70 C20 w/HEI Starter Stays Engaged, Ignition Switch Smoked

[CW4B]

Just bought, pretty rough. Just trying to get it running safely for now.

Got it running after fluids and brakes and drove it home. Replaced HEI distro cap, cables, plugs.

Started and ran but with loud screeching noise (that wasn't there before). Pulled plugs & cranked, starter seemed like it was not disengaging when I moved ignition switch back to "ON" position.

Removed & had starter tested, tested good. The solenoid spring seemed to throw gear out and it would pop back in smartly. Manually moving gear in and out with screw driver indicates smooth action and springy spring.

Attempted to check starter shim. Couldn't figure out how to manually engage starter gear (no room to manually actuate starter gear), so I double shimmed from 1/64 to 1/32 as a starting point (trial an error method). Otherwise, flywheel teeth are good and starter gear wear indicates it is engaging fully, which is about 3/4 onto flywheel gear. Has correct bolts and block looked straight with no damage to thread holes.

NOTE: Starter had 3 wires, including an R & S. Reinstalled wires to previous locations (I am pretty certain) but subsequent study leads me to believe I shouldn't need an R wire with an HEI conversion.

Reinstalled plugs.

Started, starter not disengaging still. BUT new symptom. While I was pondering my decision to buy the truck, I left the ignition in the "ON" position. I smelled something electrical burning. Checked the starter connections, felt like the S connection was getting warm. Then saw cab was filled with smoke. Disconnected battery and then searched for source of smoke. Purple and two conjoined brown wires melted where they enter ignition switch.

Disconnected the R wire from starter and taped. Started again, same smokey problem.

Not sure what to do next?

[54blackhornet]

Purple wire goes to small post on side close to block, yellow is for points , not needed for HEI if you have dedicated wire from fuse block. Sorry about the smoke in cab. Better check behind cluster for more wire damage

[LockDoc]

Originally Posted by CW4B

Just bought, pretty rough. Just trying to get it running safely for now.

Got it running after fluids and brakes and drove it home. Replaced HEI distro cap, cables, plugs.

Started and ran but with loud screeching noise (that wasn't there before). Pulled plugs & cranked, starter seemed like it was not disengaging when I moved ignition switch back to "ON" position.

Removed & had starter tested, tested good. The solenoid spring seemed to throw gear out and it would pop back in smartly. Manually moving gear in and out with screw driver indicates smooth action and springy spring.

Attempted to check starter shim. Couldn't figure out how to manually engage starter gear (no room to manually actuate starter gear), so I double shimmed from 1/64 to 1/32 as a starting point (trial an error method). Otherwise, flywheel teeth are good and starter gear wear indicates it is engaging fully, which is about 3/4 onto flywheel gear. Has correct bolts and block looked straight with no damage to thread holes.

NOTE: Starter had 3 wires, including an R & S. Reinstalled wires to previous locations (I am pretty certain) but subsequent study leads me to believe I shouldn't need an R wire with an HEI conversion.

Reinstalled plugs.

Started, starter not disengaging still. BUT new symptom. While I was pondering my decision to buy the truck, I left the ignition in the "ON" position. I smelled something electrical burning. Checked the starter connections, felt like the S connection was getting warm. Then saw cab was filled with smoke. Disconnected battery and then searched for source of smoke. Purple and two conjoined brown wires melted where they enter ignition switch.

Disconnected the R wire from starter and taped. Started again, same smokey problem.

Not sure what to do next?

You are correct that the resistor wire is not needed with the HEI. At this point I think I would replace the switch. Does it feel like the key is returning back to the run position by itself when you release it from the start position?

LockDoc

[CW4B]

Key is returning to "ON" position after I release key from "START" position, but starter stays engaged. Purple &/Or brown wire at ignition switch smok'n.

