Dual gas tank issue
I have an old 1987 Ford E-150, Getaway conversion. It has two gas tanks, listed in the cab as Front and Rear with a manual switch. After filling the tanks, one of the two situations occurred:
1. I used the rear tank first. Then I switch to the front tank. When the front tank starts to empty, I realized that a portion of its gas has been pushed to the rear tank, which ends up being about 1/3 full.
2. I used the front tank first. Given that the rear tank was full, gas began spurting out of my closed fill valve.
Obviously scenario 2 is not very safe, so I've been running it according to scenario 1, but I’d like it fixed. I am going to have a bunch of repairs done to the van this fall, and I was wondering if anyone has suggestions as to what the issue might be?
Also, does anyone have a suggestion for good mechanics in Central CA that would get into custom work? My mechanics are great, but they are kind of by-the-book and not inclined to get into anything unusual.