Starter fails to stop - Dino 246

When energizing the solenoid, the starter gear snaps onto the ring gear. However, upon removing voltage from the solenoid, the starter continues to crank. This problem has plagued me for years. I now have the engine on the test stand and can reproduce it while watching the starter engage (with the bell housing off). I initially thought it might be a bad ignition switch on the steering column. Replaced that. Had starter rebuilt. Problem continued.

I have now dismantled the starter and the solenoid. Cleaned and carefully placed minute amounts of silicone grease on solenoid shaft, Bendix shaft, etc.

With the bell housing off, I can see the starter gear meet the ring gear. However, when I remove voltage from the solenoid, the starter gear fails to retract fully from the ring gear, thereby maintaining electrical contact within the solenoid and providing ongoing current to the starter motor.

I thought, perhaps, that the starter gear was engaging too much of the ring gear, providing too much friction to retract. I used washers to space the starter away from the flywheel and the problem continues. I then thought that the starter might be off alignment, thereby wedging the gears together. I loosened both starter mount bolts and gently move the starter in various orientations - the gear stays stuck to the ring gear. This latter attempt was approached without providing current to the starter motor, only current to the solenoid. Thus, the solenoid would snap out, engage the ring gear, and without the motor turning, I would remove voltage to the solenoid. The starter gear stayed engaged with the ring gear.

The spring in the solenoid appears fine. It has significant tension, as does the Bendix spring.

Help is greatly appreciated.

Jim S.

 

with the washers in place the starter should disengage if the engine started. I have seen the starter drive gear engage too deep into the flywheel after an engine overhaul. This happens when the intermediate plate gasket is replaced with a new gasket that is thinner than the original. The easy way to fix this starter problem is to have a spacer pattern cut to fully support the nose of the starter.

 

Slewman - the starter does disengage when the engine starts. The flywheel "overdrives" the starter gear and unloads it. It then retracts.

However, if the engine fails to start, and the key is turned off, the starter continues to crank.

This occurred with an original gasket, and now occurs with a replacement (which, by the way, is quite thick). I have experimented and inserted spacer washers between the starter and the intermediate housing (in effect creating a thicker gasket), and this did not solve the problem.

Thanks for your input.

Jim S.

 

Some thoughts ..
Is there any "throw-stop" in the solenoid which limits how far it can travel? Maybe missing washer(s), (or some that can be added) on the solenoid shaft? What about how/where the solenoid closes the main circuit - is there any way to adjust where that occurs with respect to solenoid travel (ie try to get it contacting only near the end of travel, so that a only small release will cut the feed)?

 

I had exact same problems with my starter 308. The starter continue to crank after engine runs. The mechanics did clean the starter changed solenoid. They worked awhile then a month later same problem occured. At the end, they added another solenoid. Then, everything is ok since and that's two monthes ago with nearly everyday use...

 

Jim -- In your "static" test, if you jiggle the flywheel back and forth a little will it release easily from the flywheel? If not, I'd start looking at the center-to-center distance between the ring and starter gears. I know it's usually a piloted arrangement that doesn't allow easy adjustment, but if you reduce the overlapped engagement between the tips of the gear teeth (by moving the starter pinion gear axis outward slightly) I believe it's got to help the "release" action -- just a thought...

 

Perhaps the starter gear shaft is not true? The slight wobble is locking the gear to the ring gear. Just a thought.

Ken

 

Cam - there is no throw-stop other than the geometry of the soleniod lever arm. However, one can add washers to the end of the shaft to move the entire mechanism away from the ring gear. I have done this with no benefit.

91tr - Once engaged in the static test (solenoid activated, starter motor not activated), the starter gear moves onto the ring gear. When voltage is removed from the solenoid, the starter gear retracts a little, but stays mostly engaged. When rotating the flywheel back and forth with a socket on the pulley, the starter gear generally stays engaged. It does not snap back. HOWEVER, visual inspection does not show that the gears are bottoming out - that is, the peak and valleys of the gears are not hitting each other. This suggests to me that the radial distance between the turning axes of the flywheel and the starter gear is at the proper distance.

Ken - while on the work bench I have energized the starter motor and let it spin (to seat the brushes after reinstallation). The shaft appears true without a hint of wobble or vibration.

Thanks for all of your thoughts. Keep them coming.

Jim S.

 

It would appear that all mechanical issues, that may attribute to this problem, have been sorted out......and eliminated as the cause.

My "guess" would be the following: The shaft within the solenoid is worn. While it goes out easily, due to minimal resistance, it may become jammed within the sleeve portion. During retraction there is some lateral force applied by the flywheel, onto the retracting shaft........this could bind upon the sleeve, causing it to get stuck........partially retracted.