[Steeveedee]

Disconnect the battery and pull the plug off the ignition switch. You will need to cut those wires away from each other to undo the short. Don't cut them out of the harness, yet. Not knowing what they look like, maybe just pop each one out one at a time and put some heat shrink tubing on them. You can then check for resistance between those wires to verify they are no longer in contact. Figure out which wires go to the "start" and "run" circuits and verify that they are isolated from each other on the switch. The switch could be broken internally, and the "run" and "start" circuits could be in contact internally. If there is no continuity there, the switch should be OK. Only after that should you plug the connector back into the ignition switch.

[CW4B]

Thanks Steeveedee. I took ig sw out and disconnected from harness. Harness connector melted where purple & brown wires connect. Ordered replacement harness connector and another ig sw.

Meantime, believe I must have jacked something up when I wired starter because it wasn't frying before then. Will disconnect and ohm wires to ensure purple sol wire in ig sw is the one I connected to the S on the starter. Don't believe I need the R wire given it has an HEI, but will figure out where that one goes too.

Appreciate the help!!

[CW4B]

Ohm'd the purple sol wire at ig sw harness to S wire on starter, same wire = had correct wire hooked to S on starter solenoid. Was hoping I had that wrong to perhaps explain why ig sw wiring burned. Grrr.

[Steeveedee]

The yellow wire runs from the "R" terminal to the coil hot side. I stripped it completely out of the harness when I went to HEI, because a nonexistent wire won't get connected by accident somewhere else. I do my own work, but you never know. The truck could have a problem while the wife is driving it, and some animal could get in there and monkey around.

You could pop the ignition switch apart and look at the contacts, since you're replacing it. That might give you an answer.

[CW4B]

Good advice, this one has extraneous (and some burnt to a crisp) wires all over the place.

Here is my plan after the new ig sw & connector get here.
1) Verify all ig sw wires go where their supposed to.
2) Figure out where the extraneous "R" wire goes and pull it out.
3)Double the shim again (because I can't figure out how to engage the starter gear into flywheel to measure the 1/8" clearance).
4)Start it up and pray I don't burn out another ig sw and starter disengages.

Did I miss anything?

[firedemon]

if you have a meltdown like that id be checking fuse and fusible links previous owners seem to have problems and stick bigger and bigger fuses and eliminate fusible links and create more problems your yellow wire should go directly from starter to coil so should be easy to eliminate

[VetteVet]

Your ignition switch has 3 brown wires, a 12 gauge one for the accessory power to the fuse panel which has a small brown white stripe connected with it, and 2 smaller brown wires which are the brake warning light wires.

These two wires are grounded internally by the key switch when the key is turned to the S or start position. Grounding these two small brown wires is a test for the brake warning light bulb. They are not supposed to be connected to anything inside the switch but the ground.

The green wires do the same thing for the temperature light if you have a light dash.

If the switch is shorting internally when it is placed in the start position the hot red wire will be shorted to ground through these two wires and they will burn up.
The 12 gauge purple wire will be shorted to ground as well and it may burn up also. It may also be shorted to the red power wire which will continue to send power to the solenoid and keep the starter engaged.

If you haven't already disconnected everything you can test this by dropping the shift lever in drive which will break the circuit on the purple wire and the starter should disengage.

[CW4B]

Here is a picture of my project truck. Appreciate your advice on my conundrum.

[CW4B]

Originally Posted by VetteVet

Your ignition switch has 3 brown wires, a 12 gauge one for the accessory power to the fuse panel which has a small brown white stripe connected with it, and 2 smaller brown wires which are the brake warning light wires.

These two wires are grounded internally by the key switch when the key is turned to the S or start position. Grounding these two small brown wires is a test for the brake warning light bulb. They are not supposed to be connected to anything inside the switch but the ground.

The green wires do the same thing for the temperature light if you have a light dash.

If the switch is shorting internally when it is placed in the start position the hot red wire will be shorted to ground through these two wires and they will burn up.
The 12 gauge purple wire will be shorted to ground as well and it may burn up also. It may also be shorted to the red power wire which will continue to send power to the solenoid and keep the starter engaged.

