1968 lemans starting issue

Gjahn54

Gjahn54

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Im attempting to start my 1968 lemans for the first time after sitting for 20 years. I did a full tune up, replaced the battery, starter, and starter solenoid wire. When its cold it cranks over fine but once it fires over once or twice, i get nothing, no click from the solenoid, nothing. I checked the solenoid wire and i have 12.5 volts at the solenoid and starter all the time, its almost seems like the ignition switch just stops working. Has any one had a problem like this?
 
When it wont start have someone turn the key to start while you measure the voltage at the S terminal on the starter solenoid.
 
Still have 12 volts at the terminal. And the power wire from the battery to the starter has 12v as well.
 
If you have 12 volts at the S terminal of the solenoid, you either have a ground problem or a bad solenoid.
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Im thinking its a bad ground, ive checked the one from the battery to the engine and that one is good. Any suggestions?
 
Temporarily hook up a ground from one of the starter mounting bolts to the frame
 
Okay ill give her a shot next sunday i have to work till then
 
If the ground is good, then check the cables, do you know how old they are? after 10 or more years of use they can start to break down internally, and the resistance increases the warmer they get. Also if you do take the starter out, I would replace the solenoid. They also are a common failure point.
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I replaced the starter, solenoid, and the solenoid wire, i tested the big cable to the starter, and it was getting 12.5v cold, the ground cable from the battery to the block was hot when it stops working.
 
I concur with cammerjeff on closely checking battery cables and cable ends. I had a similar problem with my 72 LeMans. It would crank until it fired then lose all electrical power. No crank, no horn, no lights or buzzer, etc. Does this fit your symptoms? It drove me nuts until I traced the problem to a bad positive cable end at the battery. Replaced both cable ends and that was the end of my problem.
 
Classics Fan said:
I concur with cammerjeff on closely checking battery cables and cable ends. I had a similar problem with my 72 LeMans. It would crank until it fired then lose all electrical power. No crank, no horn, no lights or buzzer, etc. Does this fit your symptoms? It drove me nuts until I traced the problem to a bad positive cable end at the battery. Replaced both cable ends and that was the end of my problem.
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Thats exactly what happens, sometimes its fine but most the time it does exactly that until it cools down about 15 minutes later
 
Just confirming that the positive cable has 12 volts when cold is not good enough to troubleshoot your issue. When all the parts heat up the resistance can change due to corrosion either at the conections, or in the cables themselves. I still suspect you have a marginal cable.

Also are there any exhaust leaks near the starter? Hot exhaust air from either a bad gasket or cracked manifold or rusty downpipe can blow hot air onto the starter and solenoid. It will be worse if the car is idling without airflow to help cool the parts. Just something else I have seen.

The condition is usually called "heat soaked" and is a common issue with older GM Products.
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It doesnt run long enough to get hot, it just cranks over and fires and then nothing at all. Ill test the cable when its having the problem this weekend for sure and see what i have. Possibly may be a bad cable
 
You drained all the old gasoline?
Did you rebuild the carburetor?
You did a tuneup, how did you set the point gap?
You replaced the cap and rotor and spark plug wires?
These questions are related to the stalling out you hadn't originally mentioned.
 
After sitting for 20 years I would pull the distributor and at least prime the oil pump.
 
Yes i did all of that correctly ive checked it all
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It might be the neutral safety switch. When it fails to start next time try, moving the shift lever while in park while you have the key in the crank position. If there is a lot of play you might hit a point where the neutral safety switch allows the solenoid to engage the starter. If it is an automatic, you could also try starting the car in neutral instead of park.
 
The Neutral safety switch is not a bad thought at all, also known to be an issue some times.

Also keep in mind that if your cables have high resistance, just the current going thru them can heat up the cables or starter. The engine does not have to get warm to heat up those parts. If you have one of the infrared thermometers try it on the starter before cranking it, and after cranking it. See if there is a major difference. Also keep in mind that just because the starter is "new" does not mean it is good.

Is the starter you put in rebuilt or new?
 
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