Engine cuts out when warm

[Drew Pojedinec]

If it was electrical, the engine would not refire. Of it it did it would not stay running. Should be obviously misfiring at hot restart idle.

With carb overflow it would restart by just opening the throttle plates and cranking engine.

I’ve never had the boiling fuel issue kill a running engine.
Maybe the Minnesota gas is weird.

[fitter]

thx for replies . To answer a few questions. Car ran great for 20 years. No changes to set up. One hot day last summer cruising highway speed it just died. Towed it home and it restarted. Has never been reliable since. I have tried 3 different coils. ( btw Greg) its now got the tko 600 in it i got from you in columbus. Im pretty sure i tried it in cooler weather and had similar results. it is warm here now. Will try it on cooler day . Pulled gas line at fuel pump and gas runs freely from tank. Balance of fuel lines are new. Will pull and check again. I put fuel pres gauge on line to carb always reads about 8 pounds . Planning to plumb it where its visible when driving to see if there is a pres drop when it dies.  thx

[blykins]

thx for replies . To answer a few questions. Car ran great for 20 years. No changes to set up. One hot day last summer cruising highway speed it just died. Towed it home and it restarted. Has never been reliable since. I have tried 3 different coils. ( btw Greg) its now got the tko 600 in it i got from you in columbus. Im pretty sure i tried it in cooler weather and had similar results. it is warm here now. Will try it on cooler day . Pulled gas line at fuel pump and gas runs freely from tank. Balance of fuel lines are new. Will pull and check again. I put fuel pres gauge on line to carb always reads about 8 pounds . Planning to plumb it where its visible when driving to see if there is a pres drop when it dies.  thx

That's a ton of fuel pressure. 

[1964Fastback]

That's a ton of fuel pressure.

Agreed.  I hooked a vacuum / pressure gauge on mine when I had the fuel line disconnected, just to check, and it was a steady 4 lbs (mechanical pump).

Pat

[mbrunson427]

This sounds like the famous "pink resistor wire" problem to me. We had the coil on our '67 run through that wire and the spark would break up at RPM. We chased a fuel delivery issue for a year before we figured this out.

https://www.fordmuscleforums.com/threads/pertronix-and-the-pink-resistor-wire.519562/

Make sure this isn't your issue. I'm assuming that a '69 has a similar wiring harness. I'm wondering if that resistor wire isn't getting hot and causing problems once warm?

[superduty]

Does your Mustang have the factory tach?  The coil positive wire runs thru the tach to a resistor wire to deliver reduced voltage to the coil. Petronics needs full 12 volts to operate correctly.  Full 12 volts to a stock coil will overheat and possibly ruin the coil.
Make up a jumper with alligator clips and go for a ride. When it acts up, pop the hood and connect your jumper from battery
to coil positive side. This will bypass fuse panel, key switch, tach, connectors, or any Warshawsky  items that may have been hooked to the
key switch circuit over the years.

[fitter]

Car has factory tach. 12 volts to coil ,when engine shut off. 10.5 when running , about 6 volts on negative side when running. This is pertronics 1 and ive read that they didnt need full 12 volt like later models . i have made a jumper. Will take it on next road trip to test that .  I have a pertronics flame thrower coil I can try as well thx

[Gregwill16]

Hey glad to see you put the TKO to good use. I had seller's remorse and was fortunate to pick up another one that I plan to put in my 69.
Sounds like you have a good plan in place to eliminate one potential issue.

[RustyCrankshaft]

If it only takes 10 minutes of run time for the problem to show up, just jumper the coil + to battery + which will bypass all the factory wiring and eliminate the pink wire problem. The Unilite should run fine on 12v, the Pertonix 1 there are 2 different versions and I think on some they want reduced voltage. Clearly too much voltage isn't the problem since you've swapped the distributors, but in my experience Unilites are very voltage sensitive and a clean steady 13.5-14.2v when running is what they want. Below about 11 volts and they become unstable.

[fitter]

Thx Rusty Crankshaft. Unilite was just installed yesterday. No difference. As far as fuel pres its a cheap gauge and could be out of calibration. Will install better one on weekend. Ive received some good advice from members and will follow up with suggestions when I get home on weekend.  Thx

[66FAIRLANE]

I have had coils come & go with heat but generally takes a ton more heat soak than 10 minutes. Have you checked spark when it stalls?

[Joe-JDC]

After reading through your statements again, the fuel pump may be the culprit.  Is the oil level changed any?  Smell like fuel?  Joe-JDC

[Joey120373]

Jumping bat + to coil + is a good and easy plan, I need to read back through the symptoms because I am unsure now of exactly how it acts. So correct me if I am wrong.

You run it till it gets hot, it dies. Does it sputter and die or just shut off like you hit the key?

Does it fire right back up or does it have to cool down a bit ?

This didnt start happening till it got good and hot once and now it’s a regular issue ?

I don’t know that I can offer any advice that’s any more help than has already been mentioned.
But couple odd ball things to check,
No particular order.

1, gas cap vent, easy enough to check, just loosen it up or talks it off.

2, only applies to solid cam, valve adjustment? Seems counter intuitive but I have seen very similar behavior ( engine dies when hot, runs perfect when cool ) .

3, double, then tripple check ground strap to block from battery and to the chassis, then run an extra just because, same line of logic as shorting the coil positive to the battery positive. Make sure the current getting to the coil can get back to ground. Do not connect the coil negative to ground! Rather jumper somewhere near the distributor to ground.

4, double and tripple check that it’s not vapor lock, it sure sounds like it to me, but if fuel squirts out the accell pump immediately after it dies then it’s probly not that, but it could be as some have suggested, fuel boiling over in the bowls.

5,  snug up the intake manifold bolts, because grasping at straws.....

If I read correctly, you have had at least 3 coils and 2 different distributors in it? Kinda makes it hard to point the finger at spark being the issue. Assuming the coil wire to the distributor has been replaced also?

Fuel pump acting up? I recall one old car I chased my tail for who knows how long on a somewhat similar problem, acted all kinds of weird when it was warm, intermittent though, would run good for days, then would act up all the time, then fine. It was the check valve in the fuel pump, had come loose .
Totally spit balling here on all this obviously, so take it all with a grain of salt.
 

[shady]

I'm still thinking valve train. seat recession, chain, cam. Maybe pull the covers and have a look. Seems you covered all the other stuff.

[My427stang]

We need more info, Joey going the right way

- What does it do when it dies, key off behavior, or craps out slowly and blubbers and dies?
- Does it restart cold, and when it does, do you have to floor it to clear it out, or start it, or does it just go back to normal?
- If it died, could you hold it to the floor and get it started again?
- Can you verify that 8 lbs of fuel pressure?  Fixed or not, too much for it.
- Did you look in tank?  I had a rag in my F100 in the 80s, no idea who did it or how, but it took a 35 minute drive to float in front of the pickup, then floated away when it got home on the hook
- Next time it does it, IMMEDIATELY run to the gas cap and pop it and listen