Rear fuel tank not transferring to front

[Mark Rinker]

Driver calls, truck and empty gooseneck had stalled on interstate suddenly. Fuel gauge is showing 1/2 tank, he started the day with both tanks full and has only 250 miles in. Have him crack the bleeder valve at the filter, he reports fuel present.

We then check all ECM and related fuses before calling for a tow. Closest GM dealer finds the front fuel tank empty, but the rear tank full.

Cause? Low voltage to rear tank pump, so fuel wasn't transferring properly. Front tank ran out, guage showed otherwise...

This was on the 2006 K3500 flatbed, ordered out as a cab/chassis and outfitted with a flatbed. My theory is the salt/sand duty has caused corrosion on one or more of the tank senders. We'll have to drop both tanks and troubleshoot when clear of the winter weather. In the meantime, we keep the front tank full at all times!!!

[More Power]

These trucks use an electric transfer pump between tanks, which is controlled by the ECM (which gets inputs from the tank senders). Bad electric transfer pump?

Jim

[Mark Rinker]

Sorry, forgot to update with the fix. Yes, the pump was bad and everything returned to normal with a new one.

[madmatt]

There is also a couple of bulletins pertaining to this problem. was there any codes set??? I changed out the rear fuel tank on a cab/chassis truck wed for this very problem. it seems that on the original factory tank, the filler bung extends down into the tank to far and the float arm can overextend on rough terrain and get hung up on the bung. Also there is a updated software to address fuel slosh in dual tank vehicles. I have seen weak transfer pumps cause this like you said yours was.