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6.7L Cummins Fuel System – Fuel Lift Pump – Measure

Front Gear Train
The purpose of this test is to check lift pump flow.
Disconnect the filter head fuel supply line quick disconnect at the high pressure fuel pump inlet fitting.
Attach the fuel drain hose, Part Number, 4918433, fuel supply line from the filter head.
Place the end of the hose in a graduated beaker, Part Number 3823705.
NOTE: Make certain the fuel lines are not kinked or leaking after installing the test lines.

NOTE: This test is performed with the engine not running.
Make certain all air is purged from the test lines and fuel is flowing consistently before collecting data.
The lift pump can be temporarily activated by turning the keyswitch_ on and by “bumping” the starter without starting the engine. The lift pump will operate for 25 seconds.
Measure the amount of fuel flowed by the lift pump in a ten second interval.
Fuel flow rate for the lift pump (engine not running)  greater than 590 ml [20 oz] in ten seconds.
NOTE: The lift pump will operate longer than ten seconds at key-on. A separate bucket is recommended to catch
excess fuel pumped after the ten second interval.
NOTE: For an accurate measurement, it’s a good idea to collect three different flows and average the results.
If the lift pump does not meet the flow specifications, check the fuel lines for leaks from the fuel tank to the filter
head.

If the lift pump does not meet the flow specifications, remove the fitting/filter screen at the outlet side of the filter
head.
Inspect the screen for debris and clean with solvent if dirty.
Replace if needed.
Install the screen filter fitting.
Torque Value: 24 N•m [ 212 in-lb ]
Repeat the lift pump flow test.
If the flow specifications is not met, replace the fuel filter.
Refer to Procedure 006-015 in Section 6.
Repeat the lift pump flow test.
If the lift pump flow is still below specification, the lift pump is defective. For repair related information, refer to the
OEM service information.

Rear Gear Train
The purpose of this test is to check priming pump flow.
Disconnect the fuel supply line from the priming pump fuel filter head outlet.
Attach the fuel drain hose, Part Number, 4918295, 4918434 or 4918698, to the priming pump fuel filter head
outlet fitting.
Place the end of the hose in a graduated beaker, Part Number 3823705.
NOTE: Make certain the fuel lines are not kinked or leaking after installing the test lines.

NOTE: This test is performed with the engine not running.
Make certain all air is purged from the test lines and fuel is flowing consistently before collecting data. Verify that
no leakage is present at the shaft while pumping the priming knob.
Unlock the priming pump knob (1) and pull it out. Pump the priming knob a few times to push air out of the line.
Once fuel is flowing from the line consistently, pump the priming pump 10 times.
One pumping stroke is equal to the knob being pulled out and pushed back in.
Fuel volume for the priming pump- greater than 137 ml (4.6 oz] after 10 pumps of the priming knob.
NOTE: For an accurate measurement, it’s a good idea to collect three different flows and average the results.
NOTE: If no resistance is felt while pumping the knob, the priming pump check valve can be damaged or stuck open
with debris. For repair-related information, refer to the OEM service manual.
If the priming pump does not meet the flow specifications, but resistance is felt when pumping the priming knob,
check for air in the fuel. Refer to Procedure 006-003 in Section 6. Check for inlet restriction. Refer to Procedure
006-020 in Section 6.
If no problems are found , the priming pump is malfunctioning. Replace the priming pump.