1957 Solenoid gets hot when hard starting

[TbirdFan76]

Is it common for the solenoid to get hot and actually smoke when cranking engine 10 seconds or more? The positive cable casing has actually melted at the solenoid connector.

The engine is 312 V8 with original Holly List 1273-1 4 barrel carburetor. I've rebuilt the carb and fuel pump. It's still a hard starter the next day after being driven. Also after driving it can be hard to start at times and fine other times. A few squirts if starter fluid brings it around to starting. Haven't checked spark plugs and points yet.

It is annoying to have to watch the solenoid temperature when dealing with the hard starting.

Let me know if you've encountered the solenoid getting hot and if there is a way to prevent it (besides not cranking the engine more than 10 seconds). 😉

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[sre]

Do you have a good ground, engine to body ? Have the neg. and positive cables been changed recently? How about the starter wire from solenoid to starter? Negative cable from battery to engine? You are drawing to many amps somewhere.

 

[Tom Alpers]

I would say its not normal. Clean all the cable ends and make sure they are tight. If it still gets hot you may have a starter that's drawing too much current or a bad solenoid, or corrosion on the inside of the cable where it's crimped to the end lug. A voltmeter can be helpful to troubleshoot as can an ammeter, particularly a clamp around one that reads DC amps. A good starter can easily draw 175 amps... a bad one can be pulling 300+.

 

[cokefirst]

have rarely found a 12 volt starter relay that when bad. It can and does happen, but many are replaced when the problem is the battery or starter. Do the tests as above. Does the starter seem to turn slowly when the engine is warm? I did have a problem with a 1955 5 volt that cranked real slow when warm. I was blaming the starter when I noticed that the relay was unusually warm. I replaced it, and problem solved!!

 

[TbirdFan76]

Do you have a good ground, engine to body ? Have the neg. and positive cables been changed recently? How about the starter wire from solenoid to starter? Negative cable from battery to engine? You are drawing to many amps somewhere.

There is a ground cable in good condition from the engine to body but I have not tested the ground. The neg and pos cables appear in good condition, they are not corroded and were on the car when I bought it in Jul 2024. I replaced the cable from the solenoid to the starter last year.

 

[TbirdFan76]

I would say its not normal. Clean all the cable ends and make sure they are tight. If it still gets hot you may have a starter that's drawing too much current or a bad solenoid, or corrosion on the inside of the cable where it's crimped to the end lug. A voltmeter can be helpful to troubleshoot as can an ammeter, particularly a clamp around one that reads DC amps. A good starter can easily draw 175 amps... a bad one can be pulling 300+.

I've got a multimeter. Can I take the starter voltage and amp readings from the starter cable end at the solenoid? I don't have a clamp around meter so I'm guessing I need a helper to turn the key while I take the reading.

 

[Tom Alpers]

The yellow wires may be getting hot just because they are hooked to the same terminal as the big black one. With what I have to go on, I'd say either the solenoid is bad, the end on that black cable is bad, or the starter is bad. The easiest and cheapest thing to do would be to go get a new cable and new solenoid and replace them and see if the problem is fixed. I don't know your skill level so it's hard to go beyond that here. I would be testing the cable and the solenoid for resistance and measuring the current draw to the starter. If you knew the current to the starter that would let you rule out the starter as the problem. You could also measure the voltage drop across the two big terminals on the solenoid when the starter is engaged and calculate its internal resistance. I would also measure the current thru those yellow wires.

 

[TbirdFan76]

have rarely found a 12 volt starter relay that when bad. It can and does happen, but many are replaced when the problem is the battery or starter. Do the tests as above. Does the starter seem to turn slowly when the engine is warm? I did have a problem with a 1955 5 volt that cranked real slow when warm. I was blaming the starter when I noticed that the relay was unusually warm. I replaced it, and problem solved!!

I'm concerned about getting the yellow cables disconnected from the solenoid given there condition. Any tips?

 

[Tom Alpers]

I saw your message right after I posted my last one. No, you cannot measure the current with a regular multimeter, they rarely go over 10 or 20 amps or you'll either blow their fuse or burn them out. You can take volt readings. The problem I see now is that the cable end is cooked and things will never work right till that cable is replaced.

 

[Tom Alpers]

I just noticed something else. The one cable end is cooked as mentioned.... But the one on the other side of the solenoid, which would have had to carry the same current, looks fine. That suggests more strongly that the problem was with the cooked cable end being "bad" and starting the problems. Since it's so cooked, it may have also gotten the inside of the solenoid cooked too just from heat transfer. So I would again say replace both that cable and solenoid to be safe and then see how it goes. I have found my clamp around meter, which I only bought a year ago, incredibly useful for these kinds of things. Should have bought one years ago. If you do buy one, make sure it can do both AC and DC.... many only do AC. Amazon has a large selection.