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Your Diesel Questions Asked and Answered

You’ve Got Questions, We’ve Got Answers

Bruce W. Smith
Sep 5, 2019
Baby DMax Biofuel
QUESTION: Chevrolet says the 2.8L Duramax LWN engine in my '17 Colorado is B20 compatible. What would happen if I ran it on a fuel with more bio than that? Why not B100? (I'd love to start home brewing.) What mods would be necessary to burn B100 in a 2.8L Duramax?
Marc Simpson
via email
Photo 2/6   |   Using biodiesel fuels in engines that exceed the factory recommendations, such as using B100 instead of B20 in the GM 2.8L Duramax LWN, can lead to serious fuel-related mechanical issues and void the factory warranty.
ANSWER: First, it's important to understand that B20 and B100 diesel fuels are as different as apples and oranges. A decade ago, many diesel owners were asking the same questions with hopes of becoming biodiesel moonshiners. A white paper on the topic was written by the National Biodiesel Board (biodiesel.org) entitled "Guidance on Blends Above B20." According to that detailed report, B100 has a number of shortfalls that should discourage any owner of a modern diesel from using home-brewed biodiesel fuel like the proverbial plaque. Among B100's shortfalls are: cold flow properties where B100 starts to gel around 32 degrees (or warmer) Fahrenheit; B100 softens and degrades certain types of elastomers and rubber compounds over time, like those found in older trucks' fuel systems; B100 acts as a cleaning solvent that can dissolve any sediments left in the fuel tank and lines from #2 diesel fuel, clogging fuel filters; B100 has stability and degradation issues, so it has to be used shortly after it's made and shouldn't be stored for more than six months; B100 has about a 9 percent lower energy content than #2 diesel, which has a negative impact on both power and fuel economy; and blends higher than B20 can cause a large amount of unburned fuel to make its way past the piston rings and into the oil pan because the biofuel's viscosity is higher than B20 or #2 diesel fuel; use of B100 can also lead to engine oil sludge problems; B100 adversely affects lead, cast iron, zinc, and tin. Luke Langellier at S&S Diesel Motorsport says, "B100 users should also be aware it can create issues with common rail fuel systems, primarily due to how it interacts with water. Rather than moisture in the tank settling out, biofuel tends to carry the water in suspension and transport it through the rest of the system. It's not uncommon for us to get injectors or pumps in for testing that have been sitting for an extended period of time, and corrosion or scaling has occurred in the components, ruining them. We can often tell by appearance and smell if they had biodiesel." So, all these concerns need to be considered if you plan on home-brewing B100, including controlling impurities and variances in quality from batch to batch.
 
