Exclusive Content
Original Shows, Motorsports and Live Events
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit www.motortrend.com for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM

Diesel Tech Questions: You Have Questions-We Have Answers

Top Tech

Bruce W. Smith
Sep 24, 2018

Titan XD Low Fuel Pressure

Photo 2/7   |   Nissan Titan XD diesels will warn the driver the fuel level is low when the miles-to-empty indicator reads 60 to 65 miles, usually triggering a “Low Fuel Pressure” warning that will hopefully assist the driver in not running out of fuel (which can damage the CP4 injection pump and fuel system).
Photo 3/7   |   Nissan Titan XD diesels
QUESTION: I have a ’16 Nissan Titan XD diesel with 36,900 miles on it. I do a lot of towing, and on a few occasions (when the fuel-range indicator drops below 65 miles remaining), a “Low Fuel Pressure” warning displays. Nothing changes in driveability, but the first time it happened it definitely caught my attention. After filling up, the warning goes away, and it doesn't appear again until the driving range hits that 60- to 65-mile mark. Is there a problem with the fuel system or the tank? I follow the owner’s manual for all the maintenance. With only a 26-gallon tank and 10 mpg when towing, this is becoming a range issue for me.
Monte Wilkes
via email
ANSWER: The CP4 injection pumps on new diesel engines are very finicky about being starved of fuel. They’re prone to failure in low-fuel conditions, and this is costly because correcting the damage usually requires replacing the entire fuel system. The “Low Fuel Pressure” and “Low Fuel” warnings are Cummins’ way of ensuring the driver is very aware the fuel level is nearing a point of concern and that he or she has adequate time to refuel—much like diesel-exhaust-fluid warnings. When the fuel level gets below a quarter tank, the ECM triggers those warnings. It will also send the same alert when there’s a fuel-pressure drop due to debris getting into the pick-up in the tank or if there’s restriction farther upstream in the two filters in the low-pressure side of the fuel system. If the “Low Fuel Pressure” warning comes on before a quarter of a tank, there could be a pressure-sensor issue, contaminated fuel, bad fuel-filter O-ring, clogged fuel filters, a filter that has a failed check valve, a lift pump dying, or low voltage to the fuel pump. These are all items a dealership service department should check while the truck is still under warranty. If you want to extend the driving range of the stock fuel tank, you might consider installing a Sinister Diesel fuel-tank sump, which draws from the bottom of the tank. A better choice is to replace the stock mid-ship fuel tank with a high-capacity version such as the 50-gallon offerings from Transfer Flow or Titan Fuel Tanks. Either one will nearly double your current driving range.

Best Winter Tire

Photo 4/7   |   Winter driving in snow country is greatly improved using dedicated snow tires, which can cut stopping distances in half compared to the typical LT street tires that are standard equipment on heavy-duty pickups. Snow tires’ special rubber compounds and tread design make the studless versions excellent performers when the roads turn white. – Photo by Larry D. Walton
QUESTION: I hope you guys can point me in the right direction for selecting the best tires to use during the winter on my new Ford F-350 . Our family is in the process of moving back to the upper Midwest. Twenty years ago, when we lived in snow country, I used Bridgestone Blizzaks for winter and loved them.
Dan Willits
via email
ANSWER: A lot has changed over the past 15 years when it comes to dedicated snow/ice tires. There are more tires available to fit a wider range of pickups, and the technology in compounds and tread design has made today’s dedicated snow tires stellar winter performers. Our first choice would still be the Bridgestone Blizzaks, but now there are three viable replacements for the 245/75R17 that is stock equipment on your truck: Bridgestone’s Blizzak DM-V2, WS-80, and LT. A 265/70R17 DM-V2—a studless snow/ice tire—is the correct diameter (31.6 inches). It has a load capacity of 2,679 pounds, so keep that in mind if that’s your selection. The Blizzak WS-80 is also a stellar performer with the same load rating. If you need to carry heavy loads/tow during the winter, then the LT is the best choice because it has an “E” load rating (3,195 pounds) like your rig’s stock tires. The LT, however, won’t provide as much traction on snow-covered roads as its two siblings, because it has fewer gripping surfaces and a different tread design. By the way, mud/traction tires are worse than street tires in the snow/ice, while all-terrain treads are slightly better. But only dedicated snow tires (those with the Three-Peak Mountain Snowflake symbol) provide the best traction on plowed or packed-snow driving conditions. Also, today’s “studless” winter tires provide as much traction on snow as studded versions, and they are quieter and kinder to the road surface.

