1992 300d 2.5

[namron4491]

Guy's I have a question for you, my lift pump seems to be weak on long hills feels like engines not getting enough fuel, Now my question if I put an electric fuel pump at the tank and totally by pass the lift pump will harm be done to anything....Please no have you check filters, getting air in the line.....that's not what I am asking.....just will any harm be done to anything.

thanks Norm

[jt20]

no

but there are lift pump repair kits available through this site

[jt20]

however, I wouldn't bypass the LP. You want the fuel in there to keep the piston lubricated so it doesn't cause wear and ultimately leaks.

[namron4491]

look....... I just want to bypass the lift pump period, don't want to use it ok. now, I'll ask again, will there be any problems, thanks Norm

[barry123400]

The injection pump tends to be pressure sensitive. An electric pump that duplicates the preffered pressure will be hard to find and expensive. If you can locate a pump with the right pressure it should do.

Now the problem of using a lower pressure pump. The relief valve on the return line will not open to allow the fuel to aid in cooling the injection pump. Electric pumps have improved their reliability factor over the years. Are they as reliable as the mechanical original type? I still doubt it. Since the kit to rebuild the lift pump is only about ten dollars it is not a big issue. If you are trying to boost a vegatable oil situation it is another matter..

Now the brass tacks so to speak. Have you established the lift pump is substandard by conventional tests? There are many things in the fuel system that will make the lift pump appear weak. The best test is a pressure gauge inserted between the secondary filter and the injection pump. By clamping the return line the upper pressure limit of the lift pump will be indicated. All this is in the archives.

A simple test is removing the return line temporarily. Fuel should be exiting the injection pump. The problem with this test is an air leak or restriction of some sort somewhere could reduce the lift pumps ability to function normally. . Or if the return valve on the injection pump has become defective with age the engine might appear to lack fuel. Again reading the base pressure present in the injection pump is done with a cheap fluid dampened thirty pound gauge. This should be checked on all older diesels of this design.

[namron4491]

Thanks Berry that is what I was looking for.
Norm