If you haven't already disconnected everything you can test this by dropping the shift lever in drive which will break the circuit on the purple wire and the starter should disengage.


Attachment 1780942

Vettevet, thank you for your Service and for this advice. My spidy senses are tingling, so I believe you hit the nail on the head. I'll let you know how it turns out soon after the new switch & connector arrive.

[CW4B]

Originally Posted by VetteVet

Your ignition switch has 3 brown wires, a 12 gauge one for the accessory power to the fuse panel which has a small brown white stripe connected with it, and 2 smaller brown wires which are the brake warning light wires.

These two wires are grounded internally by the key switch when the key is turned to the S or start position. Grounding these two small brown wires is a test for the brake warning light bulb. They are not supposed to be connected to anything inside the switch but the ground.

The green wires do the same thing for the temperature light if you have a light dash.

If the switch is shorting internally when it is placed in the start position the hot red wire will be shorted to ground through these two wires and they will burn up.
The 12 gauge purple wire will be shorted to ground as well and it may burn up also. It may also be shorted to the red power wire which will continue to send power to the solenoid and keep the starter engaged.

If you haven't already disconnected everything you can test this by dropping the shift lever in drive which will break the circuit on the purple wire and the starter should disengage.


Attachment 1780942

VetteVet,
I have a new ignition switch and connector. Before installing, decided to ohm out the wires coming into the switch with the following results. NOTE: I have not ohmed out each wire to its destination. I did not repeat duplicate values.

CONDITIONS
Battery disconnected
Starter disconnected
Ignition Switch disconnected

KEY
SOL=Purple to starter S
G2=2 brown wires for brake warn light
IGN=Pink to power HEI
ACC=1 brown + 1 brown with white stripe to accessory on fuse box
BATT=Red wire to battery (not sure if this actually goes to battery)
CHASSIS GROUND=not a wire but chassis ground

MEASURES
CHASSIS GROUND-SOL=infinity
CHASSIS GROUND-G2=127 ohm
CHASSIS GROUND-IGN=122 ohm
CHASSIS GROUND-ACC=6K ohm
CHASSIS GROUND-BATT=7.6M ohm
SOL-ALL=infinity
G2-IGN=12 ohm
G2-ACC=6K ohm
G2-BATT=infinity
IGN-ACC=6K ohm
IGN-BATT=infinity
ACC-BATT=infinity

Should I be concerned about any of these readings?

[BCOWANWHEELS]

bushing in nose of starter is gone

[CW4B]

I also ohmed between the connections on the new ignition switch and compared it to the same measurements (OPEN/CLOSED) on the old ignition switch in two ways with the following anomolies (difference between the switches).

Bottom Line: Vettevet was correct, the old switch was shorting BATT to SOL while switch was in RUN. This caused the starter solenoid to stay energized after engine start, which caused the unpleasant screeching noise after start. Also, I believe, that the old ignition switch connector and purple SOL wire and the next door neighbor ACC wire overheated and melted when I inadvertently left the ignition switch in the run position too long when I was trouble shooting.

TEST: Ground (switch chassis) to G1stayed OPEN in the START position. Not cause of issue though and not a problem given that I don't have a temperature warning light in the dash.

TEST: BATT to SOL was CLOSED (connected) in the ACCESSORY and RUN positions, which is wrong. Should be no power to SOL during ACCESSORY or RUN ignition switch positions. This means that starter solenoid had power when ignition switch was in ACCESSORY, RUN and START positions and the circuit is neither designed to handle that much amperage continuously or keep the starter solenoid engaged all of the time, which caused the purple SOL wire to get scorching hot and melt the ignition switch connector and the adjacent brown and brown with white stripe accessory wires and of course the starter to stay engaged the whole while.

Sorry for the overly detailed explanation, but it helps me work things out. I don't want to burn up the new parts.

