Car cutting out on the highway...intermittently.

[7TCatvert 24]

Driving down the highway last night. Was on the road about 20 minutes at about 70 mph and the car shut off. I tried popping the clutch a couple times no go after a few frantic moments( was at night and I was in the middle lane of a 5 lane highway) got her to the side of the road. Shut the car off, gathered myself for a minute and the car started right up and I was on my way again.

 

 

The only thing I did notice is that before the tach was jumping erratically. I was thinking the ground was maybe loose. After it started tach was fine. The tach is a rocket man tach so it is out of the ignition loop.

 

The car has th Petronix 2, new Petronix coil, new distrib, cap, rotor, plug wires, basically everything in the ignition system is new....

 

Any ideas?

[Cruzzar 22]

Had the exact same problem with my '70. Changed plugs, cap, rotor, checked fuel filters, etc. Finally changed the electronic (petronix) pickup inside the distributor and problem was solved. Car had less than 4000 miles on if when this happened. Everything on the car was new when I built it. Problem would surface and then go away and then come back. My tach would also become erradic.

[1969vert 55]

Similar to a problem I had...did see the tack go dead and motor ....Also saw it sometime during cranking no tack jump.... no start.. Turned out to be my MSD Distributor failing...( ready to run 8352 ) swapped it out t a older Accel no problems since... MSD had way to much slack on the lower bushing. I think the reluctor was hitting the pickup... 

[barnett468 418]

if your tank is rusty you could be sucking up rust around the filter bt that would have nothing to do with the tach.

[machm1970 180]

I just had the same problem, I did all the same things you did. I read somewhere that sometime during 70 production they eliminated the ground strap from the engine to the firewall and had a ground wire that attached somewhere near the voltage regulator. Mine didn't have either. I added an engine ground strap from the parts store for $5, problem solved.

Matt

[7TCatvert 24]

The Petronix is interesting. No sure how to test that. I would hate to spend another 120 for an another Petronix.

 

I need to look at the cap and see if maybe it is hitting or jumping...

 

Tank is brand new along with all of the fuel lines and hoses. I have 3 really good ground straps( I over did these)

[SA69mach 39]

I would suspect the coil.  New or not, it is the common item,  for both spark and tachometer signal. 

 

I have had a pertronix ignition module 'fail' due to incorrect gap setting, and it will not 'repair itself ' after cooling off.  A bad coil will usually go bad after heating up, and often work again after cooling off.

[3pedal 95]

If you are running the original pink resistor wire replace it with a 12 volt ignition wire to the coil....

[Topless69GT 28]

I had the same issue last summer. I replaced everything that has been listed in all the above posts and the problem continued. Mine turned out to be the ignition switch wires. I put in a new ignition switch pigtail on my wire harness and it solved the problem. Not sure if yours is the same issue but worth a shot. The old wires in my case would heat up after the car ran a while and would start to cut out and then shut down. After a brief cooling period the car would fire right up. Upon inspection of the wires they were very hot and the wire insulation was very hard and developed cracks and some bare spots.

[3pedal 95]

Different Pertronix 's use different coils....

[7TCatvert 24]

I have the correct Petronix coil and the harness was rebuilt by the person on here who does them...

[7TCatvert 24]

So after switching out what I felt was everything. I switched out the spark plug wires out to 8mm and after 1 month all problems solved.

[1969_Mach1 333]

Similar to a problem I had...did see the tack go dead and motor ....Also saw it sometime during cranking no tack jump.... no start.. Turned out to be my MSD Distributor failing...( ready to run 8352 ) swapped it out t a older Accel no problems since... MSD had way to much slack on the lower bushing. I think the reluctor was hitting the pickup... 

There is no lower bushing or bearing on MSD and any stock Ford distributor I have seen.  What positions the lower part of the dist shaft is its fitment into the block.

 

If 7TCatvert experience an abrupt, instant, engine shutting off, then it points to something in the ignition system.  I'd check the Pertronix pick up like Cruzzar found.  If its a gradual slow shutting off then fuel related like barnett468 mentioned.

[7TCatvert 24]

2 years later and problem never came back, definitely the spark plug wires.