If I could just pump some fuel out the line I'd be a happy camper !!!

Hi all,
I'm working on an old '93 F150 4wd with dual tanks. I'm not getting any fuel to the filter. When I switch between tanks I can hear the fuel pumps both run and come up to pressure and shut off like normal. I believe it has the switch control mechanism that mounts in the tank. Nothing external that I can see under there. I'm planning to try blowing out the line from the point that the fuel filter hooks up in case it's just crud somewhere that I may be able to dislodge with a shot from the air compressor. If this doesn't get me anywhere I figure it'll be time to dig into the tank unit and argue with the switching mechanism to see if the problem is there.
Questions:
1) Any problems with my plan to try to blow out the lines from the filter point ?
2) Would it be easier to get to the tank unit/switching mechanism by removing the bed than dropping the tank ?? I don't like to drop tanks if I can avoid it.
3) Is the in-tank switch mechanism repairable or is it a replace for $$$$$$$ item ?
4) Any tricks that may work to get the fuel flowing again that anyone knows of.

Thanks for any suggestions or comments
Later, Lee

 

What ????? You didn't like the title of my thread ?????

 

The 93 has what are called fuel pump modules in each tank. They are pretty much nonrepairable. They contain a pump and check valves to keep one tank from pumping into the other. They are housed in a plastic housing. They check valves usually fail and cause low pressure because the pump pumps fuel into the other tank.
Have you checked fuel pressure at the fuel rail? I am guessing that you have replaced the fuel filter already? It is uncommon for both modules fail at the same time.

 

I don't have LOW pressure, I have NO pressure at the fuel filter. Not sure what a fuel rail is so probably not. I'm not getting any fuel to the filter at all.

 

So, you have the filter removed and it won't pump any gas out of the line?

 

Correct. Not a drop. It doesn't matter which tank it's switched to.

 

Very strange. Did the truck sit for a long time? I have seen the small lines from the pump to the sending unit in the tank dryrot or crack from sitting. You could try blowing back thru the line. Just keep your face clear of the line. It's odd that they would both do it.
I am assuming that they have enough gas in them? Stupid question, but ya never know. You could try jumping out the relay and let the pumps run for a bit to see if they start pumping gas.

 

It quit running on the previous owner. It sat for 3 or 4 years before I got it but I think the problem was its original problem. If the lines in the tank were rotted wouldn't the pump/pumps continue to run. They both run, then shut off like they're up to pressure.
hahaha !! No the question about gas in the tanks isn't stupid. I've seen a lot more basic things overlooked. I put about 3 gallons in the front one and 2 gallons in the rear the first time I messed with it.
Thanks, Lee

 

The ECM just runs them for about 2 sec. when the key is first turned on, then the ECM looks for a signal from the TFI module to keep them running. They are not run off of a pressure switch.
You can either jump out the relay and let them run or keep turning the key on and off numerous times.
You might blow compressed air thru the lines and listen at the filler neck and see if you hear and action in the tank, like bubbling fuel or air coming out.

 

Thanks for the info. At least now I have a much better idea of how it all works. I'm hoping to get a chance to tinker with it this weekend. I'll let you know the outcome when I can.
Appreciate your advice, Lee

 

Lxman1,
Well, other priorities kept me from getting back on the truck until this past Sunday. Got the battery charged back up and the air compressor ready to try blowing out the fuel lines. I flipped the ignition on and off a few times just to try to be sure the unit in the front tank was switched on and hopefully to open the right circuits. When I hopped out to roll underneath and hit it with a shot of air there was gas that had shot out and was dripping from the frame and puddled underneath. Now I hadn't done anything that hadn't been done before with no results. I was amazed. I'm still not sure if a stuck valve in a fuel module or what the problem really was. I flipped the key again and got another nice shot of gas out so I decided to leave well enough alone and put it back together and see what happened. I put in a new filter and tried to start it. It popped and sounded real out of time. I looked and someone had apparently installed the plug wires in totally random order except for number 1 which was marked on the cap. I fixed that mess and tried it again. To my amazement it fired up and after a few sputters and coughs settled in and ran smooth. I shut it down and put fresh oil and an air filter in along with a few more gallons of fresh gas. I took it out Sunday evening and ran around the neighborhood and checked things over some and it seems to be a nice old truck. The engine sounds and runs good and the rest of the drive train seems solid too. It looks like old "Freebie" is going back to work around my place.
Thanks again for sharing your knowledge. You saved me from chasing my tail in search of bad guesses on my part.