Hard hot Start Problem (common)

[SoCalCoupe]

1941 Ford flathead basically stock including 6V pos ground and generator. Made lots and lots of progress in the past year from being a real pig to drive to actually pretty good. No doubt this has been discussed extensively but my searches haven't been very good. I'll ask my Early Ford V8 club folks about this too.


Very, very hard to get the engine to crank when warm, easy when cold. In other words, the fuel and spark seem fine, the starter just won't turn over the motor when hot. I've undone and wire brushed all the electrical connections, including grounds, between the starter and battery. Maybe SLIGHTLY better but not much.


The whole point for me in having this car to have it like it was back in the day so converting to 12V is not on my list. Clearly, people started their 6V cars back in the day after they were warmed up, such as after filling up with gas.


Please help me out with a logical path forward to make the car crank when hot.

[tubman]

First, what battery do you have? About 30 years ago, I was in a bind and put in a Group 1 battery and had the same problem. I ended up raising the hood every time I parked my car on a hot day. An Optima solved that problem.

Then, about 3 years ago, I started getting nervous because although the car started every time, it just didn't seem right. After messing around with a lot of things, I ended up rebuilding the starter (new brushes and bushings and testing the armature to make sure it was good), and my confidence is back.

[Terry,OH]

Starter is grounded through the connection of the starter to the oil pan it may be a good idea to remove the starter and clean both the pan and the rear and front faces of the starter. Clean the two long bolts that attach the starter and make sure the small bracket to the oil pan from one of the starter attachment bolts, is also clean Battery is grounded to the firewall and there is a second ground on the firewall to the engine head stud.

[40ford]

I have to ask,is your battery cables size at least 00 and are in good shape.I had that problem and found one of the cables was actually corroded on the inside looked good from the outside.

[Ken/Alabama]

Also keep in mind that the starter solenoid contacts can get pitted and burned causing a high resistance in the starter circuit. Had this to happen before. New solenoid solved the problem.

[patrickdee]

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I have spent the last summer going over my 40 coupe to make it reliable again. The Fordbarn members have been a a great help. Following the advice with adding grounds and replacing to larger cables. A good battery is important. I had a rebuilt starter with low mileage on it that I was sure was not part of my hot start problem. After replacing it with a fresh rebuilt starter the difference is night and day. The car now starts almost immediately and no longer has a hot start problem. I also replaced the ignition switch that was very worn and not showing the proper resistance. Keep at it. You will get there.

[wga]

As mentioned the cable to the starter should be of 00 or 0 gauge copper, properly crimped
ends. Check that the cable is not frayed. The end crimps should not have bare wire visible, which leads to corrosion and resistance. Starter can be removed and cleaned for good ground connection. If the starter is in need of rebuild, also consider a new gear reduction style, for about the same $$ or less than a new / rebuilt stock starter.
The motors on these draw less amps and use the gear reduction to multiply the torque applied to the flywheel.
Optima battery is the way to go as well. I ditched the lead acid battery.

Had the same problem on my 49 when I first acquired it, 22 years ago.

[19Fordy]

SoCalCoupe: Check your compression. Low compression will start when cold but, can inhibit starting when hot.

[Tim Ayers]

Originally Posted by 19Fordy

SoCalCoupe: Check your compression. Low compression will start when cold but, can inhibit starting when hot.

If I'm reading his post right, the OP said the starter slows down when hot which is causing the hard start.

Low compression would certainly cause a hard start, but the starter should be spinning the same speed hot or cold if low compression is the root cause of the issue.

Someone coined the term "horse cough" for the sound a healthy starter makes. If it sounds like that every time, I would tend to think it's caused by something else other than a weak starter or improper wiring or wires or a bad ground

[19Fordy]

Good point Tim. I misread the OP.
"Very, very hard to get the engine to crank when warm,"

[SoCalCoupe]

Originally Posted by tubman

First, what battery do you have? About 30 years ago, I was in a bind and put in a Group 1 battery and had the same problem. I ended up raising the hood every time I parked my car on a hot day. An Optima solved that problem.

Then, about 3 years ago, I started getting nervous because although the car started every time, it just didn't seem right. After messing around with a lot of things, I ended up rebuilding the starter (new brushes and bushings and testing the armature to make sure it was good), and my confidence is back.

