The truck is an 86 F150 XL w/ 351W HO and dual tanks. The carb wasn't getting fuel last August and I replaced the mechanical pump which seemed to be the issue. Lately I've been running into fuel starve issues again and found that the carb wasn't getting fuel again. So I pulled the pump again and the arm flops up and down by just shaking it so the diaphram/spring inside is toast. I did have a used pump that came with a used carb I bought just hanging out so I put it on and it still seems to not be pulling fuel. But I also don't know for sure if that pump is fully functional.

So, this truck does not have pumps in the tanks, just senders and I've only been running it on the front tank because the gauge doesn't read on the rear and I wasn't sure if I was even getting fuel from the rear. So are the 3 port selector valves in these trucks the ones I hear people having a lot of issues with? And what are the usual symptoms of the 3 port valve going out?

 

My '84 has a 3 port valve and it is spring-loaded to draw from the aft tank. It requires power to draw from the front tank. Remove power and the valve automatically draws from the rear tank. I learned about this years ago when the fuse worked loose due to vibrations from retracting the parking brake lever. I had the selector switch set to the front tank, which never decreased because fuel was being drawn from the rear tank.

Not positive, but I think this was reversed on later models. I'd have to research to be sure. The spring-loaded default was to feed from the front tank.

Edit: Per the EVTM, from at least '84-86, the default was to feed from the rear tank. The '81 EVTM shows the front tank was default. I'm not sure exactly when the changeover occured, but it was somewhere from '81-84.

 

Okay so if there is fuel in both tanks and the valve's electronics stop it should still be pulling fuel as long as the valve isn't leaking or physically broken.

 

In theory, yes. This is only true if the valve passages are fully open. If there's an internal blockage such as a loose seal (You picked a fine time to leave me...), then all bets are off.

Make sure you see the edit to my previous post about the changes in the default position.

 

The 6 port valves are the ones that give the most trouble. You can bypass the 3 port you have with some line and a little ingenuity and take it out of the equation for now.

 

I bypassed mine for troubleshooting when I first started up my 82 f100 after it'd been sitting for nearly 20 years. I replaced it with one off Amazon and haven't had any issues since I replaced my rear tank with a big one and a new fuel sending unit.

 

Okay so my replacement pump pull fuel from a gas can so I'm working my way back and I'm trying to pull the selector valve to inspect it and I've read in the one or two spots on the internet that even talk about it that there's clips that hold the lines on but I don't see clips.

 

 

Those plastic clips are sometimes available in auto parts stores that have a Dorman HELP! section. They're pretty flimsy and break pretty easily.

 

So it is supposed to have clips, that are apparently not there. I'm probably going to break something anyway because that's how it goes.

 

I see no clips, looks like they are missing. I would pull straight out on the fittings, they should come off.

 

Here is a picture of the clips.

 

You can see the white clip in the fitting in the picture below.

 

They did come off with a little pry of a flathead. I didn't experience the large amounts of fuel loss that has been reported by others. The valve does not seem to be switching tanks so I will test for power at the plug next and (fingers crossed) have this ironed out this evening. I appreciate the help everybody!

 

I get power to the valve plug @ 11.6V, does anyone know the operating amperage?