Starter won't crank, battery is good - starter the only solution?

[butters]

I recently picked up a very clean '91 318i, PO had the car for 19 years and was meticulous about keeping records and the car in perfect shape. Unfortunately, I believe the starter has gone, but I'm not sure, and won't get the car into a shop for a few days.

On Saturday, I pressure washed the frame rails and hood sills. I am beginning to think this was a bad idea and may be at the root of my problems.

Shortly after, I noticed the starter struggling to crank more and more with each start, for about 3-4 starts. Saturday night, I didn't take the car out of my garage because at the end of the crank, I got the "buzz" or click of a relay? or something that I figured meant my battery had died. From then on, I get absolutely no attempt to crank or anything when I turn the key. The other electrical systems do prime as they normally would.

Sunday, I got up and took my battery to trade at Autozone. The clerk tested it, and returned 56% charge indicating that the battery was good, and my alternator was likely bad. So I returned home, set up a charger on my battery, went out and picked up an alternator and did that swap (somewhat of a PITA but a good learning process). Today, battery is charged, new alt, and I still get no response from the starter.

I tested voltage across the starter while a friend turned the key to "start" and I believe I was getting results evident of a dead starter, but the diagram in the Bentley manual of course doesn't match up perfectly to what I'm looking at, so I'm not 100% on my diagnosis. I have been researching all day, since I really don't think I am capable of changing the starter myself and all shops are closed and busy for a few days, and I see that there are possible ground issues and there is always the actual ignition itself. My grounds are good, battery compartment is very clean, though the main engine ground has lost some of its sheathing over time and isn't too pretty. But it's still bolted in place and I believe effective. Am I overlooking anything or should I just buy a starter and call my local BMW specialist? Crank position sensor? Fuses/relays? I am hopeful that it's something else, but the way that the starter slowly died and the fact that I washed in the engine leads me to believe that must be it.


On a side note - I'd love to avoid towing the car ($) but my garage is at the bottom of a very steep driveway. How long of a run is needed to push-start? I might have 30-40 feet, I'm thinking that isn't enough. If I could pull the car up my driveway, I could easily push it down the street... but do I trust the rear tow hook to hold the weight of the car?

[DesktopDave]

Seems like you're off to a good start on troubleshooting.  Welcome to the club!  I can push-start a car in about ten feet on level ground if I have two people pushing it.  The trick is to pop the clutch hard when you have a little speed, maybe only 5mph is enough?  The rear hook can easily tow the car.  Make sure your tow line has at least 10,000# rating.  A 2400# static car can easily weigh 5,000# while moving.  I use a really big nylon webbing ratchet strap rated to 22,000#.  I've done it a lot of times, even up my steep Pittsburgh driveway.

I'd hold off on a new starter.  They're really expensive, and I've never seen one go bad.  Not to say it's impossible, but they're sealed up pretty well AND they're a major pain in the ass to get out.

I'd figure the buzzing is the result of a bad ground or major un-fused short, especially since you did some pressure washing.  Buzzing means that the relays are opening but the starter doesn't have enough amps to spin.  There is also an under-voltage relay on the steering column that disables the ignition switch, so the starter never turns.  If it's really bad the car will seem totally "dead," as if there is no battery installed.  Crank position sensor isn't even in the game yet, it'll still be OK.

I'm not sure what they meant by "the battery was at 56%."  If they did a load test and the battery only got up to 56% of it's rated cranking amps it'll be OK with a good charge.  FYI, I hate taking stuff to them to test.  I've been all over & they never give consistent answers at car parts stores.  Even a good battery will discharge very rapidly if there is a short on the starter side of the motor.

So I'd bet you have a good alternator and a good battery.  I'd guess you have an unfused short-circuit or broken ground.  I'd start with the battery out of the car & get my trusty multi-meter on the positive junction block (passenger side firewall) to see if there is any continuity from there to the chassis.  Then I'd see if there's a solid ground to the motor from the frame & from the starter to the motor.