New Starter wants to run with no key! - PeachParts Mercedes-Benz Forum

mesillamaan · #1 01-06-2021, 10:31 PM

I had my starter on a 240D go.
No problem, get a "new" rebuilt Bosch and snake it up in there for a workout and attach it.
Go to attach the battery connections and the starter fires!
Fortunately it's in neutral and doesn't take off.
Check the ignition...it's off and the key isn't even in it.
Switched the connections on the starter just to see if I screwed that up...but no power goes through in that configuration.

So what did I do to cause this "open take off mode" and how do I rectify it?
Thanks!

P.S. The only other thing I did was have the key in during the starter removal and replacement so that I could crank the wheels to the right so I could snake the starter in from below...but then removed the key.

psaboic · #2 01-07-2021, 09:30 AM

I would take the starter out and take it to a shop or auto parts store and get it tested. See if it does the same thing on the bench (fires by just being hooked up). If it does you have a defective starter (most likely a stuck or shorted out starter solenoid). Or you can try rapping on the solenoid with a hammer to see if you can unstick it, but that is a temporary fix at best.

Sugar Bear · #3 01-07-2021, 09:51 AM

If the starter cranks with the key removed and with only the battery connected to the large lug on the solenoid, the problem is in the solenoid/starter assembly.

Good luck!!!

Diseasel300 · #4 01-07-2021, 10:14 AM

Did you connect the starter power lug from the battery to the wrong heavy terminal on the solenoid?

Zulfiqar · #5 01-07-2021, 03:04 PM

thats what it seems like.

but with the large wire on the wrong heavy solenoid - the motor will spin with no flywheel engagement as the solenoid wont be pulling in to kick out the starter pinion.

tyl604 · #6 01-07-2021, 07:57 PM

Hit it with a 2x4, not a hammer, if that is the route you choose.

mesillamaan · #7 01-07-2021, 10:56 PM

Thanks so much guys!

So one thing I may not have been clear about is that I did switch the two connections to the solenoid right after the first configuration to see if I had connected them incorrectly. The spinning of the starter occurred with the positive battery cable (I believe this is the large lug or large wire you guys refer to) connected to the lower solenoid terminal. So then I switched them...but found that that resulted in no power going to the car at all...turning the key produced no dash lights, no juice, nothing.

Before running off to work this morning I put in another starter that I had from an another 240D that's out to pasture. And guess what...the same thing happened! What's the chances of two starters with both solenoids faulty or stuck open?

It sounds like 2X4 time!

psaboic · #8 01-08-2021, 01:22 AM

Ok, if you have two starters doing the same thing, I am starting to suspect that the ignition switch itself may be causing it. If the ignition switch is wonky, it may be sending the "start" voltage to the starter despite the key not being in the ignition or the switch in the "off" position. I stand by my original suggestion and advise that you take (now both) starters to a shop or auto parts store and have them bench tested. If they spin once voltage is hooked to them on a test bench, then you need to buy a lottery ticket as you have two starters failing in the same weird way. If they both operate normally on the bench, I would start suspecting the ignition switch and/or associated wiring. Just my .02

mesillamaan · #9 01-08-2021, 07:39 AM

Yeah I'm thinking ignition too.

When I started the whole switcharoo, I parked over a swale in the yard so that I had room to squirrel under to take out the starter. Because there is a sweet spot down through the tie rods, I left the key on so that the steering wheel wouldn't lock as I moved the front wheels around to find that spot which I remembered from years ago...Just for yucks, the spot is about a 7/8s turn to the right...then the starter can come out and go back up in without too much effort.

So that key had been left in the on position for some days through the cold (some -F mornings and a 2+ foot snow storm) before I could get back to it.

If that is the ignition switch, where and what do I do? Is that some more 2X4 work?

psaboic · #10 01-08-2021, 09:35 AM

Hmmm... from what you were saying about leaving the switch on for "some days" it very well could be a stuck or toasted ignition switch, or possibly shorted wiring somewhere. I have never done it but replacing an ignition switch is fairly simple when you have the key. It is a horror story with a missing key.

From where we are at right now, here is what I would do if it were me. First, I would get the starters tested so you know their condition and can eliminate them if they are functioning properly off the car. Second, if the starters are fine, I would get a wiring diagram and meter out the wires to see if you have any that are shorted (you can probably find one for your car doing a search on the forum or possibly a google search) you will most likely have to remove the instrument panel and ignition switch to do this, and a search of this forum will give you plenty of instructions on how to do this.

