I started my 39 with a stock engine and helmet Dist and it ran for 30 seconds and shut down like l turned the ignition off. Not a fuel problem. Can a bad condenser cause this? Coil was rebuilt by Skip a few years ago and the resistance is good. I have tried 3 different condensers ( unknown condition) still no spark. How do you test one to see if it’s working? Mark Need to mention I have voltage to the coil and even tried a jumper wire.
39 no start
- Thread starter marko39
- Start date
Flathead Fever
Well-known member
Check the points, it's rare but sometimes their springs break. Make sure nothing is grounded inside. Check the point gap. I was a mechanic during the points era. The first thing I'd check is for coil spark which you did. No spark. The next thing I'd check is voltage to the coil. Which you did and there was voltage. You might want to disconnect the wire from the coil and measure the available voltage but let's say it was okay. The next thing is to check the points, check their gap. look for anything that could ground them out. On a normal distributer make sure it's turning and the points are opening and closing, sometimes the drive gear comes loose but that not a problem on a flathead, at least not on a pre-'49 one. Crank the engine and make sure the distributor is turning, if it still has a fiber timing gear it could have stripped the teeth off of it. That used to happen on the engines in the 60's. Just because the coil was rebuilt does' mean it couldn't not have gone bad. Check the spring on the bottom of the coil to make sure it hasn't broken off. The most important tool is to have is a voltmeter/ohm meter to make sure everything is getting voltage and the correct amount of voltage.
Condensers are checked with an ohm meter for the correct resistance. They are made with different resistances, so you need to know you are using the correct one for the coil and the voltage. Some ignition systems are wired to give the engine full voltage while cranking by by-passing the resistor. Once the engine switches to the run position the voltage is running through the resistor. The resistor can go bad to where it would start but then die the second the key was turned back to the run position.
Condensers are checked with an ohm meter for the correct resistance. They are made with different resistances, so you need to know you are using the correct one for the coil and the voltage. Some ignition systems are wired to give the engine full voltage while cranking by by-passing the resistor. Once the engine switches to the run position the voltage is running through the resistor. The resistor can go bad to where it would start but then die the second the key was turned back to the run position.
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how is this done on a helmet coil?
rockfla
Well-known member
ALSO, not mentioned.....Check your rotor, they crack and short to ground as well. IF this has happened, one way to make sure it doesn't happen again and to remove your rotor and put a length of electrical heat shrink tubing on the shaft between the top and bottom part of where the rotor presses onto the shaft and insulate the middle of that shaft.
51504bat
Well-known member
Sorry, no help on the helmet coil. I'm an 8ba guy and checking the coil is simple on an 8ba. Not so much on a helmet from what I understand.
tubman
Well-known member
This is incorrect. Condensers are electrical buffers and are rated in "farads". A typical automotive condensers is usually rated between .020 and .040 micro-farads. They cannot be checked with a digital multi-meter unless it has that specific capacity built in (most older ones don't; some newer ones do). They can be checked for functionality with an analog meter. Here is a link to that procedure : https://www.google.com/search?q=how...VSw&sourceid=chrome&source=chrome.rb&ie=UTF-8.
Overkill-F1
Senior Member
rotorwrench
Well-known member
The condenser is more like an accumulator in a hydraulic system. It charges up with breakers closed and discharges that built up pressure when the breaker opens and the magnetic field in the coil collapses. It can be heat sensitive if it doesn't have good connection either internally or externally. Capacitors always require a cap tester and most folks don't have one but they can be tested with a rigged up distributor test apparatus to check both coil and condenser.
The old Mallory design helmet distributors are best checked on the bench. If you test a coil then it has to be warmed up from dead cold in order to see if it has a temperature related break down. A person can check all the internal components much easier on the bench. The distributor only goes back on one way so timing is not an issue on the car.
This is always a good time to check and make sure the vacuum brake is functional, the mechanical advance unit is working and lubricated, and that both points sets are adjusted properly since that is your timing. Any defects in the caps or rotor should be visible. with a battery, some test leads and a way to turn it, it can be tested for spark output.
Make sure that there isn't a problem with the ballast resistor under the dash. A lot of folks don't think about that but a bad resistor can be temperature sensitive.
The old Mallory design helmet distributors are best checked on the bench. If you test a coil then it has to be warmed up from dead cold in order to see if it has a temperature related break down. A person can check all the internal components much easier on the bench. The distributor only goes back on one way so timing is not an issue on the car.
This is always a good time to check and make sure the vacuum brake is functional, the mechanical advance unit is working and lubricated, and that both points sets are adjusted properly since that is your timing. Any defects in the caps or rotor should be visible. with a battery, some test leads and a way to turn it, it can be tested for spark output.
Make sure that there isn't a problem with the ballast resistor under the dash. A lot of folks don't think about that but a bad resistor can be temperature sensitive.
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Thanks everyone for your input. I should mention car has not been on the road yet and only yard driven maybe 2 hours over 5 years since getting it running. This happened the second time I started it this summer. Without known good parts on hand I need to check everything. Sure looks like a bad coil but that was rebuilt by Skip and checked the resistance and it was good. I will be removing the Dist. next. Will keep you posted if I find anything.
Check your original ford ignition switch. On our very old cars the internal contact bakelite contact plate becomes very worn and fails to make good contact. This is a very common problem which is often overlooked. You can bypass the contacts with a jumper wire to prove the switch condition. Regards Kevin.
i have done this and no spark. i have also measured the point resistance with points closed and got almost zero.
JayChicago
Well-known member
Yeah, at this point I would try a new condenser, cuz they are cheap and easy to swap out. Any condenser from your local FLAPS that can be mounted will do as a test.
Even though you have tried several condensers, they could have all been bad. I have read that condensers will go bad just sitting on a shelf, so old ones can be expected to be bad. Tubman recommends when buying a condenser buy two, cuz sometimes even a new one is bad out of the box.
BTW, when cranking, do you have no spark, or a weak yellow spark?
Even though you have tried several condensers, they could have all been bad. I have read that condensers will go bad just sitting on a shelf, so old ones can be expected to be bad. Tubman recommends when buying a condenser buy two, cuz sometimes even a new one is bad out of the box.
BTW, when cranking, do you have no spark, or a weak yellow spark?
I have no spark while cranking and in my original post I asked if a bad condenser could cause this. Car was running and shut down as if the ignition was turned off.
JayChicago
Well-known member
Ok, so now I am moving away from condenser. I think a bad condenser would give weak spark, not no spark. (Yeah, I know your original post said no spark, but sometimes we get miss-informed on the Forum posts)
I am out of ideas. Sorry I can’t help.
ford38v8
Well-known member
Marko, i reviewed all the posts, and haven't found where you confirm that you have spark going to the coil, and if so, spark coming out of the coil. You can do this without having the engine running. Disconnect the wire from the top of the coil, and with ignition on, check that wire against ground with a continuity meter: On with ignition on, off with ignition off.
If that test is successful, move on to the coil itself. With the ignition wire re-attached to the coil and coil removed from distributor, a short jumper wire attached to the heavy coiled spring inside, and with the condenser grounded, hold the jumper wire near ground while turning on the ignition.You should see a strong blue spark from the jumper to ground. This test is high voltage, so be careful here, and tell us what you discover.
If that test is successful, move on to the coil itself. With the ignition wire re-attached to the coil and coil removed from distributor, a short jumper wire attached to the heavy coiled spring inside, and with the condenser grounded, hold the jumper wire near ground while turning on the ignition.You should see a strong blue spark from the jumper to ground. This test is high voltage, so be careful here, and tell us what you discover.