Speaking of being concerned about the new parts just getting burned up again, in a previous post, I documented the ohm measurements I took of the wires that go into the ignition switch. Was trying to determine if any of them were shorted to ground or to each other. Some of the measurements were lower than I expected, meaning I was expecting infinity or 0.L meter reading and instead saw readings of 125 ohm or 6K ohms. If anyone can take a look at the measurements I documented in the other post and let me know if i should be concerned, please do and thanks!

[VetteVet]

Originally Posted by CW4B

I also ohmed between the connections on the new ignition switch and compared it to the same measurements (OPEN/CLOSED) on the old ignition switch in two ways with the following anomolies (difference between the switches).

Bottom Line: Vettevet was correct, the old switch was shorting BATT to SOL while switch was in RUN. This caused the starter solenoid to stay energized after engine start, which caused the unpleasant screeching noise after start. Also, I believe, that the old ignition switch connector and purple SOL wire and the next door neighbor ACC wire overheated and melted when I inadvertently left the ignition switch in the run position too long when I was trouble shooting.

TEST: Ground (switch chassis) to G1stayed OPEN in the START position. Not cause of issue though and not a problem given that I don't have a temperature warning light in the dash.

TEST: BATT to SOL was CLOSED (connected) in the ACCESSORY and RUN positions, which is wrong. Should be no power to SOL during ACCESSORY or RUN ignition switch positions. This means that starter solenoid had power when ignition switch was in ACCESSORY, RUN and START positions and the circuit is neither designed to handle that much amperage continuously or keep the starter solenoid engaged all of the time, which caused the purple SOL wire to get scorching hot and melt the ignition switch connector and the adjacent brown and brown with white stripe accessory wires and of course the starter to stay engaged the whole while.

Sorry for the overly detailed explanation, but it helps me work things out. I don't want to burn up the new parts.

Speaking of being concerned about the new parts just getting burned up again, in a previous post, I documented the ohm measurements I took of the wires that go into the ignition switch. Was trying to determine if any of them were shorted to ground or to each other. Some of the measurements were lower than I expected, meaning I was expecting infinity or 0.L meter reading and instead saw readings of 125 ohm or 6K ohms. If anyone can take a look at the measurements I documented in the other post and let me know if i should be concerned, please do and thanks!

I'm your Huckleberry.



CONDITIONS
Battery disconnected
Starter disconnected
Ignition Switch disconnected

KEY
SOL=Purple to starter S Check

G2=2 brown wires for brake warn light Check
IGN=Pink to power HEI The pink wire runs to a tee and powers the Ignition, The key on fuse panel circuits, and from there to the dash cluster for power to the fuel and temp gauges.


ACC=1 brown + 1 brown with white stripe to accessory on fuse box. The large 12 gauge brown wire is the accessory wire to the fuse panel but the smaller brown /white stripe wire is the alternator exciter wire that runs to the firewall block on the inside of the cab and from there on the other side it becomes the 16 gauge brown wire to the external voltage regulator. The smaller brown/white stripe is a special wire that incorporates a resistor valued at 10 ohms to match the 10 ohms for the light cluster. It was used by the factory to failsafe the alternator in case the idiot light bulb blew. They just kept it for the trucks that had the gauge dashes without the charging light.


BATT=Red wire to battery (not sure if this actually goes to battery) This wire runs from the ignition switch to a tee with three other red wires that feed the fuse panel for key off power, the headlight switch, the horn relay, and the main one which goes through the firewall block to the main soldered junction with the alternator, battery, and regulator wires. Actually the flow is reversed from the battery and alternator soldered junction into the cab.so indirectly it goes to the battery

CHASSIS GROUND=not a wire but chassis ground Check

MEASURES
Are these measures just on the key switch or the wires in the key switch plug.? If just the key switch to ground I don't think there should be any resistance between any terminals and ground with the key off.
CHASSIS GROUND-SOL=infinity check
CHASSIS GROUND-G2=127 ohm I'm pretty sure this won't hurt but when key is turned to SOL it should be near zero ohms to gnd. It grounds the brake warning light during start to check the bulb. The other green wires in my picture do the same thing but for the temperature light in the light dashes.
CHASSIS GROUND-IGN=122 ohm I would not like any reading here, this should not be any connection to ground with key on or off. If the harness plug was plugged into the key switch and the key was on, you might see some resistance to ground through the ignition coil.


