# 69 GTO dying when hot



## Flyboy (Sep 21, 2009)

My 69 GTO has a 77 Trans AM HEI distributor. It intermittenly and randomly shuts right down as if I turned the key off. Sometimes it fires right back up and will be fine for another day, other times it wont restart unless it sits overnight. Always starts and runs fine when cold. I replaced the module, coil, cap and rotor just hoping it was one of them. Ran great for over an hour, then as I put it into 4th after going hard throught the gears, died and backfired (which it usually does either through pipes or carb when it happens). Anywhere else I should be looking? Thanks


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## jetstang (Nov 5, 2008)

Have you checked fuel delivery, sounds like it's vapor locking more than an ignition problem.


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## Flyboy (Sep 21, 2009)

jetstang said:


> Have you checked fuel delivery, sounds like it's vapor locking more than an ignition problem.


I did consider that. But it backfires when it quits, leading me to believe fuel is continuing to flow. Also, when attempting restart I can smell and see fuel entering the primaries. It also quit on me at 7:00 am July 4th in relatively cool weather after running just 25 minutes, dont think conditions would induce vapor lock. What is best way to confirm that, remove fuel line to carb and crank into a can?


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## jetstang (Nov 5, 2008)

OK, backfiring. Is it dumping fuel? Look into the carb and look if it's dripping fuel after you shut it off, that would show a bad needle and seat. Sometime you can tap on the carb and get it to stop, but that's a temp fix. I just replaced a carb on a 20 hp motor that was doing the same thing. Ran good for 1.5 minutes then started backfiring. Try to restart and it was dumping fuel, let it sit for 5 mins and it ran great. New carb worked, still don't know what the carb was doing. If the car backfires and you run a Holley carb it will take out the power valve, then the car will run rich all the time until you replace it.
On the distributor, make sure you have a good 12 gauge input hot wire.


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## geeteeohguy (Feb 2, 2008)

There are two small wires that plug to your module at the distibutor. The green one (if memory serves) likes to wear and break inside the insulation from years of vacuum advance action and wear. It will cause your exact problem. Take the cap back off, and check the magnetic pickup resistance if you can with an ohmeter. Get a tech manual to do this. The two wires go from the mag pickup to the module. Also, you need the special heat sink grease under the module to help keep it cool. You can pull the distruibutor and overhaul it, replacing the mag pickup assembly, or you could just buy a reman or rebuilt distributor and drop it in. I've redone a ton of them, and you're probably money ahead to just go ahead and replace the dist. if the pickup is bad.


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## Flyboy (Sep 21, 2009)

Thanks, I am leaning toward the pick up as well. The only thing that doesn't make sense is why the connection would always be fine when the car is cold. ANyway, I already replaced the coil and module so may as well grab the pick up and replace. If I were to get a complete distributor, is there one you would recommend?


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## Eric Animal (Oct 28, 2007)

geeteeohguy said:


> There are two small wires that plug to your module at the distibutor. The green one (if memory serves) likes to wear and break inside the insulation from years of vacuum advance action and wear. It will cause your exact problem. Take the cap back off, and check the magnetic pickup resistance if you can with an ohmeter. Get a tech manual to do this. The two wires go from the mag pickup to the module. Also, you need the special heat sink grease under the module to help keep it cool. You can pull the distruibutor and overhaul it, replacing the mag pickup assembly, or you could just buy a reman or rebuilt distributor and drop it in. I've redone a ton of them, and you're probably money ahead to just go ahead and replace the dist. if the pickup is bad.


:agree Had a similar intermittant problem with my Accel system, it was the plug into the distributor.....


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## Rukee (Feb 8, 2007)

I'd be checking for spark and fuel when it happens. Pull a plug or the coil wire and put in a spare plug and lay it on the motor so the jacket is grounded. Turn the motor over and look for a spark. If you have no spark then continue on with the dizzy pick-up. If you have spark then check the carb for fuel. If it's vapor locking or running out of gas, that could cause a backfire too.


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## Flyboy (Sep 21, 2009)

Good news , bad news. Pulled distributor, the pick up was trashed, plastic cover was disinegrated, windings were exposed, feeling confident that was my problem. replaced with new Delco unit, car wont start. Had noted rotor position and housing to orientation before I removed. Took a few tries, but was able to seat distributor with rotor facing as it was before. Housing is in same exact location as it was. IS there anything I could have donoe to throw off? So long as distributor and rotor in same location as before, wouldnt I be OK, or could have I done something when trying to line up rotor?


