Start Up Problem for a 1979 300SD?

I have a 1979 300 SD car with only 188km that is having difficulties starting during cold weather in Canada.

I have a block heater. The starter and alternator have been checked and seem to be working fine. I installed a brand new battery.

The mechanic just can't figure out what the problem may be. Any suggestions would be greatly appreciated.

Judy

Reply to
classicone
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Have him test your compression; cold. Find out what the reading is on the

1st compression stroke.

Reply to
Karl

When were the engine's valves last adjusted? Adjustment is due every

24,000 kms.

And your starting technique: At 0 degrees C. M-B wants the accelerator depressed and held there while the motor is being cranked, let off the accelerator when the motor fires. At -20 degrees C. M-B wants the accelerator pumped three times before cranking the motor, then the above procedure.

Reply to
-->> T.G. Lambach

I agree with valve adjustment... also check your glow plug system.

Reply to
Tiger

A question: How quickly does the motor shut down after the key is turned to OFF?

Almost instantly? Or does it trail to a stop - over two or three seconds?

Should stop almost instantly, otherwise could affect starting.

I don't want to go further without knowing a bit more.

Reply to
-->> T.G. Lambach

On Feb 18, 6:19=A0pm, "-->> T.G. Lambach

Reply to
classicone

You are probably on the right track about the grounding strap... the battery negative ground cable is the first thing to check and the ground strap... which is by the starter if I am not mistaken... needs to be replaced.

Reply to
Tiger

Thanks Tiger, Would these wires cause the battery to be drained in the morning? Judy

Reply to
classicone

No, a bad cable just won't be able to deliver as much current which is critical when cranking. If you leave the car until it's reached a final cold temperature, say 8 hours and it starts OK, but won't crank about the same after sitting for say 24 hours or 48 hours at the same temp, that suggests you have a small load that is not turning off and draining the battery.

You can disconnect one of the battery leads and insert an amp meter. With everything off, the current should only be 10ma or so, which would be the clock, etc. If it's substantially more, something is drawing current and you need to track it down.

Reply to
trader4

Thank you. This problem has been going on for 4 weeks. Now I can hopefully figure it out.

Reply to
classicone

If the battery has been drained overnight there are some suspects on your model:

The cursed climate control "servo" is reported to drain a battery. The car's power antenna is known to drain a battery. A stuck power window switch can drain the battery.

If you need to replace the servo I'd suggest you check out a digital retrofit system from

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I installed it on my '80

300SD and it works well.
Reply to
-->> T.G. Lambach

On Feb 19, 7:08=A0pm, "-->> T.G. Lambach

Reply to
classicone

My mechanic looked after the car for the previous owner. He checked out everything and in the shop it starts every time. Valves were done by him, the glow plugs fine. He's baffled! He said I may have to take it into Mercedes to have them run diagonstics on it. Is there anything else before I take it to them?

Reply to
classicone

My mechanic looked after the car for the previous owner. He checked out everything and in the shop it starts every time. Valves were done by him, the glow plugs fine. He's baffled! He said I may have to take it into Mercedes to have them run diagonstics on it. Is there anything else before I take it to them?

If you are talking about the starting problem it is either fuel (pump, filters, algae etc), electrical (battery, relay, glow plugs, block heater etc.) or mechanical(vacuum, valves, worn rings etc.) . Based on the report of a battery drain problem I would certainly fix the problem or replace the battery before I took it to the stealership.

If you want to troubleshoot the battery drain problem try here:

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Reply to
me

In this entire discussion there isn't a good description of exactly how it behaves when it won't start. If it barely turns over, and won't crank for more than a min, that is a very different thing than if it turns over normally, with plenty of cranking ability, but won't fire at all, etc. Does it always have this starting problem, or does it depend on temperature? Does it start perfectly when warm?

Did the mechanic leave it out over night in the cold at similar temps to when the problem occurs? BTW, I wouldn't have much faith in any mechanic who said you have to take it to MB for them run "diagnostics" on the car. There isn't any special diagnostic that MB has for a 30 year old car. It's just basic problem solving and elimination that any decent diesel mechanic should be capable of doing.

Reply to
trader4

I agree, the trail has gotten confused.

Reply to
-->> T.G. Lambach

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What kind of "diagnostics" does your wanna-be so-called mechanic think any dealership could run on a 1979 116 body 300SD??

"Valves were done by him, the glow plugs fine. He's baffled!"

How about a compression test?

How about a battery performance test?

How about finding a real mechanic instead of this parts replacer you are wasting your time with?? Test test test.

Reply to
Karl

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