We managed to hook the battery charger to each pump and they both run. I guess it is time to do a current draw test. I need to find out how to do this and what the specs are for these pumps. They are both Bosch....one is part#0 580 254 950
014 made in Germany
688040021

The other is part#0 580 254 950
014 made in Germany
688070009
Car is 1988 420sel

Really great info there. I wiill try to find that manual. Thanks.

Both pumps are the same, the 688070009 ish number is a date code or something like that. No idea what 014 is.

The pump will have a low amp draw if you test out of car since it isn't pushing against anything.

Do a amp draw test when everything is put back together, they should have about the same draw. Pumps generally fail in a no run mode, sometimes they shear the coupling between the motor and pumping element. In that case the amp draw will be low and motor speed fast.

The 1.1 amp readings for a no load pump would be what I'd expect.

The 5 amp unit is probably pushing through gummy fuel and the other one locked solid.

Just to be sure of the hookup, the meter is set to amps, positive test lead on meter side moved to "amps " socket, one wire lifted from pump, one meter lead hooked to pump, other to the wire you just removed. For a digital meter, polarity does not matter, you may get a negative reading. For an analog meter , if the the needle drops below zero, reverse the test leads.

I hooked up a battery charger with some small alligator clamps, to do the test. The black lead off the battery charger went to the negative terminal on the pump. The red wire off the battery charger went to the red lead off the multi-tester and the black lead off the multi- tester went to the positive post on the pump. The black is considered the common wire for this test?

I found these procedures on youtube, from a guy testing model airplane electric motors. Use caution working with fuel and sources of ignition. I did notice that although the pumps were dry...they still smelled up the place for the few seconds they were run....and there are sparks upon initial start up. Vaporized fuel coming out of that pump with a spark could probably cause an explosion, which ironically is what causes these machines to work, right...so don't go blaming me if you get blowd up.

The red lead off my particular Digital meter needed to have the peg at the multi-tester end, moved to the 10a dc post, as was previously mentioned.

I did briefly test them with no load since they were not pushing any fluid from them, so do these pumps get the go ahead to put back in?.

Wondering what numbers I would get moving fuel through? Would they be the same?

What to test next? If the car "should" start with a bad accumulator?
I wonder if I could test the accumulator by pouring fuel through one end to see if fuel comes out the other side, hence to check if the diaphragm is ruptured? that's easy enough to check?

Maybe the wiring harness back there is damaged? I obviously know where the pump end of the wiring harness is...but where does the other end go? I see it goes up inside the car.

On the w126 cars...does the fuel pump wiring harness enter the car behind the rear seat or behind the fuel tank in the trunk?