Yes and Yes. The switches do go bad. The valves go bad. Air gets in the system and can cause engines to run badly or quit. I know from my 89. Also the front tank has a rubber hose extension on the pickup inside the tank to reach that last 1/4 tank, it rots off completely! You will likely want to drop the front tank, add new hose (notch the bottom with upside down V so it doesn't suck to the bottom of tank!, and if like mine and leaking, you may have to smooth out the tank seal (rust) so the gasket will seal up. I used a light coat of ultra-black RTV as well. Also, check your sender with a ohm meter see if its working right. I also drained the fuel and there was a good deal of gross mud looking fuel at the bottom (I had not used my leaking front in a few years - its a local work truck) good to get that cleaned out.
I did not trust the quick connects after all those years on the supply side, so I used hose and clamps instead. I also have added an electric pump and bypassed the stock pump as I was getting a lot of fuel drainback and long cranks to start. However after installing I am seeing my filter light come on, I think I need a higher PSI pump.
I also bypassed the tank switch valve (which is trouble-prone and you end up with work to do to hook it up anyway as they sell a generic model) and connected a second cheap $29 ebay diesel pump which pumps the rear tank into the front return line which goes into the front tank upon demand. I have the pump switched with a toggle. My tank switch still works for the senders, so when the front get low, you can toggle the switch to the rear ( which only changes which fuel sender on mine) then turn on the pump and pump 3/4 of it front. I would not drain it dry, unless emergency or something, and remember to turn it off. A light that the pump is on a very good idea. AFter pumping, switch the tank switch back to front to read the fuel level in that tank.
Have fun its a bit of work and you get fuel all over yourself, but good to get it sorted out. If anyone has suggestions on a electric lift pump to get the fuel past the filter, with enough PSI, please let me know. THe one I bought has adequate GPM, but only 5psi. Runs but not as well as it could as the light comes on for filter.
Originally Posted by ollison
1988 7.3.F350 Rear tank quit working. I did power wash all the years of diesels leaks and for working on it. May of got something wet. Does these have the same distribution valve like the gas version. Had nightmares with one in gas 460. Does the switch ever go bad. It feelsl alittle funky. Also my gas gauges have never work and I relied on 2 tanks to monitor gas. Maybe related? Any experiences? HELP.