How to Check Fuel Pressure on a 5.9 12V Cummins

by Andrea Walk

The Cummins 5.9-liter, 12-valve engine is a large diesel engine that eventually became the stock engine for the Dodge Ram pickup during the 1990s and 2000s. If the Ram has possible fuel-related problems, then running a fuel-pressure test can isolate them. These engines come equipped with an easy-access test port, referred to by some as a Schrader valve. The fuel-pressure gauge can be screwed directly onto this port for testing.

Step 1

Pop the hood on the Dodge Ram and locate the test port on the left-hand front side of the engine compartment.

Step 2

Unscrew the valve cap and pull it back out of the way. Screw the end of the fuel-pressure gauge onto the test port.

Step 3

Start the Dodge Ram and allow it to run for around five minutes. Examine the fuel-pressure reading. If it still appears to be fluctuating, give it a few more minutes until the level peaks out. The pressure should read between 15 to 18 psi.

Step 4

Turn the motor off and remove the pressure gauge from the test port. Use an old towel to wipe up any spilled fuel. Replace the test port cap.

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