1995 f350 gas motor died and won't run when I switched fuel tanks? Selector valve or fuel pump? Can I bypass selector valve?

The black reservoir/fuel tank selector unit you are referring to is the fuel tank switching valve, which is designed to switch between the two fuel tanks in your 1988 Ford Ranger XLT 4X4. This valve is responsible for directing fuel from the selected tank to the fuel pump and engine.
The second fuel tank selector unit you mentioned (part number 5sv2k) is likely a replacement part for the original fuel tank selector unit. It is not intended to replace the fuel tank switching valve.
The dual fuel tank system in your Ford Ranger requires both the fuel tank switching valve and the fuel tank selector unit to function properly. The fuel tank selector unit allows the driver to switch between the two fuel tanks, while the fuel tank switching valve directs fuel from the selected tank to the fuel pump and engine.
If the black fuel tank switching valve is leaking or malfunctioning, it should be replaced to ensure proper operation of your dual fuel tank system.

I believe there is a fuel pressure regulator on each bank maybe the one not betting fuel is defective

yes these dash switches have allways been a problem the best way is to replace it with correct one from autoparts store but i usually replace tank selector valve at same time (there both about due) shield your eyes when dealing with this device as gas sprays out when removing it
a note : observe fuel level while driving on both switch posisitions the faulty one will indicate No fuel level when you know you got gas in both tanks

I am guessing that your truck is a Diesel. There is no electric fuel pump on the diesel models. The fuel filter light comes on when there is not enough fuel pressure. Possible problems include the selector vavle not fully switching, and/or an obstruction in the pick up in the front tank.

the selector valve is located underneath the truck on the inside of the frame rail on the drivers side If I remember right. Try swtiching to the front tank and tapping the selector valve assembly. If that clears up the light then the selector valve is sticking and needs to be repaired or replaced.

if the fuses and relays are good then have you check the dash switch,you may have to check the wiring(powers)from the pump back through the system until you find were you have lost power.

If you just filled up you could have some bad gas.Hope this helps.Good luck.

well, first, to find out if its the in tank fuel pump or the tank selector valve, the cheapest and probable easiest thing to do is find the selector valve under the truck and switch the incoming fuel lines. front tank to rear tank inlet, and vice versa. If the truck still doesnt run, you either have an electrical delivery problem to the in tank fuel pump or a bad fuel pump. If after switching the lines, it does run, then you need a new selector valve

You are right. There are three pumps. It sounds like the transfer pump in the front tank is bad. The in tank pumps just supply the high pressure pump to keep it primed. You need the front pump.

Just in front of the side tank is the selector.Very common problem.The rear fuel tanks pump quits.

I’m happy to assist further over the phone at https://www.6ya.com/expert/joe_a3369546f8067589

There is no selector valve on a 1995 ford f150 300 engine. The selector switch on the dash sends power to the pump in the selected tank. The pump then sends fuel to the engine. If engine won't run on the selected switch, the pump in that tank needs replaced.