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## Flyboy (Sep 21, 2009)

Flyboy said:


> Good news , bad news. Pulled distributor, the pick up was trashed, plastic cover was disinegrated, windings were exposed, feeling confident that was my problem. replaced with new Delco unit, car wont start. Had noted rotor position and housing to orientation before I removed. Took a few tries, but was able to seat distributor with rotor facing as it was before. Housing is in same exact location as it was. IS there anything I could have donoe to throw off? So long as distributor and rotor in same location as before, wouldnt I be OK, or could have I done something when trying to line up rotor?


i found TDC on #1 cylinder at plug. I aligned rotor with #1 position on cap. Made sure #1 plug wire went to #1 cap position. Still wont start, do get sputter through carb every so often. Moved distributor little left / right, no change.


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## Rukee (Feb 8, 2007)

Can you use a timing light to see were the timing for #1 cyl is durring crank?


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## Koppster (Jul 27, 2008)

Are you sure you're at #1, I ask because I've made the mistake before. I just went through a new dizzy install and it was pretty straightforward (with help from friends here).

Get #1 (forward cylinder driver's side) to TDC....I used my finger and bump-started until pressure pushed by finger out then adjusted harmonic balancer to line up with zero. *Easier if you pull all the plugs for this part.

Drop the dizzy in, ensure the orientation you choose doesn't result in the vacuum advance hitting your intake, etc., ....the rotor will be pointing to #1 at this point and you can wire your cap accordingly.

Put it all back togther and it should start as long as you have everything connected properly.

Rick

Firing Order Diagram just in case you need it, big help to me.


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## jetstang (Nov 5, 2008)

Flyboy said:


> . Took a few tries, but was able to seat distributor with rotor facing as it was before. Housing is in same exact location as it was. IS there anything I could have donoe to throw off?


Did you have to turn the motor to get the distributor to seat flush with the block? If you did, then you didn't put it back in the same location, as the oil pump gear was aligned with the original location. Did you ohm out the harness to ensure there wasn't a break in the wire, especially after installing the new module. Are you getting spark?


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## 66tempestGT (Nov 28, 2009)

did you put the rest of the wires in the right order? counterclockwise


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## geeteeohguy (Feb 2, 2008)

What Jetstang said. If the dizzy didn't seat all the way and have the rotor end up in the same exact position as it was before, the trick is to pull it back out, take a screwdriver and turn the oil pump drive shaft a hair one way or the other until it does. Sometimes it'll fight you. Also, you could have the dizzy in 180 out....it could be trying to fire when #1 is on TDC but on the EXHAUST stroke with the valve open. You need: TDC at #! compression stroke, rotor pointing at # 1 at cap, and timing mark to be between 0 and 15 on the the balancer to get it to light off. And make sure the firing order is right, and in the right rotation.....


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## Flyboy (Sep 21, 2009)

geeteeohguy said:


> What Jetstang said. If the dizzy didn't seat all the way and have the rotor end up in the same exact position as it was before, the trick is to pull it back out, take a screwdriver and turn the oil pump drive shaft a hair one way or the other until it does. Sometimes it'll fight you. Also, you could have the dizzy in 180 out....it could be trying to fire when #1 is on TDC but on the EXHAUST stroke with the valve open. You need: TDC at #! compression stroke, rotor pointing at # 1 at cap, and timing mark to be between 0 and 15 on the the balancer to get it to light off. And make sure the firing order is right, and in the right rotation.....


You were right on. It was TDC, but on the exhaust stroke. Dont know what I was thinking. To enlighten you all to me mechanical genius, I also had the distributor gear on upside down. Didnt think you could do that, but I did. Thanks for all of your help guys, always bail me out.


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## Rukee (Feb 8, 2007)

Flyboy said:


> You were right on. It was TDC, but on the exhaust stroke. Dont know what I was thinking. To enlighten you all to me mechanical genius, I also had the distributor gear on upside down. Didnt think you could do that, but I did. Thanks for all of your help guys, always bail me out.


So, you got it running now??


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## Flyboy (Sep 21, 2009)

Rukee said:


> So, you got it running now??


Like it's never run before. The pick up was the problem. Running like I am driving it off the showroom floor. Apprectiate all the input, getting all the bits and pieces of advise steers me down the right road sooner or later.


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## jetstang (Nov 5, 2008)

This is why I say to check the pushrods instead of thinking you got pressure at TDC with your finger. If it's 180 out the exhaust valve is going to be open some and have pressure on the pushrod, at TDC both of the lifters are on the base of the cam lobe and are loose. It's a pain sometime to pull the valve cover, but worth the time in a situation like this.
Congrats on getting it running!!


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## Flyboy (Sep 21, 2009)

jetstang said:


> This is why I say to check the pushrods instead of thinking you got pressure at TDC with your finger. If it's 180 out the exhaust valve is going to be open some and have pressure on the pushrod, at TDC both of the lifters are on the base of the cam lobe and are loose. It's a pain sometime to pull the valve cover, but worth the time in a situation like this.
> Congrats on getting it running!!


