47-59 Smoking Ignition Wires….Exciting stuff!

[SanJosesSteve]

My 59 GMC was converted to an HEI ignition a few years ago. Last year I dropped off the truck at a machine shop to rebuild the engine. 13 months later I get it back. Drive it home and notice that the white ignition resistor on the firewall had a scorch mark burned into it between the 2 screws. Then I remember that there was a jumper wire there per the HEI installation instructions.

Truck runs great for about 150 miles then quits on me on the freeway. Slight acrid smell and ignition is dead. Nothing looks amiss, but I swap in a new HEI module as I had one on hand. No start. I install a new jumper on the ignition resistor and the truck starts right up. Runs great for a minute while parked, then smoke starts pouring out of the dash.

Purple, pink and green wires melted at the switch. Purple was the worst…(odd that I have an original floor starter.) Replaced melted wires, Ballast Resistor, HEI module and no start. Resistor is hot. Suspect the shop reinstalled something incorrectly. Any idea where I should I start looking? Have extinguisher at the ready! -Steve

[geezer#99]

You don’t need a resistor to use an hei.
Eliminate it.
Run 12v to the distributor is all you need.
Maybe your ignition switch is faulty.

[RustyPile]

I don't have a '59 GMC wiring diagram at my disposal so I have no idea what circuit those burned wires serve. I doubt if the HEI distributor is the source, only a victim of the "fallout".. Power wire feeding the distributor should be at least a 14 gauge wire, preferably a 12 gauge.. Do away with the ballast resistor, it's jumper, and associated "light duty" wiring. .

As bad as those wires are burned, I'd think something is shorted directly to ground. IF that purple wire is designed to activate the starter solenoid and you have a foot operated starter, I'd start there.. A burned wire is easy to track down -- just follow it from end to end.. One end will be the power source and the other end (where the burning stops) is the source of the short... Fuses, fusible links and circuit breakers are designed to protect wiring from this sort of damage. Your truck has none of these safety devices -- get that corrected ASAP...

[mr48chev]

Originally Posted by geezer#99

You don’t need a resistor to use an hei.
Eliminate it.
Run 12v to the distributor is all you need.
Maybe your ignition switch is faulty.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
THIS!!!

Hei does not need nor use a resistor

[1project2many]

In the old days the resistor was used to reduce current through the points. On one side would be a red wire from the key, and maybe a brown wire to an optional electric wiper motor. On the other side would be two green wires. One green wire was connected to the coil. The other was connected to a special terminal on the starter. During cranking, power from the battery cable at the starter would be routed directly to the coil, bypassing the resistor and boosting spark to the engine.

I'm curious about where the green and purple wires in your picture go. Connecting HEI through the resistor can make the resistor hot but I would definitely track those other wires down to see what they're connected to before removing the ballast resistor.

[mr48chev]

This might well be a good investment https://oldchevytrucks.com/elw59.html

There should be a wire runnng from the IGN on the switch to the HEI and as far as ignition that is it with the stomp pedal starter.

With a 59 V8 with a key start you have the purple wire going the S post of the starter and a resistor Bypass wire running from the R post of the starter to the coil side of the resistor. That is because when you start the truck with the key you bypass the resistor to have 12 volts to the coil to start and the Ign post on the switch doesn't have power when you are cranking with the key.

I've looked at a number of GM trucks and cars that were freshly put together that wouldn't start when you cranked them with the key because there was no power to the IGN post meaning no power to the coil because the bypass wire wasn't hooked up. The last one had had an HEI swap on a V8 and because they removed the resistor and ran a new proper gauge wire from the switch to the coil they also removed the bypass wire and weren't getting any power to the distributor when cranking.

Thank 1project2many for this one that he posted in 2014. Scroll to post 12.

https://67-72chevytrucks.com/vboard/...d.php?t=643672

It looks like the green wire was the actual ignition wire.

[mr48chev]

Green to resistor should have been your ignition wire

Purple to coil side of resistor should have been the resistor bypass wire.

Red going back in from coil side of resistor makes no sense. That should have gone to the coil or coil post on the HeI. Where did the red wire go to inside?

The way you had it with the jumper wire across the resistor shold have worked fine unless the red wire is your jumper wire and I am missing the wire to the distributor.

