Beginning in 1998 and continuing through 2001, there have been sporadic cases of low engine power caused by a plastic cap left on the fuel tank during assembly. This cap is on the tank vent port, and should have been removed when the tank is installed on the truck chassis. If the cap is not removed, vacuum will build in the fuel tank and engine power will drop because the fuel pump is unable to pull against the tank vacuum.

Most caps are red in color, but a few have been black. Simply pull the cap from the vent fitting circled in red on the drawing to the left. DO NOT remove the Auxiliary fitting cap. See photos below for other views.