300SD: starter pinion not going forward enough?

I am rebuilding the starter for a 1985 300 SD for the first time, so I may be making some dumb mistake. I tested it off-car with my jump-starter. The starter runs fine, but the drive pinion only moves
forward about 1/4 to 3/8 in. I am thinking that to engage the flywheel properly, it should be moving all the way, or nearly all the way, forward to the shaft bushing. That would be about one inch of movement. I can manually move it that far forward until it is up against the bushing. I know that the solenoid, when energized, is working against the spring in the center...but it is the same spring that worked fine before.THe solenoid...or I should say starter relay (it mounts into the body of the starter)...is a new one. SO that would not be the problem. ANy idea what is wrong?
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On April 24 2005, you wrote:

I know the pinion should move forward fully before it starts to rotate. can't picture this. is there a fork operating the gear from the solenoid and if so is it the correct way round? Cheers Clive
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On 24 Apr 2005 16:10:52 GMT, snipped-for-privacy@dsl.pipex.com (Clive Turnbull) wrote:

Yes, there is a fork that forces the pinion forward. I didn't give much thonght to which way I put it in, as it looks like it is symmetrical front-to-back. Im pretty sure it is, but I guess I could double-check that. The top lever of the fork engages the spring-loaded lever connected to the solenoid "plunger". Jim
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On April 24 2005, you wrote:

Jim If the solenoid plunger is doing full travel and the gear isn't, I would have thought it must be something between the two and that only leaves the fork, unless the solenoid plunger isn't going it's full travel. Sticking in it's bore so to speak. Such a long time since I've done one. Good luck Clive
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On 24 Apr 2005 23:01:55 GMT, snipped-for-privacy@dsl.pipex.com (Clive Turnbull) wrote:

Yea it can only be that the plunger is not moving full travel, or there is something wrong with the yoke. It is a brand new solenoid (relay) assembly so unlikely to be that. Might take the center spring out and see if that lets it push the pinion out all the way then. Can't see what is happening inside. I noticed the new solenoid has a black rubber boot on the front of the plunger that mates up to the hole in the starter housing....the original didn't have this...maybe that is interfering with the plunger travel somehow? I am not sure why this is needed....as a moisture seal? Thanks, Jim
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On April 24 2005, you wrote:

Jim Could be the seal stopping the travel as you say. Anyway you could do a test without it. It is just to stop rubbish getting in really. Could do without it but it should fit without causing problems. If the fork was wrong way round would it foul the rubber then or does it look the same either way? Can't be much! Keep in touch Cheers Clive
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First, If the starter motor runs when the sol is energized, the plunger is moving all the way. There is a button in the sol that is pushed by the plunger. This switch is what starts the starter motor running. If you can move the drive gear all the way to the bushing by hand than there is something wrong with the fork. You should never be able to move the drive gear by hand more than a fraction of an inch, maybe .050 in or so. Check the engagement of the fork and the drive gear.
Paul Paul's Auto Electric

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when it come to starters use only good stuff.
i my self would have replaced the whole assembly . but i have the $ to do it. they ain't cheap but the cheap starters don't last long
the case, minus a few cans!
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