Dead Fuel Pump
 

1991 300E (103). Just got the head back on and tired to fire it up. No fuel. There are two FP's in line. The first pump is dead (bottom pump). Will the failure of the first pump stop fuel flow to the fuel distributor? Just making sure the dead pump is the reason for no fuel, and not a blockage, (The car has been sitting for approx 10yrs).

Most likely you need to have the fuel tank flushed OR replaced.

Yes, you need both fuel pumps.

Tim, I have read about folks resurrecting fuel pumps by running them backwards with diesel fuel poured into the discharge side. Of course, this is done with the pump removed and on a bench with a 12-volt battery momentarily applied to the leads. It's worth a try before replacing a dirty/clogged fuel pump.

Just replaced fuel tank. Why would I need both pumps when the top pump is working?

How do you run it backwards? Reverse the leads?

Because if the impeller isn't turning then fuel can't pass through.

Maybe I am missing something here. The first pump is dead, impeller not turning, and second pump is working, impeller turning, the first pump being dead is stopping the fuel flow to the second pump. If the second pump works, why do I need to replace it (the second pump) when the first pump is preventing fuel feed to the second pump?

You have answered my original question though, which was if the first pump is dead, would that stop fuel flow to the second pump. Thanks!

I just don't follow the logic for replacing the second pump.

Tim, reverse the leads to bump start the fuel pump backwards. It should only run for a second or two ... enough time to digest the diesel fuel.

Thanks. I'll try that.

You misunderstood what I meant...I mean for the car to run properly, you need both pumps to RUN, not to be replaced.

Thanks!