Starter problem

cashflyer · 07-01-2005, 08:23 AM

I have a 78 911SC. This problem manifested about two days ago.

The car had been starting fine, even earlier in the day. But when I went out later the same day and turned the switch, the starter only spun without engaging the starter ring.

I swapped with a brand new Bosch starter, but it still does the same thing. When the starter was out, I checked the starter ring to make sure the teeth were not damaged - they are like new.

My guesses are (a) battery, or (b) ground strap. Except that both of these seem to be ruled out by the fact that the car had been starting strongly earlier that day.

I would like to resolve this issue today after work.

Any suggestions?

Breeang · 07-01-2005, 09:01 AM

Put the car in gear (2nd or 3rd) and give it a push to turn your engine a little, try the starter again ,if it catches then you may have lost a tooth on your ring gear,(what your starter motor gear engages to turn the motor) .Pushing the car in gear turns the ring gear to a new and intact section of the teeth.Thats my only suggestion,good luck

cbeers · 07-01-2005, 09:06 AM

I have a similar problem and another Pelican suggested the Bendix something or other?

-Chris

cashflyer · 07-01-2005, 09:07 AM

Thanks, but not it. I inspected the starter ring while the starter was out of the hole, and there are no damaged teeth.

911pcars · 07-01-2005, 09:29 AM

When you purchased the new starter, it probably came with a new starter solenoid (the smaller cylindrical unit attached to it). The starter solenoid has two functions: to connect the battery to the motor and to mechanically link a pinion gear into mesh with the flywheel teeth to rotate the engine. The two motions should happen simultaneously. If the starter motor rotates, then that portion of the solenoid is doing its job. If the pinion gear doesn't rotate or mesh with the flywheel, then something's wrong (obviously).

The pinion gear contains an "overrunning clutch" (aka Bendix drive, but a little different mechanism). As it's name implies, after the engine starts, this one-way drive mechanism prevents the engine from rotating the pinion gear and starter motor. The gear ratio (running engine drives starter) would otherwise destroy the starter in short order. A return spring normally retracts the pinion gear after the engine starts.

Have you tried bench-testing the starter with jumper cables? This should verify the unit is working. If it doesn't work when installed, I'd suspect the overrunning clutch isn't working (slipping in drive mode) even though the gear meshes w/the flywheel or the pinion gear isn't physically moving far enough to engage the flywheel.

Sherwood

cashflyer · 07-01-2005, 09:50 AM

It only takes a few minutes to remove the starter, so I will take it off and bench check it.

I hesitated to try this action first because both the old and the new starters were doing the same thing.

cashflyer · 09:54 AM

Thanks to everyone who replied. Here is the answer to the puzzle.

Tuesday we used a bore scope to try and get a look at what the starter drive gear was actually doing when we hit the switch. Unfortunately the internal clearances were too close to get the scope snaked all the way over to the drive gear area. It did allow us to verify that the starter ring and everything else was not at fault.

I called a local Porsche race shop and spoke to a mechanic there. He had never heard of such a problem, but he asked if I was using a new starter or a remanufactured starter. I replied that it was reman. He said, "maybe they have the wrong drive gear on it" and suggested that I buy another starter.

I hated that idea because of the expense and hassle of buying another starter, waiting on delivery, returning one later, etcetera. But I had exhausted my options, so I ordered another starter and had it shipped by second day service.

I compared the two, and both drive gears look identical. I bench tested both for camparison. Both seem to kick out the drive gear the same distance. These findings made me less confident that this was the problem.

Yesterday after work, I put the new starter on the car. I then spoke to the car, and told it that if it would please start that I would be nicer to it and stop parking it next to my other car.

I hooked up the battery, turned the switch, and.... vroom-vroom!!

I don't know why one worked and one did not, but at least it works. In the interest of fairness I must say, since I am on a Pelican forum, that the offending starter did not come from Pelican Parts.

It also may be important to mention that on the second purchase, I bought a hi-torque starter. I wanted something COMPLETELY different than the first starter for the comparison, and also decided that if I had to buy another starter it might as well be a really nice one. Due to it's smaller size and weight of only 9lbs, it was a heck of a lot easier to maneuver into position. It was a little more difficult to get the wires connected to the main terminal, since it is located on the side of the hi-torque unit, but still not a problem.

One incidental benefit was this: When I bought the first starter, a Bosche reman, there was a core charge. I sent in my old starter and got my core money. I had kept that starter for a couple of weeks before buying the second starter, a new unit with no core charge. When I notified the vendor that I would be returning the Bosch unit, they informed me that they had already sent the core away and would not be able to return it to me. Instead, I get to keep the core money they paid to me when they received my original starter. The difference is this: If I had bought the new starter first, I would have a useless old starter lying in my garage. Instead, I have cash in my pocket.