CHASSIS GROUND-ACC=6K ohm This is enough to prevent a short to ground but infinity would be better.

CHASSIS GROUND-BATT=7.6M ohm same here, This is almost infinity


Are these on the harness plug wires or between the key switch terminals? I'm assuming it's between the key switch terminals.
SOL-ALL=infinity With key off or not in start position, yes
G2-IGN=12 ohm If this is the brake warning light terminal there should be infinity otherwise the ignition would be grounded and the battery and accessory wire would be grounded when the key was in run or start


G2-ACC=6K ohm I am not comfortable with this even tho it's a lot of resistance I think it should be more. Check it with the key in SOL(start) you should get near zero ohms.


G2-BATT=infinity Yes, the BATT wire is 12 volts hot all the time and should not be closed to G-2 with any resistance. Remember G-2 is connected to gnd when the key is in SOL
IGN-ACC=6K ohm That's enough to keep the battery from draining but it should be near zero with the key in run.

IGN-BATT=infinity key off yes, key on near zero
ACC-BATT=infinity Same

Should I be concerned about any of these readings?


I think I misread your post and you were talking about the wires in the ignition switch plug so I'll comment on them.



MEASURES
CHASSIS GROUND-SOL=infinity Check
CHASSIS GROUND-G2=127 ohm check


CHASSIS GROUND-IGN=122 ohm I believe this reading is OK because you are reading the wiring resistance through the light to ground.

CHASSIS GROUND-ACC=6K ohm This is OK as well because all the resistance to loads are switched, If the switches are off you have no path to ground. Try turning on the wiper switch, and the heater switch and then the turn signal switch and watch the resistance decrease.


CHASSIS GROUND-BATT=7.6M ohm This is OK because 12 volts would not push through this much resistance unless it was in the milliohms scale.

SOL-ALL=infinity no connection to any of the other wires but you might see some to ground, reading through the solenoid windings, I'd guess near 200 ohms

G2-IGN=12 ohm This is about right, remember the pink wire feeds the cluster panel and posers the brake warning light so you're reading the light bulb resistance between the pink and brown G-2 wires wires

G2-ACC=6K ohm Yeah no connection between the BW light and the accessory until the key switch is in run and then the light is not grounded unless the BW switch is grounded or the key is turned to SOL.

G2-BATT=infinity Pretty much the same as G-2 to ACC.
IGN-ACC=6K ohm Reading through the fuse panel and cluster feed circuits but not enough to hurt anything .


IGN-BATT=infinity None here is good no battery drain unless the key is on or in ACC
ACC-BATT=infinity Sameo sameo

Should I be concerned about any of these readings?

I don't think so but proceed with caution.


leave your battery disconnected until you have all the wiring connected and the key switch is off. Then test the battery for current flow by tapping the terminal to the negative post and look for any spark. or test for a key off drain. If you get less than 50 milliohms between the negative terminal and the negative battery cable, you don't have a short in the key off circuits. You will get more than that if you have any lights or switches turned on so be sure every thing is off.

With the key on and the negative battery cable disconnected, tap the cable on the battery and you will see some spark but not much if all the switches are off , and the doors are closed, radio is off etc.
You can't use the multimeter because it's amps reading is limited to 10 amps and you might exceed that and harm the meter.

Most everything else is fused so if any shorts to ground it will blow fuses.

That's about all I got!

[CW4B]

Originally Posted by VetteVet

I'm your Huckleberry.



