VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Trouble starting when hot ??

my 31 Chevrolet 4 door starts fine and runs great when it is cold. When I take it for a run and shut it off it only grunts when I step on the starter and try to restart it as if the battery is dead. I replaced the battery and no difference and when this occurs the battery is registering full charge. Consequently I am scared to take it for a ride as I can not shut it off. Please offer suggestions.

starter probably

blue 38,

I've had the same issue with my '34 so I just took it for a rebuild. You guys with more knowledge than I might want to explain what the problem(s) might be with the starters, what a rebuild involves, and the improvement in performance (hopefully) we could expect.

Check the voltage at the starter when hot and cranking. If less than 5 volts then check all connections or just check all connections and make sure they are clean and tight. Since resistance increases with heat any corrosion at connections dramatically reduces current to the starter. What size cables do you have? If they are marginal size then heat will make them too small. After you check all that (does not cost much $$$) then take the starter to be checked (costs much more $$$ to get it fixed). I always try to look at the easiest and cheapest to fix first.

Chipper,

I am positive all the connections on my '34 are super clean. I have put on new correct cables. They are the braided flat ground and the cloth covered large positive cable. I got the ground from Jim Carter's (near me) and the positive cable from the Filling Station. So since the starter didn't look like it had been rebuilt when it was still with my father-in-law, I decided to have that done. That may not make much of a difference but at least I will have more faith in it not failing later.

Inless burnt, which then the starter wouldnt spin or inless having "dead spots" which means the starter turns in one position and not the other, you REALLY dont have any major trouble with starters. The Brushes are more likely to be wore out than winding troubles. Extreemly wore brushes will make a starter turn hard or non at all. High mica will do this too which insulates the commutator. I would recommend looking at the commutator of the starter, have the part were the brushes ride, turned down on a lathe, if this area is wore. Cut the mica down between the commutator with a hack saw blade, one strike at a time ti'll the mica is significantly lower than the brush area, clean the starter out with a couple cans of electra-motive spray which can be found at most automotive stores, inspect your bearings for ware, oil the bearings, inspect the brushes and if wore really down, replace them. Most of the time, this rids your problems.

Would a warm engine turn easier than a cold one?

Start easier. That is if the engine is mechanically in tune. I couldnt say they turn any easier.

I still don't understand why the starter does not turn over a hot engine as easy as a cold one.

According to my '47 Delco-Remy manual,the commutator on a starter motor should not have the mica undercut,as the brushes are harder than the mica between the segments,and it will be worn down due to the brush tension on the commutator.
You could check cable sizes and ground points for corrosion,or the bushes in the starter are worn to the point where the armature is rubbing against the field coil pole pieces.

You got me there. Perhaps slight compression gain but thats being really dromatic.

I would highly question that manual. That might be what it says, but any time you have high mica, you dont have good contact for the brushes. Any interuption between the commutator and the brushes will result in little to no cranking and an exessivly HOT starter motor due to the motor will try to draw more amps to overcome resistance. If that manual actually says that, it goes against all the rules of maintaining a commutator. Any professional motor rebuilder WILL cut the mica down.

The generator armature is always undercut, but not the starter armature. You never undercut the starter armature UNLESS someone has undercut it on a previous rebuild. The professional starter rebuilders that I know will not undercut a starter armature, unless, again, it was undercut previously. Also, all of the new old stock and new rewound generator armatures that I have in stock came from the factory undercut, however, all of the new old stock and new rewound starter armatures that I have in stock are not undercut.

The manual quote above is correct because the starter motor does not use carbon brushes like the generator.

The dog is correct on that one.

I cant help what is written and what is seen. You cut the mica. I always have, personally, and i always will. Becouse it IS the proper and correct thing to do.

To quote the original post "it only grunts". My experience is that a warm oil flows easier than a cool oil. A starter has more going for it when the engine is warm than cold. That's why they plug in vehicles overnight in the winter here in Iowa. My guess is the problem is too much compression when warm. Maybe exhaust valves out of adjustment but with no symptoms until the motor is warm. Just a guess.

From my experience I would say a bad armature that's shorting out. The starter will still work pretty well when it's cold but not when the starter is warm. If this is the case the starter will draw a lot of extra current but barely turn over the engine if at all. The shops used to check the armatures for shorts with a "growler".

Arend,
How hot does it have to be to get to act up? I have had a power drill act up when it was used too much without time to cool down. I can see what you are talking about. Does the exhaust run near the starter?
Dan

waynemcmichel --I do not know how much experience you have with your car but you can take it from a rookie that has asked a LOT of questions on this chat and recieved really great,helpful and spot on answers---THE DOG IS THE MAN !!
Listen to him and respect his wealth of knowlege and you will do just fine!!

