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5cyl OM602 engine staring on only 4 glow plugs

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Old 12-15-2018, 03:30 PM
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Mercedes Benz 207D
5cyl OM602 engine staring on only 4 glow plugs

Hello! I'm in the process of buying an '82 207D that had a motor transplant from a 4 cyl OM616 engine to an OM602, 5 cyl. The owner said that after the transplant, the new relay for 5 glow plugs didn't fit or something and he used the old relay (for 4 glow plugs).

I'm not quite good with engines, but what I understand that a piston is not working properly for about 1 min (without combustion). Indeed, a diesel engine has no need of spark plugs, using the glow plugs only on cold starts. After the engine reaches a proper temperature the combustion is made just with the help of high temperature generated by high pressure. So, the rest of the way, after the 1min it needs for generating enough heat, the engine should run on optimal conditions, correct?

The owner said that when started on cold weather it makes a bit of white smoke for about 1min and he thinks this is the cause. This could be just condensation, but I'm thinking also that it can be caused by the fuel injected in the cylinder and not combusted...something has to happen with that fuel.

My final question is this If the engine worked like this for a few years, is it in danger of any major issues?
Old 12-16-2018, 04:03 AM
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I added a video of how the engine sounds made just yesterday by the seller

https://www.youtube.com/watch?v=xuCn...ature=youtu.be
Old 12-16-2018, 05:20 AM
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I think I know the reason why the new relay didn't work - I just found out that the om616 has glow plugs in series (electrically) and the om602 hast different ones that get connected up individually to the "glow relays"...and that best thing to do would be to find a donor car and change the complete wiring.

If anybody has any thoughts on this, they would be greatly appreciated

Thank you!

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