The Stovebolt Site Forums The Shop Area Engine Shop Warm Starting Issue

Hi all,

I'm trying to work out why the 216 in my '41 is difficult to start when the engine has been running at operating temp.

Here's what I know:

Starts great when it's cold.
Plugs, points, condensor, wires, cap, all brand new.
Battery brand new, engine spins fine hot or cold.
Valves adjusted to within spec (leaning toward loose rather than tight).
Carb recently rebuilt.
Timing adjusted with a light. (This is where I thought the issue was. I had been running the engine a bit more advanced than spec, so I retarded it a few degrees. However, that didn't seem to help the warm starting issue.)

I'm still going to experiement with the timing some more, but if you have any thoughts or if I missed anything, feel free to let me know.

Thanks,

John

John,

You have done a whole lot of stuff so the field of problems has been narrowed. It would seem to me it's either fire or fuel.

As the engine warms up, the coil warms with it and this will increase electrical resistance. If there is a internal short or turn to turn short, this increased resistance can cause the coil output to fall below the threshold it takes to properly fire the plugs. So a bad coil is a possibility.

I would try squirting some fuel into the carburetor throat next time it refused to start. If it fires, then lack of fuel seems like it would be the culprit. Most often, a warm engine, after it is shut off can cause the carburetor to heat and the fuel to percolate out, dumping into the intake and flooding the engine.

You would see some evidence of black smoke out the back (maybe), and it would cough and sputter as it came to life. This would be a sure sign of flooding. Do you still have the little plastic spacer between your intake and carburetor?

Taking it one step further, a weak spark in conjunction with a rich air/fuel mixture would create a 'hot' hard to start situation.

I would look at all these things, but I would also make 100% sure my point gap was perfect. Keep us posted.

Stuart

John,

Original 6v or a 12v conversion?

If it is 6v, you do not say is you put in new battery cables (positive lead and negative braided-ground to frame).

Most modern cables are 4 gauge but the original 6v cables were 2 gauge and many people use 0 or 00 gauge cables.

Most people have put in the 12v replacement cables over the years. This is the main reason why people who are having starting problems with mostly original trucks think they have to change to 12v electricals in order to have reliable starting

Similar to Stuart's response, I have read that once the starter gets warm, it gets less efficient. This is an added problem with a 6v system and the wrong gauge of battery cables.

Tim

Hi Stuart and Tim,

Thanks for your notes. The electrical is the original 6v set-up. All the cables have been replaced with 6v repros meant for the application and I have cleaned all the terminal ends and ends that mount to the starter motor and ground point.

Coincidentally, I talked to my dad about the problem this morning and he also thought it might be the coil becoming less effective as it gets hot. I'm going to pull the coil off my '42 this weekend and put it on the '41 to see if that makes a difference. I'll let you know how I make out.

John

Coils can fail when they are hot because the windings expand with heat and if there is a bad spot in the insulation it will fail, but that is usually a thing that happens while driving, but it could be the culprit. I would look closer at fuel though. Unleaded gas is much more volatile than the old leaded gas these critters were built for. Do you have an insulator between the carb and the manifold? If so, I sometimes stack a few extra gaskets to keep the carb from perculating. Try holding the throttle wide open when you crank. This will give it some air if it is flooding. Also a dragging starter will take voltage away from the ignition. I make sure my starter bushings are good and I install high performance in my starters. My 6 volts crank almost as good as 12 volt.

Thanks for the last note. I currently have the stock spacer between the carb and the manifold, which is made of a composite heat-resistant material, about 1/2" thick.

One other thing that I'm going to check into is that I'm getting a slight dripping of fuel around the outside surfaces of the lower butterfly shaft when I toggle the accelerator by hand. My suspicion is that the raw gas which the accelerator pump is discharging into carb throat is collecting on the interior section of the shaft and is then trickling past the bushings in the carb body to get to the outside of the carb. Given the comments above about flooding, I'm thinking this could be contributing to that. I'm also thinking this might be contributing to a vacuum leak. My '42 carb, which is slightly different for military applications, has rubber insulators on the shaft to prevent this type of vacuum leakage. I don't recall the civilian model having those, but if the coil doesn't turn out to be the culprit, I'm going to pull the carb to see what the fit is like on the butterfly shaft.

It could be the ground cables, many here have had problems with repro cables not being heavy enough.

Finally had the chance to put a different coil in. That seemed to solve the problem.

Thanks to all for the input.