Starter on 6volt 35 Buick very slow cranking when hot.

[Buick35]

I know this has probably been discussed before but after I got to a car show yesterday I went to move my car to a different spot and the starter wouldn't turn fast enough until the motor cooled down then it started fine. I'm wondering what's the best way to solve this problem.The starters been rebuilt and the grounds are good or so I think. Would a heat shield around the starter help or some type of heat insulater between the starter and the block? It would have to be very thin though. Any thoughts will be greatly appreciated.Thanks.

[edinmass]

Well, you obviously have a problem. When heat related it’s usually a poor ground or a partial armature or field issue. Occasionally it can be a binding in the armature from alignment issues. 
 

To diagnose it you need to perform an amperage draw hot and cold to determine what is happening. 
 

Be sure your battery is 6.1 volts. 
 

Buicks tend to have small batteries and you need as much amps as you can get. Running two Optima 6v will give you 1400 amps…. Enough to spin it over effortlessly. Bigger cables, an extra ground strap, are good ideas. Many battery disconnect switches are cheap junk and can’t handle loads so look there also. 
 

Often times it’s several issues all adding up to a no start condition. 

[Buick35]

Thanks,I'm not sure where Id install two batteries.I have another starter but it needs a solenoid. Do you have a good starter rebuilder  recommendation?

[1wonton]

Also, if the engine is newly rebuilt it may be tight bearings that are making it difficult to turn over when hot.

 

 

[Pete O]

You mention the starter was rebuilt.  I had a situation with my starter after it was rebuilt that the armature shaft bushings were too tight, and when the starter got hot it bound up.   I took it apart and honed the bushings a little until the shaft would spin freely, and that helped.

[Buick35]

21 minutes ago, 1wonton said:

Also, if the engine is newly rebuilt it may be tight bearings that are making it difficult to turn over when hot.

 

 

It was rebuilt back in the 70s so I don't think that's it.

[Buick35]

Thanks for the replies but I noticed another couple of problems also. I just went to recover it but I thought I'd check under the hood after yesterday's run.I saw that my fuel pump was wet with fuel on the top around the gasket at the top so I tightened the screws a bit and the two cap plugs and that seemed to help and a rusty water stain on the garage floor.Hopefully that was just from the overflow tube but it seems to be on the other side.I can't see a leak when its running.One problem at a time. Old cars,gotta love them!

[DFeeney]

Check all 4 ends of your battery cables.

[edinmass]

6 hours ago, Buick35 said:

Thanks,I'm not sure where Id install two batteries.I have another starter but it needs a solenoid. Do you have a good starter rebuilder  recommendation?

They are half the size of the original, and fit in the same box.

[Buick35]

15 hours ago, edinmass said:

They are half the size of the original, and fit in the same box.

Thanks,I might do that.I know,dumb question,how do I connect the cables as not to increase the voltage just the amperage?

[1wonton]

1 hour ago, Buick35 said:

Thanks,I might do that.I know,dumb question,how do I connect the cables as not to increase the voltage just the amperage?

Positive to positive, negative to negative.

[MCHinson]

The obvious potential problem does not seem to have been mentioned. What type of battery cables do you have on the car? If they have been replaced with modern smaller cables designed for 12 volts, replace them with the proper size cables. Also you need to make sure that all of the connections are clean, tight, and that the ground is attached to bare (not painted) metal. 

 

If you can have someone else attempt to start the car while you hold onto the battery cables, if they are getting hot, you have found at least one of your problems is a battery cable. New correctly sized battery cables installed correctly will often fix slow cranking 6 volt starter problems.  

[TimFX]

16 minutes ago, MCHinson said:

The obvious potential problem does not seem to have been mentioned. What type of battery cables do you have on the car? If they have been replaced with modern smaller cables designed for 12 volts, replace them with the proper size cables. Also you need to make sure that all of the connections are clean, tight, and that the ground is attached to bare (not painted) metal. 

 

If you can have someone else attempt to start the car while you hold onto the battery cables, if they are getting hot, you have found at least one of your problems is a battery cable. New correctly sized battery cables installed correctly will often fix slow cranking 6 volt starter problems.  

I literally just came in from the garage, unable to start my 35 Olds, and the positive cable was red hot. It says (1) on the cable so Im assuming its too small?

A 00-gauge is needed?
would the modern equivalent be a 2-0? 

[pmhowe]

Hey Tim,

 

I think you will want be very specific: Was most of the cable hot? If so, I'd say bad cable. Was just one or both terminals hot? Bad connections.

Phil

Edited April 3, 2023 by pmhowe
spelling (see edit history)

[edinmass]

Hot cable can be caused by.....

 

bad ground

bad solder or terminal connection

bad brushes in starter

bad armeture in starter

bad battery disconnect switch

 

Thus........one needs to figure it all out. Battery cables are never big enough as a rule of thumb. Post photos of the starter, cables, and batteries........we can start from there. 

[Buick35]

2 hours ago, MCHinson said:

The obvious potential problem does not seem to have been mentioned. What type of battery cables do you have on the car? If they have been replaced with modern smaller cables designed for 12 volts, replace them with the proper size cables. Also you need to make sure that all of the connections are clean, tight, and that the ground is attached to bare (not painted) metal. 