I very respectively disagree. Undercutting a starter armature is really not the proper or correct thing to do. Unlike the generator brushes, copper starter brushes are not as susceptible to wear from mica because the brushes used in starter motors have a high copper content which is required because of the large current draw thus eliminating the need for undercutting. The result of undercutting a starter armature is that the space between the comm. bars becomes clogged with copper residue from the brushes and the armature segments could become shorted due to the copper dust between the comm. bars.

I know...there are fellows that insist that the starter armature should be undercut, and that is their preference, but it definitely is not necessary. If the starter armature has been undercut before then when the starter is rebuilt the armature will have to be undercut again to remove all of the copper dust between the armature comm. bars.

A friend of mine, before he retired, owned a major starter, generator and alternator repair shop. His shop worked on domestic and large commercial accounts as well. I can remember that when a starter came in for a rebuild and if someone had previously undercut the starter armature he would always go ballistic and say a few choice words.

One thing about this site is that you get a lot of advice, some excellent some ok and some kinda bad then some that is really bad. When you wonder which is which, invest in a genuine Chevrolet shop manual and a genuine Chevrolet Parts manual, and then doubt notit also helps to have the Service news collection for the year of your Chevrolet and a couple of the following years, just to check the advisors. I also know several of the VCCA members here and have always gotten better advice from them than from the camp followers and wanna-bs (JMHO)

The starter is on the opposite side of the engine block from the exhaust system.

Slow Poke, and others,

There are several factors that determine how fast a starter can turn an engine. Among them are viscosity of oil, resistance in starter (field, armature, brushes, bushings, bearings, etc.), resistance in wiring to the starter, ground path back to battery, power of starter, rolling resistance of engine, compression resistance of engine, ignition timing, accessories attached to engine (generator, water pump, fan, etc.), mesh of starter gear and ring gear, and power available from the battery.

While it is true that the viscosity of the oil is lowered by higher temperatures, the fit of engine parts may be the opposite. While the power available from the battery may be higher at higher temperatures the resistance in the wiring and circuits is also higher possibly reducing the effective power. Those are illustrations of how complicated determining exactly why an starter performs as it does. Then there is the rate which the gasoline vapor/oxygen burns in a cylinder which is faster at higher temperatures. Then there is the expansion of the starter shaft and bushing possibly increasing its rolling resistance. My head is beginning to hurt.

Im not going to drag the thread out about cutting mica, thats dumb right there.

What im talking about are motors using carbon brushes. They havnt used straight copper brushes for literally YEARS to my knowlage. If they have had, yes i can see were perhaps MAYBEE cutting mica is not needed. But definitly NOT for carbon brushes.

I have left high mica on a couple motors in the past, just to see what would happen. Both responded in a sluggish and poor way, drawing higher amps to overcome the mica. The motors got reasonably warm aswell.

I took the motors back apart, cut the mica and the motors spun just like they would brand new. No problems. I never have, never did and never WILL leave high mica on a motor again.

Im not going to set here and proove the fact of cutting the mica down. I cant proove were i've read old books about rebuilding motors and it stating undercutting the mica.

I will take note of what JYD said about discovering factory motors with the mica undercut. THEY DID THAT FOR A REASON and it wasnt for cosmetical looks.

Gentlement & JYD, im not going to say what im about to say without saying that it is said WITHOUT any harsh feelings, were all freinds here, i think. That said, I know i dont rank as high as some of you here on this site, im fairly new/old, i know the ropes, but i challange the man that says undercutting the mica is not needed and i question his true expertise in that department. Have they actually expereiced a motor with high mica Vs. one undercut? Have they been through the actual hands on mechanical expereince i have had? Have they whitnesses what i have whitnessed?

Again, no hard feelings ment. and i mean that. But when i say something needs to be done, you need to look into doing it. Im not an expert, just a highly expereinced garage mechanic without any awards or metals. But you do need to know i will not stear anyone wrong with *i think* suggestions, if i dont know, i will SAY i dont know, and i cuss the thought of anyone confusing me with just another wrench turning "wannabe". That is a slap in my face! I have quite a reputation to stand up too, i wont screw that up with a false statement.

Thats enough of that now. You get the picture.

Back to the motor and topic at hand, yes a growler would tell you if the motor has any dead spots. Thats what a growler is for...but a brush will tell you that too.

You do have winding trouble if the things i've suggested, failed. Ultimatly, that IS a rebuild...but troubleshooting outweighs an expensive rebuild right off the bat and it be all the same if simply replacing brushes or again, undercutting the mica after a turn down, does the trick.

You learn too, sometimes you cannot go by what a book says. I cant tell you how much of that crap i've had thrown in my face just to prove it wrong through time and opertunity. ofcource noone knows any diferent but me.

Take my advise with a grain of salt if you must, but keep it in mind. They'll be a time were i may have just told you so.

thats enough.

Hope your head is OK.