'75 240D lift pump leaking fuel...

[AcIdBuRn]

Hey guys..

Well, I thought I was going to have my fuel leak fixed today as I noticed my delivery valves were leaking a bit. Replaced the upper and lower seals on the valves but the drip I was seeing under the car continued.

I started looking around under the hood and noticed fuel spraying from the primer on the lift pump. I shut the car down and loosened the primer and tightened it back down. The spray stopped but I'm still getting a steady drip from somewhere on the lift pump.

I'm not certain if its coming from the primer or the fittings on the pump.

Is this a common issue?

Ive done some searching and came up empty... Found a few threads on rebuilding the pump which is most likely what I'll do but I want to make certain that I'm getting the right parts. Is there a way to ID what lift pump I have?

Thanks
-Chris

[gmog220d]

Hey Chris,

Spray that lift pump down with brake or carb cleaner to dry all the fuel off. Crank up the engine and watch it under good light to see if you can tell where it's leaking.

Probably a good time to put a new primer pump on it anyway. They're not expensive and they eliminate all that messy fuel leaking when priming the system.

[AcIdBuRn]

I've got a Bosch dealer near by.. Gonna give them a call this morning and see if they have the parts in stock. If its cheap, I'll go on and get a rebuild kit for it too.

[gmog220d]

If you can get a valve/seal kit for the pump from the Bosch dealer don't spend more than about $30. That's what it cost from the local ABQ Benz dealer. You can replace the valves and o-rings and install the new primer without removing the large plug, though it's best to do so so you can be sure of absolute cleanliness throughout the insides.

I also got the gasket for fitting it to the IP from Benz since it was not included in the kit for these older style pumps which are held on by two studs instead of three.

[AcIdBuRn]

Aaaannnddd... I ordered the wrong kit apparently. Didn't realize mine was the 2 bolt pump.

Anyone have a Bosch part number for a complete rebuild kit for the "M" style 2 bolt lift pump??

[AcIdBuRn]

Ok,

from a bit of digging... apparently the only difference between the lift pumps (2 bolt "M" pump and the 3 bolt "MW" pump) is the valve design. From what I gather, all of the seals and crush washers will be the same.

I ordered a Bosch DGK-301 which is for the 3 bolt MW pump that uses the "T" shaped valves.

Now I cant find a picture of the kit anywhere, but apparently the DGK-306 comes with disk valves.

At this point, I will probably just reseal my pump as it seams to be doing its job still (car starts easily... no idle issues... no power issues that I'm aware of).

I ordered everything from the local Bosch dealer.. 15 for the seal kit and 20 for the hand primer.

-Chris

[gmog220d]

Might as well get the correct kit and replace the valves since you're going to take the thing apart. There's a pic of the kit as it comes from Benz in this thread:

http://www.peachparts.com/shopforum/vintage-mercedes/368673-w115-220d-240d-lift-pump-valve-rebuild-kit.html

Do the W123 pumps use o-rings to seal the two fuel fittings to the pump body?

[AcIdBuRn]

Not sure... this is all just from reading which seems to be an unreliable source when it comes to the lift pump on these...

I'll call Monday and see if I can change the order but they had to order the kit and its supposed to be there Monday... don't really want them to have to hang onto it so we'll see.

-Chris

[gmog220d]

If you end up eating that later style kit I bet someone around here would step up and buy it from you.

[Left Coast]

There were dozens of iterations of both the two bolt and the 3 bolt pumps. They are used on a wide variety of diesel engines. The two Bosch kits **301 and **306 are sort of generic rebuild kits for the two basic styles, and they include some bits that aren't needed in some applications. This info is from my local diesel injection guy, who has 30 years experience and an awesome knowledge base.

I think that your problem leak is probably coming from a hose or a bad connection between hose and fitting. The pumps don't start leaking. They give out internally.

That said, it never hurts to give it a refresh. As it happens, I have a DGK306 kit, unused and unopened, that I'd gladly trade for a DGK 301. Unfortunately, the 306 comes with the 3 bolt gasket. Send me a PM if interested.

[AcIdBuRn]

Thanks for the offer man but the dealer let me change the order. Parts will be here tomorrow.

I figure its just a fitting leaking or a fitting seal as everything on the car is dryrotted from sitting.. so gonna go on and freshen it up while its off.

Thanks guys
-Chris

[AcIdBuRn]

Pulled the pump last night and I'm glad I did...

Once off, I pushed the roller/plunger and fuel sprayed out of the back side of the pump.. injection pump was full of diesel fuel. All of the o-rings were shot.

I then discovered that the DGK306 kit is wrong as well. That kit has the right valves but none of the seals are right.

I spent a few hours talking with my Bosch guy and I got a full break down of the pump and all of the legit Bosch part numbers... all of the new seals are Viton as well. The seals I needed will be here tomorrow and I'm going to post a new thread with all of the part numbers.

I'll post up pictures later.
-Chris