My W201, '84 190D 2.2......looses prime when I park, nose uphill, with less than 3/4 tank.....the PO had installed an electric fuel pump in line before the fuel filter, kinda just hosed in there.....it has never been hard wired in, I just touch the lead to the battery positive terminal and pump up/prime the system...

Been thru the fuel thermostat and fuel heater.....no leaks there, but by passed at the moment.....am thinking about replacing the lift pump, the only thing that I can think of is that the fuel is gravitating back to the tank somehow....like maybe a stuck check valve/ball in the lift pump...

This has been a minor issue with this car since I've owned it, getting around to fixing it properly....

SB

__________________

Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

if there are no symptoms after it runs for a bit, then its possibly the delivery valve o-rings and copper washers.

...in addition to the usual connections one would expect.

__________________

There are no obvious fuel leaks when the car is running, and the engine lube oil is not increasing...which would indicate a leak within the FIP, internally.....

SB

__________________

Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG