Fuel pump wiring diagram

V8 two wheel drive automatic 167000 miles.

I recently have had random shutdowns while driving my truck. Driving along at fifty five mph and all the sudden a loss of power. Pull over to the side. I turned key off then on again and it started.

A few blocks down the road it did it again very quickly though. It lost power (like not getting fuel) slowed down and then it came back and I continued on to the gas station. I thought fuel problem (3/4 of tank of gas) so I got some STP gas treatment at the station.

No problems for a couple of days and then all of the sudden it did it again. This time it would not come back on. I was thinking fuel pump. But I noticed something strange. When I would turn the key to the "on" position all the gauges (gas gauge/oil gauge/battery gauge) would move a little but go back to the flat position. This made me think it was some sort of electrical or relay problem. I opened the hood and found the relay box and just gently tapped on the top of the relays etc.

I got back in the car and when I turned the key to the "on" position all my gauges were working (coincidence? ). The truck started and worked fine.

Is there something other than a relay that can cause this kind of symptom. If the relay is bad would it cause the fuel gauge to not respond?

Checked the relays, and under the box I do not see any corrosion or anything that is loose.

When problem happened last time:

1) Lost power (like out of gas).

2) would not start but starter would crank.

3) Gauges, fuel gauge would not register fuel but power was going to the gauges. When I turned the ignition to on the fuel gauge would rise eighth of an inch but then drop back down. After messing with relays etc (about five minutes). I turned Ignition to on and the gauge worked and then the truck would start.

That was yesterday and it has not happened since.

After reading your message, I am wondering if it is electrical. Is there something under the dash or in the steering column that if it were to short would cause the symptoms I have described?

If the fuel pump is bad will you still have fuel reading on the dashboard gauge? Or is that controlled by a different mechanism?

I tried cleaning connectors, swapped relays.

Drove fine since July 7th.

It happened again today July 13th. This time it provided me with another clue. I notice where the odometer readout is, the words "no bus".

I opened the hood and messed with relays and nothing happened. I turned key off then on again and odometer was normal but fuel gauge did not read anything. I plugged in my code reader and waited and then the odometer read "no bus" again.

I figure that it is the PCM or the connections to it. So I took my screwdriver and lightly tapped a small black box that is located behind the Relay box (Is that the PCM?)

I got in and turned the key to on and the fuel gauge went up. Truck started.

Is there something I can do to check the connections and rule out that the PCM (computer) is bad?

Anything else I should check given this new clue?

Thanks