WHY THE CP4.2 FAILS

AND HOW YOU CAN KEEP YOURS OFF THE SCRAP PILE

MIKE MCGLOTHLIN

By now you’ve heard of all the problems surrounding the Bosch CP4.2, the high-pressure fuel pump that’s made its way onto most common-rail engines in the pickup truck segment. You know the story well: the pump self-destructs, sends metal fragments through the lines and rails, into the injectors, and then out the return circuit.

The failure is rarely noticed before it’s too late, and by then you’re usually out a pump, lines,rails, injectors, a tank cleaning, 30 hours’ labor, and anywhere between $6,000 to $10,000. As expected, this potential catastrophe has many late-model truck owners a little uneasy about their $60,000 to $90,000 investments.

With its ultra-tight tolerances, the CP4.2 does not tolerate anything other than diesel fuel very well. But which unwanted contaminant is most common? Air. That’s right, aeration is the number one killer of these pumps.