6.7L Turbo Upgrade

QUESTION: I have a ’13 Ford F-350 equipped with an Edge Products programmer, along with a cold-air intake and aftermarket exhaust. What are the best turbocharger upgrades out there that won’t break the bank? I want a little more power when towing hay trailers and ranch equipment.
Randy Luscombe
via email
ANSWER: There are several turbochargers that can be used to replace the problematic twin-style compressor blades and shaft on the 6.7L Power Stroke engine. BD Diesel Performance’s Scorpion turbo kit is based on a BorgWarner S364 and is an excellent combination for towing. “I also recommend our air-actuated exhaust brake for safety and durability, as well as the Flow Max lift pump and filters,” says BD President Brian Roth. “The pump’s lifetime warranty protects a 6.7L from the stock CP4 failing from lack of supply-fuel pressure,” Roth says.
Another good option is Industrial Injection’s Viper PhatShaft 63/68 turbo, which Industrial’s Alec Hembury says features a forged-mill compressor wheel for faster spooling and dual-groove bearings for maximum oil flow. Another popular upgrade is swapping out the CP4 for a CP3 injection pump. It’s better to make the change before the CP4 fails, otherwise you could be looking at a complete fuel system replacement instead of just the pump.

Broken Shift Lever

Photo 5/7   |   Broken shifters on Ram pickups with the G56 six-speed manual transmission are not unusual. The most common break is at the rubber vibration isolator, just above the point where the handle attaches to the shift mechanism. A common fix is to cut off the isolator and weld a short piece of thin-wall DOM steel between the two shafts.
QUESTION: What is the best way to repair the shift lever on a six-speed manual transmission? The shifter on my ’10 Ram 2500 busted at the large round tube (with rubber in the center) near the middle of the lever. Can I just weld a piece of steel tube in there to hold the two halves together?
Matias Malnati
via Facebook
ANSWER: The shift lever breaking at the rubber damper is a common issue, and, yes, you can cut off the damper and weld the two pieces together. TIG-welding a short piece of DOM thin-wall tube that has an inner diameter large enough for the shifter rods is a good fix and looks similar to the stock setup. However, eliminating that original damper may increase some transmission harmonics through the shift lever and transmit a little more noise into the cab. Another option to consider if you don’t want to replace the shift lever with a stock one is installing a one-piece, short-throw lever such as the one offered by Ohio Diesel Parts (p/n TRK-1038S).

Low-Speed Miss

Photo 6/7   |   Done properly (by only using the upgrade parts manufactured and offered by Bullet Proof Diesel), “bulletproofing” 6.0L Ford Power Stroke engines corrects the well-known shortcomings of stock powerplants. However, owners should also be vigilant about upgrading and maintaining the injection system with aftermarket lift pumps and filters to ensure a long engine life.
QUESTION: My ’06 Ford’s 6.0L Power Stroke diesel engine misfires on normal acceleration and when cruising along at lower rpm and up to 40 mph. Run it hard and all seems fine. There are no diagnostic trouble codes according to the service technician at the Ford dealership I take it to for service. I bought the truck used with 64,000 miles on it because it “had just been bulletproofed,” according to the Ford paperwork. The problem is concerning, as I thought I was getting a trouble-free truck.
C.W. Baines
via Internet
ANSWER: If your truck’s engine has a misfire under light throttle or steady cruise at lower rpm, it should be easy to detect by a scan tool, using the Power Balance test that monitors each cylinder. This applies to just about any diesel. The best tool for a Power Stroke, of course, is the Ford Integrated Diagnostic System. Expensive, but worth the price for a diesel repair shop.
“Monitoring Power Balance using IDS is very accurate and never misdiagnoses a problem in my experience,” says Kenneth Tripp, a former Ford engineer and owner of Tripp Trucks in Rock Hill, South Carolina, a highly respected diesel-repair shop. “If you can make the truck repeat the concern consistently, have the technician ride with you while he monitors the Power Balance, and that should identify which cylinder is misfiring. Just because there are no trouble codes doesn't mean anything, and frankly, I never go off of those codes anyway.”
Ken also says just because a 6.0L has been upgraded with cylinder-head studs, new oil and EGR coolers, a water pump, and fuel-injection-control module doesn’t mean everything related to the engine is trouble-free. “The process doesn't really involve anything to do with the fuel-injection side of things, aside from the high-pressure oil system and fuel-pressure-regulator upgrades,” Ken says. “But if all the updates are done and studs are torqued correctly when the work is done, you should have a reliable engine for many years.” We recommend performing a full service regardless of what a seller says has been done. “Proper oil changes and adequate fuel quality and pressure are the lifeline of the fuel injectors on the 6.0L Power Stroke,” Ken adds.

