Hot damn—hot start
Or should I say “Hot damn if it starts hot?”
One of the common problems I often get questioned about and experience in the shop is about cars that start great when they are cold, but are very difficult or impossible to start when they are hot. This can be a very complex or a very simple problem.
First of all, a tired engine can lose compression when hot, making it hard to start and not a whole lot can be done. To find out if this is the main problem, take a cold compression reading and then take it again after the car is warmed up good. Be careful, don’t burn your fingers.
Compare the two readings and if you average more than a 5-pound drop on all the cylinders, this is probably the main problem and you probably need an overhaul. Even healthy engines can have this problem and some of these solutions may help out a tired engine.
Your problem is either going to be fuel or ignition. The most common fuel problem is vapor lock, which generally can be solved with an auxiliary electric fuel pump (in parallel, obviously). You should also check the float level to make sure you are not flooding. If you are flooding, it could also be bad gaskets or looseness in your assembly.
Another possible fuel problem is the insulator between the carb and the manifold, causing the fuel to percolate in the carburetor bowl, add an extra gasket—it won’t hurt. If you have a nonvented gas cap, you could be having a problem with fuel flow.
As for ignition problems being the problem, the first place is to suspect the starter. It could be dragging enough to both not turn the engine over fast enough or pulling so much current that there isn’t sufficient voltage to fire the engine. The best solution for this problem is to have a good starter man rebuild it and put in high-output field coils. The last car I did this for, the owner accused me of converting the car to 12 volts.
Another point to check is for resistance or broken strands in the wire from the switch to the coil. An easy way to check this out is to put a jumper wire to the input side of the coil direct to a battery source. You should also check the wire from the distributor to the coil. If it is too long, replace it with new wire and make sure you have good terminals.
The next thing you want to check is the points. Make sure the gap is right and look for signs of pitting or peaking. This could be an indication of either a bad coil or reversed polarity. Remember, ’41s and older have a positive ground—never forget this!!! If you are lucky enough to find an NOS armored cable-type coil, make sure you have the right polarity.
What you can do, and you will see it a lot, is to get a replacement coil of the type with two primary terminals on the top and run a hidden wire from the switch to the proper terminal of the coil. The armored cable cap can fit over the bottom of the coil and it will look original, if you hide this wire in the firewall.
Make sure the coil you use is designed for 6-volt use. A
12-volt coil just will not give you a hot-enough spark to start the car,
especially when the car is hot. The best coil I have found for these old cars
is available from
Just because a coil is fairly new does not mean it is not the problem. They are very temperamental and go out on the way home from the parts store, or they could last forever and a day.
Here again, I cannot express the importance of observing the correct polarity. You want to be sure the timing is correct, and if it tries to buck back on you as you try to start the car, you have the distributor advanced too far.
Of course, if you never let your car get hot, this won’t be a problem. Otherwise, after doing all or part of the above, you should be able to shout “HOT DAMN, IT STARTS HOT!!!”
See ya next month.