To get my car to start reliably? Im sick of this crap. Im also sick of not having hardly ANY reserve power. My friends 420sel has a tiny gasser battery and NEVER has any issues with cranking amps. He can play his radio for hours and his car cranks over just as fast. If i leave my lights on in my 300SD for ten minutes im SOL. So should I shoehorn in a 1000CCA battery and put two giant deep cells in the trunk? That should do it! That along with a 100amp sabb alternator and I should finaly be confident that my car will start






I had my alternator tested and it gives 67amps
My battery is brand new and tested great on the bench



Is this just part of owning a mercedes diesel? How could a 5 cylinder engine with twice the compression use several hundred more cranking amps than a v8? Sure, the v8 has less compression, but should have LOTS more friction.

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1981 300SD 512k OM603

I am not sure about the electric..

but the reason your engine has high torque down low is because the throws on the crank are so long. You also need to compress the air.. blah blah blah - you know all this already.

as soon as a gas engine starts turning and the ignition has potential energy, combustion is assisting in turning the engine with the battery / starter.

diesel is all battery and a little heat when starting out.

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Which battery did you purchase and was it rated at 850 CCA or above?

Sounds like a bad/weak battery or bad wiring. Or perhaps a bad starter motor that's drawing way too many amps. I can crank my diesel for 15-20 seconds easy with my white 1100CCA MB battery, and it doesn't even slow down in that amount of time. Normally my car fires up in like 1-2 rotations anyways. (All 4 of our diesels start in under 2 seconds cold, less warm) How much cranking does your engine need to start? Do you have a working glow system and plugs?

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

well, now I feel like an idiot. Its was my ground strap AGAIN

It loosened up, caused weeks of charging troubles, replaced the alt, changed it back, changed batteries, ect ect. Finally I took a wire from the alt to the battery and it began charging. I didnt think that bell housing bolt would be loose already


And its the ONLY one that keeps loosening. GRRRRRR...


I have the MB battery. But even under normal circumstances, I never feel like i have much reserve (with any battery). Its frustrating...

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1981 300SD 512k OM603

You have a contact issue somewhere. Running dino oil in the winter I have cranked the full 30 second cycle before, using a 1000cca walmart battery. I also have 2ga. wires connecting everything

Syntheic oil will help too-Mobil1 15-40 ought to get you a bit less resistance cranking.

EDIT: Fab up a second soldered 2ga ground strap straight from the alternator to the frame too.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

after charging for only a few minutes it cranks FAST now





Another question:


Whats your charging voltages. I rarely get over 13.5 BUT the bench tester at kragen said it could deliver 67 amps. This alternator charges fine, and quick, but shouldn't I be seeing 14.5 under a few thousand rpm?

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1981 300SD 512k OM603

You "might" see 14.5 if the battery is weak and the vehicle is under heavy demand load (lights, blower, wipers etc.). You'd need to be over 1500 rpm for this to occur.

The only time my 300td let me down was when the battery went w/o warning. Turned the car off in a drive thru and then barely one revolution when I went to restart. Jumped easy enough, then tested the alt. at Auto Zone. Good! Tested at Advance-- Good! Everything looked OK, got home and my pocket alt tester lit up the yellow and green lights--good! Kept an eye on it and checked it frequently and sometimes only the yellow light was lit indicating 12V or a little less. Long story short, sometimes the alt. was putting out just fine, sometimes not at all. I found a reman at the Zone (in stock) for about 125$ and haven't had a problem yet. Maybe I could have replaced the voltage regulator for cheap, but the original alt. was caked in dirt dauber nests and I didn't know any better at the time. Now if I can get the reman to last 25 years....

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83 300TD 219K HOMER

This is in CA, but when I tested my Cranking amperage with an inductive Amp Meter it only pulled aproximately 155 amps. This is about the same as a lot of big V-8s.

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84 300D, 82 Volvo 244Gl Diesel

155 amps @ 12 volts= 1860 watts

850 amps @ 12 volts= 10.2kw

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1981 300SD 512k OM603

Do you have two ground straps? ONe to the body and one from the engine to the body.

I always check the grounds first when having starting or charging problems. It is the problem a largish part of the time.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.