Can't tell what group the battery is. There's a sticker where the group can be selected by punching a hole but none is selected. Group 1 isn't a choice. it starts at 24 and goes 24F, 25, 26, 26F, 27, 27F, 34,.....96R. There are three sets of numbers stacked like this:


31
35/75
34/78

Originally Posted by Terry,OH

Starter is grounded through the connection of the starter to the oil pan it may be a good idea to remove the starter and clean both the pan and the rear and front faces of the starter. Clean the two long bolts that attach the starter and make sure the small bracket to the oil pan from one of the starter attachment bolts, is also clean Battery is grounded to the firewall and there is a second ground on the firewall to the engine head stud.

That sounds like a worthwhile, low-cost, minor project.

Originally Posted by 40ford

I have to ask,is your battery cables size at least 00 and are in good shape.I had that problem and found one of the cables was actually corroded on the inside looked good from the outside.

the + ground to the firewall is a braided strap. The negative cable to the solenoid is 2 GA. The negative cable to the battery is a cloth covered replica with no marking, can't get to the bare cable without removing insulation to measure anything. There's no 2nd ground to a head stud. Nothing connected to any head stud. Don't recall ever seeing or hearing of that.

[TJ]

Frankly unless the braided + cable is new I would ditch it. I've encountered more than one old Ford with the same hot start problem and it turned out to be the braided cable. It gets corrosion on it easily, especially if you live near salt air from the ocean.

[swedishsteel]

Had same trouble on my '36 with Optima battery. Bigger cables and battery as close to the starter as I could get--problem solved.

[SoCalCoupe]

Originally Posted by swedishsteel

Had same trouble on my '36 with Optima battery. Bigger cables and battery as close to the starter as I could get--problem solved.

That's encouraging; sounds simple.

Originally Posted by TJ

Frankly unless the braided + cable is new I would ditch it. I've encountered more than one old Ford with the same hot start problem and it turned out to be the braided cable. It gets corrosion on it easily, especially if you live near salt air from the ocean.

The braided cable seems relatively new but I'm not averse to replacing it.


I'll look on the lug of the cloth covered cable tomorrow to see if there's a size. Think I'll replace the braided ground and the 2 ga cable to the solenoid. Replacing the cloth covered cable will get me a little further away from original but there are already quite a few non-original parts so this won't ruin my fun, especially if it works!


I see on ebay that you can buy 00 cables of any length, red or black. Any particular recommendations? 00 cloth covered cables available? I'd like to look period correct but am not a slave to it; they're just battery cables. I've already made some other period correct (late 40's, early 50's) mods.

[Gene1949]

Hard starting heat soaked flatheads were a fact of life back in the 6 volt days.

[SoCalCoupe]

Originally Posted by Gene1949

Hard starting heat soaked flatheads were a fact of life back in the 6 volt days.

So maybe this is part of the bargain of being period correct.

[chuck stevens]

you can check for high resistance in those old cables by feeling them after trying to start,if the cables are good and the starter is grounded good she'll crank hot or cold with a good six volt battery.

[Gene1949]

Originally Posted by SoCalCoupe

So maybe this is part of the bargain of being period correct.

Great minds think alike. With the questionable reliability of todays flathead parts I understand why the "period correct" guys are struggling. I would rather drive the car than futz with something I have no control over.

I went to the "dark side" (12 volt and electronic ignition) a long time ago. I had a no start in traffic when I failed to slip the clutch enough moving away from a stoplight. Motor died and we were forced to push it. Huge mess and in my opinion a major safety issue

[Seth Swoboda]

Originally Posted by Gene1949

Hard starting heat soaked flatheads were a fact of life back in the 6 volt days.

That's not my experience. I have driven my flathead powered cars/trucks for a 50+ mile trip in the summer, parked for a short time and restarted with no issues. They also don't run hot. My cure for a hard start when engine is up to 180 degrees, ignition system must be operating at 100% efficiency as well as the cooling system. If so, all should be well. I'm a period correct guy and loving it.

[JayChicago]

Originally Posted by Gene1949

Hard starting heat soaked flatheads were a fact of life back in the 6 volt days.

Because lots of people were driving old, tired cars that had maintenance problems. When all is well, no hot start problem.