Hey all. 89 F250 460 dual tanks. So the front tank hasnt worked since I bought it bought the truck 9 months ago. (big surprise) I was going on a long drive with it and I thought it would be nice to have both tanks, ya know cause it so fuel efficient. I took out the 6 port tank valve and took it all apart and cleaned 1/2 cup of sand out of it. I re assembled it as best I could ( I may have damaged some parts in it getting it apart.) I headed on my trip next day and stopped for fuel130km in (I had damaged the valve so the front tank still didn't work) Then I noticed fuel pouring onto the ground. The rear tank was now back feeding into the front tank. Took it to a repair shop and he just bypassed the valve and made it rear tank only. After my trip the new valve I ordered arrived. I installed it no prob. no leaks. I started it on rear tank and it ran as normal, switched to front tank, it started to run like crap, back to rear tank, still running like crap eventually died and would not restart. I put the old valve back in with the by pass. started fine ran as normal. Now,2 things to mention. First, fuel in front tank was at least 9 mo old and I know the kid who sold it to me said it never worked for him so fuel could be years old. Two: when it wouldn't start i pulled the line off the frame mounted pump and there was almost no fuel there. After re-installing old valve and bypass, fuel started running out of line I left off at pump. So I guess what the question is after typing this novel is do you think it is more likely crappy fuel or cheap Chinese valve?

 

The fuel pumps need to send correct pressure to the Dual Function Reservoir (fuel tank selector valve) in order for it to function properly.
With the key off, jumper "A" to "E" at the diagnostic plug, that should be under the hood near the driver's side fender.



Disconnect the wiring from the in line, frame mounted fuel pump.
Get a gasoline rated container, and disconnect the front tank fuel line, at the Dual Function Reservoir. The front tank line is the top line, closest to the center of the truck.
When you turn the key on, with the front tank selected at the dash mounted selector switch, the front fuel pump should pump 6 ounces of fuel into the container, in 5 seconds.
I do this outside for safety reasons.
You can do the same for the rear tank fuel line.
I would guess that the old fuel is an issue.
If the fuel pumps put out correct pressure, then the problem is likely the Dual Function Reservoir.
There are similar tests to confirm that, by removing the return lines one at a time, from the rear of the Dual Function Reservoir, to determine if it is routing the fuel properly.
I put this Dual Function Reservoir on my '88 in August of last year. So far, so good.



I would also recommend disconnecting and blowing or flushing out the fuel lines, between the fuel tanks and the Dual Function Reservoir, since you had a sand issue.

 

Thanks for the info. I'll be doing the jumper thing soon. I did find one problem. I dismantled the new valve. it was full of very fine sand. the valves under the diaphragm were stuck. I spent some time cleaning it out. I got the valves moving like budda. I need to put the fuel filter in the new one when it gets in. I found a eco-friendly place to get rid of 80L/19 gal of crappy gas. so if it ever stops raining here I'll drain the tank. Then it'll have to come out for cleaning. I might just replace everything. I can get a tank, sending unit w/ pump for $300.