Why does my starter run-on after the motor catches?

[fspGTD]

On my Rabbit, after the starter gets the motor running on it's own, and I release the key, the starter makes a noise, which sounds like it's running on afterwards, perhaps stuck-engaged to the flywheel teeth, for maybe .5-1 seconds.  What could be causing this - does the starter need some freshening up somewhere, or does that bushing pressed into the transmission need to be replaced/lubed?

thanks in advance!

[BlackTieTD]

you mentioned a problem before that you thought might be traced to a faulty ignition switch... could this also be the ign. switch? the previous owner of my car warned me of this and said "i'd get a feel for" the ignition switch to make it stop happening..... but i've never had the problem  :?:

[fspGTD]

No, I think the electrical signal is stopping when I release the ignition switch.  From what I can best guess is going on, it seems the starter is just not immediately disengaging like it should.

[cheng]

hey jake
use an indicator light or a remote starter switch to confirm that its not your ign switch.

you may have a weak or broken return spring in your starter solenoid.

the contacts, if badly pitted could be welding themselves together occasionally, or it could use some lubrication on the sleeve.

if you do lube the sleeve make sure you use a very thin coat of dielectric grease so as not to cause other problems

hope this helps
and thank you for all of the info you provide

ken

[fspGTD]

Thanks... I could try hooking up a multimeter to the starter trigger voltage signal and verify that voltage stops when it should be.

I can recall this problem happening on a previous starter as well.  But I can't remember if it was with the same transmission or not.  The starter it happened on was an earlier, non-gear reduction style starter.  This latest starter I'm running is a later, gear-reduction unit.  I have another later-style starter I can try swapping on and seeing if it changes the behavior.

[fspGTD]

Well, I changed my starter bushing that's in the tranny.  I also lubed it nice and good.  The old one looked a little scored, possibly was a little dry so I'm hoping that will do the trick.  I can't test it to see if it works yet though, because I'm having the thrust bearing surface of my vacuum pump hole block-off plate surfaced by a machinist.  Can't run the motor without it.

[fspGTD]

Tested it quite a few times now and it seems there are no more odd noises coming from the starter.  

[BlackTieTD]

sweet. was just the bushing then? out of curiousity, how much was that part and how long did it take to replace? when i bought my rabbit the PO must have told me 10 times "the starter bushing was just replaced".  :lol:

[fspGTD]

I actually did swap starters as well, so I'm not 100% sure it's the bushing but IIRC, the after-run noise would happen no matter what starter I had in there and no matter what version (A1 or A2 diesel starter) with the old bushing, so I'm pretty sure it was the bushing.  I paid like $4 (full retail) at a local VW specialist for a genuine VW bushing.  Didn't matter to me because they had it in stock, no ordering / coming back to pick it up.  To get the old one out I ran a tap into it.  Forgot the size (could have been standard non-metric size) but it was just big enough to score and bite into the ID of the bushing, then hit the end of the cavity, at which point further rotating of the tap screwed the old bushing right out.  I have heard of them being changed by filling the cavity behind the bushing with grease, putting in a tight-fitting rod into the bushing and slamming it with a hammer; the hydraulic force then presses out the bushing.  The important part is to grease the new bushing.

The starter drive pin is always engaged in the bushing; when the starter gets energized the drive gear slides out on the pin over the flywheel teeth as it starts rotating under power.  The whole assembly (pin and gear) rotates under power from the starter.  For whatever reason there was an audible noise after the starter motor stopped, probably from the starter continuing to rotate (think of what RPM is must be turning at to crank the motor over at... 300rpm or so?  And compare diameters, the starter must be overdriven vs the crank by a very large factor!  So it's got to take a little while for it to spin down.) and I think once the gear disengaged from the flywheel teeth the "dry rotation" of the pin in the not adequately lubricated, somewhat scored old bushing caused the vibration, and vibration = audible noise.  Souded sort of like an old cat making a low-pitched angry meow.  It's usually a good idea to change these bushings whenver you have a tranny rebuilt but I just forgot about it when I had my most recently rebuilt and installed tranny (the 4k) out.  You can still do it installed in the car though, just kind of hard to see what you're working on.  Using one of those mirrors-on-a-stick helps.

[Hammy]

Hey Jake thanks for the info on the bushing. I'm going to try it out also. BTW, when your starter was making noise did it seem to crank a little slower also. I have a well charged new battery (1050 cca), and I'm just not sure if the starter is baffed or not. Any suggestions as to what kind of starter and suppliers to use?
Thanks

[fspGTD]

If the bushing was badly scored enough, it might slow down the starter, although I don't think mine was that far gone as it seemed to just make noise.

I did however experience a slow starter problem, which I fixed by improving the ground connection between battery ground strap and transmission mounting bracket.  I added a serrated ground washer (the strap was not OEM) and it's amazing how much it helped the starter spin.  But anyway that taught me how touchy the electrical connections are for proper starer operation.

I noticed what looked like an extra ground strap on an '84 or '85 Jetta turbodiesel.  It was an extra strap that went between transmission mounting bracket and a nearby bolt on the transmission housing.  VW probably wouldn't have bothered adding it if it weren't a problem!  I want to add one onto mine.  It looked OEM, but I couldn't find it in the parts fiche.  If you are having slow starting performance, I would try and measure for excess voltage drop across ground connections while the starter it being actuated to try and pinpoint if there is one connection causing a lot of voltage drop.

A low internal resistance battery, such as an optima or absorbed glass matt battery, will also help get the starter turning over more quickly than a stanard liquid acid battery, since the voltage across the terminals will drop less during cranking.

I haven't really found a good source on rebuilt starters.

[VWRacer]

I noticed what looked like an extra ground strap on an '84 or '85 Jetta turbodiesel. It was an extra strap that went between transmission mounting bracket and a nearby bolt on the transmission housing.

Funny you mention this, Jake. I saw a grounding strap like this under my car (attached only at the trans mount) and wondered where it was supposed to attach at the other end.

Good stuff...!

[Hammy]

I also meant to ask what the charging output should be? Mine is 13.2V, which normally I would have called a little on the low side. My wife's '99 TDI charges around 14.5 or so. But a couple of vw shops said 13V is fine. What are your opinions on this? Has anyone heard or seen any higher voltage regulators.

[fspGTD]

I have a voltage gauge.  On my little denso alternator, I see around 13V right after starting when the battery is charging very quickly, and > 14v when the battery is charged and no electrical loads are on.  The voltage is pretty sensitive to whether or not the battery is charging and if electrical loads such as a radiator fan, or lights, etc are turned on.  Anyway, I guess the answer is, charging voltage depends but generally anything 13V or greater tells me the alternator is working.  And it peaks at 14.4 volts when the battery is totally charged and all electrical accessories are turned off.