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  #1  
Old 11-12-2020, 10:28 PM
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Strich Acht
 
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Location: Istanbul / Vancouver
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Dying starter motor? W115 240

Hi folks,

Just in time for the cold and rain up here in the Pacific Northwest, my 1974 240D has developed a starting problem.

I'm thinking it's probably the starter motor but wanted to get folk's opinions before I start going ordering things!

The other day, the car really struggled to turn over and wouldn't start. It had been below freezing the night before so I had thought maybe the diesel was gelling. Later that day I tried to start the car (temperature was way warmer) and still had the same problem.

A jump start from the local towing company got it running, and the battery was tested, showing that it was less than perfect.

So, I just replaced the battery... and the car still struggled to start. Same slow/laboured turn over before eventually firing up.

To me, this sounds like the starter is on the way out. Is it likely to be anything else?

Thanks!

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Last edited by j-galap; 11-12-2020 at 10:46 PM.
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  #2  
Old 11-12-2020, 11:02 PM
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What is the ambient air temp and what weight oil is in it?

Does it have a block heater? Block heaters make a big difference. If equipped, check the cord condition before using, they deteriorate and can be a fire hazard.

Valves adjusted?

Yes the starter may be going bad, if replacing it use a Bosch 300D/5cyl version.

Measure the voltage drop/difference between what is in the battery while cranking vs. what reaches the starter to test for a high resistance positive cable. Check the ground to the engine, use a jumper cable from the battery to the engine to see if it helps.

Good luck!!!
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  #3  
Old 11-12-2020, 11:39 PM
dkr dkr is offline
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You could have a grounding issue or a voltage drop issue. You should be getting 12.6V at both the battery and the starter motor.

I wonder if the starter performs any differently when the engine is hot. That would rule out any cold start issues like the weight of the oil or diesel gelling.

What has been your previous experience with cold starts on this car?

Dkr.
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  #4  
Old 11-13-2020, 01:22 AM
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Location: Sunny So. Cal. !
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Post Stater Woes

Since you didn't mention ever touching it before my bet is it's in fact in need of service P.D.Q. before you cook it from the slow cranking .

I'd agree that replacing it with one from a 5 cylinder is the wise thing to do .

Remember : ONLY BOSCH branded rebuilts ! your F.L.A.P.S. or local NAPA won't have the one you need & want, they'll have one done by a local rebuilder that won't last anywhere near as long as your current one did .

Don't be foolish over a few dollars here .

The bitterness of low quality remains long after the sweetness of low co$t has been forgotten .
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  #5  
Old 11-13-2020, 10:46 AM
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Check battery voltage and the condition of your chassis ground strap. You could have a charging problem masking itself as a starter problem. I had slow cranking on my 350SD and the issue was the chassis ground strap from the transmission to body hanging on using only the "Force". Replacing it restored normal cranking with the same starter motor and battery.
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  #6  
Old 11-13-2020, 11:25 AM
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To measure the voltage drop you use your voltmeter with one probe on the battery terminal (not the cable clamp) and the other probe on the Stud and Nut that holds the Battery Cable to the Solenoid or do the same with the negative cable; Battery Terminal to the chassis and the ground cable.

If your cables or their contacts are working OK when you crank you should see no voltage on the meter. If you see voltage it means there is resistance in the cables and voltage is bypassing through your voltmeter.

Remove and clean all batter cable contact areas to the bare metal. Look under the insulation on the Battery Cables especially the Positive cable at the battery terminal to see if it is corroded inside under the insulation.

If you remove your Starter you might as well take a look and see if your Starter Brushes are worn out.

My issue acted as if it was a bad starter solenoid but the Brushes were worn down to about 1/4th of an inch. I also noticed that 2 of the brushes were worn more then the other 2.

With the end cap off you can check the armature for shorts.
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Dying starter motor? W115 240-checking-voltage-drop-voltmeter.jpg  
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Last edited by Diesel911; 11-13-2020 at 11:37 AM.
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  #7  
Old 11-13-2020, 01:31 PM
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Strich Acht
 
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Thanks for all the info folks. Thinking about it, my chassis grounding strap is pretty crusty (probably the 46 year old original), so I'll start with that and see how we go...
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  #8  
Old 11-13-2020, 02:35 PM
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Strich Acht
 
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Here we go:



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Last edited by j-galap; 11-13-2020 at 04:47 PM.
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  #9  
Old 11-14-2020, 08:55 AM
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Mine only crank fast enough to start with synthetic oil when it's cold. 617 engine in all. Besides starting perfectly, not having to spend time changing the oil so frequently is another advantage.

