F134 Hard Starting When Hot

4F134 engine, Carter YF, single action mechanical fuel pump, IAY distributor ignition with points.
I've been having issues with my F head not starting well when hot and the outside temperature is above 60 or so. It starts very nicely when cold. If I've been driving a good distance and shut it down it restarts fine if I start it right away. If I let it sit for 5 or 10 minutes it doesn't want to start. It cranks fine but doesn't fire. If I apply choke I can smell fuel in the exhaust so I don't think it's a vapor lock issue. I don't smell fuel to start so I don't think the carb is spilling and flooding it. After more cranking than I like to do it will finally start to sputter and start. If the engine sits for an hour or so after I shut down it will fire right up with no choke.

An additional factor is I've had the engine sputter a couple times when driving in hot weather. Just a second or so then it catches again. Not sure if this is related.

Driving in cold weather the engine runs like a champ.

I'm hoping to do some troubleshooting later this week. Does anyone have suggestions on where to start? The only thing I can think of to start is if the ignition coil is starting to go bad. Any suggestions are appreciated.

Thanks,
Ken

 

I'd start with verifying tune up specs for points and timing, possibly replace the cap, rotor, and condenser if it's been a while. Clean and gap your plugs, too. I have never had a coil fail.

Can't hurt and might help, and is the starting point for any logical diagnosis.

 

Thanks for the reply. I'll have to check my cap, rotor and condenser. Not sure when those were last changed. Are the caps and condensers all the same for the F134? I found a listing for a rotor that specified it was for the IAY series distributor but not for the other parts.

 

Much talk here in the past about modern condensers being very poor. Try to find NOS (new old stock) or at least Blue Streak brand.

 

Rather then go to all the trouble (and expense) of throwing parts at it, why not troubleshoot and check the basics first when the condition occurs.
Pull coil wire out of distributor and check for spark.
Pull a sparkplug wire and check for spark.
Remove the air cleaner and observe whether fuel is present from accelerator pump action.

 

I agree, although what parts I suggested were no more than I would consider a routine annual service.

 

How close to the exhaust is the fuel line? Too close and the gas in the tube may turn to vapor.

 

Thanks for the replies. I'll try and get it hot on Friday and then see if I can troubleshoot. Check spark and fuel delivery. The vehicle always seemed to run worse when hot than cold but this is the worst problem I've had. I'm using 87 octane E10, same as always. The temp gauge is normal so the cooling system is keeping up fine. The fuel line has what I think is good spacing from the exhaust and has an insulating jacket on it. My fuel lines are rubber.

 

I have had significant problems with rubber fuel lines lately from auto parts stores. Deteriorating within a year and leaking fuel kind of problems. To counteract that issue in this last build I used NiCopp and AN style fittings. Inspect your rubber lines. No one want their jeep to light on fire.

 

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