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Your Diesel Questions Asked and Answered

You’ve got questions, we’ve got answers

Bruce W. Smith
Feb 13, 2019
Photographers: Bruce W. Smith

High-Mileage Injection Pump

QUESTION: I took delivery of my ’11 Chevrolet Silverado 3500 in April 2011. The odometer now displays 384,485 miles. I commute 204 round-trip miles per day, five days a week—plus occasional trips with a car hauler or a 34-foot fifth-wheel RV trailer. I changed the glow plugs at 250,000 miles and the DPF at 286,000 miles, because it would no longer regen. The one “Top Tech” question that caught my attention was the CP4 versus CP3 injection pumps. Am I living on borrowed time with the stock CP4 pump? Do you recommend converting to the CP3 or replacing it with another CP4? I’m not experiencing any issues, but the CP4 now concerns me. I plan to retire the truck in another 100,000 or so miles.
Mike Colledge
via email
ANSWER: Based on the experiences other 6.6L Duramax LML owners and diesel shops shared with us, your truck’s CP4.2 is living on borrowed time. Thousands of the Bosch CP4.2 injection pumps went out during the warranty period, and many others failed long before 150,000 miles. They flow less volume than their CP3 predecessor, and that, combined with the low lubricity in today’s ultra-low-sulfur diesel fuel, means the tappet that rides on the cam-like shaft inside the pump isn’t getting the type of lubrication it needs to last hundreds of thousands of miles in this application. When the pump fails, metal fragments end up in the entire fuel system from the tank to the injectors, necessitating replacement of everything to the tune of about $10,000. The problem is so bad there were at least two class-action lawsuits filed late last year—one in California, the other in Texas—related to the use of the CP4.2 pumps in Ford, GM, and Ram diesel trucks built between 2010 and 2018. The choice to replace the CP4.2 with another one, or “upgrade” to the older and more robust CP3, is a fairly easy decision in our mind: CP3. If you want your truck to remain “emissions-legal,” S&S Diesel Motorsport offers a CP3 conversion kit that’s 50-state complaint. We highly recommend installing a quality lift pump (FASS, AirDog) with either of these pumps to help ensure the fuel is clean and air-free and to take some of the workload off the injection pump itself. Most of the other CP4.2-to-CP3 conversion kits require “deletes” and ECM tuning that will create some issues when trading in/selling your truck at a later time. We can’t stress this point enough: The CP4.2 is highly sensitive to bad fuel and any air getting into the system. To that end, we suggest never letting the fuel level get below a quarter of a tank and taking great pains to get every bit of air out of the system before starting the engine after changing fuel filters. Also, use a quality fuel additive that improves lubricity with every fill-up.


QUESTION: I have a ’12 Ram 3500 and love the truck. But I wish it had the “keyless go” feature. I know this feature was offered on some other Dodge products, like the Charger and Challenger for the same year. How do I add it to my truck? I’d like to find a shop or someone who has installed the OEM keyless system and has a parts list.
Mike Jones
via email
ANSWER: Anything is possible if you have enough time and money. It will require a lot of both to convert your remote-start, keyless-entry system to the “push-to-start” system that has almost become standard in today’s automotive world. You will need to find a good parts person at the Ram dealership who will take the time to track down all the components and a detailed wiring schematic. “Installing a factory system after the fact will be a real pain,” says body shop owner Warren Spears of Spears Auto Repair in Long Beach, Mississippi, who has plenty of experience wiring pickup bodies. “That [OEM] system is integrated into the truck’s body-control modules and wiring harnesses by the factory. I doubt many shops would tackle retrofitting it without a donor truck’s complete wiring harness that has the correct, factory-installed ignition system.” A much simpler route, which will cost around $600, is to install one of the newest aftermarket kits, such as the Digital Guard Dawg 2Go “iKey” keyless system. Installed, it looks every bit OEM, right down to the same round “Engine Start Stop” button Ram uses in the location where the key normally is. The company says it can be installed on any vehicle that has power door locks. There are even videos on YouTube that detail how to install it.

