I installed a new fuel sending unit in my 740 this weekend. The sealed wires were all corroded, so my intank pump was not working. It was an "Upgraded" part. The electrical connector, and fuel line locations were different. Line locations were not a problem, and I replaced the fuel lines to acomodate the extra distance. I am a little concerned with the electrical rework. The color wires were not the same. I had a pink to pink, but the other two:new unit has two grey/white. Old connector has a grey/white and brown. Will it matter which grey/white goes to the brown.
All seems to be working with the intank pump, but now my main pump whines, and the car stalls when the gas pedel is pressed, if it starts at all. Any possiblity my main pump just failed, or is the something between the two that could have developed a problem with the intank pump now working. - Thanks

Implementing Colin's excellent suggestion would be a breeze (by jumpering 2 fuses) on a 240. Not so easy on the 700, but here's what I would do...

1) Disconnect the fuel line at the injector rail and route it into a safe container.

2) Remove Intank pump Fuse 11 and improvise a jumper wire to apply voltage to the Fuse 11 terminal that is farthest away from you, i.e., toward the engine.

You can get battery voltage from the Fuse 1 terminal closest to you, after the fuse is removed. Use a jumper wire with a flat male terminal on each end, to take voltage from F1 to F11.

The Intank pump should push a good flow of fuel (thru the unpowered Main pump) all the way to the injector rail.

To run/test the Main pump, jumper voltage to the other F11 terminal, the closest one.

NOTE: This is from a '93 Green Book wiring diagram, which is all I have. It should work for you if Fuse 11 is for your Intank pump.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Great idea, and it worked well to help me get the problem resolved. The wires cannot get turned around. The main power going in to the unit gets split inside. It did help me diagnose that I had the fuel lines reversed. I made the mistake of assuming that the orientation of the lines on the new sending unit was the same as the original. It was not until I took the unit back out, and got the supply line connection point identified. Thanks for all the help, all is well now.

Tony

Check that the in-tank pump is actually pushing fuel towards the main pump.

If the wiring is wrong the in-tank pump may running in reverse.

Colin.