fuel relay

[93punow]

93 6.5t fuel relay is not working replaced twice still not working could lift pump be causing problem

[slagona]

There are many threads on trouble shooting the lift pump available in this forum. Use the search feature (found in the upper right hand area of this screen) - it is below the three butons labeled "New Topic", "Post a Poll", and "Post Reply". Try searching for "lift pump" and you'll get a bunch of reading material.

To start with, when the truck is running, open the drain valve (Brass valve with "T" handle" near front of engine). Fuel should come out of the hose and the engine should continue to run. If no fuel comes out or the engine dies, your lift pump system is not functioning correctly, but it does not mean the lift pump is bad. Power is supplied to the lift pump via an Oil Pressure Swithc (OPS). The OPS is a weak point in this system. Member HowieE has a mod which uses a relay between the OPS and the lift pump so power is not drawn through the OPS - seems to prolong the life of the OPS.

You'll find many of references to HowieE's mod if you do the search for Lift Pump, or look here (go to the Oil Pressure Switch section):

HowieE's Web Site (http://mysite.verizon.net/vze54tx9/id13.html)

Good luck in trouble shooting your lift pump.

--Scott

[HowieE]

The fuel pump relay is only in the circuit during startup on the 93. If your truck runs after attempting a start then the fuel pump is OK. At that point the power to the pump is through the OPS once oil pressure reaches 4 lbs.