Tune for Towing

Photo 7/7   |   Even though Ram 2500/3500HDs may share the same running gear, they have different trailer-towing limits based on meeting SAE J2807 testing requirements. Contrary to some beliefs, flashing a 2500’s ECM with the same calibration as a Ram 3500 or installing heavier springs, hitch, brakes, and other components, will not change the factory tow ratings for that make or model truck.
QUESTION: My truck is a four-wheel-drive ’15 Ram 2500. Can the ECM be reprogrammed with the same settings as the 3500 for more towing capacity, since they have the same 6.7L Cummins engine and 68RFE automatic transmission? I asked my local Ram dealer about doing just that, and they didn’t have an answer.
Raphael Rojos
via email
ANSWER: Nothing you do to a pickup will increase its hauling or towing capacities, because they are set in stone by the manufacturer—like the VIN. You can add a programmer, helper springs, bigger sway bars and shocks, and a huskier hitch or even change axle ratios. It may help improve handling and power, but the bottom line from a legal (read “liability”) standpoint is the manufacturer’s rating remains unchanged for that engine, transmission, and axle ratio as it came from the factory. Towing above that limit places all liability on the driver of the vehicle should it be involved in an accident. In addition, if it is still under warranty, whatever components have been changed/modified will be voided. Towing “heavy” can also result in fines if a weigh master or DOT enforcement officer wants to be a stickler on the topic. The reason the vehicle manufacturers place cargo/towing limits on their vehicles is because they have determined—through extensive on-road and track testing in accordance with a meeting regime of requirements in SAE standard J2807—that’s the maximum safe level that particular truck’s cooling, braking, steering, suspension, axles, and drivetrain can handle. Part of the J2807 testing includes accident avoidance maneuvers.
Furthermore, reprogramming the ECU will have little effect on towing capacity in the first place, as your truck’s engine and transmission are already tuned the same as they would be in an equivalent Ram 3500.

Learning Curves

QUESTION: I’ve always wanted a diesel, and now I have my first one: an ’08 Dodge Ram 2500 with a six-speed manual transmission. I’m 23 years old and have only driven pickups with automatics, and I’m having a little bit of a challenge shifting smoothly. Sometimes I get a little gear grind. Could there be a problem with the transmission that is making it so difficult—or is it the “young gun” behind the wheel?
Robert Strebb
via the Internet
ANSWER: Congratulations on your first diesel! Stepping away from an automatic and moving to a manual six-speed also deserves credit. Many Dodge Ram owners have found replacing the G56 transmission’s synthetic ATF with a synthetic SAE 50 lubricant, and over-filling by 1 quart, helps improve shifting. (Beware that over-filling a transmission, differential, transfer case, or other component that runs gearsets can cause aeration of the oil, and, as a result, cause degradation of cooling). Others have found combining a quart of Amsoil 5-30 Synchromesh with a synthetic 50-weight engine oil is a good combination. However, the lubricant inside the manual transmission is just a small part of achieving smooth shifts with a Cummins/G56 six-speed package. It’s the driver that really makes the difference. Seasoned owners of manual-equipped diesel pickups (and most race car drivers) know the secret to making smooth, slick shifts: double-clutching. It’s a very basic concept—letting the transmission gears match the speed of the engine before making that shift up or down. When you want to shift up, say from Third to Fourth, push the clutch in, lift off the throttle for a second, shift to neutral, let the clutch out, wait a brief moment, then push the clutch back in, and slide shifter into Fourth. That brief clutch in/out/in period allows the engine and transmission gears to be closer to the same rpm they would by just trying to slam the shifter home in one motion, which usually results in a little gear grinding. The same principle applies to downshifting: clutch in, shift to neutral, clutch out, blip the throttle so engine rpm comes up a couple hundred, then clutch in and make the downshift. Once you get the hang of it, making smooth shifts becomes second nature—and fun. Drivers that are really good at it can shift up and down through the gears without touching the clutch once the truck is rolling, just like professional big-rig drivers. One other item of note to consider when driving diesels with manual transmissions: Keep your foot off the clutch pedal when you aren’t shifting. “Riding” the pedal tears up throw-out bearings. Keep your left foot on the floor until it’s time to shift, double-clutch while making the shifts, and you’ll be good to go.

Overheating 7.3L

QUESTION: I have an ’00 Ford F-250 I use to haul a small backhoe to job sites. The trailered load is about 10,500 pounds. The truck never misses a beat and runs great, but the 4R100 automatic transmission’s and 7.3L engine’s temperatures creep way up in stop-and-go traffic and on long grades. I am thinking the fan clutch may be bad, causing both issues described. I have an electric fan running continuously on the outside of the transmission cooler. Your thoughts?
Lester Holtz
via email
ANSWER: One of the common upgrades ’99-to-’03 Ford Super Duty owners make is replacing the stock transmission cooler with one from an ’03-to-’07, which has a very robust cooling design. It’s a simple swap that usually results in temperature drops of 20 to 25 degrees across the board. The original transmission cooler on the ’99-to-’03 7.3L trucks is a puny 9-row piece compared to the 31-row version used on the later-model rigs. You should also check a few other items: The torque converter could be going out, causing excessive heat buildup, and/or the fan clutch and water pump need to be replaced. But first, whenever there’s an overheating issue with those older engines, it’s a good idea to thoroughly flush the cooling system and replace the thermostat, then check off the other components that are integral to the cooling system as a whole, if a problem is still there.