Hi,
I'm new to this forum and I'm a new owner of a 1993 6.5L TD. I'm trying to determine whether the Lift Pump was installed correctly. It was replaced by the previous owner about 300 miles ago. It does not seem to be working and I question whether it ever worked.
I've ordered the Service Manuals, but haven't received them yet so I don't have the wiring diagram. Of course, I'm too impatient to wait, so I got online and found this site.
Here is my basic question: Where are the wires that attach directly to the Lift Pump supposed to go?
The reason I ask is that I've tried applying 12V directly to the Fuel Pump Fuse (as suggested in another forum) and I've tried jumpering the Fuel Pump Solenoid (as suggested in this forum.) Neither worked. But if I put 12V directly on the Lift Pump, it works. At the pump itself, there is a short ground wire attached to the frame, which has been cleanly cut off. The connector sticking out of the wiring harness has a tan wire going forward and a black wire going back toward the tank. I tried to follow the black wire and I think I found the end of it sticking out of the wiring harness in the air (!) back near the back of the tank, where two other wires appear to go to the fuel gauge sending unit. I'm tempted to just ground that black wire and see if the pump works, but I don't understand why the pump isn't just grounded right to the frame. Is the black wire supposed to go to a low-fuel sensor in the tank? If not, does anyone know why the black wire takes a long trip to the back of the truck to be grounded? Perhaps this is a strange artifact of the Ambulance-specific wiring? I'm inclined to just cut the black wire up near the Lift Pump and splice it to the nice heavy (previously cut off) ground wire that's already attached to the Lift Pump bracket. Any reason not to do this?
Any help is much appreciated. Thanks!
__________________
Steve Bachman
1993 6.5L TD Ambulance (Collins?); Silverado 3500 dually chassis; Former Fire Dept. vehicle, demoted to work truck.