Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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

Re: Hard hot Start Problem (common)
 

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

Re: Hard hot Start Problem (common)
 

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

Re: Hard hot Start Problem (common)
 

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


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




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.

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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

Re: Hard hot Start Problem (common)
 

That's encouraging; sounds simple.




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.

Re: Hard hot Start Problem (common)
 

Re: Hard hot Start Problem (common)
 

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

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

Re: Hard hot Start Problem (common)
 

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.

Re: Hard hot Start Problem (common)
 

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

Re: Hard hot Start Problem (common)
 

Look for voltage drop in your starting circuit by connecting a voltmeter across a cable and try engaging the starter. If the meter moves up more than .05 volt, get the connections cleaned or a heavier cable. Connecting from the battery negative to the starter terminal and engaging the starter should not show more than 0.1 volt. You have disclosed that you do not have a cable from the firewall to a head bolt. You need that cable. You also need to check for voltage drop by connecting the voltmeter to the positive of the battery and to a head bolt and engage the starter. Again, the meter should read 0.1 volt or less. You have an Optima battery? Puts out very satisfactory starting capability.

Re: Hard hot Start Problem (common)
 

the sound of a Flathead cranking on 6 volts is part of the experience for me

Re: Hard hot Start Problem (common)
 

Re: Hard hot Start Problem (common)
 

OK. Just went through lots of flathead engine compartment pictures on eBay and did what I should have done first, looked it up in the EFV8 club 41-48 Ford book.


Of course you are right.


"Three threaded studs for ground strap are swaged into the firewall. As the battery on a 6-cylinder car is on the driver's side, while the V-8 battery is on the passenger side, two studs are provided, one of which will be unused on any particular car. A third ground stud is located near the lower center of the firewall for a ground strap that will connect to the engine via a convenient head or manifold bolt."


Located both the 6-cylinder and engine ground studs. Never noticed them before. No engine ground strap. One more thing not done right by the previous owner(s). Before I even get my hands dirty messing with the starter bolts, I'll buy and install that firewall to head/manifold strap.


Not my car, but here's a picture from something on eBay. I see the engine ground strap just to the right of the starter solenoid. Looks like it's connected at a head bolt but a little blurry.
https://www.fordbarn.com/forum/pictu...ictureid=45247

Re: Hard hot Start Problem (common)
 

Re: Hard hot Start Problem (common)
 

[QUOTE=SoCalCoupe;2188109]OK.

"Just went through lots of flathead engine compartment pictures on eBay ..."

What were you actually pulling up on eBay. I could not find anything under "engine compartment" except pictures of aftermarket electric fans, no original engine compartment pictures.

Re: Hard hot Start Problem (common)
 

[QUOTE=Lawson Cox;2188680]Sorry, not clear. I was looking up 1941 Fords for sale hoping that one of them would have an engine compartment picture showing the engine ground strap.

Re: Hard hot Start Problem (common)
 

I found this one. Don't know if it's correct or not >
https://dealeraccelerate-all.s3.amaz...per-deluxe.jpg

And this one > Battery to firewall connection?
https://images43.fotki.com/v270/phot...1tan104-vi.jpg

Re: Hard hot Start Problem (common)
 

Again not my experience -Every one I know who has had problems with reliability in their car have had it either "restored" by a shade tree mechanic and/or have upgraded it for reliabilty with mass produced modern inferior parts that Henry's quality control inspectors would have consigned to the scrap heap instantly. After 88 years and 105,000 miles my car is stil running many of the original electrical components with no problems. For me the functionality and relability of such old technology is part of the charm of owning an old vehicle -but each to their own

Re: Hard hot Start Problem (common)
 

I made the cables for the battery, ground, and starter. I forget the place I got the cables, but it was all high quality copper wire that I crimped and soldered the ends on to. All cables came in the length I specified.

For purist, it was plastic shielded, but I slipped that black tar covering over them and you'd be hard pressed to tell they aren't original.

I'll try to find the site I got them from. Quick shipping and great price for US made copper cable.

