Check For Air In Fuel
- Install a length of clear PVC hose in place of rubber hose between fuel filter outlet and injection nozzle return system. Run engine at 3000 RPM and check for bubbles in clear hose. Fuel should flow from fuel filter/water separator toward fuel return system. On vehicles with dual tanks, check with tank selector valve in each position for am minimum of 2 minutes.
- If fuel flow direction is okay and bubbles are less than 1/16" (1.58 mm) diameter, go to next test. If fuel flow direction is okay and bubbles are greater than 1/16" (1.58 mm) diameter, proceed to FUEL SYSTEM AIR LEAK TESTING . Repeat this test when the air leaks have been eliminated. If fuel flow direction is not correct, proceed to the CHECK FUEL RETURN PRESSURE test. Repeat this test when fuel flow direction is corrected.