Ran great past few days, was convinced the pick up was the culprit. Driving aling yesterday and it just died on me again. All electical works, getting fuel, no spark. Once it sits overnight, it will fire right up again. Replaced coil, module, pick up, cap, rotor, plugs, wires... dont know where else to look. Any suggestions? Thinking ignition switch, connections, ground etc.. but cant figure out why letting it sit overnight corrects the problem.


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## Rukee (Feb 8, 2007)

Does the coil still have keyed power when it dies?


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## Flyboy (Sep 21, 2009)

Didnt think to check the coil. I just checked for spark at the plug. So with ignition key on, check the B term on HEI coil?


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## Rukee (Feb 8, 2007)

Yes, it should have 12v + with the key on.

*EDIT*
To correct myself, it should have battery voltage with the key on.


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## Flyboy (Sep 21, 2009)

let me check that, force me to buy a volt meter which I have been meaning to get for a while anyway


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## geeteeohguy (Feb 2, 2008)

Flyboy, the reason a lot of electrical problems cure themselves overnight is due to 2 things: Heat, and resistance. In most automotive electrical circuits, copper wire is the conductor of electricity. The hotter it gets, the higher it's impedence to voltage gets, and its resistance (ohms on the ommeter) goes up. If there is some corrosion or oxidation in the circuit, it doesn't take much heat at all! If the circuit is compromised, or worn thin, it'll still pass voltage, but can't carry the amperage load and will heat up even worse. Example of this would be a battery cable that reads 12 volts at the starter, but when you hit the key, nothing happens. You check out the cable and find one out of 25 strands is still connected, the others are broken. So, suspect a corroded or faulty circuit on the primary side.....you COULD run a temporary jumper wire to see if this fixes the problem....then you could track it from there. If you do, be sure to check the specified resistance value of the coil wire...a lot of coils take less than batt voltage, and yu could damage the coil. Cars use resistor wires, ballast resistors, etc. in this circuit much of the time.


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## Flyboy (Sep 21, 2009)

geeteeohguy said:


> Flyboy, the reason a lot of electrical problems cure themselves overnight is due to 2 things: Heat, and resistance. In most automotive electrical circuits, copper wire is the conductor of electricity. The hotter it gets, the higher it's impedence to voltage gets, and its resistance (ohms on the ommeter) goes up. If there is some corrosion or oxidation in the circuit, it doesn't take much heat at all! If the circuit is compromised, or worn thin, it'll still pass voltage, but can't carry the amperage load and will heat up even worse. Example of this would be a battery cable that reads 12 volts at the starter, but when you hit the key, nothing happens. You check out the cable and find one out of 25 strands is still connected, the others are broken. So, suspect a corroded or faulty circuit on the primary side.....you COULD run a temporary jumper wire to see if this fixes the problem....then you could track it from there. If you do, be sure to check the specified resistance value of the coil wire...a lot of coils take less than batt voltage, and yu could damage the coil. Cars use resistor wires, ballast resistors, etc. in this circuit much of the time.



Thanks GTO guy. I am running a 78 Trans am HEI distributor, so I believe it needs a constant 12v, no resistor wire or ballast.


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## Flyboy (Sep 21, 2009)

and are you talking about running a jumper wire from Battery to B+ of HEI coil, bypassing the ign switch?


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## Rukee (Feb 8, 2007)

Yes, to see if that stops the dieing when hot. If so, then you know it's in the car's wiring and not the dizzy.


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## Flyboy (Sep 21, 2009)

Rukee said:


> Yes, to see if that stops the dieing when hot. If so, then you know it's in the car's wiring and not the dizzy.


Thanks, will give it a try


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## Flyboy (Sep 21, 2009)

Flyboy said:


> and are you talking about running a jumper wire from Battery to B+ of HEI coil, bypassing the ign switch?


So was trying to make it 2 miles from my house to the shop to have diagnosed, and it dies a mile into the ride. It has never done this while cold, this was something new. I put a test light to the battery feed at the distributor and I was getting juice. So ran a jumper from the battery to the B+ terminal on distrubutor just to make sure was getting full 12V needs, and still wouldnt start. Had it towed, letting my shop figure it out. Throwing up the white flag.


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## Rukee (Feb 8, 2007)

If it's got power at the dizzy yet no spark, and you've changed the pick-up, it's probably going to be the distributor module. Or possibly the tach wire is shorting out between the distributor and the tach. Did you use that thermal paste under the module?


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## Flyboy (Sep 21, 2009)

Rukee said:


> If it's got power at the dizzy yet no spark, and you've changed the pick-up, it's probably going to be the distributor module. Or possibly the tach wire is shorting out between the distributor and the tach. Did you use that thermal paste under the module?


Hey Rukee, I did use the paste under the module. Funny you mention tach wire, the car did not have a tach. I installed an original out of another GTO, so the wiring from the tach to the distributor is about as old as my problem. The tach lead shorting out would cause a no spark situation?


