Starter problems

After driving my 78SC to Mt Zion 300mi rt my starter motor will not crank (I dont hear the solenoid clicking)its done this only after I have driven on the highway for more than 1 hr.
I can bump start it and it will work fine again but it seems to do this every time I drive the car on the freeway for over an hour

The starter also gives me no problems driving around town with 30-40 minute trips and several times restarting the car almost daily for months
It started this about 8months ago after a 3hr trip and I had to bump start it and it hasn't given me a problem until now

Any ideas?

Sounds like a problem the factory had during development of the 908 race car with starters ... way back in '68!!!

Is it a SR-17 , or a SR-68 starter (0.8 hp or 1.5 hp), or do you know?

it sounds to me like the starter has a build-up of rust, dirt, or a lack of good, moly lubricant, causing a 'marginal' hp output, exasperated by a good 3-hour heat soak!

My suggestion is to remove, disassemble, clean, and lubricate the bendix mechanism, and solenoid linkage with a premium moly grease. What I tend to do every 3-5 years, whether symptoms appear or not!

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Warren Hall
1973 911S Targa

Thanks Warren
its a .08 starter,my car is totally rust free
(original owner purchased car new from George Follmer Porsche in Pomona Cali)it may have some oil leaks on the starter though

Any tips on removing the back bolt on starter?
Maybe its time to have it rebuilt at a starter shop?

Both nuts on the stater require a 10 mm Allen drive bit, and the top one is probably a little easier to get at with the driver's side wheel off ... if you reach over the top of the transaxle. The nuts are different, one is turned-down a bit for clearance, and the bottom one can be replaced with a plain, 17 mm nut, just like VW's use. The only explanation i know of for how the inside of a starter gets rusty ... is spashed water from puddles, because my car's underside isn't rusty, either, but there WAS rust on the solenoid shaft, inside the starter!

0.08 hp, huh, no wonder it's a little 'feeble' when hot!

I usually make the determination on rebuilding based on the condition of the commutator ... pitted and grooved gets sent to the shop for an appointment with a lathe.

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Warren Hall
1973 911S Targa

Years ago my starter would not work after the engine had gotten hot. Very similar to your predicament. In the end, found out that wear had resulted in the "bendix" section not returning to the initial condition. It hung up about 1/8 inch shy of full return. In that position, the solenoid could not make electrical contact and therefore could not "click".

[This message has been edited by Brian K. Haggard (edited 05-27-2000).]

This is a GREAT BB. Very intimate awareness of these cars.

I fail to do the maintenance Warren describes, but starters get "gucky" (a technical term) and give problems. A good cleaning makes good sense. Often when starters quit, a good cleaning returns their function. On some, you can flip the solenoid contact over so the electrical contact will happen on a fresh surface.

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'83 SC