[fauXGT]

The infamous GM purple ignition wire meltdown. Happened to my dads 58's and my '91 S-15.
I just upped the gauge to 12 to save the current draw overheating.
The later didn't have the resistor, but have heard time and time again of the purple wire issues.

[franken]

Something on an unfused or with no fusible link shorted would be my guess. Maybe both.

[SanJosesSteve]

The red and one of the green wires from the resistor run across the dash to the firewall connector on the passenger side of the truck. Other green runs to the ignition switch. Pink one as well. Purple wire runs from ignition across the dash to the firewall connector as well. Will investigate where they go from there tomorrow.

Really reluctant to eliminate or bypass the resistor again as that’s when all the fun started last time! I have the wiring diagram from the shop manual, but it depicts a starter solenoid which I don't have. Pretty confident it was built this way though. Gramps bought it new in 59. Cheapest one on the lot. Not even a heater in it. He put 92K on it before I got the keys in 93. Thanks, -Steve

[mr48chev]

Originally Posted by fauXGT

The infamous GM purple ignition wire meltdown. Happened to my dads 58's and my '91 S-15.
I just upped the gauge to 12 to save the current draw overheating.
The later didn't have the resistor, but have heard time and time again of the purple wire issues.

The purple wire either fails because the solenoid is taking too many amps to kick the starter in. Or because it comes in contact with the exhaust manifold because someone changed it's route when they were working on the starter.

This lavender/purple wire in his photos is the resistor by pass wire. That should fasten to the stud on the stomp pedal switch.It may run up into the cab and back out though the gromet,

1 diagram that I found for 59 GMC six cylinder wiring said that wire should be yellow. That one didn't have the rest of the wiring from the switch so I didn't use it.

[franken]

Yep, too much current melts stuff, get a bigger wire.

[mr48chev]

OK you said you had an HEI. WHAT hei do you have? GM converted to run in the GMC or an aft?

Has the truck been converted to an alternator"

Show us a photo of the side of the engine showing the distributor and wiring to it or what is left of it.

Show us photos of the left side of the engine (compartment) showing the red wire and where it goes.

To me that looks like the one of the wires shorted out on somthing or was hooked to a ground causing a short when you turned the key on. Shorts under the dash of an early Chevy/GMC truck can happen any place a wire passes over the edge of a sheetmetal piece. Usually under the dash. Most often because it rubbed.

To me that red wire has absolutely no possible reason to be connected to that side of the resistor. The only wire that should connect there except the wire to the coil is the resistor bypass wire from the solenoid. Nothing on the truck has a reason to be connected there except those two things. I'm thinking someone got lazy and connected a wire to the alernator or regulator there rather than where it should have been connected and then it was connected on the wrong side of the resistor.

Going back to your first post, Resistors ALWAYS GET HOT because they provide a resistance just as the element in an electric heater does. Basically they are a heating element.

Secondly, unless you have some off the wall aftermarket "HEI" rather than a converted GM HEI you shouldn't need a resistor at all. That is the first thing in instructions for converting to HEI = do not use a resistor.

Disconnect and tuck that red wire out of the way, It has no business being there and you can figure out what it was supposed to be doing later and connect it to the correct spot then. The correct spot is most likely a junction block or the back of the ignition switch.

Show us those photos of the distrbutor side of the engine and the wiring from the solenoid/starter and the left side of the engine hopefully showing where that red wire goes.

[57tailgater]

I agree the HEI probably doesn't need the resistor. On a points ignition I had one resistor start smoking because I had a short. Fortunately I was sitting and was able to find the short quick which was down by the starter.

[mr48chev]

Originally Posted by 57tailgater

I agree the HEI probably doesn't need the resistor. On a points ignition I had one resistor start smoking because I had a short. Fortunately I was sitting and was able to find the short quick which was down by the starter.

That short would have been down stream from the resistor though. Either at the resistor it's self or at the coil.


I'm thinking that his burned wires are partially due to too many cooks who aren't very good cooks adding stuff to his stew.

That red wire was someone's idea that they could pick up switched power there rather than get up under the dash and connect to the ignition switch as they should have. Then they connected it on the wrong side to boot. There is no viable reason to connect another wire to that spot except the coil wire and resistor bypass if needed. With direct 12 Volts from the switch to the HEI he shouldn't need the resistor bypass at all with the stomp pedal on that truck because it is Key on, stomp on the pedal. V8 or changed to an electric solenoid setup and key start and yes you do need the bypass because those switches don't put power to the coil in "start" mode.