I'm betting on a bad switch, but to be honest, I'm impressed the battery held a charge after the ignition switch was left on for several days in below zero temps..

Please keep us posted on how this turns out.

Diseasel300 · #11 01-08-2021, 09:58 AM

Testing the switched leg is simple. Leave the small wire off. The chances of having 2 different starters do the same thing are less than your chances of winning the lottery.

If the motor still cranks, you are wiring something wrong. End of story. If you touch the small wire to the terminal on the solenoid and the motor cranks the engine, you have a bad ignition switch or something funky going on with the wiring in the car.

mesillamaan · #12 01-08-2021, 10:16 PM

I didn't have the chance today to do any more work on it...but tomorrow I hope to.

I'll do the test on the starter as you guys have described...but I'm really thinking it's a switch stuck or froze open. When I say I had the key turned on, the battery was disconnected the whole time, so no drawdown on the battery. The key was just "on" so I could turn the steering wheel and get my route open for taking out and putting in the starter.

And just so I'm clear on the starter wiring and terminology being used...the lower heavy terminal connects with the large wire/power lug or positive wire from the battery. And the small wire is connected to the upper heavy terminal. There's a third very small wire which is connected with a small phillips screw...but I'm guessing that's some sort of ground and it doesn't come into play with anything we're discussing so far. Sound right?

Thanks guys!

Diesel911 · #13 01-08-2021, 10:31 PM

Quote:

Originally Posted by mesillamaan

I didn't have the chance today to do any more work on it...but tomorrow I hope to.

I'll do the test on the starter as you guys have described...but I'm really thinking it's a switch stuck or froze open. When I say I had the key turned on, the battery was disconnected the whole time, so no drawdown on the battery. The key was just "on" so I could turn the steering wheel and get my route open for taking out and putting in the starter.

And just so I'm clear on the starter wiring and terminology being used...the lower heavy terminal connects with the large wire/power lug or positive wire from the battery. And the small wire is connected to the upper heavy terminal. There's a third very small wire which is connected with a small phillips screw...but I'm guessing that's some sort of ground and it doesn't come into play with anything we're discussing so far. Sound right?

Thanks guys!

Just for clarity in the attached pic #2 is where the Positive Battery Cable goes.

I am going to give you an extremely remote possibility. There is a wire that goes from the Starter to the Glow Plug Relay. When you are cranking the Glow Plug Relay is on during cranking.
The remote possibility is that there is something screwed up in the Glow Plug Relay and the Glow Plug Relay is sending voltage/current down to the Starter causing the Solenoid to activate and the starter to crank.

That is easy to check on. Just unplug the Electrical Connector on the glow plug relay that has the small multicolored wires on it.

Diseasel300 · #14 01-08-2021, 10:35 PM

Your solenoid has 3 terminals on it.

Referencing the photo from D911 above, Terminal 3 should have the heavy wire coming out of the side of the starter motor itself attached to it. Nothing else connects to this terminal.

Terminal 2 should have your battery wire and the other heavy (smaller) wire connected to it. The 240's don't have the junction block on the fender and this is the power wire to other parts of your car.

Terminal 1 where the tiny wire that connects with the screw is the wire from the ignition switch.

mesillamaan · #15 01-09-2021, 03:38 PM

Yeehaw!
Well it was a wiring connection!
So after looking at what is visible at the connection of Terminal 2, I was wondering why the little rubber boot never fit well over the connection of the big and small wires. What I couldn't see, unless I had the head of a snake or weasel, is that the small wire was bound with a thickness of electrical tape. Unwrapping that it was apparent that it was an old cob-job to keep the small wire connected to its contact which fits over the terminal. The wire appeared to have been cut for some reason...who knows when...it's an '81 and I've had it since '17. Anyway, that connection, from me wrenching it around half a dozen times with my starter merry-go-round, was no longer in contact. My own soldering cob-job has rectified that, and even with it being 20F out and the starter like a frozen pot roast and a frozen ham, she started right up!

So thanks so much you guys for all your help getting me through this with your good advice and teaching me some necessary lingo. The starter (both of them) are good...but I'll keep my Bosch on there as I've had enough practice.

Now I can begin my search for vacuum leaks. Are you guys up for helping me with that? Haha...maybe a new thread

Thanks again!