85 Mustang will not strat after it warms up or gets hot

[bwlsn13]

It very well my be a duraspark issue. I managed to buy a new engine harness from Fox Resto since the ends of mine are all ate up. The wire coating is gone and wires are exposed. Looks pretty rough.

[at_the_junkyard]

I'll chime in on the Duraspark box, they are far from bulletproof. Usually when they fail it is like someone turns off the key. Driving down the road it just dies, you coast to the side it won't start. You wait, walk home, etc., come back and it starts right up. That is the sign of a failed Duraspark box.

Good luck.
Kenny

Yes that is exactly what mine did...just shut off randomly or wouldn't start for short or a long while. Not a good feeling to die in the middle of traffic

[erratic50]

Coils are hit and miss it seams. My 86 has its original at 1/2 million miles and gives no hint of failing. Others report failures at less than 100K miles. Dunno

[854vragtop]

My guess is fuel boiling in the bowls. I see you live in Houston where it's relatively warm. Did you re-install the thick OEM carb gasket with the plastic dowels between the carb and the EGR valve plate? Did you re-install the aluminum heat shield below the carb? This same symptom happens on hot days on my '85. It will start right away after I shut it down when it's hot, but if it sits for 5 minutes the fuel in the bowls will start boiling which lowers the fuel level in the bowls. Then, it behaves as if it's flooded. Push the gas pedal to the floor and hold it there while cranking. Don't stab the gas pedal back and forth, just hold the throttle plates open to clear out any excess fuel in the intake manifold and the cylinders.

On the other hand, if the fuel level in the bowls are too low because of fuel boiling over, that may be causing the starting problem.

Adding a 1/2in or1/2in phenolic carb spacer will help to insulate the heat from soaking into the carb. You'll have to check the clearance between your air cleaner and your hood pad to see what will work, otherwise you'll end up abrading off the 5.0L decal on your air cleaner.

What's the choke position when this happens? Is it fully open? If it's closed for some reason when it's hot, this may be the culprit.

One of the easiest ways to determine whether you have a fuel or ignition problem is to spray starting fluid down the primary barrels. The stuff is so volatile (ether) that it is waaaay easier to ignite than gasoline. If there's a spark (and it's not too flooded), it will light off a motor very easily.

[bwlsn13]

Update!!! The car is now running and will start up on command. Turns out that the harness from the Duraspark box, Ac compressor, Tach, etc. was in bad shape. I ordered one from Fox Resto, put it on and there ya go. Thank you guys for all the input and direction. Now moving on to the carb. Happy New Year.