Re: Hard hot Start Problem (common)
 

OK, we have had this topic many times but I like to here it as it means my friends are driving (or want to be) their old iron. I have had many old 6volt flatheads, Ford , Lincoln, Dodge and Cadillac. The Lincoln Zephyr and the 46 Cadillac were the ones that tested my knowledge on starter draw and cranking speed. First and foremost, you have to have the cold cranking amps. On the caddy I use two optimas in parallel just to put my wife at ease when she drives it without me around. The Optima batteries have the most cold cranking amps in the 6volt field these days and you can hide on inside the case of your ford batterie case for show. Second , Cables need to be big , the bigger the better and the finer the wire strands the better. A lot of the new cables look big but just have more insulation and less copper. Look closely as I was fooled by a on line vender myself. Wire routing is next, the positive ground cable should be attached to the engine, mine are on the head bolt/studs. The negative should go to the solenoid in as short a path as possible. The same goes for the cable from the solenoid to the starter' Next, it's the solenoid that turns on the the starter circuit . These are simple switches that can work well for thousands of starts but eventually the contacts will burn and create resistance . If your solenoid get hot when starting you should replace it(heat is resistance) with a quality one. The starter motor is the hardest working part of this system. Just because it works doesn't mean it works well . These can be tested by a good electrical shop . I have taken most of my starters apart(even the new ones) and lubed the head or nose bushing with molly bearing grease to reduce the friction as well. This does seem to make a difference. If you follow these simple steps and have good clean tight connections. You ford should start in any condition, hot or very cold. May there always be road , Tim

Re: Hard hot Start Problem (common)
 

Welding cable makes the best battery cables. It is very fine strand and the insulation remains flexible in all temps and won't crack, like battery cables you buy at the local box store. Your local welding shop usually has it bulk, or there are various online vendors as well. As stated previously the bigger the better. I use at least 1 gauge or if running a little distance 0.

Re: Hard hot Start Problem (common)
 

Others have said it. You must verify that you have available voltage with a voltmeter. You cannot work on electrical stuff without a digital voltmeter. Otherwise, you're just guessing. If while cranking, you have the proper available cranking voltage then you have resistance somewhere in the circuit. You can't check with on ohmmeter for resistance because the meter is only using a very small amount of current to check for resistance. That works on small current circuits but not on large ones. That amount of "meter" current can easily flow through a large cable or solenoid. The parts will show no resistance. But when a large amount of current like a starter tries flowing through, it cannot. So, the way you check for this is by doing a voltage drop test. It's easy, its fast and it will find the problem if its resistance.

Forget its electrical and let's assume it has water flowing in it. If it was a very large pipe the water would come out the end with no pressure because the pipe offers no resistance. Now if the pipe had a restriction somewhere in it and you had access ports and were able to take pressure readings at different spots along the pipe when you found the restriction the water would try and flow around the restriction and out the access port and through your pressure gauge. That is exactly what is happening when you do a voltage drop test. If the area between your two-meter leads is okay, there will be no back pressure there because the cable, connection or device offers less resistance than the meter. does. When you put your leads on either side of the restriction with current flowing and there is a restriction in that spot the current will try to flow around the restriction and through the meter.

Voltage is electrical pressure. So, on a 12V system if your meter read 1.5V that means there is a 1.5V pressure drop between your two leads. Only 10.5V of pressure would be making it to your starter and it would crank slowly. That entire 12 Volts has to be accounted for. If the battery measures 12.6 volts across the posts and you put the meter leads across both ends of the positive cable and it measures .1 volt. You put the leads across both sides of the starter cable, and it reads .2 volt. You put the leads across both ends of the ground cable and it reads .1 volt. That is .4 volt drop That means that it you put the leads across the positive side and negative side of the starter you should see 12.2V. There cannot be any missing voltage. So, what if if the starter shows a 10.2V drop. Somewhere we are missing 2 volts. Let's try putting one meter lead on the positive battery post and one lead on the positive battery cable and crank the engine. The meter reads 2 volts. There it is the resistance is in the battery terminal to battery post connection. Do a voltage drop test across the starter when it's cold and when it's hot. If you want to just, try this test. Set the meter on the 12V DC scale and stick the positive lead on the batterie's positive post and the negative lead on the cable and turn on the headlights. It should read zero. Turn off the lights, remove the battery cable and just barely set it back on causing a bad connection and turn repeat the test. You will get a voltage reading on your meter, that is the drop in voltage across that bad connection. This is how electrical stiff must be tested.

Here is YouTube video showing a voltage drop test.

https://www.youtube.com/watch?v=paw80mS_Kxg

Re: Hard hot Start Problem (common)
 

Problem solved.

Engine ground strap arrived in the mail and I installed it today from the firewall to the intake. This part was missing when I bought the car a year ago. Hot cranking is now just as good as cold cranking. Just as good as a 12v conversion for my purposes.

Thanks to FordBarn for helping me identify the missing part.



No more fears about restarting after stopping for gas or stalling the engine with bad clutching.

Re: Hard hot Start Problem (common)
 

Good news, thanks for the update.
I'm another member of the "6V works fine" group. Back in high school I started my 52 sedan on 6V when the engine was boiling over, definitely a "hot" start and no problem for the 6V system (the radiator on the other hand was terrible).