rocketraider

You may remember me mentioning the 93 F150's recent throttle body ills. That's fixed and truck is running well, but since that episode a truly weird problem has surfaced.

When it came home from the TB work, it had about 3/4 tank of fuel in the front tank and rear tank full of Walmart Murphy 89.

Well- that front tank emptied out quick, mileage figuring to 12.5mpg (normally 17-18). Figured it just used a bunch while the shop was troubleshooting. Switched to rear tank and drove forever on it. When I filled it at 1/2 tank, mileage figured at 23.1 which I knew couldn't be possible.

Scenario repeated the next two tanks. I couldn't find a leak anywhere so I'm scratching my head.

Then while running on front tank another driver told me gas was pouring out of the rear tank.

Ford shop book was useless diagnosing it, but nosing around Ford truck forums I found that plenty of folks have had this issue.

Instead of a selector valve switching the tanks, when the tanks are switched pressure from the pump that has just started closes a check valve in the other tank's fuel pump assembly. Apparently the check valve in the rear tank pump has failed and when the front tank pump runs, it's pumping the front tank contents into the rear tank.

So, there's a tank drop in my future. Pfft.

I just thought that issue a couple years back with the Gray Ghost wagon's tank and pickup was weird, but it was working as designed. Don't think a Ford truck is designed to act this way!

I can't prove it, but I think that Murphy gas had something to do with it. It smelled pretty loud, almost like old gas, and the rear tank pressurized while it was in there. This truck has never pressurized either tank, even in 100° temperatures.

Just frickin weird.