39 pickup having trouble running

39pickup

39pickup

Junior Member
Hi guys I'm new here and have tried searching for answers but can't seem to find them. Any help would be greatly appreciated. I have a 39 pickup and started off with it not running. I had no spark. Changed out the coil and the resistor under the dash and she roared to life. Now I seem to have an issue with it breaking up and eventually stalling out after about 15-20 min of drive time. After it stalls out it takes about half hr or so and she will restart. Noticed the resistor on the firewall is cherry red when she stalls out. Not sure if that should be this way or not? I understand that the resistor will get hot but that seems too hot to me. Any help on possible causes or solutions would be great. Thanks in advance for any and all advice.
Eric
 
Is this a 6 volt or 12 volt system? I had the same problem with a 39 pickup also after I went to 12 volt. The problem was this. The coil was getting hot and breaking down causing the engine to stop as if the ignition switch was turned off. The solution was to install an external resistor before the coil. That cut down the voltage to the coil and kept the coil from overheating. No problems since. I went through the whole ignition system then and the resistor was the solution.

Run your engine and when you experience this problem place your hand on the coil. I bet that it will be too hot to even hold on to for very long. I believe this is your problem and the solution is the external resistor.
 
Sorry its original 6volt. There is an external resistor on the firewall behind the dash. Im not sure if this would be the same thing as whay you are referring to or you are suggesting running 2?
 
The resistor was def the problem. I changed the coil and nothing. Replaced the resistor and it fired right up
 
Check the condenser. With a DIgital Multi Meter you should get 21 - 30 micro farad and infinite resistance (open circuit). If a DMM shows a resistance value replace the condenser.
Point gap should be set at .014"-.016". A tighter gap and condenser resistance will flow more current through the coil and resistor.
 
Check the voltage at the coil. Some coils do not have an internal resistor. You may need to run the resistor on the firewall and an external resistor on the coil. It may be the condenser but if the condenser were bad you would get hard starting and rough idle. I would add an external condenser. Check your voltage first at the coil.
 
It is not uncommon to have a coil go bad. Unless your coil has been rebuilt, it is at least 73 years old. The wires in the coil will break down. Skip Haney in Fla does a great job rebuilding coils. If there is any doubt about the coil, he is your man
 
First off, what a pretty truck.

Second not to sound like a broken record, send your coil to skip and maybe replace the condensor to a napa ih200. The ultimate condensor to be debated and respectfully heard.

Good start anyway.

3-4 volts at the coil.

After that consider fuel delivery.
Outside a dizzy problems... Cracked rotor or caps.
 
Send your old Ford coil to Skip Haney and your problem will be gone. He has rebuilt over 20,000 old Ford coils if that tells you anything? ALL original old Ford coils have the problem you have when they get hot. Some take a little longer to get hot but heated on a coil test machine they all fail when hot. Check your spark from a plug wire to a HEAD NUT, cold it will have a crisp blue spark and jump 1/2", the hotter the coil gets the shorter the spark gets. When it gets down to a short fuzzy yellow spark it will have difficulty running. The small yellow spark jumping across the spark plug gap is blown out like a candle from compression. This can be observed on a Champion plug machine. There is a viewing window to watch the spark. On a bad plug it will fire good with no compressed air entering the chamber. As the air pressure is increased you can see the spark blown out, this usually occurs at 25 to 30 lbs pressure where the compression is over 75 lbs. G.M.
 
Thank you for the compliments and all the responses. I am very grateful for everyone's opinions and thoughts. Not to sound ungrateful but the coil is new purchased from a reputable early ford parts retailer. I ill def look into it anyway and maybe even send the old one off to skip regardless. Im just throwing things at the wall here but the ignition resistor gets so hot it looks like an electric heating element. Is this in anyway a possible issue ? As in voltage regulator putting out too much voltage, generator over charging etc? Like I said im new to the 6 volt flathead thing so I may be asking silly questions but im just trying to learn as I go. Again thank you guys for the warm welcome, help so far*and answering my questions. It is very much appreciated.
 
Are you running the 39 flathead engine with the "divers helmet" style distributor or a later 59A engine with crab or pancake style distributor? In other words I'm just wondering what type of coil you have. If it's mounted to the distributor or if it's the later style?
 
Its the 39 style with the coil mounted to the distributor. Oh and to answer someone else's comment about fuel delivery I dont believe it is an issue. Filter is new and the p.o. hooked up an electric fuel pump on a toggle switch. It runs fine on either manual or the electric when cool but makes no difference when the truck has run for a bit. It still breaks up and eventually stalls out.
 
I'd check the voltage at the coil also. Should be around 3-4 volts if the resistor is working well.
 
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