The fuel tank is rigidly attached to the cab, the cab is
supported by shackles in the rear where it is free to move as
the frame twists. The steel fuel line is rigidly attached to
the frame. A little common sense seems to indicate that there
should be a flexible connection betwixt the two.
The steel line feeding the fuel pump is last attached to the
frame approximately 30" back via a clip on the rear engine
crossmember. The engine with good motor mounts moves very
little and there is very little flex in the front half of the
frame, so even though the line is rigidly attached to the
fuel pump, it does not move enough to reach it's yield
point. And apparently the cyclic load that is present, is
not great enough to cause metal fatigue, at least not
within the life cycle of these trucks. I've never heard
of one failing, unless it was improperly installed.
dg
Last edited by Denny Graham; 03/30/2015 2:25 PM.