 

If you can have someone else attempt to start the car while you hold onto the battery cables, if they are getting hot, you have found at least one of your problems is a battery cable. New correctly sized battery cables installed correctly will often fix slow cranking 6 volt starter problems.  

It has the original type big cables but just now while checking the cables I noticed the braided flat negative ground cable itself not the ends had a lot of that blue corrosion.I tried cleaning it off with battery cleaner but didn't work very well,I'll try baking soda next.But wouldn't a bad ground cable act bad if it's cold or hot? I'll probably just order a new one from Bob's along with a fuel pump rebuild kit.

[edinmass]

Why not just go through everything and make it bullet proof? It's not hard, or expensive. Selective repairs usually just mean more break downs and disappointments. 

[MCHinson]

If it has old battery cables, I would put new correct battery cables on it to start. Have you had the battery tested? How old is the battery? A good new battery and good new cables would be a good start, but do check out everything.  

[Bloo]

3 hours ago, Buick35 said:

It has the original type big cables but just now while checking the cables I noticed the braided flat negative ground cable itself not the ends had a lot of that blue corrosion.I tried cleaning it off with battery cleaner but didn't work very well,I'll try baking soda next.But wouldn't a bad ground cable act bad if it's cold or hot? I'll probably just order a new one from Bob's along with a fuel pump rebuild kit.

The issue with starters cold or hot, ignoring any possible issues with car's engine for the moment, is that electric motors get less efficient when they get hot. If the starter can do it's job and more, you will never notice when it gets weaker hot. If the starter just barely does it's job cold, it probably won't be able to do it's job hot.

 

It is true that you don't want corrosion on the strap, but out in the middle, if it's not deeply damaged, it may not be the problem. The current flows in a circle from the battery to the starter an back. The connections are the most important part, like where the outside of the battery post contacts the inside of the terminal. Or where the metal is pressed together where the end of a cable bolts to a starter terminal, or to an engine/transmission, or a frame. It's the hidden part of the connection that matters, where the current actually flows. Corrosion on external surfaces is highly undesirable, but won't stop things from working, at least not until it spreads to a place that matters.

 

Follow the circle to the starter and back. It all has to be equally good. If the ground cable goes to the frame instead of the engine/transmission, then there needs to be an equivalent heavy cable or strap from the engine/transmission to the frame to complete the circle. It's just as important as the other cables. Hint: If any connection gets hot while cranking or trying to crank, it is bad.

 

[Bloo]

6 hours ago, TimFX said:

I literally just came in from the garage, unable to start my 35 Olds, and the positive cable was red hot. It says (1) on the cable so Im assuming its too small?

A 00-gauge is needed?
would the modern equivalent be a 2-0? 

If it is getting hot it is probably inadequate, or bad, or both. Some 6 volt cars had 1 gauge originally. 00 is far more desirable in my opinion. If you replace any cables, get 00 (or equivalent straps).

 

From small to big it goes 6-4-2-1-0-00-000-000-0000. 12 volt cars typically have 4 gauge or worse, and so that it what most parts stores stock. I would interpret "2-0" the same as "00". If it was a connection on the cable that was getting hot, like where it was clamped on a battery post or something, take it apart and have a good look inside the connection.

 

 

[Matt Harwood]

In addition to all of the above, I always add a second ground cable from one of the starter mounting bolts (clean metal) to the frame near the battery ground. The starter grounds itself through its body and then through the block, through the engine mounts, and through the paint, and through the dirt, and through the grease, and, well, you get the point. Make a good, clean ground path from the starter and things might perk up.

[Buick35]

Thanks for the replies,I'll add another ground stap.It is grounded to the frame and there's a smaller ground from the starter to the frame.My question is still if a ground cable is at fault wouldn't it cause a problem regardless of the heat? Anyway I ordered a new cable.Greg

[Jubilee]

Has anybody mentioned pulling the coil wire and cranking over when it’s hot?
If it spins, timing advanced too far. Doesn’t take much.

[Bloo]

10 hours ago, Buick35 said:

My question is still if a ground cable is at fault wouldn't it cause a problem regardless of the heat?

Yes, that's correct, but heat is a smoking gun. The worst spot in the circuit is likely to get hot.

 

[MCHinson]

11 hours ago, Buick35 said:

My question is still if a ground cable is at fault wouldn't it cause a problem regardless of the heat? 

It takes more effort to turn the engine when hot. A marginal starter circuit problem will show up when hot. If ignored, over time, it would probably get to the point that it would not be able to turn the engine when cold. 

[Buick35]

I think I've found the problems.I removed the old ground strap and as that it had a crack through the terminal end.Then I removed the battery and saw the sticker on it that said 1/16 ! I had it tested and it showed it was bad. I ordered a new one which would be in after four o clock. I hope it lasts another seven years.

[Jolly_John]

Ah yes, we're learning that old adage all over again (and again). How many times have I forgotten to check the simple stuff FIRST? This is a little like the kitchen light bulb not working, and then eventually figuring  out the power to the house had been disconnected! Glad you appear to have gotten to the bottom of your problem. John

Edited April 7, 2023 by Jolly_John (see edit history)