911pcars · 07-08-2005, 09:58 AM

Thanks for providing the final solution. Should be helpful for futur reference.

Starter motors are pretty universal items; the main difference for multiple applications is the configuration of the adapter plate that allows the motor and solenoid to work on a particular engine.

And it so happens that many engines use the same or about the same adapter plate. It sounds like, instead of the correct one, you got a reman. starter assy. that had an "about the same adapter plate." A thicker plate, for example, might have positioned the pinion gear out of reach of the ring gear. I understand this happens on certain 930 engines (on at least one occassion); same symptoms you had.

I guess the lesson is to bring the old part to compare when you purchase a new/rebuilt part to make sure it's the correct one. This applies to, among other things, brake calipers and pads, master cylinders, alternators, power steering pumps, coolant hoses, water pumps and .... starters.

Sherwood

cbeers · 07-08-2005, 10:28 AM

Hey Cash,

For reference, can you tell us which high torque starter you got? I have a similar issue that I have always thought was bad teeth on the ring gear or something. The starter in my car now was put in by the PO and I'll have to check if it was remanufactured or new. Either way, if I could fix the issue with a new starter, I would be happy

-Chris

cashflyer · 01:37 PM

Chris,

I obtained my hi-torque starter from [another retailer].

It appears to be the same as the one sold here at Pelican, but about $50 cheaper. BUT this starter is "remanufatured". If you absolutely want a NEW unit, spend the extra $50 for the one from Pelican.

As for your starter ring, this may help.
I found that you can inspect the starter ring by using an inspection mirror and a flashlight to look into the starter hole once the starter is removed. Just get a friend to turn the crankshaft slowly while you watch the ring go around.

Of course, be sure that the battery is disconnected. It's unlikely that the engine would fire being turned that slowly, but never chance it. Besides, you needed to disconnect the battery to prevent arcing possibility when removing the starter. And be careful not to put your fingers in the hole while the engine is being turned. There is a lot of leverage at the pinch points.

randywebb · 07-08-2005, 11:13 AM

Were there any bevels on the leading edge each gear cut?

I've also been told that there can be a tad of adjustment radially needed - this prevents the gears from meshing too tightly. My problem was that a starter I had stopped releasing from the flywheel - or at least didn't release very quickly.

cashflyer · 07-08-2005, 11:38 AM

Randy,

I'm guessing you mean on the starter drive gear. If so, yes. Each tooth should have a bevel on the end to allow meshing without crashing into the ring teeth, which a squared-off tooth set would do. The starter ring on the flywheel/pressure plate does not have beveled edges.

Your problem could be gears meshed too tightly, but it could be your starter if it has a lot of age on it. Sherwood can correct me if I'm wrong. The way I understand it starters rely on the solenoid to kick out the drive gear to mesh, and are spring loaded to retract. If that spring gets old and weak, then it may not retract properly.

When I installed the first starter and was still looking for solutions, I could not find any way to adjust the thing radially. Not saying it can't be done, but I sure couldn't do it. Now this is not the case on some other cars - like GM products.

Almost all of the old GM starters required using shims to get the right gear mesh. Sometimes you will hear a Gm start up in a parking lot and the starter will make a LOT of noise (whine, high pitched screech, etc). You can bet the last mechanic either did not shim it or shimmed it wrong.

The above does not apply to MoPars. They were all noisy.

-cashflyer

"Well, once again we find that clowning and anarchy don't mix."

randywebb · 07-08-2005, 02:25 PM

Yes, the starter's drive gear.

There is a tad of slop in the mounting holes - a pry bar can help push it out radially from the center of the flywheel as you tighten the bolts.

In my case, the starter had about 50 miles on it... it was from Performance Products. I replaced it with a Pelican sourced unit - the latter was also lighter.

I hope your and my travails will help the next person...

Tricky D · 07-09-2005, 02:05 PM

Just helped me - thanks fellas!

randywebb · 07-09-2005, 03:41 PM

Have that keg delivered to me at:

666 Demonic Towers
right downtown in Greater Metropolitan Nimrod, Oregon

cashflyer · 07-12-2005, 06:34 AM

Just as a final follow-up on this thread, I have a photo to post comparing the two starters I tried. I think it's obvious in the photo which is the Bosch and which is the hi-torque mini starter. I didn't weigh the Bosch but the mini starter was right at 9 pounds.

- cashflyer

randywebb · 07-12-2005, 04:13 PM

nice pic -- the wts. are in my database on Thom's web page -- rennlight.com