I sent a 15,000 mi sample from my Cummins to Blackstone and they said the wear materials looked very good - but I don't generally run past 10,000 mi and do the oil changes before it turns cold unless mileage is low enough to make it through the winter.
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  #10  
Old 11-15-2020, 09:36 PM
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Quote:
Originally Posted by j-galap View Post
Hi folks,

Just in time for the cold and rain up here in the Pacific Northwest, my 1974 240D has developed a starting problem.

I'm thinking it's probably the starter motor but wanted to get folk's opinions before I start going ordering things!
I had similar symptoms to yours for about a year or more. My engine has great compression. Starter would barely turn it over at times. Turned so slowly I was surprised it started. I kept putting battery on charge and with fresh battery it was a bit better.

Finally, the starter would not work at all. I took it in to a local auto-electric shop that rebuilds starters/alternators. He put in a bunch of new parts (more or less rebuilt it) Cost about same (or more) as a reman starter, but he did this overnight for me. Back on road next day!

The difference is amazing! Spins engine over fast and it starts immediately.

Check everything others have said, but this is the best thing I have done for my car in a while!
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85 300D,72 350SL, 98 E320, Outback 2.5
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  #11  
Old 11-16-2020, 02:04 AM
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I suppose it is possible for it to be a solenoid issue. Because when activated the Solenoid pushes a plate against 2 contact points inside of the Solenoid and it is possible for those contact points or the plate to be not making good contact and not allowing enough amperage or voltage to turn the starter properly.

The attached diagram is a Bosch Starter. The green circles are the high amperage contact areas. On most Starter there is a circular plate instead of that wedge shaped on shown.

Picture of my worn Starter Brushes in post #36 and in #37 the armature.
Starter rebuild issue...

Anyone have good source for starter rebuild parts
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Dying starter motor? W115 240-bosch-starter-diagram.jpg  
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  #12  
Old 11-16-2020, 10:06 AM
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Strich Acht
 
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Turned out to be the chassis grounding wire in the end. The block end of the wire refused to budge so I cleaned it up, gave it a coating of penetration oil and then left it a day. Still wouldn't come off. Tried heating the bolt up too - still nothing - think I need to use an impact gun on it.

Anyway, after that the wire and both connections were both very clean so I decided to test the starter - works like a charm now.

I still need to change that wire at some point but the problem is solved and there's no laboured starting any more. Back on the road again
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  #13  
Old 11-16-2020, 11:40 AM
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Quote:
Originally Posted by j-galap View Post
Turned out to be the chassis grounding wire in the end. The block end of the wire refused to budge so I cleaned it up, gave it a coating of penetration oil and then left it a day. Still wouldn't come off. Tried heating the bolt up too - still nothing - think I need to use an impact gun on it.

Anyway, after that the wire and both connections were both very clean so I decided to test the starter - works like a charm now.

I still need to change that wire at some point but the problem is solved and there's no laboured starting any more. Back on the road again
I perfect example of how basic stuff and the cheapest way to go is most often the fixes issues.

Think about how many people have replaced their Starters due to a bad ground or other connector.
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  #14  
Old 11-19-2020, 06:03 PM
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Strich Acht
 
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Location: Istanbul / Vancouver
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Turns out the starter is fried after all. Oh well!

Now in the process of pulling it from the car. Bolts at the front are fairly straightforward. I would recommend using an offset 17mm wrench for the motor mount nuts as well as removing the throttle linkages in the vicinity to allow more access. Ran out of dry weather before I could get to the hex bolts on the back side!

Anyone got a part number for a W115 240D starter motor by any chance?
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  #15  
Old 11-21-2020, 03:06 AM
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Post 1974 240D W115 Starter

Here are two BOSH rebuilts, I'd go for the SR61X

Starter (Rebuilt)
(1 customer review)
Part #: 003-151-07-01-88-M14
[ More Info ]


View in Catalog: Starters
This part fits your 1974 Mercedes-Benz 240D Sedan

Brand Rating
$189.00

Starter (Rebuilt)
Part #: SR-61-X-M14
[ More Info ]


View in Catalog: Starters
This part fits your 1974 Mercedes-Benz 240D Sedan

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