Topic: Hot Flathead will not start


crapr3@yahoo.com    -- 07-25-2019 @ 7:55 PM
  Have 47 Ford Coupe with Flathead. Converted to 12 volt( not by me) no spark when shut down after running and up to temp. Starts and runs like a top when cold, no missing and good idle changed coil( twice) new condenser, new rotor, new spark plug wires. Help!


carcrazy    -- 07-25-2019 @ 10:29 PM
  Are you running your ignition wire to the 12 volt coil directly from the ignition switch without a resistor? Most 12 V coils do not require a resistor in the external wiring circuit as one is already built into the coil. If you have an external resistor in the primary circuit between the ignition switch and the coil, as the resistor heats up it will increase the resistance and reduce the voltage available at the coil.


TomO    -- 07-26-2019 @ 6:50 AM
  Check to see that the - or dist connection is going to the distributor if your car is NEG ground, which it should be for 12 volt system.

Check the voltage at the input to the coil when you have the no spark condition. Check the specifications of the coils that you are using to make sure that the input voltage meets specifications.

If the input voltage is correct, and you have a dwell meter, connect the dwell meter to the coil wire going to the distributor and check for proper dwell (34-36 degrees). If you do not have a dwell meter, connect your Ohm meter between the coil wire going to the distributor and ground. Crank the engine with the ignition off to check whether the points are opening or there is a short to ground in the primary coil circuit.

Tom


37RAGTOPMAN    -- 08-07-2019 @ 11:48 AM
  hi
is that a made in USA condenser ?
I bought a new one for a car and the parts place they have made in USA, parts
When condenser came was made it Taiwan,
I did not get 20 miles out of the condenser., kept on dying out like it was starving for gas,
fiddled with the fuel filter, thinking that was the problem.,
replaced it with a NOS DELCO.
NO MORE PROBLEMS,. try another condenser,
My 2 cents 37RAGTOPMAN




supereal    -- 08-27-2019 @ 10:16 AM
  When the complaint is "won't start when hot, be sure to say if the starter is cranking the engine as when it is cool, or is cranking very slowly when hot. The starter gets hot when the car is use, causing high resistance in the winding, lowering current which, in turn, starves the ignition system, reducing spark. We use a "hot start" circuit connecting the coil to the starter motor side of the solenoid, with a diode in the middle of that link. This boosts the power to the coil. Many later cars did the same thing via a pole on the ignition switch or starter. Many years ago I posted he diagram here on the Forum. If anyone wants it, I'll dig it out and repost it.


4dFordSC    -- 08-28-2019 @ 10:29 AM
  I'd like to see it, Supereal. Thanks.


MG    -- 08-28-2019 @ 11:37 AM
  Supereal's resistor bypass circuit pictured/attached below....

This message was edited by MG on 8-28-19 @ 11:47 AM


supereal    -- 09-01-2019 @ 10:25 AM
  Thanks MG. I am still searching for the original. I had it on my old system, but switched from Dell to Mac, and I am still trying to add from one system to another. The "hot start" works fine. The only complaint I've had is when the diode is reversed. I address the problem on my instruction sheet. The diode is a sort of "check valve" that allows power to flow to the coil, but prevents it from trying to run the starter. The circuit doesn't handle high power, so the diode doesn't have to be heavy duty. Just be sure that it "faces" correctly with the plus end toward the coil.


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