Topic: 1940 Ford starting/running problems when hot


Shiphandling Cowboy    -- 07-18-2026 @ 5:43 PM
  This is my second summer with my 1940 Ford Deluxe and I’m having significant problems getting the car started/keeping it running.

Last summer it would start up easily, but if you ran it for a while and shut down, it could be a challenge to get it started again, although I could usually get it running. I chalked it up to flathead Fords being hard to hot start.

This summer has been a bit more of a challenge. Recently on a hot 90F+day I couldn’t get it cold started at all. Figured the battery was weak (older one). Replaced the battery (6 volt)and once the new battery was fully charged, it started and ran fine, although it was a cooler day.

Today (90F), it started up right away. I drove it over to the pump about 200 yards away. Shut down, filled up and it wouldn’t restart. After about 10 or so minutes, I was able to get it started again, but as soon as I put it in first gear and started to drive, the engine stalled. Nothing I could do to get it started again.

Fuel doesn’t seem to be the issue. I have an electric pump and we verified the throttle is putting fuel in the carb. Battery is brand new. Starter seems to crank fine.

Does this sound like an ignition coil issue, or is there something else I’m missing?


carcrazy    -- 07-18-2026 @ 7:17 PM
  Yes, this sounds like an ignition problem.

Check to see if you have spark right after this problem occurs. If not, check the primary ignition circuit for any loose connections.

Try spraying some starting fluid into the air cleaner. If the engine won't even try to fire, there is no spark.

When coils go bad they frequently exhibit problems like you are experiencing.

Your condenser may be bad.


51504bat    -- 07-19-2026 @ 5:36 AM
  Trying removing the gas cap. Could be a venting issue. Or not.

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trjford8    -- 07-20-2026 @ 7:56 AM
  I would also check the resistor going to the coil.


TomO    -- 07-21-2026 @ 12:33 PM
  Flathead Fords do not have a hot starting problem if everything is in good condition.

Check the voltage at the coil. It should be 6 Volts or more with the points open and above 3.0 Volts with the points closed. If you don't have readings like this, your problem could be the ignition switch or ballast resister on the fire wall. If the points open is below 6 Volts, check the output of the ignition switch. If the voltage is low with the points closed, remove the ballast resister and restake the rivets.

Take one spark plug wire off and start the car. Use insulated pliers or screwdriver to hold the wire that you took off near a head nut. You should have a nice blue colored spark about 1/2" long. If the spark is orange in color, you have an ignition problem. Try replacing the condenser and rechecking the spark. If it is still orange you have a coil problem, send it to Skip Haney in FL. for rebuilding.

If both of those are OK, try starting the engine with the accelerator pedal to the floor, to clear a flooded engine.

If the engine cranks slowly, perform a voltage drop tst on the starter circuit.

Tom

This message was edited by TomO on 7-21-26 @ 12:35 PM


37RAGTOPMAN    -- 07-22-2026 @ 10:33 AM
  hard starting HOT
run the engine till it get hot,
then try to start the engine
if it does not start
TRY A ICE PACK on the coil
let it set for a few minutes,
if it starts
the coil is breaking down,
USE A VOLT METER and make sure it is getting at least 3 1/2 volts to the coil
common problem with flathead FORDS,
I would send the whole distributer with the coil condensor and have it rebuilt
its worth every nickle
there are several people doing this service, SKIP has done mine
Hope this helps 37 Ragtopman.


Shiphandling Cowboy    -- 07-26-2026 @ 6:39 AM
  Thanks for the ideas. Ended up replacing the coil and condenser and it seems to start/run much better. Waiting for temps to get hot again to really check.

When we pulled the ignition coil off the case was clearly cracked at the point where the brass tab comes out to attach to condenser.

That condenser was a pain in the arse to remove/reinstall, but we got it done.

If the case itself is cracked, is it worth sending off to Skip Haney or junk it?


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