I have a '79 150 with a rebuilt 351M. I know there are plenty of threads about similar situations but it will not draw from the front tank nor does the gauge work when front tank is selected. The selector switch is good but somewhere along the line someone hot-wired the the truck to run off just the rear tank because the front tank leaked and nor does the truck run on the front tank as i already stated. I suspect that the tank selector is bad. I found a broken ground for the front sending unit so that issue can be dealt with but is the least of my concerns right now. I'm replacing the front tank.

What I want to know exactly is if I could just eliminate the selector valve completely and put a T fitting in its place so that the pump would draw from both tanks simultaneously? Will this cause any problems? It's just a work truck so I really don't care if the gauge doesn't read correctly as I do realize that it would be inaccurate unless I wired up two gauges. I just want to know if it will run right. Thank you very much for any help

 

I am not an expert in fluid dynamics, but I would be concerned if the fuel pump would be strong enough to pull from two separate sources at the same time, and whether any difference in fuel level between the tanks (and one emptying before the other) would draw air into the fuel line when the first tank empties, causing a loss in siphon or hiccup at the instant the one tank stops contributing to the fuel flow. Furthermore, after the first tank empties, the pump would draw a mixture of fuel and air, which is definitely bad. You'd somehow have to keep equal amounts of fuel in both tanks at all times, which would be further complicated by any difference in flow rate between the two tanks. So no, I don't recommend doing this.

At the very least, it seems like if Ford could have saved the cost of a selector valve and switch on all trucks with dual tanks, they would have; but they didn't, possibly for the reasons stated above or something else I'm not thinking of. Like I said though, I'm not an expert; I could be way off base. I would be pretty surprised if anyone on here has tried that though. Most people just stick with the one tank that works or fix the actual problem.

 

I would say that if both tanks are nearly full it would "probably" work, but once the level went down you'll start having problems with fuel flow.
The pump should be strong enough to pull from both tanks (it doesn't really "know" there are two tanks). But unless the truck is level all the time, one or the other tank will be fuller than the other, then fluid dynamics take over.
You can try it "T" fittings are relatively cheap. You can try it and see what happens.
If one tank empties first, it will suck air and stop pumping fuel.

 

I have a similar issue to deal with soon, it's an interesting idea you have with the T fitting. I don't see it working though; I think as mentioned you'd be better fixing the issue or maybe just using one tank...verify the level sensor is good and maybe bypass the selector valve all together.

 

are you worried bout the electrical selector? Put a manual selector in or ...just replace the selector..dunno bout the T fitting...may or may not work..