500hp 12-Valve

QUESTION: I have a stock ’95 Dodge Ram with the 5.9L 12-valve Cummins engine. My goal is to get 500 hp and 1,000 lb-ft of torque with it. What type of modifications to the stock automatic transmission should I make to handle this much power, and what would be the most cost-effective way to achieve this kind of power on a limited budget?
Spencer Finlay
via email
Photo 2/5   |   Top Tech 500hp 12v Build
ANSWER: Source Automotive in Clackamas, Oregon, focuses a lot of time on building both 12- and 24-valve Cummins engines for customers, so we asked Manager Bill Allen what it takes (parts and labor costs) to give a ’95 Dodge Ram that kind of performance. We also asked the same question of our sled-pulling/drag-racing friends at Scheid Diesel Service Company in Terre Haute, Indiana. Like anything one does related to hot-rodding any engine—diesel or gas—there are many ways to achieve performance goals. Keeping costs down at the expense of reliability never pays off. So maintaining reliability at the power level you want necessitates paying attention to the proper machining of the block and head, installing ARP cylinder-head studs and Hamilton Cams valvesprings and retainers for higher rpm, and then choosing the right turbocharger, modifying the P7100 injection pump, installing 90hp injectors, adding a lift pump along with freer-flowing intake and exhaust manifolds, and 4-inch exhaust tubing. Then there’s the transmission. The 47RH is quite stout, but it will require several modifications to handle that amount of torque. For example, both Scheid Diesel Service’s (PN 9134RH4X4) and ATS Diesel Performance’s Stage 2 47RH transmissions built for moderate power upgrades include a billet input shaft and forward hub, upgraded torque converter, and a high-performance pump, clutch packs, and bands. The transmissions also feature modified valvebodies to handle the increased fluid demands and higher line pressures 1,000 lb-ft of torque requires. Those transmissions cost around $5,000. Even if a local transmission shop does the work, a sizeable investment is necessary for making that transmission and torque converter durable enough to handle the load. So we estimate a “500hp budget build” costing approximately $8,000 to $12,000, depending on how much sweat equity you put into project and how much you pay for the parts.

Bigger Cover

QUESTION: Do higher-capacity aftermarket differential covers run cooler and help the differential last longer? I put a lot of cross-country towing miles on my ’16 GMC Sierra 2500HD. I’m thinking about swapping the stock steel cover for a bigger one.
Tom Gillam
via email
Photo 3/5   |   Aftermarket differential covers have been popular upgrades and bling accessories on diesel pickups for decades. But video-documented, in-depth testing by Gale Banks of Banks Power shows they may not offer all the benefits we originally thought.
ANSWER: Until last year, we would have said, “Yes, because they hold more lubricant and the aluminum aftermarket differential covers dissipate heat better than the stock steel covers do.” Today, the comprehensive testing and compelling technical commentary that Gale Banks has posted on YouTube shows exactly what’s happening inside the differential using such covers. Gale’s three-part investigative report, “Do Diff Covers Work or Are They Just Bling” (youtube.com/watch?v=09JsDorR6tw) leaves no angle uncovered when it comes to evaluating their worth. Gale’s attention to every detail of testing high-fluid-capacity, flat-back-aluminum differential covers shows they are more of a problem than a solution. According to Gale, their design hinders the proper lubrication of the pinion shaft bearings, as the differential paddles its way through the lubricant and throws it up against the back of the cover instead of allowing the lube to splash forward to the pinion and its bearings. Part 2 of his video report, which uses a clear cover on the back of a well-known aftermarket aluminum cover, clearly shows how the fluid is thrown around inside the differential—most of that lubricant hits the flat-back wall with little slinging forward to the pinion bearings. He also shows (and explains in detail) how the extra quarts and higher fill level of lubricant create more heat and aeration. Aeration is a bad thing when it comes to lubrication. A massive amount of air bubbles in the gear lube means less lubrication on areas where load forces need it most. And whatever heat-dissipation advantages the aluminum covers provide is offset by the added fluid getting heated by the differential spinning in the foamy soup. That same paddling effect, according to Gale, has a negative effect on fuel economy. If you want “bling,” finned aftermarket aluminum differential covers fit the bill. But if you are trying to maximize the longevity of a differential, you might want to leave the stock cover alone.