Just my thoughts!

 

Jim -- The gear tip meeting the gear root won't ever be the location of a too-much-contact problem (the "interference" is along the flank surfaces of the teeth). They generally greatly over-relieve the tooth form in the tip and root so that unwanted contact in those areas is never a problem (even if the center distance is much too close for good function). I know this is a b*tch because you really can't test it without essentially doing it, but unless your tooth engagement already seems overly minimal, I'd still say move it out some -- JMO.

 

I think Steve is right, there should always be clearance (some back-lash) between the gears. In the static test, can you for example get a feeler gauge between the teeth, or more simply can you feel some back-lash?

If not then I guess you need to increase the gear centre distance somehow.

my .02

 

Steve and Richard - I suspect that you are correct in the that the overlap of the teeth may be excessive. However, I really have to shim the starter shaft quite a bit to go from full overlap to 1/2 tooth, for example.

That said, I think HenryK may have made an interesting obervation. The solenoid moves quite freely without load, but under load the shaft may be binding. I will disassemble and place a lateral load on the solenoid shaft to see if it binds. Part of my interest in doing this is that finding a replacement solenoid is relatively easy (albeit expensive). Finding and replacing a ring gear and/or starter gear may be more difficult.

More to come.

Jim S.

 

Jim -- Not talking about how much the gears overlap in the direction of normal engagement, but what's the distance between the centers (i.e., moving the starter gear axis out radially from the ring gear axis so that the tips of the gear teeth don't overlap too much in the radial direction) -- a much harder thing to change

 

Steve - Thanks for the clarification. As the radial distance from center to center is defined by the crankshaft and the intermediate housing, it is virtually impossible to alter this. One could "oval" the mounting holes in the intermediate housing, but that is asking for trouble.

After I read your posts, I went back to the shop to again disassemble the starter and solenoid. I think HenryK may have identified the problem. Without load, the solenoid, when removed from the starter, actuates and returns perfectly. However, if I try to manually move the solenoid while placing a lateral load to it with my hand, it binds.

I will start by replacing the solenoid. More to come.

By the way, I have been purchasing most of my parts from GT Car Parts in Arizona. Bill and David have been very helpful. I believe their prices are in line with everyone elses. They are very responsive and my parts arrive quickly.

Jim S.

 

Jim -- No disagreement from me that such a modification is troublesome and undesirable, but if you turn down the pilot diameter on the starter mounting flange and just bias it outwards as much as possible during the mounting process this would keep the main engine parts unmodified. If the mounting thru holes are super-tight on the starter mounting screws, this might be the next limit so you'd need to judge that for yourself.

You mentioned you tried "shimming". Did you try any non-parallel shimming that would help move the nose end of the starter away from the ring gear? The mounting bolts still might be a limit here, but if you could get a .005"~.010"~.015 shim in the right place to angle the starter nose out away from the ring gear it might give a clue without too much pain.

 

I have no technical input to your query Jim, but if you need to make an aluminum shim, Coca-Cola cans can be the ticket (BTDT).
Philip

 

Steve and Philip - I shimmed the starter towards the pulley end - to reduce gear overlap. However, as Steve suggested, I used two washers of equal thickness between the starter and intermediate housing. Thus, there was no "tilt" of the axis introduced. I think your idea, Steve, of asymmetric shims is a very good one. This will point the axil of the starter armature away or towards the crank axis.

Philip - had not thought of using a Coke can as a shim - great idea. Do you think Miller Lite would work as well?

Jim S.

 

The continuing saga:

I procurred a new solenoid. No help. Starter continues to crank even after voltage is removed from solenoid tab.

With Tom C's help, I contacted a company in Massachusetts (Gloucester). Gustafson Manufacturing. They make gear-reduction starters that are mechanical "black boxes" of a car's starter. He would like me to send my Dino starter so that he can create a mechanical template for mounting. His starters are mechanically superior, spinning at greater RPM but with gear reduction. They use less current, weigh less, and are small in size. Typical pricing, complete, is around $350. This includes solenoid. I suggest that those interested do their own homework on the cost of a new starter for the Dino (if available). You don't have that much money!

I am still working on mine, having studied a friend's Dino starter that is also out of his car. There is a missing spacer at the end of my armature that I believe may prevent the teeth from overlapping too much.

More to come.

Jim S.

 

Check the amperage the starter is drawing, you may need to take it to a starter rebuilder for this. If the amperage is excessive your armature is shot, it could be shorted etc., which is why it's sticking.