Engine quits after 25 minutes on the road - Pontiac GTO Forum
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post #1 of 13 (permalink) Old 07-09-2012, 02:57 PM Thread Starter
 
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Engine quits after 25 minutes on the road

Hello All;
I took my vehicle on the local roads today for about 25 minutes and the engine suddenly quit three times at the end of the 25 minutes. There was no problem for the first 20 minutes. After I let it sit for about 5 minutes (after each time it quit), I was able to start the engine and proceed closer to my house. The aftermarket 25 year old temperature gauge shows the engine is running at about 200 F. Iím inclined to think heat has something to do with this stalling problem but Iím here asking for advice.
Any clues why this is happening?

A little history; this vehicle was in storage at my dadís house for about 4 years. Before it was returned to me, he had a GM dealership do a little work on it (his mindset is to go to the stealership). They installed a new carburetor (runs a lot better) and fuel pump.

67 GTO, 400 cubic inch, automatic.
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post #2 of 13 (permalink) Old 07-09-2012, 03:00 PM
 
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Need to know if there is spark after it dies. Then we can go after the problem.

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1966 Pontiac Lemans Convertible
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post #3 of 13 (permalink) Old 07-09-2012, 03:12 PM Thread Starter
 
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I believe there has to be spark. Right after the engine quits, I can start it for about 1 second and then it quits. After a 5 minute rest period, the engine started and ran for another 3 miles before quitting again. Perhaps I should start by replacing the points or going with an electronic ignition?
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post #4 of 13 (permalink) Old 07-09-2012, 03:28 PM
 
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Just check for spark first. Should be able to find an inline spark tester at most part store. There are 2 power sources going to the coil. One has 12 volts for starting. The other is a resistor wire that runs around 6v. Points will not reopen if closed.

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1966 Pontiac Lemans Convertible
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post #5 of 13 (permalink) Old 07-09-2012, 06:27 PM
 
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I'm no expert, but I had a coil that was going bad that acted like that when it got hot, cool it down and run, get hot and quit.
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post #6 of 13 (permalink) Old 07-10-2012, 09:46 AM
 
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replace the condensor, a bad condensor will drive you nuts trying to figure out why your car keeps cutting off after warm up.
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post #7 of 13 (permalink) Old 07-10-2012, 04:03 PM
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Also, right after it stalls out, remove the air cleaner and blip the throttle with your hand and see if you're getting fuel into the primaries of the carb. I had a similar issue years back, and it was a vapor lock issue in the fuel line. If you're getting no fuel, and it starts right up if you spray carb cleaner down the carb throat, that is your problem. Simple stuff first, before throwing parts at it, IMO.....
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post #8 of 13 (permalink) Old 07-10-2012, 09:12 PM
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Catch it in the act, then quick as you can figure out if you're missing spark and/or fuel. Easy way to test for spark is to pull a plug wire and hook up one of these:

Great Neck/Adjustable ignition spark tester (25069) | Ignition Tester | AutoZone.com

(Saves you from getting bit)

Check for fuel like GeeTee said - pull the air cleaner, look down through the carb while opening the throttle by hand. You should see fuel squirting.

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post #9 of 13 (permalink) Old 07-11-2012, 03:46 PM Thread Starter
 
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OK, I’ll check to see if the carb is getting fuel next time this occurs. I’ve heard of vapor lock but didn’t really know what it was. How is vapor lock corrected? Meanwhile; I’m replacing the points anyway and going with the Pertronix Ignitor 3 and Flame-Thrower 3.
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post #10 of 13 (permalink) Old 07-11-2012, 04:51 PM
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"Vapor lock" is when the fuel in the lines get's warm enough to start turning into vapor. It can be compounded if there's any sort of air leak that allows air to get sucked into the line. Mechanical fuel pumps don't move air/vapor very well (at all), so when it happens you might as well have an empty fuel tank.

If you're going to swap ignition parts, don't do it until you've positively id'ed the problem. Points systems worked just fine for many many many years. They're both sound and simple - much easier to troubleshoot than anything electronic.

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