My '84 300D turbo wouldn't start the other day, then a few minutes later it started. Then, the next day, after filling up with gas it wouldn't start again. I figured it was the battery.

So, I get a new battery, and there are no problems, but it does seem like it cranks a little slow still, even with the new battery.

When I picked up the battery, the mechanic wasn't in and his asst. gave it to me. I asked him to check to be sure the alternator wasn't going or gone, and he said if its running after a jump, the alternator is working. I said this is a diesel, does that make a difference, and he said no.

It seems to me that a diesel will run without continuing electrical power. Is this true? What about power steering, etc.?

Also-is there anything else that could cause the intermittent inability to start other than a bad battery or a bad connection to the battery? I truned the key and it seemed exactly like a dead battery, but I'm still alittle suspiscious.

a diesel will run without a battery or alternator. they run off combustion. if there is none of the above then the lights and anything electronic wont work. the power steeering is driven by a belt by the engine. the starter could also be bad.

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have no worries.....President Obama swears "If you like your gun, you can keep it

Just a couple of weeks ago the alternator died on my 240D. It was weird because the battery/alternator light on the dashboard never lit up.

First thing I did was replace the external regulator with decent used one that had longer teeth..... no help.

Then I charged up the battery and got about 3-4 days worth of starting and driving in between charges.

Local garage measured alternator output at a mere 12.3 volts and the semi-depleted battery tested at only 500 amps, low for a diesel battery.

True enough the diesel will run without electricity, but it takes a battery with balls (900 amps or so) to start the high compression engine. Better hope they didnt sell you a regular automobile battery.

What you want is the biggest, meanest battery you can find. Hell, I even encourage my friends who drive gasoline cars to upgrade to a giant diesel engine battery.

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Last edited by 300SDog; 08-06-2004 at 03:27 AM.

If you have a new Battery and the Starter itself is in good shape then I would be taking a close look at your Chassis Grounds and the main power connections to the starter solenoid and the starter itsef. A bad power or ground connection will cause a huge voltage drop regardless of how good your battery is.

A weak Alternator will only show up if your Battery isn't being charged up enough which will eventually cause poor starting performance.

Andy.

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1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

I definitely agree with Dervman. Check the grounds. Especially the main grounding strap connecting the chassis to the engine.

I came across these identical symptoms on my 126 recently. The bracket that the grounding strap attached to, on the engine side, was loose. I also saw inaccurate and/or fluctuating guages from this problem.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Orkrist,

You should fill your 300D with Diesel fuel, not gas.

P E H

Kmaysob,

Gasoline engines "run off combustion" too as do jet engines, rocket engines, non atomic steam engines, ETC.

P E H

I am assuming that when you say it won't start that you mean that you turn the key and the engine will not so much as turn over.

If that is the case, the problem likely lies with the starter solenoid. If you will use your lug wrench and momentarily short between the positive cable where it connects to the solenoid and the low terminal on the starter motor, you will jog the starter and it will most likely then turn over. That is the emergency measure. If that works it's time for a starter or starter solenoid.

Good luck,

Okrist,

If the started doesn't crank the engine when key is turned, it could also be a bad key switch or neutral switch.

240Dieseldog,

A Diesel car battery isn't any different than a Gasoline car battery. The Group 49 battery for MB cars has about the same out put as high quality batteries made for gas cars ~ 1000CA new. But as the battery ages, the CA become less and less as the battery plates deteriorate.

P E H

Paul, Thanks for reminding the room that batteries suitable for diesel engines are the same design as regular car batteries, only one helluva lot larger and more powerful than typical automobile batteries.

You never know when somebody might think that batteries for diesels have no zinc plates, or connector stems for cable attachment, or even a rectangular shape and plastic case. A very good thing you cleared this up for us.

On the starter issue, typical solenoid symptoms include zero response NOT slow cranking speed. Solenoid is electrical/mechanical device that prods the starter into engaging the flywheel, either it kicks or it doesnt.

Best remedy for a sticky solenoid is to smack it with rubber hammer or harpoon the solenoid pool-cue style using a 2x4. Friend of mine with a BMW carried a rubber hammer in his car for 2 years on this account.

The guy was just too damned lazy to pull the manifold which is required for access/replacement of the deaply buried BMW starter motor.

C'mon back Ork, and tell us exactly what the car does when you turn the key. Is it completely dead and do headlights dim, or is it just really slow??

As Paul wisely advizes, if it is the neutral safety switch - which should be bypassed and hurled into the bushes anyway - then wiggling the shift lever back and forth might help diagnose this problem.

P.E. Haiges- Yeah, yeah, I know. I did say it was a stupid question, though.

As for my mechanic, he's awesome, but he disappeared a few days ago, and his asst., who is like 20 years old, is running the shop. When I was going to the shop to get the battery, my regular mechanic drove past me in the other lane in a Testarossa. I guess he's preoccupied.

Anyway, I think its probably the neutral switch, or key switch, as the car also continued to run after turning it off today, so I turned the key back to position one and then off again and it turned off. That makes more sense. And, the steering lock isn't working lately either.

filled up with gas huh? i think thats where i would start looking for problems.

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1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

Is 85 or 91 octane the recommended choice for these fine engines?

DieselDog,

Batteries for Diesel engines don't have zink plates, nor do batteries for gasoline engines.

They both have lead plates.

If you compare a size 49 battery, the one that fits most MB (diesel or not), to the the best battery for other full size cars, the output of both batteries is similar.

Naturally batteries for large Diesel engines like railroad engines, will be much larger. But there are no batteries for large Gasoline engines, because there are no large Gasoline engines.

P E H