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Discussion Starter #1
Stock 1968 Mustang 289 V8 engine stalls after getting to about 175 degrees.

With ignition key in run position, battery connected, coil red/green + wire disconnected from coil, I measure 12.5 volts across red/green wire and battery negative post.
Is this correct? I thought I would measure between 4.5 and 6 volts, due to wire resistance.

Engine will not restart. Is there a problem? I have new points gapped at 0.021, a new condenser, original yellowtop coil. Gauge cluster is out of car for testing.

What is wrong here? I need some help.
 

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Discussion Starter #3
The choke is opening. I have rebuilt the carburetor. I did find the float level too high and reset it to the Ford Repair Manual spec of 3/8 inch from bowl lip (dry calibration not wet). By the way, this engine had been run many times and was pulling 20 inches very steady at idle.
 

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Resistance wire can only drop voltage while current is flowing thru it. An open circuit test like you did will just show battery voltage.
 

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GAS? Is it not starting due to the temperature or is that just a coincidence? When it gets to the point of not re-starting, do you still have spark? Try shooting a little starting fluid into the carb and see if it fires. You could be either running too rich or too lean.
 

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Does the engine crank over normally when you try to restart it after it warms up, or does it sound like the battery is dead and having a hard time cranking it over?
If the latter, your timing may be a little too far advanced.
 

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If you have a '68 with the gauge cluster disconnected then you aren't providing power to the voltage regulator and the battery is probably discharging until you lose spark.
 

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If you have a '68 with the gauge cluster disconnected then you aren't providing power to the voltage regulator and the battery is probably discharging until you lose spark.
Could you please explain this alittle more? And how I could resolve that? I’m having the same problem on my 66 I didn’t think that dash out had anything to do with it but it starts up great runs great. But when I shut it off and go to start it again nothing... cranks like battery’s dead doesn’t start. And then when I wait a little bit it starts right back up!
 

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Okay. The voltage regulator requires a power signal from the ignition switch to work. On a gauge cluster with an alternator warning lamp, the lamp wiring continues on to the regulator and connects to the "I" terminal on the regulator. On a gauge cluster with an ammeter, it's a wire from the ignition switch "C" terminal that goes to the "S" terminal on the regulator... the "I" terminal is not used. Removing the gauge cluster with an ammeter won't affect the charging system but the one with an alternator warning lamp will.

Henre, when you try to restart the car is the engine cranking normally... at regular speed? Do you smell gas? The first thing to determine is if you have an ignition problem or a fuel problem. Did this start suddenly? Was there any event... work done, fuel tank filled, etc., just prior to your issue?
 

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Could you please explain this alittle more? And how I could resolve that? I’m having the same problem on my 66 I didn’t think that dash out had anything to do with it but it starts up great runs great. But when I shut it off and go to start it again nothing... cranks like battery’s dead doesn’t start. And then when I wait a little bit it starts right back up!
Your problem is different than henre's problem (I think... haven't heard a response from him to my earlier comment)… and I apologize to henre for the hijack.
When you start the car the engine heats up and the choke opens up and vac advance on the distributor opens up as well. If you shut it down and try to start it again and the vac advance is pulling too much, your spark will be happening too early... actually pushing the pistons backwards, which is why it sounds like your battery is dead... starter trying to roll the engine one way and spark fighting against it. Retard your spark a little. I wasted money on a new battery a number of years ago just for this reason. Had it set at 12 BTDC, set it back to 10. Problem solved. That was 2016. Car's been running great ever since.
Sorry henre. Back to your own business now.
 

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Your problem is different than henre's problem (I think... haven't heard a response from him to my earlier comment)… and I apologize to henre for the hijack.
When you start the car the engine heats up and the choke opens up and vac advance on the distributor opens up as well. If you shut it down and try to start it again and the vac advance is pulling too much, your spark will be happening too early... actually pushing the pistons backwards, which is why it sounds like your battery is dead... starter trying to roll the engine one way and spark fighting against it. Retard your spark a little. I wasted money on a new battery a number of years ago just for this reason. Had it set at 12 BTDC, set it back to 10. Problem solved. That was 2016. Car's been running great ever since.
Sorry henre. Back to your own business now.
Thanks for the input I really appreciate it!...sorry to hijack the thread!
 

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Discussion Starter #13
OK, no problem with hijack. I want to learn. My Mustang was equipped with an ammeter, but it was not working. I have replaced the ammeter with a voltmeter, but have not reinstalled the gauge cluster. To answer other questions, there was no flooding, the battery does seem to turn the engine normally, there is gas in the carb, the alternator is charging because I have an external ammeter installed at the solenoid. As mentioned in my second post way above, I have installed new points at .021 and a new condenser. The choke opens and no gas smell. Spark plugs are newish and gapped at .035 per spec. I did find one bad ignition wire on Cylinder #4. Ignition wires are original.

