting the 12 V from that 50 year old ignition switch to the batt terminal on the HEI.

Unlike pertronix modules which have a reputation for intermittent problems, any HEI failure that I have ever heard of, including one of my own, when they die, they die.

Originally Posted by geezer#99

If the resistance wire from the ignition switch to the distributor is still being used then he won't have 12v. Likely nearer 7v which causes undue heat in the module.

Sounds like it's time to grab a multimeter and start testing some stuff.

[zachste]

Think I may have found the culprit? Blue wire was very loose. Pushed back up in a bit and tried starting and it wouldn't start. Came right out when I gave it a light pull.

[zachste]

Or is that just a tach wire?

['68OrangeSunshine]

Tach wire is the one in the back [in this orientation]. The terminal we see in the ''front'' is/should be [BATT +] 12 VDC hot Ign "ON" wire from 12 volt source. I would crimp a new connector on the end to minimize intermittent contact.
In fact, if it was my truck I'd replace the blue line with a fresh 12 ga wire in red, add a Packard [locking] connector and run the feed end of the red line from IGN UNFUSED in the fuse block on the cab firewall.
You can get sets of ''Batt'' and ''Tach'' connectors, each with a color coded 12'' wire lead, for pretty cheap from Jegs or Summit. Red for BATT, Black or Brown for TACH. They slot right into the HEI cap and have extra tabs to prevent mis-connecting in the wrong slot. Jeg's p/n: 555-10552, $11.53.

[zachste]

Originally Posted by '68OrangeSunshine

Tach wire is the one in the back [in this orientation]. The terminal we see in the ''front'' is/should be [BATT +] 12 VDC hot Ign "ON" wire from 12 volt source. I would crimp a new connector on the end to minimize intermittent contact.
In fact, if it was my truck I'd replace the blue line with a fresh 12 ga wire in red, add a Packard [locking] connector and run the feed end of the red line from IGN UNFUSED in the fuse block on the cab firewall.
You can get sets of Red ''Batt'' and Grey ''Tach'' connectors, each with a color coded 5'' lead, for prett cheap from Jegs or Summit. They slot right into the HEI cap and have extra tabs to prevent mis-connecting.

You're saying the blue is the power wire? I thought it was power wire in back, tach in the front. After pulling it out from the connector, tried putting it back in and crimping. It actually fired right up, like a dummy I tried the multi meter while running and it died as soon as I grounded it. Started back up, but tried to rev it a tiny bit and it cut out and died. Started back up though. I seem to be causing more problems for myself here. Wiring tends to be out of my wheel house. Unless it's just a bad connection on the batt side.

[Steeveedee]

You want a fat and sassy wire to the power on the HEI coil. You can also buy that pigtail mentioned at Autozone or O'Reilly's. Also, as has been mentioned, look for an IGN Unfused connector. When cranking, the ignition switch sends power to the starter only, in this year truck. In it's original configuration, your truck had a (yellow) wire coming from the the "R" terminal on the solenoid that fed the coil power during cranking. That blue wire has enough resistance to give you grief, as has been noted. It's entirely possible that that blue wire is fed power through the factory resistance wire. I've seen that. The vehicle runs much better when the ignition gets enough 'trons.

['68OrangeSunshine]

Originally Posted by zachste

You're saying the blue is the power wire? I thought it was power wire in back, tach in the front. After pulling it out from the connector, tried putting it back in and crimping. It actually fired right up, like a dummy I tried the multi meter while running and it died as soon as I grounded it. Started back up, but tried to rev it a tiny bit and it cut out and died. Started back up though. I seem to be causing more problems for myself here. Wiring tends to be out of my wheel house. Unless it's just a bad connection on the batt side.

Good catch. OK you got me, I was just shooting from memory, I should've double checked. Looking at RichardJ's post #22, the correct orientation is shown.

But intermittent on the Tach line shouldn't have affected ignition. That's what threw me off.
By ''wheel house'' do you mean the engine bay, at the bulkhead terminal block? Or the cab. [Kind of a salty nautical handle for a truck cab if it is. lol]

I'm referring to pulling a tap off the inside-cab fuse block. Just easier to get to.

