later today, i am going to look at a 300td with a bad lift pump. i've never heard of this. is there another name for it, or is it just something that never comes up in discussion? i've seen the rebuild kit listed on this forum, and it doesn't seem like a really big job from what i can see on paper. anyways, what the heck is this thing?

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1980 240D, 197580 miles - "The Stuttgart Stomper"

Its the pump that 'lifts' the fuel from the tank and supplies the injector pump with fuel. Be careful and don't let the seller claim the problem is the lift pump, which fail very rarely, when it is really the injector pump, which could be very expensive.

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Muleears
'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K

A lift pump "lifts" fuel from the tank, pumps it through the fuel filter and into the injection pump.

DO NOT RUN an engine with a dodgy lift pump, if the diaphragm leaks it leads to sump dilution and ultimately a runaway diesel... BANG!

The proper name is "fuel pump."

Would you happen to have a picture of this alleged "diaphragm?"

As long as it's not your car, run it. Have the current owner start it.

If a car is a non-starter at time of sale it should be sold as such (for much le$$).

When shopping for a diesel, put your hand on the engine before any start attempt so you know it is cold. If it's not, and you like the car, ask when you can come back later (tomorrow) to a cold engine.

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Cheers!
Scott McPhee

1987 300D

LMAO

A mate of mine, whenever he agreed to buy a car, said, OK, look, here's the cash, follow me home, when we get there I'll give you the cash and run you back home.

He'd then drive 80 all the way home.

If the following car didn't make it, no biggie..

If it doesn't run, it needs a new engine & trans. If AC isn't cold, it needs complete refurb, not fill.

If problem is so minor, PO should have repaired before attempting to sell. Let him fix it or you get a discount for your trouble (and risk).

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

X2

VERY sound advice!

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'95 E300D ("Tank") - 231,000 miles
'79 240D ("Biscuit") - 197,250 miles (Sold)
'83 240D ("Ding-Ding") - 217,000 miles (Death by deer)
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"Back off, man. I’m a scientist” ~ Peter Venkman

Actually, its proper name is "fuel lift pump" but there we go.

The diaphragm is not "alleged", some lift pumps are made to be serviced and you can buy a new diaphragm / service kit, others are "sealed for life" but still have a diaphragm, just drill out the rivets and you'll find it...

Not according to the MB FSM.

Depends which one you have I guess...

My copy of WIS correctly calls it a fuel lift pump, but then it also correctly calls the trunk the boot, the hood the bonnet, the fender the bumper, etc

Just one problem. We are not discussing "some" fuel pumps.

sigh...

no, we are discussing MB fuel pumps...

Fuel Pumps come in the following varieties.

Centrifugal / Gear / displacement.

only displacement pumps will LIFT fuel, eg self prime with negative head.

This is why this type of pump is called a fuel lift pump, not a fuel pump....

MB Fuel lift pumps are displacement.

A displacement pump ALWAYS leaks, just like a piston and rings in a barrel always leaks compression... you leak this into the "case drain" back into the supply line, but, the actuator can still leak...

When a pump is powered by a cam on an actuator, it is always a displacement pump.

A diaphragm is what you use to prevent pump leakage getting into the sump.

The Bosch engineers apparently had a different idea.

Nope, they didn't....

In actual fact the usual problem with diesel w124 lift pumps (which are on the side of the IP, not the engine block) is the vacuum line comes off, or leaks, which limits the fuel pump delivery stroke.