The fuel pump didn't look like is was pumping and my 300D definitely was not firing. We bypassed the fuel pump to the IP and it fired up. Any ideas?

I'm looking for a good DIY page for Fuel Pump replacement, the one that has the weak primer pump on it. I have found ones on replacing the whole IP but I just need something to look at for the Fuel Pump. Thanks...

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1985 Mercedes 300DT

Unscrew the outlet plastic hose and unclamp an pull of the inlet hose.

Depending on your model you have 3 or 2 nuts or bolts that you unscrew.
The only caution here is that the Fuel (Supply) Pump flange is thin an they can be brittle.
Depending where the Engine stopped the pump could be under some spring tension; you will not know until you start to back out the little nuts/bolts.
Just try to back them out evenly all the way a round buy turning one a liitle and going to the next one.
It the Fuel Supply Pump wants to push out try to push it back in until you get all the nuts/bolts out.

When you are ready to install the Fuel Supply Pump get a Flashlight and a Mirror and turn or bumb the Engine until the lowest spot on the Cham that drives the Fuel Supply Pump can be viewed. This should allow you to push the Fuel Pump all the way with little or now tension on the spring.

If you are going to take the Fuel Supply Pump apart use soft metal Jaws on the vice and again becareful not to put any stress on the Fuel Pump Flange.

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84 300D, 82 Volvo 244Gl Diesel

Thanks Diesel 911!

This is some good info...So can they be rebuilt?

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1985 Mercedes 300DT

Yes on the Rebuild.
Fastlane sells a new spring and valve kit with 2 springs and 2 valves.
However, you want to inspect the inside of the Pump under that big nut. The Pump spring sometimes breaks. If the spring is broken get a new one from a Bosch Autorized Fuel Injection Shop.
Someplace there is a thread with a pic of the pump taken apart. Can't help find the pic as I managed to erase my notes.

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84 300D, 82 Volvo 244Gl Diesel

Thanks again for the info...And yeah, I can't find that thread as well.

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1985 Mercedes 300DT

Hi Veg,

Could it me the thickness of your fuel that has caused the pump to colllapse ? Or the line towards the tank (id=10 mm?). I must admitt I have not heard these pump collapse on SVO/WVO since they are able to suck like "Monica", but I do know that some of my German friends have mounted an extra Facet/Hardi near to the tank as a way to avoid any problems. have you also checked the strainer in the tank ?

Cheers,
Ingmar

When testing Fuel Supply issues it is sometimes best to get something like a 2 gallon spare fuel container filled with Diesel Fuel and disconnect the Fuel Inlet Hose and ad a longer one runing to the spare fuel container.
This bypasses anything to the rear and using Diesel Fuel you bypass problems that might be caused by the alternative fuel.
If your engine runs OK with the separate fuel container your problem is to the rear.

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84 300D, 82 Volvo 244Gl Diesel

Definitely did the spare container thing...It wouldn't suck a glass jar full of diesel up. It only started when we by bypassed the fuel supply pump and fed it fuel.

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1985 Mercedes 300DT

OM617.951 and .952 Lift pump Repair kit W126.120 300SD W123.133 300D
OM617.951 and .952 Lift pump Repair kit W126.120 300SD W123.133 300D

Here's my payback! Diesel Primer Pump Replacement
Here's my payback! Diesel Primer Pump Replacement

Diesel Injection:
Diesel Injection:

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