With gauge cluster out and engine cold, it starts and runs, then stops when heated up. I think I did the resistance wire incorrectly, but I now have clear instructions on how to do the test, which I will do when it stops raining here on the West Coast.

Woodchuck, this problem happened instantly. This engine was running very smooth at idle and pulling 19+ on vacuum gauge. I have idled the engine many times to keep lubrication up, and I recently was running the engine and watching it heat up, and it stuttered, ran a second, stuttered and died. Could not restart it.

Thanks to everyone for input. My preliminary diagnosis, is that I have an intermittent electrical open in the coil. I plan to install a new coil and new ignition wires and see what happens.

I would appreciate any further thoughts as I am flustered.
 

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You could test the coil resistance when it heats up again and quits... Coil primary test - multimeter set to ohms scale, red lead on coil+, black lead on coil-, reading should be 1.5 ohms +/-. Coil secondary test, set multimeter to 10k ohms scale, red lead on coil+ black lead in high tension tower, reading should be 7.5k to 12.5k ohms +/-. If that check out okay then it would seem it's either a failing condenser (heat related) or a wire broken inside the insulator somewhere between the firewall harness and the ignition coil that's expanding and breaking the connection (aka the "pull it, wiggle it test). LOL.
 

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Discussion Starter #15
Finally got back on to the problem.

I did the following test to confirm existence of resistance wire.

"If you are measuring the voltage at the coil with the coil unplugged or the points open you are going to measure 12v. The circuit needs to be hooked up and closed in order to measure the voltage drop. Make sure the wire is connected to the + side of coil, put your red test lead on the + side of coil and black lead on a good ground, Take a jumper wire and supply a good ground to the Neg. side of coil and take your voltage reading. If resister wire is in circuit you should show the reduced voltage."

I found 5.5 volts at Bat post of coil, so resistance wire is intact while ignition key is in run position. I did the test with a new Blue Streak coil, engine not running.

I will continue to work on problem.
 

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My vote would be on coil as well. They tend to be finicky beasts before they truly die, and usually it's at higher temps. Ignition modules such as the Pertronix I are also known for this problem, though you are unlikely to have that issue with points/condenser as far as I know.

Last year my coil started to go bad on me and it would just cut the motor dead even when running at 85 MPH. From there it would be slow to crank but would sometimes catch, sometimes not. It eventually died and really wouldn't restart some 20-30 miles later. I hit it with a hammer and then it worked again for another 25 miles... at which point it truly died and could not be revived, even with a larger hammer. Replacing the coil fixed the problem.
 

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Discussion Starter #17
Thanks for the reply. I have installed a mechanical oil pressure gauge. In the process of working this issue and the last time the engine ran, I noticed it clattered more than usual. So I pulled the oil filter and found the filter had no oil in it. However, there was evidence that the filter pressure relief valve had lifted because there was carbon debris on the exterior of the antireturn thingy. This is the second filter since bringing this baby back to life. So I think the filter was plugged with debris.

I decided to pull the valve covers and see what I could see. Many rockers look dry. So I am checking the push rods for oil flow by the following method (this is my way because I am old and lazy and working alone). This is how I figure: Since the lifters have leaked down and they are riding on the cam lobes, the push rods are at their lowest point in travel no matter what stroke they are on, so I measure the distance from the top of the rocker stud and the top of the rocker nut for each valve. I then remove the nut and clean up the rocker, rocker nut, pivot ball and the push rod. I have found
some debris in the push rods and clogged oil hole in the push rod end of rocker. I then reinstall the push rod and rockers, and tighten the rocker nut down to the same height as when it was loosened. All the measurements of the stud threads is 3/8 inch plus or minus a 1/32nd. I figure that this adjustment would be close to good, and can be tweaked later. The 1968 Mustang repair manual says take each cylinder to TDC on compression, tighten the rocker to point of no play and tighten a further 3/4 turn.

After I do this on all cylinders, I plan to drop the pan and check the oil pump intake screen and clean the pan. This engine has a lot of carbon debris in it, so I will probably be changing out a lot of oil filters.

I am always open to comments.
 

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Your above post does not sound like anything that would cause the engine to die when it reaches 175*F.
 

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Discussion Starter #19
Well, this post has drifted a bit, but up in the middle I posted that I think the problem is an intermittent open in my original yellowtop coil. I have yet to restart engine with a new coil because I am chasing down an oil problem after using up two oil filters. The engine is carboned up and I do not want to fire it up again until I clean the pan. See post #13 and #16.
 

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If you've got debris in the pushrod oil holes you've got enough evidence to tear down the ENTIRE engine. Chances are that you have debris throughout the oil passages which can and probably will get into lifters, bearings, etc. In fact, you might want to pull the distributor and run the oil pump with an electric drill.... I wouldn't be a bit surprised if a bit of carbon got in there and sheared the oil pump driveshaft or twisted it like a pretzel.
 
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