Intermittent P0401

QUESTION: I've owned my ’14 Ford Super Duty since it was new, and I love her dearly. I use a diesel-fuel additive with every fill-up and have all maintenance performed by Ford technicians. The truck is unmodified and has more than 73,500 miles on it. My concern is it started flashing a Check Engine light while I was on a trip, and, according to Auto Zone where I stopped to have it checked, there’s a diagnostic trouble code: P0401. The Check Engine light flashed off and on a few more times during the trip, and when I got home the dealer said it’s a plugged EGR cooler, which needs replacing. It will cost me about $800. I had the water pump and a few EGT sensors replaced under warranty. Now I am getting nervous as I inch closer to the powertrain warranty’s expiration. I just would like to know why the EGR plugged at 77,000 miles.
Photo 4/5   |   Intermittent Check Engine lights with a P0401 diagnostic trouble code on a 6.7L Ford-powered Super Duty usually means the EGR cooler is not flowing properly. Carbon, the sooty byproduct of unburned fuel in the exhaust, cools down and accumulates inside the cooler cores, which eventually have to be cleaned or replaced. On the 6.7L, the coolers are two separate units stacked side by side—one is the “hot” side, the other is the “cold” side. It’s the cold-side EGR cooler that always plugs up first.
ANSWER: The ’14 Ford Super Duty has a robust powertrain. As long as you have the transmission flushed and refilled with new fluid every 50,000 to 60,000 miles, there’s normally little to worry about. But there’s no way to sugarcoat an EGR cooler being plugged up. That’s just an evil, inherent drawback for emissions-compliant diesels. As carbon, the unburned (now sooted) diesel fuel in the exhaust cools and ends up accumulating inside the EGR cooler’s cores, which eventually have to be cleaned or replaced. On the 6.7L Power Stroke engine, two separate coolers are stacked side by side (one is the “hot” side, the other is the “cold” side). Both are cooled by a secondary water coolant system that’s also responsible for cooling the fuel, automatic transmission, and charge-air cooler. It’s the cold-side EGR cooler that always plugs up first. The biggest contributor to EGR coolers becoming clogged is idling the engine. Of course, removing any diesel vehicle’s EGR cooler(s) and subsequently fooling the ECM through tuning resolves the plugging problem. But doing this also puts you on the wrong side of federal emissions laws. Deleting emissions equipment also makes it difficult to resell or trade in a truck. Replacement runs in the neighborhood of $1,300 to $1,600 (including EGR valve), according to our buddies at Mobile Diesel Service in Oakland, Oregon. As for the intermittent Check Engine light, you may be seeing it because the secondary (cold side) EGR cooler is not flowing like it should during the drive cycle. The EGR sensors detect the reduction of flow because it’s outside the acceptable parameters, and the ECM triggers the code accordingly. Ford technicians use a proprietary IDS, Snap-On Tools Versus, or other high-end scan tool to confirm the P0401 codes, then they typically perform a Key On Engine Running (KOER) self-test. If that results in a P2457 code, it means the EGR cooler core needs to be replaced, along with the EGR valve. A good technician may also do an EGR cooler “performance test” to confirm exhaust flow through the cooler. This is done by running the engine at 1,200 rpm while using the scan tool to monitor MAF and EGR temperatures, first with the EGR bypass in the Open mode, then with the bypass closed. If the EGR temperature and MAF do not change by at least a specified amount when the bypass is slowly opened and closed, the cooler is considered plugged. When the EGR bypass is slowly closed with the scan tool, the MAF reading should decrease significantly and the EGR temperature should drop very quickly if the cooler is working properly. (When the EGR cooler bypass valve is closed, exhaust gases pass through the EGR cooler to the intake manifold. Consequently, when the EGR cooler bypass valve is open, exhaust gases pass directly to the intake manifold without passing through the EGR).

