HEI issue - JeepForum.com
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post #1 of 33 Old 09-19-2020, 07:10 PM Thread Starter
Jafo220
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HEI issue

I was running about 70 to 75 mph today on the interstate and the engine just shut down on me. As I was crossing lanes to the shoulder, smoke started out from under the dash. Got stopped and the smoke dissipated. Got under the dash and seen where the wires going into my factory dash had melted the jacket on the wires going into the tach. I accidentally pulled the 10gauge wire out of the ignition switch. It did not melt the factory wires. It did melt the 12 gauge wire I used when hooking up my HEI. So I noticed under the hood, it melted the entire length of 12 gauge wire from the distributor all the way back into the dash. I used a jumper wire from the battery to the hei to get home.

I have dealt with HEI's for many years with no troubles. I have always used 12 gauge wire for the power supply. Um I believe the original GM HEI hook up had 10 gauge wire supplying power. But I'm at a loss as to why all of a sudden, this wire melted it's jacket like it did. I have ran this distributor for several years now with zero problems. I have noticed in the last week or so though that I have noticed an hot or burn odor while driving, but could never trace it down. It only happens after driving at higher speeds for longer times. Driving stop and go around town, I never notice the odor. Could the tach or ignition switch have shorted out? I noticed that when I checked the original wire coming from the ignition switch, with key off I still have 12 volts. That shouldn't be. I don't recall it being that way when I installed it. I know the 12 volt source has to run through a switch. So I am wondering if the ignition switch may be shorted. But it done a number on my factory tach though.

Any ideas?

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post #2 of 33 Old 09-19-2020, 08:43 PM Thread Starter
Jafo220
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Oh and also, I put most of my wiring through the same loom and there were areas where the batt wire got so hot, it melted completely through it's jacket and the tach wire jacket where bare wiring was kind of fused together by the melted jacket. That wire got super hot in along certain areas. I assume this created a short.

I think my plan forward is going with 10 gauge wire and connector for the Batt. wire. Fix where any wires got melted through, maybe just totally replacing any wires with bare wire showing. Replace the ignition switch and inspect the tach and replace the melted wiring there.
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post #3 of 33 Old 09-20-2020, 01:49 PM Thread Starter
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Ok, cleaned up some wiring in the engine bay area. Replaced one wire. Rest look good.

Replaced ignition switch.

Ran a new 10 gauge wire for HEI.

Now the problems. First I somehow broke my tach. Needs replaced anyway because the tach retaining part broke a long time ago. Somehow broke my washer marking light get the tach out. So I have two parts I need to find. I lost my hookup for the tach wire. Not a good day.

I can live without a tach for awhile, but I can't figure out why the power is not being switched off to the HEI wire. Have no clue to what I am missing here. Except the tach, all wiring is still the same. Somehow a 10gauge wire got unhooked out of the ignition switch yesterday. Wonder if I got it back in the wrong hole on the connector or it goes somewhere else.
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post #4 of 33 Old 09-21-2020, 04:42 AM Thread Starter
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Well, still haven't figured out exactly what happened. What I have decided to do is do something I never did with an HEI install. I am going to run it through a relay circuit instead. It's taken me a minute to figure out what wires are. But I have a couple wires left and we'll see what happens. This should work much better than how I had it wired before. This is cleaner. I was looking at some of the wiring I had and have no idea what I was thinking or even how it worked so long the way it was, but it did.

Basically, I will ran the 10 gauge accessory supply wire (original) to a battery for power supply for that. Then use a 10 gauge wire from the HEI to the relay, another 10 gauge wire from the starter battery side of my battery isolation solenoid to the relay then a 16 gauge wire from probably my elec. choke wire because it is controlled by the ignition switch for power, then of course a ground wire from the relay. Hopefully this should work without any shorting problems or any problems alone.

As far as the tach, I am going to try and fix the one I have. I will have to solder new wires on the back. As far as those wires under the dash, the tach wires were the only damaged wires. I decided to just connect two red wires together the went to the tach. I assume one is an in and the other is an out from the ignition switch. I will have to figure out how to hook the tach back up as I can't seem to find where I had my tach wire hooked to. I was being passed by 80 mph cars when I was on the side of the road unhooking wires to try to figure out how to get home. So wasn't paying attention to what I was doing. May need some help figuring out that part soon.
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post #5 of 33 Old 09-21-2020, 09:10 AM
ccoyle71
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I don't have a tachometer, but this is how mine is wired. Works great.

3-wire-tach-relay-wiring-1.jpg
I did need a diode wired to the smaller of the alternator wires to prevent engine run-on.