CONDITIONS
Battery disconnected
Starter disconnected
Ignition Switch disconnected

KEY
SOL=Purple to starter S Check

G2=2 brown wires for brake warn light Check
IGN=Pink to power HEI The pink wire runs to a tee and powers the Ignition, The key on fuse panel circuits, and from there to the dash cluster for power to the fuel and temp gauges.


ACC=1 brown + 1 brown with white stripe to accessory on fuse box. The large 12 gauge brown wire is the accessory wire to the fuse panel but the smaller brown /white stripe wire is the alternator exciter wire that runs to the firewall block on the inside of the cab and from there on the other side it becomes the 16 gauge brown wire to the external voltage regulator. The smaller brown/white stripe is a special wire that incorporates a resistor valued at 10 ohms to match the 10 ohms for the light cluster. It was used by the factory to failsafe the alternator in case the idiot light bulb blew. They just kept it for the trucks that had the gauge dashes without the charging light.


BATT=Red wire to battery (not sure if this actually goes to battery) This wire runs from the ignition switch to a tee with three other red wires that feed the fuse panel for key off power, the headlight switch, the horn relay, and the main one which goes through the firewall block to the main soldered junction with the alternator, battery, and regulator wires. Actually the flow is reversed from the battery and alternator soldered junction into the cab.so indirectly it goes to the battery

CHASSIS GROUND=not a wire but chassis ground Check

MEASURES
Are these measures just on the key switch or the wires in the key switch plug.? If just the key switch to ground I don't think there should be any resistance between any terminals and ground with the key off.
CHASSIS GROUND-SOL=infinity check
CHASSIS GROUND-G2=127 ohm I'm pretty sure this won't hurt but when key is turned to SOL it should be near zero ohms to gnd. It grounds the brake warning light during start to check the bulb. The other green wires in my picture do the same thing but for the temperature light in the light dashes.
CHASSIS GROUND-IGN=122 ohm I would not like any reading here, this should not be any connection to ground with key on or off. If the harness plug was plugged into the key switch and the key was on, you might see some resistance to ground through the ignition coil.


CHASSIS GROUND-ACC=6K ohm This is enough to prevent a short to ground but infinity would be better.

CHASSIS GROUND-BATT=7.6M ohm same here, This is almost infinity


Are these on the harness plug wires or between the key switch terminals? I'm assuming it's between the key switch terminals.
SOL-ALL=infinity With key off or not in start position, yes
G2-IGN=12 ohm If this is the brake warning light terminal there should be infinity otherwise the ignition would be grounded and the battery and accessory wire would be grounded when the key was in run or start


G2-ACC=6K ohm I am not comfortable with this even tho it's a lot of resistance I think it should be more. Check it with the key in SOL(start) you should get near zero ohms.


G2-BATT=infinity Yes, the BATT wire is 12 volts hot all the time and should not be closed to G-2 with any resistance. Remember G-2 is connected to gnd when the key is in SOL
IGN-ACC=6K ohm That's enough to keep the battery from draining but it should be near zero with the key in run.

IGN-BATT=infinity key off yes, key on near zero
ACC-BATT=infinity Same

Should I be concerned about any of these readings?


I think I misread your post and you were talking about the wires in the ignition switch plug so I'll comment on them.



MEASURES
CHASSIS GROUND-SOL=infinity Check
CHASSIS GROUND-G2=127 ohm check


CHASSIS GROUND-IGN=122 ohm I believe this reading is OK because you are reading the wiring resistance through the light to ground.

CHASSIS GROUND-ACC=6K ohm This is OK as well because all the resistance to loads are switched, If the switches are off you have no path to ground. Try turning on the wiper switch, and the heater switch and then the turn signal switch and watch the resistance decrease.


CHASSIS GROUND-BATT=7.6M ohm This is OK because 12 volts would not push through this much resistance unless it was in the milliohms scale.

