Hi, what I’m seeing in fuel in site glass on primary fuel filter is 1/2 full, what this is telling me the
O-rings on top and bottom of site glass need replacement. To verify this start engine and note: two
things the level of fuel in plastic site glass at idle and air bubbles in site glass. Next have someone
speed engine up very high idle and again note: level in site glass along with air bubbles in site glass.
What I expect you will see is a decrease in fuel level in site glass along with air bubbles at engine idle,
Next at high idle fuel in site glass will be very low in site glass along lots of air bubbles. This test is without any load put on engine such as climbing hill etc. that will require more fuel needed to run
engine along with information, yes engine will still operate but at power loss. Last this test fuel is
under suction from fuel tank up front to inlet side of fuel transfer pump than on discharge side of
fuel transfer the fuel pressure reading 58 psi at idle and 75 psi at high idle. This is where your power
loss comes into play because on entry on air at primary fuel filter, and in most cases location of
problem is the o-ring seal top and bottom of plastic site glass along side of primary fuel filter. Last
Your secondary fuel filter it is recommended for your 3126 engine a 1R-0751 2 micron caterpillar only
Fuel filter. Dave Atherton Retired Cat mechanic