Okay, here's the story. There is a recall kit for several years of F-250 trucks (including 93) which consists of two in-line check valves and a new fuel pressure regulator. The valves go in the supply line from the fuel pumps to the tanks and prevent fuel from flowing into the tanks from the supply lines. This kit was issued by Ford to prevent two problems: fuel flowing from one tank into the other through the supply lines, and long cranking times due to fuel running back into the tanks after the vehicle was shut off.
The pressure regulator was included as good practice. In my case, I had the two valves and the pressure regulator installed. Sure enough, the long cranking time stopped, but I still had fuel going from one tank to the other. Yes, I verified that fuel was flowing from one tank to the other. The final solution was to replace one of the fuel pumps (only one because Ford wants ~$250 for the things and if that WASN'T the problem, I wasn't out $500). Voila! I replaced the front tank fuel pump, and fuel would still flow from the rear to the front, but NOT from the front to the rear. I will replace the rear pump in a couple of weeks, and the problem will go away completely. The problem seems to be that the fuel pumps were going bad, and not putting out enough pressure to open the return valves in their own tanks, but putting out enough pressure to flow through the return valve in the OTHER tank.
Let me explain. In one of Ford's "better ideas", some turkey decided that each fuel pump should have its return line flow through the pump assembly through a valve. Okay. Not how I would have done it, but okay. However, to make the valve open only when that pump was activated, a minimum amount of pressure must be maintained in order to open the valve sufficiently so that fuel can return ONLY through that valve. The problem is that when that minimum amount of pressure is not available, fuel will flow through the *other* tank's return valve, which is what was happening to me. I suppose it's another way to indicate that a fuel pump is going bad, but it seems like a simple pressure sensor would be better. And cheaper. Anyway, that's what it was. Runs great now. I highly recommend anyone who has one of these trucks and is experiencing the long start-up time to get the valves placed in the lines. It solves the problem immediately.
Thanks for the time. --Dana Burgess
Message me at BobHewitt@Misterfixit.com
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