Transfer Pump Inlet Restriction

PURPOSE
To determine if there is excessive restriction of fuel flow from the inlet fuel line to the fuel tank(s).

Vacuum Gauge:

RECOMMENDED PROCEDURE
Remove the short rubber hose at the fuel inlet line (left side of engine close to the frame rail). The larger of the two fuel lines is the fuel inlet. The smaller line is fuel return. Install a "T" plumbed to a fuel restriction gauge (0 to 30 inch-Hg vacuum). Measure restriction at high idle (maximum engine speed out of gear with the brakes set and the wheels blocked). If restriction measures above specification, there is a blockage between the engine and the tank.

POSSIBLE CAUSES
- A kinked or severely bent fuel supply line or blockage at the pickup tube could cause restriction and cause high restriction.
- The switch valve for fuel tanks could be damaged.
- In very cold ambient temperatures with No. 2 fuel, the fuel could be jelled in the lines and cause restriction.

TOOLS REQUIRED
0 to 30 inch-Hg vacuum gauge, "T" to access full line (fabricated locally from common fittings)