I suspect I may need to replace the lift pump in my 1983 W123 300TD. How difficult is it to remove/replace, as in-
1) will I need access from underneath the car? (no shop or lift, just a parking lot-but I *could* jack up the front if necessary in order to reach up, although it doesn’t look like great access from the bottom either)
2) are there any special/unusually shaped wrenches needed to undo the three nuts (because of tight spaces or whatever) and-once the three nuts are removed-will it be a bear to get it off the injection pump body, or does it typically come off easily?

I plan on changing the oil anyway, so I’d be draining the oil before taking off the pump. I’m just trying to get some idea beforehand about what I’m up against, time and aggravation-wise. Thanks in advance for any input!

Shouldn't be difficult, done from topside. Have something to catch fuel under the car.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I removed and replaced the lift pump on my car with a rebuilt one in 2017. I referred to this thread for help: Lift Pump Rebuild...

I checked my service notes- I wrote down that the oil line banjo connection at the injection pump needed to be loosened to allow better access to the lift pump nuts/studs. The oil line banjo connection uses a pair of small copper seal rings which are the same size as the seal rings on the cooling system "J" pipe at the water pump housing.

Edit to add: The small copper seal rings are 8 mm ID X 12 mm OD x 1 mm thickness. https://www.pelicanparts.com/More_Info/007603008109.htm?pn=007603-008109-M131&bc=c&SVSVSI=2369

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Marshall Welch
Seattle, WA
1982 300D-T

Straight forward job.

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Jim

thanks to all..as time goes by I find myself less willing to plunge into things, knowing how I can get in over my head. This all sounds encouraging.

Get the Bosch DGK301 rebuild kit, and the Bosch 2 447 010 038 primer pump beforehand.

https://www.peachparts.com/shopforum/1785303-post1.html

https://www.pelicanparts.com/More_Info/2447010038.htm?pn=2-447-010-038-INT&srsltid=AfmBOopFiJYm8JNFY-ZEnWOdI7zmYm5Eie0LmA6nUXStaYiaPjlN1oDVbLg

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Some other issues to it. I think you will find it a benefit to have a short wrench with a box end on it.

You need to be careful of the thin brittle flange casting. That means backing out the retaining nuts a little at a time all the way around. More so when re-installing it.

When I removed those types of lift pumps where I worked I world remove the hand primer before removing the lift pump from the fuel injection pump body and if there was room, I would loosen the 36mm plug before I removed it.

If you have the shiny aluminum hand primer with the hard plastic knob the aluminum is so soft, it usually body deforms when a wrench is used, and you destroy it getting it off. People have used a plumbing basin wrench to grip the body and loosen them.

Those vary same brittle flanges can break off if you are not careful on how you put the pump body in a vice to remove, I think it is the 36mm plug in the middle of the pump.

There is a small 5mm O-ring that needs to change. Be sure to get all of the old copper crush washers out.

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84 300D, 82 Volvo 244Gl Diesel

I wouldn’t mess with the 36mm plug. It’s a monster to remove. Unless the o-ring is leaking (it won’t be) or you’re changing the spring (you won’t be), sleeping dogs, etc

Well, when I did it I worked in a shop and when a fuel injection pump is rebuilt the plug has to come off to inspect the spring inside. No one on this forum has reported it but on other Bosch fuel injection pumps occasionally one of those springs' breaks.

I cannot find a picture of the real Bosch wrench for the job but it looked like the one in the attached picture but there was no rubber on the handle and the handle was a bit shorter.

On the vehicle you remove the hand prime and you push on the wrench and hold it in place while you strike the handle end with a hammer. You can do the same if you have the lift pump carefully gripped in a vice (whe had copper jaw shields for the vice).
When you give it that sharp wrap with a hammer it breaks loose from the stiction of the copper crush washer.

In order to use a socket you need to grind or sand it down flat down to the line in the picture. This is a GM Oil filter type socket. You don't need a Hazet socket. The cheap GM 36mm type sockets are around $11 or less. Get a steel one as there are aluminum ones out there.

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84 300D, 82 Volvo 244Gl Diesel