W123 Starter Mystery

[AKillion]

My 1977 240D starter wore out (brushes were toast) so I got a heavy-duty (refurbed) replacement. Two weeks ago, I installed it on the car and when I tried to start it there was just an initial click with the solenoid but no crank. Tried two or three times but eventually, there was no solenoid click. Checked the battery, no issues. Neutral Safety Switch is brand new and replaced a month ago. Re-checked all my connections. Ground, positive everything - still no workee. Cursed, and packed up for the day.

Pulled the new starter back out of the car today and bench tested it by connecting it to the battery directly with ground and positive and then jumper from the control terminal to positive and what do you know - a solid kick of the solenoid and strong fast spinning of the gear. Tested this 2 or 3 times and was good every time. So, I reinstalled the starter, got in and turned the key briefly without waiting for the glow plugs and she was trying to turn. Great. I needed to replace the glow plugs so after that was done, I got in the car, heat the plugs and she turns over and fires up faster than she ever has! YES! I let her run for about 10-15 minutes while checking the charge from the alternator - all looks good.

Shut her off and go wash up before I take it for a test drive (just installed a new speedo cable). And I go to start her up and there's just an initial click, no turnover. Then subsequent tries - no clicks at all. F%$K

Battery reads 12.63v when measured using the positive on the starter and starter body. I double checked the continuity of the circuit as it passes from under the dash through the neutral safety switch and got solid measurement when it was in park and in neutral so that seems fine. Still no luck on starting. Just in case, I bypassed the neutral safety switch with a jumper wire - still didn't work. OK, maybe my battery has a problem under load, so I hook the jumper cables to my Chevy and try that with nothing coming from the starter. I checked the voltage at the starter again - 13.5v (while hooked up to my Chevy). With my ignition key on, I got a jumper wire and connected the starter control wire and touched it to the positive terminal - NOTHING.

By process of elimination:

It's not the neutral safety switch since I tested it's circuit as well as bypassed it.
It's not the wiring since I'm getting solid voltage when tested at the point where it's getting to the starter.
It's not the battery since I did a jump with my other car and let it run for 20 min and left it on while attempting to start.

So - I'm thinking it's the refurbed starter only works intermittently?? Next, I plan to pull it out again and bench test it once more. Any other ideas are appreciated.

[Diesel911]

You have to do this with the starter installed. If nothing happens again take a piece of wood like a 2 feet of a 2x4 and put it on the steel part or aluminum part of the housing and give it 2 shape raps with a hammer don't beat on it hard enough t do any damage and stay away from the solenoid. If that works either your brushes are sticking inside or the solenoid is sticking.

You also did not mention doing anything to your grounds. Remove the ground straps and clean the contact areas. A good general maintenance thing to do regardless if you are having starter issues or not.

It is extremely unfortunate that rebuilt items have the poor record they do.

In the past I went to some starter sites and they were selling solenoids for borsch starters for $16 each. Imagine what the quality on them is. And rebuilders are using them.

I have also found the term "heavy duty" to be kind of bogus as far as Cars go. Some pickup trucks and larger Trucks have heavier duty starters but the physical dimensions on them are usually different.

[Alec300SD]

Check that the braided copper wire from the starter to the solenoid is not contacting the case for the starter motor.
If the braided cable gets grounded to the starter motor case, this can cause a no start senario like you are experiencing. BTDT.

[AKillion]

Thanks Diesel911 -- I will try knocking it into action (and refrain from getting carried away) to see if that shakes anything loose.

I didn't do anything with the grounds. I figured since I was getting proper voltage tested at the starter itself using the ground on the body of the starter this wasn't an issue - but what the hell, I'll clean up the ground strap anyway.

The "heavy-duty" was my description since it seems a little beefier than the OEM starter even though it's the prescribed replacement - I can't remember if the product description said that.

[AKillion]

I'll check that Alec300SD - thanks.

[Diseasel300]

Just another possibility that happened to me - I had a rebuilt Auto-Zone starter in my 300SDL that would intermittently fail to engage. Sometimes you'd get a click, other times nothing. Neutral safety switch wasn't the issue, nor was the ignition switch.

I pulled the solenoid and found it *PACKED* with grease. The solenoid should be dry inside, maybe rubbed with oil, but never grease. Cleaned all that garbage out and it never caused another issue. Same starter is still running my 350SD with no so much as a single hiccup.

[barry12345]

Since you have jumper cables. Hook one to the negative terminal of the battery. Plus the other end to the engine. Try to get good connections.


Reading voltage from the body to the starter terminal means nothing. It might from the engine to the starter terminal. If there were a ground issue from the body to the engine.


