Our E 300 D usually starts fine. Occasionally when we turn the key to the start position the starter will not engage. Instead we get a soft continuous beep or buzz. We will typically try both of our keys multiple times with no change. eventually it has always started, so far, but it is getting worse. I thought I would have to have it towed tonight, but it finally did start. Does anyone have an idea as to what is going wrong?

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'97 E 300 D

I'm thinking you have a battery issue. How old is the battery? What is the year on the car?

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Jim

The battery is only about 3 years old and when the starter engages it cranks with gusto. Since I got at least 12 years on the original, I consider this one to be in it's prime.

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'97 E 300 D

Do you or have you ever heard a grinding noise when you turn the starter? I had that recently on my W123 and it turned out to be a bad bearing on the starter. If I tried it a few times, it would eventually move the flywheel and find a stronger position.

Dkr.

My first thought may be the Neutral Safety Switch but it could be the starter solenoid inside the starter. It is not making good contact to let the cranking current to go thru. You started eventually indicates the contacts may be badly corroded.

You can try to start in Neutral and see whether it makes a difference. If it does not then it is probably the solenoid.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

It does not grind but I have had that problem on a past old car.

I didn't think about the neutral safety switch or I would have fiddled with the shifter.

I have never actually seen the starter on this car. I assume it is under the oil filter/cooler. Most diesels I have fooled with have a solenoid on the starter and an intermediate relay, that is typically a solenoid like is used on a gasser. Is there another relay on this car in addition to the one on the starter?

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'97 E 300 D

I do not think there is another solenoid. The solenoid in the starter pull a hefty relay to crank the engine. The contacts may be badly corroded. This is my guess if the battery is fully charged or new.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

My 95 does this about once every 150 starts. It usually engages on the second try, sometimes the third.

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2009 E320 Bluetec 117,000
1995 E300D 306,000 Sold
1996 Ford Taurus LX 130,000 Sold
1985 300TD Still 225,000 Sold
2016 Ford Fusion 24,900

I would clean all ground connections related to the starter circuit first. Plus the battery connections. Cheap and easy to do.

This would include all the connections on the starter. Then you have a possible baseline if it is something else.

Another test then is to have two people present. When the starter will not engage have the other person tap it. If it activates change it. Making sure the wires on the back of it had good connections before doing so.

My viewpoint is these cars are well past their intended service or lifespan by design. You are going to get age related maintenance items to attend to.

You usually live with that situation until the frequency gets very high.

I had this problem in my 95, it was resolved after extending the evaporator drain tube away from the NSS and repairing the dodgy wiring joint that was in the little harness that comes from the NSS to the cabin connector.

I found that the A/C was dripping straight on the NSS and also the wiring looming was punctured and the was tied to the A/C condensate drain from inside of the car (my car's PO mechanic had some really interesting views on 12V DC circuits - dont ask)

After the resolution, it started every single time.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

If it is not as others have suggested above the solenoid I would check the bendix gear. It could be it's not pushing the starter cog into place.

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David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)

Thanks for the feedback from everyone. The next time it happens we will mess with the shifter to see if it seems like a NSS problem. However, with my luck it will probably turn out to be the starter. Thanks again for the suggestions.

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'97 E 300 D

This is just a follow up on my solution to my intermittent failure to crank problem. I did some reasearch on the starting system, and found that there is a starter relay in the relay box at the front of the computer compartment. This relay box often has a 40 amp fuse and is often called a K-40 relay, but in this mechanical injected car it has only three smaller fuses. I removed the relay box and opened it up, expecting to find a bad solder joint. The circuit board and the relays looked fine so I replaced the box and removed and installed the fuses and the plugs several times to make sure the connections were good. I assumed I had done nothing, but the problem has not returned. It has only been a couple of weeks but we had the problem nearly every day before I did this, so I am fairly confident that the problem is solved.

PS I tried starting in neutral and had the same problem, so I felt sure the problem was not the neutral safety switch.

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'97 E 300 D

The W210 has the "touch start" function whereby you just make contact in the start position and let go, and the starter runs until the engine fires. It knows when to let go by the increase in rpm or it times out if the engine does not fire.

The relay that drives this feature is part of the K40 module in the relay box under the hood.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech