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Old 04-08-2002, 05:24 PM
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1975 240D How to Replace Diaphram on Injection Pump?

Help! I posted a problem last month, 1975 Mercedees 240D, where the engine idles Ok, and goes fast Ok, but otherwise the engive revs up and down. (it also smokes super bad when started untill it warms up).
Unfortunately, only got one response but was greatfull for that.
I order the diaphram part for the fuel injection and started to take off first the first part with the 4 screws so that I can see the diaphram. It actually looked OK but have since ripped it while trying to pull it out to get to the pin that holds the diaphram on.

Question: I can see the snap clip that holds the pin onto the diaphram but no way to get my fingers in the hole to get it off (without removing the next whole plate that covers the injection pump.) I started to remove this large plate but diesel is dripping out.

Is there any way to get the diaphram rod out without taking off that wide plate? (it covers most of the back side of the injection pump) (note: also one screw head that holds the wide plate is stripped and can't get it out).
I have the mercedees manual but it doesn't show me much detail and instructions are vague. I was told this should be 1.5 hr. job but the screws have been on so unbelievably tight and can't get channel locks on it.

Can I somehow get the whole rod out with the diaphram?
Can I get a fax copy of what this looks like?
What else would cause my engine to rev up and down?
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Old 04-08-2002, 05:38 PM
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Join Date: Oct 2001
Location: Seattle Area
Posts: 373
sfk, I haven't replaced the IP diapgram in any of my cars so can't help there, but I have suggestion for the erratic idle (it is only revving when sitting at idle right?)

In my W123 (can't remember in my old W115) the idle will surge when I leave the 'idle-speed' switch on the dash in the far-right (starting-only) position. Try playing around with that first by backing off the starting position. When my car has run funny in past, I could always tweak the switch to lower/raise the idle to a point where it was smooth.

As for smoking at start up, it may be your diaphram in addition to the IP timing. I've replaced just about everything there is in the fuel delivery/filtering system in my W123 and it still smokes on cold start and even at idle after warming up. As I understand from several sources - the IP timing is the likely culprit - make sure and get the IP timing set properly after getting the new diaphram in. It could be one, or any combination of the above items.

Good luck,
- Ryan
'95 E420 - 'Shadowfax' 138kmi.
'92 Volvo 740Turbo Bard 193kmi
'74 240D - 'Ol' Green' 4spd Manual 104kmi. (sold )
'77 300D - 'Red' 223kmi (sold)
'75 240D - 'Bianca the Blue Bomber' (sold)
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