Thanks UTN for these pics.
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post #6 of 33 Old 09-21-2020, 10:32 AM
John Strenk
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What year is your jeep? I had a couple of surprises with my 84 harness the other day when one of the wires for the ignition circuit pulled off.
Someone at the factory did a poor soldering job. Surprised it lasted so long before it pulled apart.

We can get your tach hooked back up. Did the wires get so hot it melted the solder and wires pulled off?

I don't know your wiring setup but did it melt from the the distributor plug all the way back to the switch?
Where is your choke hooked up? Where is the splice for your choke?

It won't be easy running a stock tach with a HEI Relay setup. You'll need to run new wires which defeat the purpose of the relay or buy a tach adapter to adapt the tach signal from your HEI to the Stock tach.


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post #7 of 33 Old 09-21-2020, 02:41 PM Thread Starter
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Quote:
Originally Posted by ccoyle71 View Post
I don't have a tachometer, but this is how mine is wired. Works great.


I did need a diode wired to the smaller of the alternator wires to prevent engine run-on.


Thanks UTN for these pics.
I'll have to look it over when I get home. I can't hardly see the schematic.

I am mostly through making my relay circuit. I do need to incorporate an inline fuse as well.
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post #8 of 33 Old 09-21-2020, 02:56 PM Thread Starter
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Originally Posted by John Strenk View Post
What year is your jeep? I had a couple of surprises with my 84 harness the other day when one of the wires for the ignition circuit pulled off.
Someone at the factory did a poor soldering job. Surprised it lasted so long before it pulled apart.

We can get your tach hooked back up. Did the wires get so hot it melted the solder and wires pulled off?

I don't know your wiring setup but did it melt from the the distributor plug all the way back to the switch?
Where is your choke hooked up? Where is the splice for your choke?

It won't be easy running a stock tach with a HEI Relay setup. You'll need to run new wires which defeat the purpose of the relay or buy a tach adapter to adapt the tach signal from your HEI to the Stock tach.
It's a '79 CJ7, 304.
The harness itself looks amazingly well behind the dash. Not saying anything has or hasn't pulled off. Everything works except the HEI. I was so sidetracked with smoke coming from under the dash, trying to get over two lanes to the shoulder, I did't think about looking to see if the tack was still operational at the time. It should have been, the wire was intact until I took it out in a hurry after I seen the tach wires under the dash were fried.

As far as the tach itself, I did a number on it trying to get it out. The soldered connections were still intact. The wires are cooked though. It looked like it got hot inside the tachometer right where the solder joints are just inside. You can't take these apart I don't think to inspect the inside. At least it doesn't look that way.

Ok. Yeah looking at the wiring I did, I'm not sure what I was thinking at the time. But it did work for a few years. From the plug it was ran over towards the starter solenoid where for some reason I put a jumper wire to the starter side small post or the "S" side. Then the 12 gauge wire ran over to the fuse block tapped into the accessory power wire which is a 10 gauge wire. From there it supplies I believe the headlight switch and highbeam maybe? But I tied it in there. Somehow it was controlled by my ignition switch. From there I think it's all stock wiring. But that is where I am kind of lost and am looking to just run a separate circuit for the HEI alone off the battery. I am just aiming at getting the thing to where it will run and shut off properly, then move on to the tach gauge.
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post #9 of 33 Old 09-21-2020, 02:59 PM Thread Starter
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Thinking about it, maybe the tach wouldn't be working if the HEI is dead. Wither way, the stock tach is wired into the ignition switch or through it. Those two wires have connectors and taking the tach out, I just put those to together at the switch in case they supply something.
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post #10 of 33 Old 09-21-2020, 03:06 PM
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Quote:
Originally Posted by Jafo220 View Post
I'll have to look it over when I get home. I can't hardly see the schematic. I am mostly through making my relay circuit. I do need to incorporate an inline fuse as well.
Definitely take John's advice over mine - he's an expert in this department. As I mentioned - I don't have a factory tachometer so didn't have to worry about that when wiring it up. I did use a fusable link between the battery and the HEI....just FYI.

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Originally Posted by Jafo220 View Post
I am just aiming at getting the thing to where it will run and shut off properly, then move on to the tach gauge.
I'd go ahead and order a diode if it were me. Once you have a relay controlling the power to the HEI - turning the key "off" likely won't kill the engine and you'll need it, IMHO.


