P0093 The Good, The Bad, The Ugly

Keith Browning · October 30, 2022

I just toiled with a 2017 Medium Duty with the code - happens only when loaded and or towing. Sound familiar? Search all of your on-line forums and groups and you will see the same thing - many different opinions and fixes claimed. If you know, you know, the MD trucks while they have the same hardware and electronics also know they don't exactly work the same. When you get to the pinpoint tests that require control of the PCV and the VCV you realize you CAN'T control one or both. Makes following the tests impossible. So, you initiate a Hot-Line report, and their recommendation is:

"The injectors can be further tested during step 15 of pin point test M by first unplugging all the injectors. (electrical connectors). Then while the injector return port line id bypassed from the secondary fuel filter, crank the engine. There should still be no fuel leaking from the open injector return port line. If there is any fuel leaking, the return line assembly can be removed from all the injectors and replaced with clear fuel hose. When the engine is cranked again, the leaking injector/injectors will be identified. If there is no injector return port leaks, the glow plugs can then be removed and again crank the engine. There should be no fuel misting out of any of the glow plug hales while the engine is cranking. (injectors still unplugged). If there is no injector leaks, the PCV should be removed and inspected. If there is any signs of rust, the high-pressure fuel system will require replacement. If there is no rust but there is any debris, the VCV will then need to be removed and inspected as this will confirm that the high-pressure fuel pump has failed. (system replacement). If there is no debris or rust found when removing the PCV, Replace the PCV ensuring to follow the tightening procedure. The PCV must seat in the bore of the left fuel rail. If it is suspect that the PCV is not seated in the rail, replace the rail as the replacement comes with a new PCV (and FRP) pre-installed in the rail."

Okay. Great advice but in the real world you know this is probably not happening pretty much anywhere especially with no low pressure system concerns and no other performance concerns - passes relative compression, power balance good, injector fuel mass adjustment good as well. After removing and inspecting the VCV and PCV finding no debris or evidence of contamination the VCV and left-hand fuel rail were replaced. I have a sickening feeling this is not the end of this story. This truck also needs a turbo for setting a low boost code KOER. The turbo is caked with hardened burnt oil... to be continued.