SOL-ALL=infinity no connection to any of the other wires but you might see some to ground, reading through the solenoid windings, I'd guess near 200 ohms

G2-IGN=12 ohm This is about right, remember the pink wire feeds the cluster panel and posers the brake warning light so you're reading the light bulb resistance between the pink and brown G-2 wires wires

G2-ACC=6K ohm Yeah no connection between the BW light and the accessory until the key switch is in run and then the light is not grounded unless the BW switch is grounded or the key is turned to SOL.

G2-BATT=infinity Pretty much the same as G-2 to ACC.
IGN-ACC=6K ohm Reading through the fuse panel and cluster feed circuits but not enough to hurt anything .


IGN-BATT=infinity None here is good no battery drain unless the key is on or in ACC
ACC-BATT=infinity Sameo sameo

Should I be concerned about any of these readings?

I don't think so but proceed with caution.


leave your battery disconnected until you have all the wiring connected and the key switch is off. Then test the battery for current flow by tapping the terminal to the negative post and look for any spark. or test for a key off drain. If you get less than 50 milliohms between the negative terminal and the negative battery cable, you don't have a short in the key off circuits. You will get more than that if you have any lights or switches turned on so be sure every thing is off.

With the key on and the negative battery cable disconnected, tap the cable on the battery and you will see some spark but not much if all the switches are off , and the doors are closed, radio is off etc.
You can't use the multimeter because it's amps reading is limited to 10 amps and you might exceed that and harm the meter.

Most everything else is fused so if any shorts to ground it will blow fuses.

That's about all I got!

Can't thank you enough for such a thorough response. This is study material that's making the wiring diagram I've been studying and the wire tracing I've been doing make more sense.

I didn't clarify well, but I was conveying measures taken on the wires only - not the ig sw. Chassis ground to each one and then each one to each other.

I pulled the purple SOL and yellow R (to non-existent coil) all the way out to the firewall, separated and then rerouted the purple SOL wire back to starter. The yellow R wire had been spliced to the resistance wire that goes into the fire wall with another spliced yellow wire that went down to the passenger side of the engine, crossed over to the driver's side between the engine and transmission and then dangled there but connected to nothing. This second yellow wire was wrapped with a green one that connected to a temperature sensor on the driver's side of the block. Very circuitous route for the green wire given that it went into the firewall on the drive's side as well. Not sure if that was factory looped around for resistance reasons or someone was having bad day when they installed it under a shade tree?

I plan to wait until after I get her running again before I cut anything, but I think I can simply cut that yellow R and the resistor wire going into the driver's side firewall out of there completely. Don't think it is needed with the HEI.

The spark test method at the battery is brilliant. Now I can wade into this and possibly avoid another smoke fest if there still is something else wrong.

Thanks Vettevet

[54blackhornet]

I would suggest buying Leon a beer or lunch or dinner or something !

[CW4B]

Originally Posted by 54blackhornet

I would suggest buying Leon a beer or lunch or dinner or something !

I was just talking with my family about this forum and how amazingly helpful you guys are. I hope to be able to return the favor, but certainly agree I owe Vettevet a beer at least. Just let me know when you're in San Antonio!

[VetteVet]

I pulled the purple SOL and yellow R (to non-existent coil) all the way out to the firewall, separated and then rerouted the purple SOL wire back to starter. The yellow R wire had been spliced to the resistance wire that goes into the fire wall with another spliced yellow wire that went down to the passenger side of the engine, crossed over to the driver's side between the engine and transmission and then dangled there but connected to nothing. This second yellow wire was wrapped with a green one that connected to a temperature sensor on the driver's side of the block. Very circuitous route for the green wire given that it went into the firewall on the drive's side as well. Not sure if that was factory looped around for resistance reasons or someone was having bad day when they installed it under a shade tree?

I plan to wait until after I get her running again before I cut anything, but I think I can simply cut that yellow R and the resistor wire going into the driver's side firewall out of there completely. Don't think it is needed with the HEI.

