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back of engine, always bolted up so the drive end is in-plane with the flywheel
lift no, stands yes, looks straigt forward in WIS and Haynes, but its crowded work at best, so not very easy I expect. Some stuff from above, some below, major danger if you do not disconnect the battery!!!
Sounds like the solenoid is not working right. Might be something that you or an auto electric shop can fix. Check that the power cables to it are tight etc, and also check the engine ground cable(s).
Have rebuilt or used unit in mind?
The starter motor has permanent magnets instead of field coils. The motor is also 'high speed' relative to older designs and has a planetary reduction gear to multiply torque. The unit is quite small... by historic standards.
Haynes shows the unit being taken apart to replace the brushes. But the running hours on a starter are so few, I can't imagine that this would be needed. EPS shows parts for the starter, solenoid, gears, bearings, pinions etc.
The motor indicates that it can work ok, the description of the problem suggests that the solenoid is intermittant. The solenoid it self might be fouled and might be salvageable. It in turn needs to throw the pinion drive gear forward into the flywheel teeth. If that is fouled and the it will not move, then that prevents the solenoid from moving all the way. The solenoid has two functions, one to engage the pinion drive gear with the fly wheel, and the other to close the main contactor to suppply full power to the starter motor. That contactor does not work until the solenoid is fully retracted. And if the pinion drive gear does not allow the solenoid to move fully, then the starter does not get full power. So the pinion starter gear would be what I would check out first. What lubricant to use on that? I do not know, perhaps an auto electric shop would advise, but perhaps they run well mostly clean and dry.. do not know. I would apply a light film of high temp moly grease.
Also make sure that the heavy connector from the starter motor to the solenoid has a clean tight joint.
No one wants to describe how these things work in detail anymore. Here is my expectation:
The solenoid has two coils, one to ground and the other to the solenoid output to the starter motor. When the starter relay engages, current flow though one coil and then to ground. Current also flows through the other coil and through the starter motor and then to ground. This provides a small pilot current to the starter motor to create some rotation to help the pinion engage the flywheel. The resistance of the one coil on the solenoid limits the starter motor current. After the solenoid had fully engaged and closed the main current contactor, the coil that was in series with the starter is then 'shorted out, and sees no or very little current and is then inactive. The coil that connects directly to ground then continues to get current and it holds the solenoid in the closed postion. The two solenoid coils can be designed for a balance pull-in power and hold-in power. If these modern starters have eliminated the need for a pilod current to turn the motor during pinoin engagement, then that second solenoid coil may not be needed at all. Variations may exist across different starter designs. If someone knows the specifics of the solenoid design on the Saab starter, I would like to learn more.. please post.
So if it is a two coil solenoid design as described above, if the solenoid cannot move mechanically for one of the two reasons suggested above, then the motor never engages the flywheel and the pilot current from the solenoid coil in series with the starter allows the motor to spin up and make a whirring sound. I have never heard this, but I expect that it makes a sound that is higher pitched because of the high speed design and the planitary gears may also contribute to the sound of the starter in this situation.
Note that this design with permanent magnets might spin fast enough to self destruct if power were applied directly to the motor without engagement to the flywheel, that is one purpose of the solenoid. So do not apply power in that fashion to 'test' it, you might not like the results. The armature might spin so fast that the coils tear out of the commutator sections or some of the commutator sections may shift out and then the brushes do not track well... or worse. (I have seen locomotive traction motors that have been 'over speeded' on runaway diesel electric mining trucks. The motors are a mess of shreaded metal inside, looks like someone put the coils and brush gear into a food processor.)
posted by 66.142.222...
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