'49 Dodge Flat Head No spark 12v

The Classic truck page would not open for me; please indulge me. Trying to start a 1949 Dodge 6 cyl flat head. It has been converted to 12V; ballast resister with no bypass. Power to the coil; points open and close, and test light flashes when cranking. Coil was hooked up backwards on the primary, set it right. No spark. Supposed to have run 4 years ago. My next step is going to bypass the ballast resistor...just as a test. Its got a started plunger above the gas pedal.

Have you checked for spark directly out of the coil's high-tension tower? If "yes", you could have a bad rotor or cracked distributor cap or a mismatch of parts there that don't function together.

If no spark there and test light is indicating points are opening and closing that would point to a bad condenser or a failed coil.

Got a spare "presumed good" condenser lying around?

That's the first thing I'd try.

If it was converted to 12 Volts, you can use EITHER an old 6 volt coil PLUS an external series voltage dropping (12 down to 6) Ballast Resistor. If its a full true a 12 volt coil, you dont use a ballast resistor or ballast by pass circuit when cranking..

If your test lamp on the coils output to distributor terminal is flashing ON (when points open) and fully OFF (when points closed) when cranking that tells me the points are operating opening and closing the coils current as they should.......

Remove the coil wire from the dist cap (leave coil end intact) and place its terminal within 1/8 inch or so from tractor iron turn her on and crank her over TO SEE IF THE COIL IS FIRING a spark to ground ?????????

If so, the coils working and there may be a problem in the dist cap or rotor ......... Ive seen many rotor tips short out to dist shaft and dist caps with a crack or carbon trace or full of moisture preventing spark at the plugs

If the coils NOT firing it could be bad

If the condensor is shorted out the coil wont fire

If the condensor is open or weak it can still fire but a weaker spark and the points will burn soon

Check easy things first like points and condensor and dist cap and rotor BEFORE the more expensive coil although sure if all else is okay that can be the problem

Check out my Troubleshooting Procedure when theres no spark, it can help find the problem

John T
John Ts Ignition Troubleshooting

Its now called Yesterdays Trucks. Go on modern view and scroll down till you find it.

Pull the coil wire out of the cap and hold it close to the block. Spin it over with the ignition on. You should get a blue/white spark from it that jumps a 1/4 inch gap. If you don't then to point need cleaned or you have a wiring problem. If you do then try that at all the plug wires. If no park at the plug wires then bad cap or rotor.

TD 110 or TD 120 ? Doesn't really make much difference. Start over, clean fuel. Electrons to the coil and distributer. Check timing. Those things don't need much compression, but SOME is required. I'm not convinced you have a problem. I've had those suckers start with only 4 cyls. having compression. One of the best engines ever other than the 225 slant 6. Just sayin'.

If you have spark at the plugs maybe you are working on the wrong problem. Pop the air cleaner off an look down there with a light, give the accelerator linkage a stroke or two and see if the accelerator pump is squirting any gas. If nothing dump 3 or 4 tablespoons of gas down the carb and see what happens.

Thank you all. I have no spark. Repeat no spark. Test light flashes on the coil on the distributor side. Points and condenser appear to be newer; but condenser substitution may be in order. Trying to trial start on ether, boiled and sealed the gas tank but fuel pump won't pick up or shot. This is a charity case and trying to keep cost down and just get it outta the shop. Will rig a jumper to bypass the ballast resistor to the starter motor.

Do a simple hot wire. Run a wire from the non ground side of the battery to the ignition side of the battery. With the points closed when you touch the coil you should see a small spark. With the points open no spark. If you have those hook the wire up and check for spark. No spark says bad condenser or bad coil

Thanks for the feedback, you now post

1) Thank you all. I have no spark. Repeat no spark. Test light flashes on the coil on the distributor side. Points and condenser appear to be newer;

2) Will rig a jumper to bypass the ballast resistor to the starter motor

NOTE if its a full true 12 volt rated coil DO NOT USE a ballast as that will weaken the spark !!!!!!!!!!! A ballast is used ONLY if its a 6 volt coil on a 12 volt tractor


3) In case you missed it, heres my response yo your original post



If it was converted to 12 Volts, you can use EITHER an old 6 volt coil PLUS an external series voltage dropping (12 down to 6) Ballast Resistor. If its a full true a 12 volt coil, you don't use a ballast resistor or ballast by pass circuit when cranking..

If your test lamp on the coils output to distributor terminal is flashing ON (when points open) and fully OFF (when points closed) when cranking that tells me the points are operating opening and closing the coils current as they should.......

TRY THIS Remove the coil wire from the dist cap (leave coil end intact) and place its terminal within 1/8 inch or so from tractor iron turn her on and crank her over TO SEE IF THE COIL IS FIRING a spark to ground ?????????

If so, the coils working and there may be a problem in the dist cap or rotor ......... Ive seen many rotor tips short out to dist shaft and dist caps with a crack or carbon trace or full of moisture preventing spark at the plugs

If the coils NOT firing it could be bad

If the condensor is shorted out the coil wont fire

If the condensor is open or weak it can still fire but a weaker spark and the points will burn soon

Check easy things first like points and condensor and dist cap and rotor BEFORE the more expensive coil although sure if all else is okay that can be the problem

Check out my Troubleshooting Procedure when theres no spark, it can help find the problem

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

John T
John Ts Ignition Troubleshooting

Those old dodges were easy starters even on 6 volt. We had 2 of them and still have one. They ran good on 6 volt. We could start them in below zero weather on the little 6 volt battery. I would check for gas coming into the carb and if it squirts with the movement of the throttle linkage. If no then bad fuel pump or no gas flow from tank. I would also check like has already been stated for spark in sequential order from battery to plugs juice to coil then points then plugs. With a wire as Old said direct from battery to coil check spark then distributor and then to plugs. those engines had to have good points to start. Condenser not so much. Clean and check all connections. Recheck coil hook up it if was running and now switched wire on coil and don't start it could be grounding the spark out.