difficult 6 volt warm starting

mrlaser

mrlaser

Senior Member
I have a stock flathead 8BA v8 with a 6 volt, positive ground system. The battery is a 6 volt Optum Red Top that measures 6.4 volts when the system is off. The battery cables are 0 or 1 gage and are essentially new. The voltage regulator output a 1500 to 2000 rpm measures 7 volts. The starter was professionally rebuilt by an old time auto electrical shop. There is no issue with cold starts, but when the engine is fully warmed up, the engine turns over very slowly. It does ultimately start, but not nearly as quickly as when the engine has not been run. I strongly suspect that increased electrical resistance is the issue, but wonder what suggestions and or experience others might have had that might help mitigate this situation ?
 
Check and "Clean" all your grounds to shinny steel, then use a dab of dielectric grease to keep them nice and clean, no paint obstructing the contact surface of both. ALSO make sure the face of your starter where it makes contact to the bell housing is ALSO Nice and clean, again, no paint or anything obstructing the contact surface of both. IF you have the flat braided type ground strap, you can try doubling it. OR maybe try running a ground from the starter mount bolt to the frame.
 
sounds like the battery and voltage regulator are both working properly...

but my short answer is to verify that the starter is a 6v starter and not a 12v starter. which was the root cause of all my misery... (hint) 12v starters typically have four brushes, 6v starters typically have two. if you're luckier than me, information on the casing will answer that question. the loooong story follows for the those that dare. :)



i had pretty much the same problem. engine would turn over the engine (not quickly) and start the car when cold, but when warm would barely turn it over, sometimes not at all. the battery would be dead after only about 20 seconds of cranking, max, before needing to be put on the charger.

i replaced all the battery and ground cables with 00 copper wires and cleaned up all the connections too, but still didn't seem to fix the problem. there was an old starter in the trunk of the car that bench tested successfully so i removed the supposedly new starter that was recently put in the car by the previous owner, and THAT fixed the problem, although i'm not convinced that there was anything physically wrong with the new one...read on.

i can't be sure, but i think that when the previous owner began messing around with an 8v battery (which was in the car when i purchased it) and tweaked the voltage regulator too, they not only burnt up a couple of gauges on the dash, ruined the voltage regulator, but also installed a new 12v starter (there are no markings but there are four brushes which is usually an indication that it is a 12v motor) that didn't, doesn't, won't and never will work properly with either an 8v or 6v battery. why did they install a 12v starter, i'm not sure and will probably never know, but it could have been in error or it's possible that they just didn't know what they were doing.

in any event, my car now has all new 00 copper battery and ground cables, a new 6v battery, a new 6v voltage regulator, some new gauge (all of them now work), and wiring under the dash and its original 6v starter and works wonderfully to start the car, whether cold or hot. and can crank for quite a long time (NOT that it needs it, mind you!) before the battery loses power. :)

it's good to keep in mind when dealing with electrical circuits, that heat increases resistance. meaning problems are more likely to show up as temperature increases.
 
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19Fordy said:
Remove the starter and check the starter brushes and bearings.
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I agree with Jim on this AND all the ground point cleaning.
Even if a good shop rebuilt it, maybe it was done in haste or by someone other than the owner., a new hire or incompetent one. I got burnt like this with a distributor I bought as "rebuilt".
 
I'm also in the "check the starter" club. "New doesn't necessarily mean good." I had a fresh rebuild from NAPA that would hardly start the engine a couple of years ago. Replacing it with a known good used starter fixed my problem. Brushes and bushings are readily available (at least they were a couple of years ago) and cheap. They are easy to install if you have a large enough soldering iron.
 
Take a digital voltage meter and do a "voltage drop test" on every cable, starter solenoid and starter. What it does is measures the voltage drop across each component while the vehicle is cranking. It's the only way to see if you have resistance in the starting circuit and where that resistance is located. Chances are it's going to be the starter, but this test will verify the starter cables and solenoid are good. YouTube has lots of videos that show you how to do this test. I was a professional mechanic, 99% of the time I could throw a new starter in and that would fix it but every once in a while, I'd get a car with hidden resistance. I even had a brand-new car that they did not remove the plastic from around the battery cable when they crimped the battery terminal on it. Sometimes it started and sometimes it didn't. You would never guess in a million years that the brand-new cable was bad. I only saw that one time in 30-years, but I found plenty of other faulty parts using the voltage drop test.
 
Thanks everyone for the great ideas. I will give all the suggestions a try. I happen to have a spare rebuilt starter. Fingers crossed.
 
mrlaser said:
Thanks everyone for the great ideas. I will give all the suggestions a try. I happen to have a spare rebuilt starter. Fingers crossed.
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If your spare starter works, rebuild the old one and keep it as a spare as starters with a bendix drive are getting a little harder to find.
 
52flthed said:
Why wouldn’t heat soak explain this? Why do you guys all point to electrical as the reason?
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when diagnosing problems, the most likely solution addresses all symptoms. heat soak does not address the failure to turn over the engine at the proper speed.

i've successfully addressed heat soak in these engines and in other british engines of the 50's and 60's and IME, there is no tendency whatsoever to show signs of decreased speed at which the engine turns while starting.

the underlying problem WRT heat soak has always been shown to be overheated fuel in the carburator's floatbowl and/or jet, causing a lean mixture.

proof of that, has been shown by actually using the manual choke (if available) to richen the mixture and thus start the engine. and the long term solution and simple one, IME, is to open the hood after quiescing the engine if heat soak is anticipated.
 
An easy way to test ground as your issue is to run a straight ground from your battery to the starter with a jumper cable. If it turns over better you have an over restored starter. I would think though you would have bad starts all the time with a bad ground. As stated above brushes and bushings are easy and that would be my next step as well as cleaning the communicator, after I confirmed the armature wasn’t rubbing on the coils.

JB
 
I don't think this hs been mentioned, but as a teen ager I had a '37 Ford on 6v. For months It would start good cold and not turn fast enough when warm. I always had friends around to push it off when it wouldn't start. For some reason, one day I took the ground cable off the firewall and put it on an intake manifold bolt. That solved my problem for good! Looking back, maybe I could have cleaned all the ground connections with the same results. To this day I always put the ground cable on the engine and jumper to the body and frame from the engine.
 
Wow! More great thoughts. I am embarrassed to admit that when I rechecked my "spare" starter it was actually the one that I had rebuilt. I have accomplished this rebuild over 5-6 years and that's probably not the last lapse in memory that will have been included. I'll post again once I have followed through with the suggestions. Thanks again for your help
 

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mrlaser said:
Wow! More great thoughts. I am embarrassed to admit that when I rechecked my "spare" starter it was actually the one that I had rebuilt. I have accomplished this rebuild over 5-6 years and that's probably not the last lapse in memory that will have been included. I'll post again once I have followed through with the suggestions. Thanks again for your help
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