Starter motor replacement 73 911T

[hbf]

I need to replace my starter motor - the car starts easily when cold but will not even turn over when hot. Seems heat in the aged solenoid is the cause. All other potential causes have been ruled out.

My question to this forum: should I replace with a rebuilt motor or with a high torque item. Is there any benefit on a low compression engine like the CIS 2.4 liter to having a high torque starter? I have no experience with them.

Comments will be welcomed.

[RSTarga]

Just use a stock higher output starter motor from a newer model.

[T77911S]

you can try this if you have the tech skills. it can revive and old solenoid.

SOLENOID and STARTER rebuild......finally

since it does start good cold you could try some grease on the solenoid plunger (inside) so it slides easier. I don't remember if you can get to the plunger on this solenoid,

my personal opinion is they were made better back then and if you can keep or get the old one working you are better off.
you also need to make sure you have good power to the yellow wire on the solenoid, it takes a lot of current to pull in the solenoid,
try measuring the voltage with it hot and not starting

[gamin]

I installed the hi-torque starter in both 911's. They start every time, hot or cold. Nice weight and space saving too. The old Bosch is a big heavy lump. Friend put a hi-torque starter in his 2.4 and is very pleased. Spins it nicely.

[hbf]

Thanks all for your comments and advice. I took the lead offered by T77911S and decided to tear down the starter before spending $250 on a replacement. I followed his instructions which made the tear down a whole lot easier.

On the electrical side things were bad with not any hint of uncorroded metal anywhere. However, on the inside the motor shows no noticeable signs of wear, except for the commutator. I cleaned that up on the lathe and it is now as good as new. The brushes are still fit for purpose.

I have cleaned the external rust and repainted the pieces. I will assemble and install tomorrow once the paint is dry.

From what I found I am confident that I now have a perfectly good starter and there is no need for a replacement. I will a report back on the results.

Thanks to T77911S for his suggestion and guidance.

[RSTarga]

Check all your power supplies an your ground straps

[RichardNew]

If you're going to replace your starter make sure that you save the old one. At some point another owner will rebuild it so they can have a correct 911.

Richard Newton
Insurance Costs

[john walker's workshop]

The replacement "rebuilt" bosch starters are much smaller now. They seem to work ok, but the solenoid is clocked a bit higher than stock and the battery cable barely reaches. Good old bosch

[Joe Bob]

A good whack on the solenoid will free it up when hot.

[john walker's workshop]

Unless you hit the plastic end....

[T77911S]

did you take the solenoid completely apart and clean/rotate the contacts.
those get burned really bad.
if you want to send me the solenoid I will do it for free. just pay shipping.

things like this is what working on your own car is all about.

[hbf]

An update: I have finally resolved the problem.

After trying all the suggested solutions above and by a process of elimination I found that the batteries were not up to the task. With two new batteries installed the car now starts easily hot or cold.

I cannot explain why the batteries should have been affected in this way.

Thanks agin for all the suggestions and help.

[DRACO A5OG]

Congrats!

If I may suggest, get a plug in cigarette lighter Voltage Meter to monitor the charging system.

I had issues with my connectors, my positive side had a hairline crack on the underside, just enough to drive my arse crazy trying to figure our my non-start and worse due to low battery issue.

J