fuel injector pump compatability

[BaronYoungman]

I am helping a friend out to try to get his 1969 280sl (bulid 11/68) running, I know his fuel injector pump is bad # PES - 6KL - 70B120 R21 can I use my known working pump PES - 6KL- 70b120 R24?  What is the difference?
Bob

[twistedtree]

I think it will be fine.

[280SE Guy]

Perhaps the attached chart will help in your decision on the pumps.

The chart was taken from the infamous "The Mercedes Collector" magazine issue number 6 dated March 1993.

Regards,

280SE Guy

[BaronYoungman]

So overall cant hurt it?

Has anyone tried it?  I just don't want to hurt the engine.
They look the same and reading the chart it seems that it does not have starting magnet which does what exactly?

[jacovdw]

The starting magnet (solenoid) is only there to push the rack to a full rich position for improved starting.

I don't think that you would do any harm to the engine.

The main issue in terms of the differences between the injection pumps boils down to the "fuel map" or 3 dimensional cam.
Changes were made during the production run to accommodate the changes in vehicle emission standards at the time.
The fuel mixtures were mostly leaned out slightly in the lower ranges.

The only possible issue that might arise, is the fuel by-pass valve on the injection pump. You need to remove it and see if it matches the
fuel feed pump fitted to the car.

Fuel feed pump with connected by-pass system = fuel by-pass valve without vapor hole.
Fuel feed pump without connected by-pass system = fuel by-pass valve with vapor hole.

[glenn]

Do all injection pumps mate up with any and all venturis??   The injection pump arm moves in sync with the venturi arm.   Are the angle relationships all the same?   Does a 230 pump mate with a 280 venturi?   Does a 280 pump mate with a 230 venturi?   Pagoda-ol-ogy question. ..

Also, what is the fuel bypass valve vapor hole??

[twistedtree]

Bob, are you planning to make this swap permanent, or is it just to verify whether the FIP is the source of a problem?  If it's just an experiment, which is what I presumed from your original post, I can't see any issue with doing it.  But I'm not sure I'd leave it in long term.  The document that Glenn posted, for example, shows the R24 is for low-compression engines, where your 280 is high compression.

[jacovdw]

...Also, what is the fuel bypass valve vapor hole??

You will find that in the outlet screw fitting of the fuel injection pump.
Once removed, the small vapor hole can be seen on the valve disk when looking at it from the bottom.