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QUESTION: The “Change Fuel Filter” indicator lit up while I was towing an equipment trailer over the Sierras with my ’15 GM pickup, which has about 70,000 miles on it. A couple minutes later, the engine lost power, leaving me stranded. The dealer says the CP4 injection pump failed for some inexplicable reason. The $8,500 in repairs to replace the fuel pump and injectors and flush the fuel system is covered under warranty. Are there any upgrades that can be done to ensure this doesn’t happen again when the truck is out of warranty?
ANSWER: CP4.2 injection-pump failures happen, just as failures happen to any part that has exceptionally tight working tolerances under high loads. Such failures are usually the result of poor fuel quality, low lubricity in the fuel, contamination, or the result of cavitation from running out of fuel. The injection pump essentially grinds itself to failure. When a CP4.2 pump “grenades,” the metal debris from its internals finds its way through the fuel-pressure regulator and into the rails and injectors, and back into the tank. That pump works extraordinarily hard pulling fuel from the tank and supplying the high rail pressures for the injectors to work. One of the common upgrades to ease the minds of those who have fears of CP4.2 pump problems is to install a pressure regulator that does a better job filtering the fuel before it reaches the rails and injectors. Exergy Performance offers an inlet metering valve for the ’11-to-’16 6.6L Duramax LML product called the System Saver (PN E05-10505), which filters down to 25 microns using a double-layer stainless mesh, whereas the stock single-mesh screen filters just 80 microns. The upgraded fuel-control actuator (FCA) assembly that is part of the CP4.2 doesn’t prevent fuel pump failure. It only mitigates the damage caused by metal debris circulating through the entire fuel system before the engine shuts down. The company claims the finer stainless-steel screen of its FCA traps more pump debris and contaminants sooner, plugging and shutting down the engine before extensive damage is done to the rest of fueldelivery system—but it does help keep the repair costs down compared to staying with the stock FCA. Beyond that, you can take some of the workload off the CP4.2 by installing an aftermarket lift pump/filter system, which helps ensure the fuel getting to the pump is as clean as possible at the same time. Keep in mind: Contamination of fuel and the lack of proper lubricity in ultra-lowsulfur diesel are the common killers of CP4 fuel pumps. A CP4 uses a lower volume of fuel than its CP3 predecessor, so its internals are getting less lubrication. The way to be proactive in protecting a CP4.2-equipped diesel from an early demise is being diligent about using fuel additives that add lubricity with every fill-up. Ideally, you want diesel fuel with a lubricity that meets the minimum ASTM standard of 520 microns High Frequency Reciprocating Rig (wear scar) rating. HFRR is currently the internationally accepted, standardized method to evaluate fluids for lubricating ability. This is a very important number when it comes to diesels running ultra-low-sulfur fuels that don’t have very good lubricating properties without dosing with an additive. The larger the number, the poorer the lubricity. The poorer the lubricity, the quicker the road to pump failure. If you can, use a fuel additive that lowers the HFRR of the fuel into the 300s. Additives such as Opti-Lube’s XPD or XL have shown some of the highest lubricity improvements in comparative testing.
Source: Diesel Power Magazine, April 1, 2019
2015 - 3.0 Ecodiesel/Big Horn/1500/QCSB/4x4/8HP70
2019 - John Deere 1025R/120R Loader/260 Backhoe
2019 - Iron Bull/Equipment Trailer/83”x16'/10,000 GVWR
2018 - Iron Bull/Dump Trailer/6'x12'/10,000 GVWR
2016 - Arctic Fox/22G Travel Trailer/LP Cummins Onan Generator
Stihl saws - MS 271 Farm Boss, 034, HT 56 C-E