karl ruiter

So my S4 started cranking hard the last week. Got so bad that I will have to park it tomorrow. Once it starts it idles and feels fine, and I released the thrust plate and checked the end play (about 0.010") two years ago, so I am thinking (hoping) it is not a TBF. Battery is fresh and contacts are clean.
Anybody ever had the bearings in the starter go bad? Had some monsoon type weather here last month with some deep water and it probably got pretty wet under there.

outbackgeorgia

Well, yes when I first got my S4 at about 90,000 miles it would not start the car so I removed it and cleaned/lubed it, polished the commutator and it has worked fine since , has 145,000 miles now.
Dave

Rob Edwards

The starter on my GT stranded me at a gas station near home. Swapped out the one from the GTS, which cured the car. I have since rebuilt the GT starter but have not tested it on a car. Have the makings of a rebuild thread but haven't had a chance to write the text. Rebuild kits (containing brushes and brass bushings) can be had on Ebay for 23 bucks.

karl ruiter

Cool. Let's hope it is something that can be fixed with a clean and lube, or at worst a starter. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. Please no TBF. etc.

Bill Ball

Since you checked the endplay 2 years ago, you shouldn't fear TBF. Plus with TBF, the car starts OK when cold, stalls once warm and then becomes hard to start.

SeanR

Yup, they go out. Replaced mine at around 150k

AO

Mine went out at around 155k during SITM last year (or was it the year before that?)

outbackgeorgia

Just a follow-up, I had the same starter issues with my 79 and 87, both 5 speed so not necessarily indicative of TBF.
Dave
87S4 5Sp

Tony

Interesting. Got any more specifics on what to search for? or actually what fails?

Rob Edwards

Tony: Not exactly sure, but I think that the brushes were just completely worn down.

Disclaimer- This isn’t a complete rebuild, as I didn’t replace both bushings and didn’t mess with the solenoid. I haven’t tested this on a car yet, so I don’t know if the rebuild ‘worked’, so caveat emptor. My ’90 GT (114K) miles stranded me a while back due to a weak starter, hadn’t really noticed it getting gamey but a replacement starter cured it. Anyway, here’s a description of installing new brushes.

Starting point:



Here’s the rebuild kit:




Starter solenoid connections- the two flathead screws are usually buried in epoxy of some sort, they hold the solenoid case together, no need to touch them (or dig them out of the epoxy) unless you know there’s a solenoid problem



You need to undo the M8 nut, to undo the braided connector (under the tail of the arrow) so the field frame and its windings can be separated from the armature :



At first I figured I would have to completely separate the solenoid and bendix from the main starter shaft (and I guess you would if you would were you to replace the mainshaft brass bushing between the field frame (the case holding the windings) and bendix, but I chickened out and didn’t ‘go there’…) but this is not necessary to simply replace the brushes.

Picture of the field frame partially separated from the nose gear housing:




Disassembly:

There are two flathead machine screws that run the length of the main case- they are very tight, use a big screwdriver or impact driver to avoid stripping them.

Remove the commutator cover (2 small Philips screws), note E-clip, washer, and felt seal washer:



Armature windings with field frame removed:



Field frame showing old brushes and degree of wear:



Exploded diagram:



This is the degree of wear in the old brushes vs. a new brush:



The brush assembly is ‘floating’ above the main windings on the four braided brush cables. So to replace the brushes, you need to desolder the old brush cables. Only I couldn’t get them hot enough to melt with my soldering iron, I ended up cutting them, then dremeling the surfaces smooth. With all 4 cables cut, the entire brush plate assembly is separated from the field frame, so you can disassemble and reinstall each brush. Best to go one at a time- each brush is held in with a coil spring, you just have to hold back the spring with a hook tool and slide the new brush in.

After grinding the surfaces where the old brushes were soldered (brazed? tack welded????), I made a groove in the bar to give a surface to lay the new brush cable onto:





The rebuild kit had 2 brushes with bare-end cables, and 2 with pins soldered on. There are no corresponding holes for these pins, so I ended up grinding off most of the pins, leaving a ‘flat’ I could solder onto the frame:

Brushes after soldering (I ended up having to buy a bigger soldering iron to do this, got one of the propane powered Weller portables, it has plenty of horsepower for this) :









To polish up the armature ever so slightly, I ended up chucking the whole armature assembly in the drill press, then turned it while holding emery paper to the contacts:






Windings after blowing the case out and hosing everything down with electronic contact cleaner to get the carbon out- it's really messy! :





I pushed the old commutator rear cover bushing out, and installed the new bushing with a 10 mm socket in the vise:




Assembly is the reverse of disassembly.

Just checked Ebay, there is a 928 starter rebuild kit listed. The pic shows pins on the brush cables, it would be cool if a vendor could find a source for brushes with the 'naked' cables,it'd be a lot easier to just install them. (Maybe there are some MY starters that have provisions for pins in the field frame windings?) I really don't think replacing the bushings is essential, though I have no idea what kind of runout there was in my starter, nor how important that is.

http://cgi.ebay.com/ebaymotors/Porsc...Q5fAccessories


Anyway, if anyone sees anything glaringly wrong, holler, so I don't burn whatever car I install this on to the ground...


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karl ruiter

Wow, nice writeup. I think my problem is with the starter bushings. I cant explain it, but it feels like there is some grinding going on and it turns slowly. Once it comes to life and the starter disengages it feels fine. At first I did not suspect the starter because I have never had trouble with a 928 starter. In the 914 world, replacing starters seems to be an annual event, but 928 starters seem quite solid.

Alan

Let me start over here...you say it "starts hard" - do you mean it labors while cranking (e.g. slower than normal speed...).

If that is the primary symptom (admitedly along with sounding different)... then I'd say the first suspect is the battery no? have you charged and tested to be sure its good. Batteries die slowly an awful lot more often than starter motors and starter motor failure symptoms are more usually failure to spin or engage ...

so ...look at the likely, simple & cheap options first - you may get lucky

Alan

Randy V

Yes.

It's the same starter for all model years - not just S4.

karl ruiter

Yes, it labors while cranking, but I am pretty sure it is not the battery. Its hard to explain but there is a grinding feeling and a feeling of resistance, that comes back to the driver. Also the battery is quite new and has not been mistreated in the way I normally do my batteries. I did check the posts and ground wires anyway, and they are fine.

ROG100

Interesting topic as I have had four new ones go bad in the space of the last 4 weeks. All Bosch factory rebuilds. Being doing some checking and noticed they can be different starters - as in different solenoids and even permanent magnet type which also just failed in Australia. All in the same factory Bosch boxes and all in theory SR27X units. I will update once I have some further feedback from Bosch.