Yes, a female terminal taps into a recessed positive terminal in the fuse block.

Without getting obsessively technical-- the 20 ga. Orange/White/Purple wire coming out of the bulkhead connector on the drivers side firewall, feeds nominal 12 VDC at start, then, being a resistance wire, increases resistance as it heats up and cuts down to 9 - 7 VDC, to keep from burning up the points. HEI modules fed voltages under 12 VDC heat up and fail. At the other end of the resistance wire it splits into two 20 ga Yellow lines, one to the Coil positive terminal and the other to the starter. No longer needed in the HEI system.

[zachste]

Originally Posted by '68OrangeSunshine

Good catch. OK you got me, I was just shooting from memory, I should've double checked.
But intermittent on the Tach line shouldn't have affected ignition. That's what threw me off.
By ''wheel house'' do you mean the engine bay, at the bulkhead terminal block?
I'm referring to pulling a tap off the inside-cab fuse block. Just easier to get to.

By out of my wheel house I meant out of my comfort zone doing electrical stuff. More comfortable doing suspension, body/paint work, those kinds of things.

So I checked, that black Batt power wire already runs to the fuse block.

Would pushing that multi meter almost through that power wire possibly cause new issues? The truck started again, but sounds like it's trying to suck too much air when you tap the throttle, to the point if you press it too hard it will stall out. Seems to idle alright for a bit though. I have a video but have to get it uploaded since the photobucket BS.

[zachste]

Originally Posted by '68OrangeSunshine

Tach wire is the one in the back [in this orientation]. The terminal we see in the ''front'' is/should be [BATT +] 12 VDC hot Ign "ON" wire from 12 volt source. I would crimp a new connector on the end to minimize intermittent contact.
In fact, if it was my truck I'd replace the blue line with a fresh 12 ga wire in red, add a Packard [locking] connector and run the feed end of the red line from IGN UNFUSED in the fuse block on the cab firewall.
You can get sets of ''Batt'' and ''Tach'' connectors, each with a color coded 12'' wire lead, for pretty cheap from Jegs or Summit. Red for BATT, Black or Brown for TACH. They slot right into the HEI cap and have extra tabs to prevent mis-connecting in the wrong slot. Jeg's p/n: 555-10552, $11.53.

So I looked on the coil cover, and confirmed, the blue wire is the Tach and the black wire is the Batt. I think I'm going to heed the advice to run a new 12 gauge wire from the fuse block to the HEI. I'm also safe to assume the module is burned up due to undue heat from not receiving enough volts correct?

[zachste]

There should be "male" connectors for the female end to plug into the fuse block correct?

[GASoline71]

With an HEI... always carry a spare module and some heat sink grease. Do not use dielectric grease on the back of the module.

Gary

[Stocker]

Originally Posted by GASoline71

With an HEI... always carry a spare module and some heat sink grease. Do not use dielectric grease on the back of the module.

Gary

That's been on my to-do list for years. One of these days I might get around to it before I get bit....

[toolboxchev]

If you need more help check this: http://www.crankshaftcoalition.com/w...EI_distributor

From the bottom of the page additional informative links:

Resources

Spark plug cross-reference
Exploded view of an HEI distributor
Ported vs. manifold vacuum
GM HEI rebuild, install info
GM HEI distributor notes, etc.
Description of an HEI rebuild

Return to: Distributor shaft end play adjustment, above

HEI vacuum advance specs
GM points-type vacuum advance can specs and info (Lars)

Return to: Vacuum advance, above.

Crankshaft Coalition wiki articles:

Firing orders of various engines.
Several articles on valve adjustment
Carb vacuum port ID
How to install a distributor
Determining top dead center
How to find the number one cylinder in an engine
How to make a timing tape
Timing tabs and damper TDC lines SBC
Estimating timing chain wear
How to make a timing tape

Here is another accurate source of info: http://www.hotrodhotline.com/md/html/ignition.php