There is a ground strap under the car. From the body to the engine. Cleaning and putting some treatment on the ground connections when they are this old does no harm anyways. Another simple test is to short the small terminal on the starter to the large terminal. If the starter engages the ground section of the circuit is intact. Make sure the car is in neutral.

Also make sure those battery terminals are clean. It is not uncommon for the starter to draw so much current a connection goes open.

[AKillion]

When I was reading voltage it was positive terminal and ground from the body, I meant the body of the starter where it bolts to the transmission housing. (This is the same point where I successfully bench-tested it while it was out of the car) I assumed I wouldn't be getting a good voltage reading this way if the ground to the engine wasn't well connected but I'll recheck the grounds and battery connections again.

Originally Posted by barry12345

Since you have jumper cables. Hook one to the negative terminal of the battery. Plus the other end to the engine. Try to get good connections.


Reading voltage from the body to the starter terminal means nothing. It might from the engine to the starter terminal. If there were a ground issue from the body to the engine.


There is a ground strap under the car. From the body to the engine. Cleaning and putting some treatment on the ground connections when they are this old does no harm anyways. Another simple test is to short the small terminal on the starter to the large terminal. If the starter engages the ground section of the circuit is intact. Make sure the car is in neutral.

Also make sure those battery terminals are clean. It is not uncommon for the starter to draw so much current a connection goes open.

[Diesel911]

Originally Posted by AKillion

Thanks Diesel911 -- I will try knocking it into action (and refrain from getting carried away) to see if that shakes anything loose.

I didn't do anything with the grounds. I figured since I was getting proper voltage tested at the starter itself using the ground on the body of the starter this wasn't an issue - but what the hell, I'll clean up the ground strap anyway.

The "heavy-duty" was my description since it seems a little beefier than the OEM starter even though it's the prescribed replacement - I can't remember if the product description said that.

Well there is enough voltage verses enough amperage.

As hypothetical example the skinny wire going from the Ignition to the Solenoid. If there was a lot of broken wires inside of it you could get good voltage but it is possible for not enough amperage to pass through it.

Oddly you are having the symptoms my Starter had before I rebuilt it. Not only were the brushes worn but when I took it apart I found the stuck in place. Before I took it apart the wood thing and hitting wood with a hammer apparently jarred the brushes enough to allow them to make contact.

In which I learned something from one of the Members as I never realized the Solenoid would not work if the Brushes were not making contact.

[tyl604]

If the 300D has a terminal box on the right wheelwell (like my SD), you can cross two screwdrivers and jump it. The solenoid should jump and the starter should spin. Just take off the plastic cover, hold the screwdrivers on two of the bolts which pin down the cables, and cross the screwdrivers together.

Wondering if you tried that?

[Diesel911]

Originally Posted by tyl604

If the 300D has a terminal box on the right wheelwell (like my SD), you can cross two screwdrivers and jump it. The solenoid should jump and the starter should spin. Just take off the plastic cover, hold the screwdrivers on two of the bolts which pin down the cables, and cross the screwdrivers together.

Wondering if you tried that?

Unfotunatly the OP has a 1977 240D and there is no terminal block on the fender well.
Also I thought the SD's had their terminal block below the battery tray.

[tyl604]

It is located just in front of the battery tray on the right fender well. Came in handy when my NSS went SNAFU and until I got another.

[AKillion]

Originally Posted by Diesel911

Well there is enough voltage verses enough amperage.

As hypothetical example the skinny wire going from the Ignition to the Solenoid. If there was a lot of broken wires inside of it you could get good voltage but it is possible for not enough amperage to pass through it.

Oddly you are having the symptoms my Starter had before I rebuilt it. Not only were the brushes worn but when I took it apart I found the stuck in place. Before I took it apart the wood thing and hitting wood with a hammer apparently jarred the brushes enough to allow them to make contact.

In which I learned something from one of the Members as I never realized the Solenoid would not work if the Brushes were not making contact.

Ah, this makes sense. OK well, as soon as I can get work to slow down I can check on things. Thanks for everyone's input.

[vwnate1]

This is why I keep telling you : BOSCH branded rebuilts only ~

The weak solenoid is a well known issue .

Once it begins to hesitate it's kaput .

I hope you get this sorted out .

[barry12345]

I would never accept a rebuilt German starter without a new bosh solinoid. Did it a couple of times in the past. Was all it took.


Chain store operations are profit motivated and buy from the cheapest supplier. Usually Mexico. Even if you get something that works you cannot count on it to continue doing it for a reasonable time. Original quality solinoids are not cheap. Other than to bosh perhaps.