Smokey 12-Valve

QUESTION: I bought a ’97 Dodge Ram 2500 with less than 5,000 miles on a rebuilt 5.9L 12-valve Cummins engine. The truck is well cared for and the engine looks new. It runs strong, but it gets poor fuel mileage, and the black smoke that pours out of the exhaust will kill every mosquito around it when you hammer the throttle. The injectors are rebuilt injectors and the turbocharger is new. So, what causes smoke and poor fuel economy?
Ersel Thurston
via email
Photo 5/5   |   Grinding the P7100 injection pump’s cam plate flat (right) is a surefire way to create excessive exhaust smoke from a 5.9L 12-valve Cummins engine. The process, often referred to as a “zero” plate, is a backyard way of increasing fuel delivery from the injection pump. However, a zero plate also raises EGT and pours on the fuel all the time, so it’s not good for towing or fuel economy. The stairstep-like profile of BD Diesel Performance’s #10 fuel plate (left) adds horsepower and improves fuel economy over a stock plate without the smoke issues.
ANSWER: Is the air-fuel controller (located at the back of the Bosch P7100 injection pump) checked or modified? The P-pump is the component that makes those older Cummins engines so popular. It can easily be modified to add up to 100 hp. However, P-pump mods almost always increase smoke and reduce fuel economy. One common way to easily boost the 12-valve’s power is to turn the star wheel toward the passenger side of the engine so the fuel rack opens more and delivers more diesel to the plungers in the pump. But turning the wheel too far will result in heavy smoke. Someone could have also removed the factory rack plug (located on the injection pump facing the timing case) and replaced it with a “Mack rack plug” that allows two more millimeters of rack travel and another 70 cc of fuel. Again, more power along with more smoke. Another popular backyard performance trick for that engine is to modify the fuel plate the AFC sits on. Some grind the cam plate flat, which is called a “zero” plate. “While this modification adds more fuel (and therefore increases power), it also produces excessive black smoke from unburned fuel while elevating EGT under load compared to a properly profiled fuel plate,” says Cam Rose, a customer-support technician at BD Diesel Performance. “The profile of a fuel plate is what schedules fuel delivery, so different cam plates are suitable for different injection pumps and power levels. A ‘zero’ cam plate will not give you an ideal fuel curve, so although the truck will go faster, it won’t perform as well or run as clean as it would with a properly chosen fuel plate. Fuel economy will be compromised, too.” It’s also a good idea while you are checking out the P-pump to take a close look at the throttle-stop adjustment screw to make sure the head wasn’t flattened from decades of use. It’s not unusual for the soft metal head of the stop to get beat down, which will make it difficult to adjust the idle.

VW AdBlue Heater

QUESTION: The Check Engine light in our 2.0L TDI-powered ’13 Volkswagen Passat lit up. I took it to the dealership, where technicians checked for diagnostic trouble codes and replaced a bad NOx sensor, to the tune of $655. The warning light came on again, and the mechanic says the P203B code for “Redactant Level Range/Performance” most likely means the “AdBlue” heater needs to be replaced. The estimated cost: $1,270! Are we being taken for a ride?
P. Baldwin
via the Internet
ANSWER: The failure of the AdBlue tank heater and related selective catalytic reduction emissions components has been of great concern in those ’09-to-’16 VW, Audi, and Porsche vehicles with 2.0L and 3.0L TDI engines. That system heats and injects diesel exhaust fluid, called AdBlue, into the catalytic converter to reduce NOx. (AdBlue is a version of diesel exhaust fluid that’s trademarked and marketed by Germany’s Association of the Automotive Industry.) It’s used in Audi, Volkswagen, Porsche, Mercedes-Benz, BMW, and other European diesel vehicles, and the fluid is the same formula as the DEF found under other brands: 32.5 percent urea, 67.5 percent deionized water. Here’s the good news: Double-check with your dealer’s service manager because VW sent out a “service action” in July 2018 (VW Action Code 26K4; 07-18-2018) that calls for the updating/replacement of the AdBlue heater system across many years of emissions-compliant TDIs. At about the same time, an Emissions Compliant Recall for VW Generation 1 2.0L and Generation 2 3.0Ls to replace the entire emissions system along with an extended warranty up to 10 years/120,000 miles on the ECR parts that are replaced was released. You should have received notification on both as a VW TDI owner. The “Emissions Modification Phase 2,” according to VW documents, says, “The second part of the emissions modification will involve outfitting your car with new emissions control parts to ensure system reliability and durability over time. If your car exceeds 40,000 miles (for automatic transmissions) or 70,000 miles (for manual transmissions), we will install updated emissions control system hardware—specifically a new diesel particulate filter, diesel oxidation catalyst, and selective catalytic reduction converter—that is needed to maintain emissions performance for the full useful life (150,000 miles) of your vehicle. As part of the Phase 2 modification, we will also install a second NOx sensor and corresponding software to improve the performance of the OBD system. The Phase 2 updates are expected to have no further impact on overall vehicle reliability, durability, fuel economy, engine sound, performance, or driveability.” The ECR also made provisions for dealers to reimburse owners on repairs they had made previous to this recall along with other compensations.