Help Tracing Fuel Problem
 

Have a 87 half ton, 4x4, 350, and dual tanks. Before and after restoring the truck it had a periodic issue running on the auxiliary tank, which turned into an occasional problem running and getting a gas gauge reading. And now it just won't run or get a fuel level reading from either tank.

I got a new switch for the dash. Testing the wires I found the tan/white (#120) to be dead. I expected it to be hot. Thinking this was the issue I made a hot jumper and ground jumper for the tan and gray wires (#920 & #921). This did make the fuel gauge work, but the truck wouldn't run.

Thinking the tan/white (#120) being dead as the problem I traced the wire to the fuel relay on the firewall. I bought a new relay, which didn't fix the problem. Then began checking the wires in the plug for the relay with a test light. None of those wires were hot with they key on or while cranking. There should be some hot wires like the orange (#440) from the battery and the dark green/white (#465). It doesn't make sense to me that all these wires should be dead.

Any advice from anyone? The diagrahm shows a fuse on the orange wire (#440). Does anyone know where that is? I haven't seen it. Thanks.

Re: Help Tracing Fuel Problem
 

It's the ECM B fuse in the cab.