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## Rukee (Feb 8, 2007)

Flyboy said:


> Hey Rukee, I did use the paste under the module. Funny you mention tach wire, the car did not have a tach. I installed an original out of another GTO, so the wiring from the tach to the distributor is about as old as my problem. The tach lead shorting out would cause a no spark situation?


Yes it would... and it would be easy enough to check, just unplug the tach wire.


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## Flyboy (Sep 21, 2009)

Rukee said:


> Yes it would... and it would be easy enough to check, just unplug the tach wire.


Of course I have to tow it to the shop because wont run. When they go to look at it, starts right up, and workign on it a day and a half and they cant get it to die. They did look at the tach wire, it is fine from tach to coil. What they are looking into is why they are getting voltage through the wire itself. They say they cant hold on to the wire for more than a second the voltage through it is so strong. If my memory serves me right, think it had 14 or 16 Gauge, wonder if it needs to be 12?


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## Rukee (Feb 8, 2007)

Which wire can't they hold onto??
You can't "feel" voltage going through a wire.


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## Flyboy (Sep 21, 2009)

Rukee said:


> Which wire can't they hold onto??
> You can't "feel" voltage going through a wire.


sorry, not very clear there. The wire from the tach to the coil, saying they are getting "zapped" through it when they grab it.


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## Rukee (Feb 8, 2007)

That's just a signal wire, there should be no 'zapping' going on from that wire....
Sure you have the coil wired right under the coil cover??


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## Flyboy (Sep 21, 2009)

Rukee said:


> That's just a signal wire, there should be no 'zapping' going on from that wire....
> Sure you have the coil wired right under the coil cover??


I went down to the shop. It is not the wire, but the terminal at the tach where the wire from the distributor attaches, if you touch the stud there is pretty strong current felt. Should that be?


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## Rukee (Feb 8, 2007)

Flyboy said:


> I went down to the shop. It is not the wire, but the terminal at the tach where the wire from the distributor attaches, if you touch the stud there is pretty strong current felt. Should that be?


Okay. I just checked on a `81 GP I have with a chevy sb with an HEI and working aftermarket tach. I have to wet my finger, but yes, I can get tingle from that tach supply terminal while running.


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## Flyboy (Sep 21, 2009)

Rukee said:


> Okay. I just checked on a `81 GP I have with a chevy sb with an HEI and working aftermarket tach. I have to wet my finger, but yes, I can get tingle from that tach supply terminal while running.


Thanks so much for doing that Rukee, much appreciated. Good to know that is normal. Nothing i can do but wait for it to quit on me again, been driving around 5 straight hours trying. Funny how when I try to go 2 miles to the shop i cant make it, but then it fires up for them and I've been driving 100 miles without a hitch. At least i am prepared with a plan of attack when it goes again. Borrowed a spark tester, and have a jumper wire to go direct battery to coil. Narrow it down to fuel, which I know i have been getting, or something in the coil/distributor. If I am getting 12 volts to the coil and no spark...must be something between. I have replaced everything, but that doesn't mean anything I guess.


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## Rukee (Feb 8, 2007)

...make a million parts it's hard to get a million good ones. Once and a while you'll get a bad one.


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## likethat (Oct 5, 2007)

You need to make sure that the 12v lead to the HEI is a 10 or at least a 12 gauge wire and make sure you are by passing the original wire to the coil as it is a resistance wire for the points coil. You will loss a lot of volts through a to small wire as heat.


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## Flyboy (Sep 21, 2009)

Rukee said:


> If it's got power at the dizzy yet no spark, and you've changed the pick-up, it's probably going to be the distributor module. Or possibly the tach wire is shorting out between the distributor and the tach. Did you use that thermal paste under the module?


Finally nailed it down, and you were right Rukee. I had replaced the complete distributor, figure for $50 worth knowing all was new. It then dies on me again right in front of the shop that helps me out. Pulled the tach wire, and runs fine. So it was a short in the tach. The lead is 14 gauge clean connection, so would thinkk it is not that. I know there is a bulb that fell into the unit, I wonder if that could be rolling around and shorting it out sometimes? The part that still doesnt make sense is why it would start again when let it sit overnight?


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## jetstang (Nov 5, 2008)

Flyboy said:


> The part that still doesnt make sense is why it would start again when let it sit overnight?


because the part that is failing is overheating, when it cools it works. Bulb shorting it out doesn't fit, should be laying low in the unit.


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## Flyboy (Sep 21, 2009)

jetstang said:


> because the part that is failing is overheating, when it cools it works. Bulb shorting it out doesn't fit, should be laying low in the unit.


Thanks Jetstang


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## Rukee (Feb 8, 2007)

Remove or replace the bulb from inside the tach and see if it works, if it still dies when hot and then works removing the tach wire, replace/rebuild the tach, or just leave it disconnected.


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