The spark test method at the battery is brilliant. Now I can wade into this and possibly avoid another smoke fest if there still is something else wrong.

Your assessment on the yellow wire is correct. It's purpose is to send a full 12 volts to the stock ignition coil during startup to provide a hotter spark when the engine is cold. It does this by shunting the 12 volts at the starter R terminal on the solenoid to the resistance wire, that runs from the firewall block to the positive terminal on the coil. The purpose of the resistance wire is to lower the voltage to the ignition coil and the points during normal running, to prevent them from overheating and premature failure. It connects to the pink ignition wire from the key, on the inside of the firewall block.

Yes the HEI requires a full 12 volts all the time, eliminating the need for the resistance wire and the bypass yellow wire, and in fact removing them from the firewall block, and replacing the resistance wire in the bloc with a regular 12 gauge wire to the distributor, is a common way to feed the HEI distributor

Here is a visual of the resistance wire and the yellow bypass wire. The resistance wire is the white orange purple wire on the right edge of the diagram. Follow it up to the starter solenoid and it connects with the yellow wire at the starter solenoid, and then the yellow wire runs over to the coil positive.




Here it is in the firewall block and the colors have long since faded. It is the whitish cloth covered wire.






The routing of the green wire is probably something the factory did to facilitate the installation during the build. The green wire is just a path to ground for the temperature sending unit so length is not a factor.

I though the trouble shooting method might be helpful to you and to all the other members of our truck forum. VV

[6T7 C10]

Late to the party here but I was going to say feedback from your HEI or alternator was getting to your starter and to check wiring or add a diode. Glad to see another San Antonio C10 fan.

[CW4B]

Originally Posted by VetteVet

Your assessment on the yellow wire is correct. It's purpose is to send a full 12 volts to the stock ignition coil during startup to provide a hotter spark when the engine is cold. It does this by shunting the 12 volts at the starter R terminal on the solenoid to the resistance wire, that runs from the firewall block to the positive terminal on the coil. The purpose of the resistance wire is to lower the voltage to the ignition coil and the points during normal running, to prevent them from overheating and premature failure. It connects to the pink ignition wire from the key, on the inside of the firewall block.

Yes the HEI requires a full 12 volts all the time, eliminating the need for the resistance wire and the bypass yellow wire, and in fact removing them from the firewall block, and replacing the resistance wire in the bloc with a regular 12 gauge wire to the distributor, is a common way to feed the HEI distributor

Here is a visual of the resistance wire and the yellow bypass wire. The resistance wire is the white orange purple wire on the right edge of the diagram. Follow it up to the starter solenoid and it connects with the yellow wire at the starter solenoid, and then the yellow wire runs over to the coil positive.

Attachment 1782108


Here it is in the firewall block and the colors have long since faded. It is the whitish cloth covered wire.


Attachment 1782109



The routing of the green wire is probably something the factory did to facilitate the installation during the build. The green wire is just a path to ground for the temperature sending unit so length is not a factor.

I though the trouble shooting method might be helpful to you and to all the other members of our truck forum. VV

The previous owner wired the HEI BATT straight from the fuse box. I'll leave it that way for now but may replace the resistance wire with a regular wire and connect it to the HEI instead.

Perhaps I should pull out the key troubleshooting aspects of this thread and put them in a new thread for others to get to your salient points more quickly? As soon as I figure out how to do that.

Meanwhile, I'm fixing to do the install and tepid power on methodology you recommended. Fingers crossed.

Thanks,

[VetteVet]

In relation to the resistance wire replacement for the HEI conversion, I found this very good example of how to do it. Kudos to the author DMJLambert for the excellent write-up.

http://67-72chevytrucks.com/vboard/s...d.php?t=708975

[CW4B]

Vettevet, thanks for sharing the other post about the resistance wire, very useful.

Also, Your post ig sw test method was great. Fortunately, no problems. Now to get the carb adjusted so that it will idle & not sputter when I drive away. LOL