How to Prime a 6.7 Cummins After Fuel Filter Change

The 6.7 Cummins diesel is the successor to the massively successful 5.9 ISB Cummins and packs significant torque into light-duty trucks, earning itself an excellent reputation for reliability and durability.

Both 5.9L and 6.7L Cummins engines utilize a Bosch common-rail fuel injection system with high pressure capability using Bosch CP3 and CP4 pumps for fuel delivery.

Turn the key to the Run position.

Once your fuel filter has been drained and filled with fresh diesel and the appropriate OE filters, the first step in priming your system should be priming. To do this, cycle your key back and forth 10-20 times between run and no start positions without starting your engine in order to allow the pump to fill all new filters with air while filling old ones up as they are installed by purging.

Crank the engine until solid diesel fuel appears at the bleeder at the VP44 injector line banjo bolt in the head – this indicates all air and water has been flushed from your injection system. Crank it up again and allow some fuel to spurt from your injector lines for several seconds; if your engine starts and runs without white smoke or miss, then you are ready to begin driving!

• Wait 15 seconds.

As soon as the 6.7L Cummins engine hit the market, it quickly earned praise for its million-mile durability and unparalleled performance potential. These traits helped it quickly become the preferred engine choice in diesel motorsports competition.

The 6.7L is equipped with a high-pressure common rail fuel system equipped with a Bosch CP3 injection pump to generate over 23,000 PSI of fuel pressure.

Given their high pressure nature, it’s crucial that both injection pumps and injectors be properly flushed of air after changing a fuel filter. To do so, simply cycle your ignition key multiple times without starting up your engine; doing this activates the fuel transfer pump to begin circulating fuel throughout your system to eliminate air.

• Turn the key to the On position.

The 6.7L Cummins comes equipped with several emissions control parts not found on its 5.9L predecessor, such as EGR system, DOC, and DPF filters.

Before replacing a secondary filter, first the primary fuel filter must be drained of its contents by opening its water drain valve at the bottom of its housing. When all the fuel has been removed from its canister cap and two quick-disconnect fuel lines has been completed drained.

Once the new filter is in place, the fuel pump must be primed by cycling the key from Run to Off repeatedly without starting the engine. This process bleeds air from the system while priming the filter – this should take approximately 15 seconds. If it doesn’t work as intended, an O-ring may have become damaged or misseated and must be addressed first before continuing this procedure.

• Wait 15 seconds.

People had high hopes when the 6.7 Cummins diesel engine made its debut. People expected it to fulfill many of the characteristics associated with its predecessor – 5.9 Cummins engines were famously long-lived.

The 6.7 was designed to comply with EPA emissions requirements, featuring an EGR valve and DPF (diesel particulate filter). Additionally, there are new emission-related parts which may alter engine performance.

When replacing fuel filters, it is crucial to cycle your key between run and stop several times with enough time between each cycle for the lift pump to fill your filters with fuel and purge the system of air. Priming should take only 10-15 seconds – any longer may prevent its filling with fuel by the lift pump.

• Turn the key to the Off position.

The 6.7L Cummins comes equipped with an exhaust gas recirculation (EGR) system, diesel oxidation catalyst and particulate filter; in 2013, select-catalytic reduction was added as another emissions control feature.

If your 6.7 Cummins is missing fuel or cranking slowly after changing its filter, chances are the injection pump and injectors were not properly primed after priming with fresh filter oil. To rectify this situation, cycle your key repeatedly between the CRANK position and Off position without starting your engine – be sure to catch any fluid that comes pouring off! Repeat the process until all cycles have taken place (usually 10-20); turn your key back off when finished and return it to normal operation before turning the key to Off again.