Good luck - That sure sounds like an eventful Jeep trip! Glad you got it to the shoulder safely!
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post #11 of 33 Old 09-21-2020, 03:11 PM
shadoow
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Quote:
Originally Posted by Jafo220 View Post
Those two wires have connectors

without the tach those 2 wires should be joined together using their connectors (assuming your ignition circuit at that point hasn't been modified). The tach is part of the ignition circuit so if the tach is removed (or goes dead) your stock ignition circuit won't work unless those wires are joined.
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post #12 of 33 Old 09-22-2020, 07:06 AM Thread Starter
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Originally Posted by shadoow View Post
Quote:
Originally Posted by Jafo220 View Post
Those two wires have connectors

without the tach those 2 wires should be joined together using their connectors (assuming your ignition circuit at that point hasn't been modified). The tach is part of the ignition circuit so if the tach is removed (or goes dead) your stock ignition circuit won't work unless those wires are joined.
That's the notion I had when I was looking at it. Same style connectors. Figured if they were meant to be separated, they would have been different style connectors.
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post #13 of 33 Old 09-22-2020, 07:15 AM Thread Starter
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Originally Posted by ccoyle71 View Post
Quote:
Originally Posted by Jafo220 View Post
I'll have to look it over when I get home. I can't hardly see the schematic. I am mostly through making my relay circuit. I do need to incorporate an inline fuse as well.
Definitely take John's advice over mine - he's an expert in this department. As I mentioned - I don't have a factory tachometer so didn't have to worry about that when wiring it up. I did use a fusable link between the battery and the HEI....just FYI.

Quote:
Originally Posted by Jafo220 View Post
I am just aiming at getting the thing to where it will run and shut off properly, then move on to the tach gauge.
I'd go ahead and order a diode if it were me. Once you have a relay controlling the power to the HEI - turning the key "off" likely won't kill the engine and you'll need it, IMHO.


Good luck - That sure sounds like an eventful Jeep trip! Glad you got it to the shoulder safely!
I can get a diode pretty easy and they are usually pretty cheap. So what could it hurt?

There is this happening in everything else, then there is it happening in a CJ doing 70 plus mph in the inside lane in traffic. Definitely and an oh %$*#& moment. My Jeep is like a buddy. Then I got that feeling, I just didn't want to leave it on the side of the road you know? It's usually my everyday driver. I have become very attached.😁 I love driving my Jeep. Even through all the headaches and money, it would be the last vehicle I let go.
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post #14 of 33 Old 09-22-2020, 04:08 PM
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Originally Posted by Jafo220 View Post
My Jeep is like a buddy. Then I got that feeling, I just didn't want to leave it on the side of the road you know? It's usually my everyday driver. I have become very attached.😁 I love driving my Jeep. Even through all the headaches and money, it would be the last vehicle I let go.
I can relate to all this! Except for me, she's not my daily. AND - then I feel terrible leaving her in the garage all day....by herself. Occasionally, I tell her bye in the morning.....and that it's not her fault I'm leaving her....especially if it's raining or just too hot out. I think she understands. One day, when I'm retired..... or just don't need to drive as many highway miles.....she'll be my daily driver.
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post #15 of 33 Old 09-23-2020, 03:55 PM Thread Starter
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Quote:
Originally Posted by Jafo220 View Post
My Jeep is like a buddy. Then I got that feeling, I just didn't want to leave it on the side of the road you know? It's usually my everyday driver. I have become very attached.😁 I love driving my Jeep. Even through all the headaches and money, it would be the last vehicle I let go.
I can relate to all this! [IMG class=inlineimg]/forum/images/JeepForum_2016/smilies/tango_face_smile_big.png[/IMG] Except for me, she's not my daily. [IMG class=inlineimg]/forum/images/JeepForum_2016/smilies/tango_face_crying.png[/IMG]AND - then I feel terrible leaving her in the garage all day....by herself. Occasionally, I tell her bye in the morning.....and that it's not her fault I'm leaving her....especially if it's raining or just too hot out. I think she understands. One day, when I'm retired..... or just don't need to drive as many highway miles.....she'll be my daily driver.
You know, I understand the ones who want to do ground up restorations. I get it. They look fantastic when they are done. Since I bought mine 4 or 5 years ago, I have been seeing some nice CJ's every so often restored. I just wanted to be different. Before this Covid thing turned my work hours upside down and change my route to work and time I leave, I used to run into a guy with an early 80's tan and white Laredo unrestored. Drove his almost everyday on the interstate. My '79 is just the Renegade, but it's unrestored with all the bumps and bruises it's original owner put on her. Myself being just the second owner, I just couldn't bring myself to restore it back to new. Every dent and scrape has a story to it you know? It'd be like erasing it's history. I like it just like it is, a little rust, dents and scrapes. It looks respectable, and I try to keep it that way, but it's no shiny coin. I like the "patina" look. I don't have to worry about scratching the paint etc. It eventually is hitting some trails after getting some critical things done, brake lines, roll bars etc.
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