No start when hot

37 Cab

37 Cab

Well-known member
Lately I have been having trouble getting my 37 started when hot. Fuel pressure is good. Accelerator pump is delivering fuel. What I found is no spark while cranking. With a little push it fires right off. Yesterday I noticed when starting it cold it was taking more cranking than usual to get it started. Then it fired just as I let go of the button. I am thinking my coil is getting weak and will not fire when battery voltage is down during crank. Anyone have thoughts on this? I am running a crab distributor and a round cylindrical coil with the coil wire out the bottom and the wires on each end. One on top and one on the bottom. Have not been able to locate one like it. Is this the type Skip rebuilds?
 
You could be on the right track. Have the battery checked for output. Charge up the battery and have it checked at the local auto parts store. 12V or 6V?? what is the coil primary resistance? Are you using a resistor in the ignition circuit? Who Mfg. the coil? Have a photo of it? Does it have a model number?
 

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I had that problem years ago. The resistor was going bad and needed to be replaced. As a check, bypass the resistor and try starting the car.
 
could it be the starter? check the amp draw or park on an incline. let it roll down and pop the clutch. if it starts quickly. thank starter.
 
As the others have said ,your getting a voltage drop as soon as the starter draw drops you get full voltage to the coil .Go over all connections clean the ING switch .by pass the resister as a test as flat attack says, soder all joints ,run heavy cables to the battery .Ted
 
The coil is a Mallory.. 6V... Duh.. I blame that on old age.. I will do a draw test as soon as it cools off a little around here. Crank speed seems the same hot or cold though. IMG_0593.jpg

IMG_0597.jpg
The second pic is sideways don`t know how to rotate it..
 
Terry said:
You could be on the right track. Have the battery checked for output. Charge up the battery and have it checked at the local auto parts store. 12V or 6V?? what is the coil primary resistance? Are you using a resistor in the ignition circuit? Who Mfg. the coil? Have a photo of it? Does it have a model number?
Click to expand...

What was this Ford coil with the 2 primary terminals off? I've never seen one like it. Walt
 
Your coil is a "Master" Made by Mallory. I have a couple of examples I will check to see if it requires a primary resistor to lower the input voltage.
IF it does NOT require the resistor and you were to add one (or keep the Ford installed resistor) the coil primary voltage would be low and the secondary voltage low (spark) Let me check.
 
Sorry to take so long. I measured the primary resistance of two NOS Mallory Master coils, both at 1.0 ohm I also measured a Mallory "Best" coil at 1.0 ohm I have the manual from Mallory for the Best coil and it does not use a resistor external to the coil. The Master should not have one either. If you still have the Ford resistor you could just add a wire jumper wire across it's two terminals or place all the wire lugs on one terminal of the resistor. Either way the Ford resistor will be bypassed and the voltage to the coil increased.
 
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