Replace it if you jump it and the fuel pumps work.
OR if you read a voltage drop across it.
Sorry I have never tried to buy one as I have a few on hand off of other trucks that I parted out and a few I picked up at salvage yards.
The fuel pump is inside the FDM (Fuel Delivery Module) that is inside of both fuel tanks.
For bench testing just put 12Volts on the red wire and ground on the black wire that run from the top of the hanger to the FDM. That will tell you if they run or not. If they run they should pump fuel. But some fuel pumps will run for a while and quit when in service.
Do not run them very long, just check to see if they run.

The sender should read 145 ohms in the full position and 22.5 ohms in the empty position.
High ohms a lot of fuel, low ohms no fuel.

 

If you are not getting power to the pumps, as indicated by your tests so far, why pull the bed to check the pumps? You need to get power TO the pumps before they will turn on. Perhaps I am missing something here?

 

I would guess he is pulling the bed and taken the pumps out to check the condition of the tanks more than the pumps.
This because of what was said in post #13 & 14 above in this thread.

 

I am going to check the voltage in to the inertia switch to see what it looks like since I know what it looks like coming out of it in to the tank selector switch.

Regardless of the outcome of this test, I am still going to pull the bed to check the condition of the tanks and test the pumps and sending units. While the bed is off, I will probably just replace the pumps since I am already at them. Any recommendation on a specific fuel pump (FDM) brand?

Once I get the bed off, will there be more room to get the fuel filter off? I tried to get to it to replace it the other day and I just couldn't seem to get to it well enough. I suppose there is a trick to it.

 

I hate taking these filters off, theres no real trick to it, but I've found a "high quality" line disconnect tool helps immensely (instead of say, the cheap stamped one, which tend to break easy). I don't have a preference for the pump though, without changing out most of the fuel system for something more performance based, lol.

 

Some parts stores list it as,,,, Fuel Pump Cut-Off Switch

 

OK, here's the latest update. I tested the power wire coming into the inertia switch from the relay and only read a maximum of 7 volts. I'm gonna do some more tests on the circuit from the fuse to the inertia switch because I suspect the problem lies somewhere in that area due to the voltage drop. I know the power to the fuse is 12.6 or so volts and is the same going out of the fuse. So somewhere from there to the inertia switch it drops. I'll post the results of my tests when I have them.

 

Check the connections at the Fuel Pump Relay socket. A very common problem area.

 

You are using a meter is why you are reading the 7 volts. That is why I always say use a test light to load the fuel pump circuit as a meter will lie to you.

By the way the 7 volts you are reading is coming from pin #8 of the computer and not the fuel pump relay. This is the information pin for the computer for the fuel system so it knows if you have a bad pump or the relay is not working.

 

I see this in the wiring diagram but why would pin #8 back feed 7 volts if it wants to see 12? Does this mean the relay isn't supplying any voltage?

 

Others have ran into this and read voltage at this point with meter and they have worked for days because of it. That is why I say never use a meter in the fuel pump circuit.
The voltage should not 7 volts by the way it should be 5 Volts as pin #8 has a 1K pull up resister to the 5Volt supply inside the computer so maybe your meter is a little off.

Yes the relay is not supplying any voltage.

 

Didn't have a whole lot of time today for various reasons but I did manage to re-test the input wire into the inertia switch with a test light. The light came on for about a second and then went off. Is this going to be an indication of 12v and my meter was just too slow to register it correctly?

The bed is coming off tomorrow to remove the pumps for a bench test, and also to examine the inside of the tanks and check the float resistance numbers. Hoping it will also give me more room to remove and replace the fuel filter.

 

About a year ago I got an old air force truck for cheap, a 1995 f150 4.9 E 4od. The truck sat for several years with the tanks half full of today's crap fuel. Did all the stuff your doing and ended up dropping the tanks, they were both toast along with the FDM,s, got a spectra tank ( front) and a cheap auto best FDM, from rock auto cca $ 150 with shipping, I then had fuel pressure at the rail, but no still no start, believe or not all six injectors were bad, had them rebuilt locally for about 15 bucks each, afterwords fired right up, no issues for 12k miles and counting. The big six kicks but!! Good Luck.

 

I believe the problem has been solved, but not yet fixed. Pulled the bed today and took out the fuel pumps. The rear tank wasn't bad inside but the pump had some slimy sludge on it causing the float assembly to stick and, I suspect, had the pump gummed up inside. The front tank was a total disaster. The pump housing was a very dark brown from about 2/3 down and it too had sludge buildup enough to stick the float assembly. We "bench tested" them both out in the yard and while we could hear them clicking, they weren't turning or pumping. Also, the fuel lines were a witch to get off at the disconnections, but that I suppose is irrelevant.

Now that I know, or think I know, what the problem is, I'm going to the scrap yard tomorrow to pull a tank to replace the one that is for sure too far gone to use. Just gonna use the other one after cleaning it out. Now, I'm leaning toward buying two new pump and hangar assemblies but at $200 or so each it's a real kick in the pants. Would I be OK re-using the hangar assemblies and just buying new pumps?

 

Yes you can.
Most posters just buy the pumps this way and you can also just buy the gauge sender.