OK, so the spring in my spare IP is about 3.5" long.



Take this with a grain of salt, though. I know that the spring in the '74's pump is longer, but I don't know by how much. It also has fewer coils than the one pictured, and the ends are not formed with the same couple of coils formed together. In other words, there are variations of this spring. I wish I could recall what year car that parts IP came out of, but it's been something like 15 years since I got it.

I'm still curious about "Inadequate pressure/volume from the lift pump? Overflow valve not holding adequate pressure in the IP's fuel galley?"

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Thanks that is very useful, does the ip have a plate on the side to identify it?

My spring just measured again is 105mm 4 1/8”

My spare pump is:

PES4M 55C320 RS58
0400 114 066

The pump in the '74 is:

PES4M 55C320 RS47
0400 114 064


I happen to have a copy of the parts list for a few PES4M pumps. In it there are no less than six (6) different part numbers for this spring. The PES4M pump was used in OM621, OM615, and OM616, so these variations are not unexpected.

I'm thinking that the spring in your pump is probably correct and OK. Could you post a photo of it?

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Black smoke as you know is incomplete combustion. Pretty much have to start with a compression check. Since the timing and injectors have been dealt with.

One or two really weak cylinders compression wise could do this. Two next to each other could be a head gasket even.

Timing chain looks good, maybe 2 degrees. Engine had supposedly only covered around 80k so I’m keen to try and make the best of it!

Here's the list of pumps for OM615 and OM616 (and NA OM617) from the engine manual printed in 1980:








So my RS58 IP came from a '75 or '76 with OM616.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Attached a pic of mine, as usual it’s hard work when others have potentially messed about with things..

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That spring does look a little wonky. It could have been stretched.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Yes plus previous owner had 3 shims on it, I believe it’s supposed to have 1 spacer washer.

Question would be, where does one buy a spring for a 1970’s Bosch vac governor?! Even a part number would be a start.

I’ve got a diesel test kit coming tomorrow, my petrol one tops out at 300psi 🙂

There's an array of shims listed, from 0.2mm thick to 2.0mm thick. My spare IP had two; a thick one and a thin one.

You could source a good, correct spring from a shop that works on these pumps. Look for a PM from me . . .

I might be able to give you the correct part number for the spring in your pump if can give me the information from the ID plate.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Well, I can't send you a PM. Your membership here must be too new. Can you send me a PM (a.k.a. private message)?

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Sent you a message (says email) private message appears to be for those deemed more trustworthy..

I know a resource out in CA, a fellow who rebuilds these pumps, and has for a long time. He might have the spring you need. I don't want to post his information in a public forum, though.

Any chance you have a decent Bosch shop near you?

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

I’ll start with compression then explore ip further, it seems there is no magic cure until I’ve checked a few more basics out..

I’m in the UK so plenty of Bosch guys but not many vintage German Bosch guys!