Fuel System Operation and Tests
FUEL DRAIN BACK TEST PROCEDURE
Fuel draining back through the fuel system may cause
hard starting. This procedure will determine if air is
entering the system at connections and allowing fuel to
siphon back to the fuel tank.
1. Disconnect fuel supply and return lines at fuel tank.
IMPORTANT: Fuel return line MUST extend below fuel
level in fuel tank before performing this
test. Fill fuel tank if necessary.
2. Drain all fuel from the system, including the fuel
transfer pump, fuel injection pump, fuel filters, and
water separator (if equipped).
3. Securely plug off the end of the fuel return pipe.
CAUTION: Maximum air pressure should be 100
kPa (1 bar) (15 psi) when performing this test.
4. Using a low pressure air source, pressurize the fuel
system at the fuel supply line.
5. Apply liquid soap and water solution to all joints and
connections in the fuel system and inspect for leaks.
NOTE: Connections may allow air to enter the system
without allowing fuel to leak out.
6. If any leaks are found, take necessary steps to repair.
7. Reconnect supply and return lines and prime system.
8. Start engine and run for approximately 10 minutes.
9. Allow engine to sit overnight and try starting the