[SanJosesSteve]

I followed the purple wire, it runs to the stud on the side of the of the starter stomp switch. Red wire off resistor runs to lower right leg of the HEI module. 1 green wire runs to ignition switch and the other runs to the positive post on the coil.

Now the zinger….. the pink wire off the resistor. It has continuity with the body! I disconnected it from everything but the segment to the Tell-Tale Lamp (where it’s color changes to brown) and the ARM terminal on the voltage regulator. Original generator was rebuilt along with the motor and new voltage regulator installed. I think this is part of the problem. There should be no continuity between the ARM terminal and the body right? It got dark so I had to punt further investigation to tomorrow morning.

[geezer#99]

Where’s the pic of the distributor?

[SanJosesSteve]

Here is the distributor, the wiring diagram and the link to the kit. All worked well for years until the machine shop did the tear down and reassembly.
Still wondering about the continuity implications…..
http://devestechnet.com/Home/HEIInstall

[geezer#99]

Not an hei!
The discussion about wiring is all fubar.
Would have been nice to see exactly what distributor in the beginning.

[SanJosesSteve]

It is….. the pickup and reluctor are hidden under the modified original distributor. It’s made to look like stock but isn’t. Verbiage from the kit…….

“ This HEI Kit installs in your stock distributor with no modifications to your vintage distributor. It's a breakthrough that allows us to have the same precise ignition system as the more modern vehicles while maintaining the vintage look!”

[geezer#99]

Just like a pertronix.
But you say hei and this big cap one comes to mind by everyone.
Confusion then reigns supreme.
Here’s an hei for a 250. Not sure if one is available for a 235.

https://www.amazon.ca/Team-Performan...075SNZ6FJ?th=1

[SanJosesSteve]

I couldn’t find one off the shelf for my GMC 270 when first looking. This kit was the closest I could get. Still, it worked for a few years until torn down by the machine shop. Could be a coincidence but I’d bet against it.

[mr48chev]

The instructions clearly state that you either bypass or eliminate the the resistor.
The only reason for keeping it is that you are carrying the distributor pieces, points, point plate, condensor an whatnot to convert it back to points if the hei module fails. Other than that there is no reason to have it on the truck except to serve as a connection point for wires but then if you have someone else work on the truck they might screw it up again thinking that it is hooked up wrong because they are thinking points.

Since you are not running points and a resistor and you have a stomp pedal, you do not need or want the resistor by pass wire (lavender) remove it.

I don't know why you have that snake pit of coiled wires but I would trim each to a comforable length and put a new terminal on the end. That is just messy clutter.

The only wire you want hooked to the ignition wire from the IGN post on the switch is the wire from B on the module that should run directly from B to the + post on the coil. Absolutely no other wires hooked in that circuit. The Ignition switch should havetwo IGN posts 1 for the ignition wire to the coil the second to connect the things that have to be on when the ignition is on but are not "accessories" That usually runs to the fuse block or junction block were other things connect to it.

[dsraven]

once you get it figured out I would rewire the thing and route the wiring such that it can be strung in a proper harness and tied up neatly. ensure the circuits are fused properly and run relays as required to avoid oversized wires on longer runs etc etc. ensure everything is grounded properly as that side of the circuit is just as important as the visible wires. pick up a small parts container/tray from the dollar store and keep a few fuses or whatever you think you may need on the roadside and keep that under the seat or somewhere for insurance in case.

[mr48chev]

The kit that he put in is very similar to the HEI conversions that GMC Bubba was doing on distributors. It's a reliable setup that works pretty well.

It's far from the first modified rig that someone who didn't know how it was set up caused and issue on because they made an assumption rather than researching out what they were looking at and that research could have been a call to the owner "hey, how have you got this ignition setup on this thing".

A lot of these old trucks including mine have had too many quick fixes done on them over the years that end up causing problems because we didn't want to or think that we had the time to do it right the first time. Then those fixes cause issues such as electrical fires or someone undoes your fix because they think "that's not the way it should be" and don't study the whole picture to figure out the Why it was done that way.