Maximizing MPG
QUESTION: I own an '06 Ford F-250 and want to know how I can obtain better fuel economy than the 13.5 mpg town/highway I'm seeing from the 6.0L Power Stroke engine. The only things I have added are a 4-inch straight pipe from the turbocharger back and Gearhead's SLR+ ECM tune. I've also added a 4.5-inch lift with 35x12.50R20 tires. Axle gearing is stock 3.73.
Jake Roberts
via email
Photo 3/6   |   Lift kits and bigger tires are common ways to personalize one's ride and give it more ground clearance. But doing so has negative effects on fuel economy that come from a combination of increased aerodynamic drag, heavier rolling mass, and other factors. Vehicle speed also has a significant effect on reducing fuel mileage.
ANSWER: The vast majority of our Diesel Power readers love to personalize their rides, which includes installing custom ECM tunes, lifts, tires, and wheels. Such modifications really change both the look and overall performance of a diesel pickup. However, the changes come with at least one hit on performance: loss of fuel economy. Check with the person who wrote the calibration for your truck's engine to see if he or she did so with fuel economy in mind, or power, or both. If it's the latter, ask at what engine rpm on the fuel map the tune controls the engine to achieve the best fuel economy. From a mechanical aspect, what you are seeing is the role aerodynamics and friction play in ruining fuel economy in any vehicle. Any time the height of a vehicle is raised— especially pickups and SUVs, which have very high frontal mass, blocking wind flow, i.e. creating drag—fuel economy takes a hit. The higher the lift and the wider and taller the tires, the more drag is created. Lifting the truck allows more wind to flow beneath it. That wind catches and tumbles over and around axles, springs, exhaust, and anything else that isn't smooth. Taller, wider tires add to drag and induce more rolling resistance. Bigger tires and wheels are also heavier, which means the engine has to use more fuel to get the truck moving and to maintain speed. Taller tires also change the truck's final drive ratio, which, in turn, means you have to use a heavier right foot to accelerate and maintain speed than you would when the truck is stock. It also means the engine rpm is now lower (than stock) at your intended cruise speed. That probably means the engine is at an rpm lower than its mpg sweet spot for that speed. The optimum engine speed for balanced power and fuel economy in some light-duty diesels is about 100 to 150 rpm more than the engine's maximum torque rpm for whatever cruising speed you are trying to maintain; others may be 150 to 200 rpm below the engine's maximum torque rpm. You will have to perform tests with your truck to see which gives the best mpg number. By the way, the 6.0L Power Stroke's maximum torque comes in at 2,000 rpm. (Re-gearing to bring the final-drive ratio back to what it was before the lift and tires helps restore acceleration performance, but it doesn't regain lost fuel economy because of the factors noted above.) There's also vehicle speed to consider. Speed has as much or more impact on reducing fuel economy as weight and rolling resistance. The negative affect of aerodynamic drag on fuel economy really begins around 50 mph, and above 60 mph the negative effect drag has on fuel economy is exponential. According to research conducted by the Department of Energy, vehicle manufacturers, and others who study the effects of wind drag on vehicle fuel economy, 50 to 55 mph is the optimum speed window for best fuel economy. The studies also show the typical car, which has far sleeker lines than our big diesel pickups, takes a fuel-mileage hit as speed increases:
- 3 percent less efficient at 60 mph
- 8 percent less efficient at 65 mph
- 17 percent less efficient at 70 mph
- 23 percent less efficient at 75 mph
- 28 percent less efficient at 80 mph
Take away another 1 to 2 percent from all the above for a pickup's bigger size, and you can determine if your 6.0L Power Stroke is getting 18 mpg in stock trim. Driving 65 mph will cut mileage by about 1.5 mpg. A speed of 70 mph will decrease fuel economy to about 14.5mpg. (A fun speed/mpg calculator can be found at mpgforspeed.com.) Now add in the negative impact the lift, tires, tune, and gearing play in the overall scheme of mpg, and it's easy to see why your F-250 has a combined city/highway of only 13.5 mpg. Our suggestion to improve that number is to always drive with a light right foot and keep your highway cruising speed close to 55 mph.
 
Snowplow Trans Cooler
QUESTION: The transmission on my '08 Ram 2500 gets warm when plowing snow in mall and business parking lots. Would installing a small fan to the torque-converter cooler next to the engine help cool things down?
Mark Thompson
via email
 
ANSWER: That stock transmission cooler you are referring to is just a tiny heat exchanger and adding a fan to it probably won't result in any noticeable difference when it comes to reducing the transmission-fluid heat generated when plowing snow at slow speeds. What most snowplow operators do is add an auxiliary transmission cooler equipped with an electric fan and thermostat that functions like a real radiator. Some owners stack a pair of auxiliary transmission coolers in front of the radiator. But when plowing at slow speeds, that additional airflow restriction in front of the radiator isn't a good idea. Our suggestion is mount the thermostat-controlled auxiliary cooler, such as those offered by BD Diesel Performance, Derale, and Flex-a-lite, fan-side down under the truck between the frame and transmission. Get the biggest auxiliary cooler that fits in the mounting space. Installing a transmission cooler in this fashion pulls cold air upward and through the cooler, maximizing the heat transfer (the cooler could also be mounted vertically). Mount the cooler above the lowest part of the frame or transmission crossmember to protect it. Also, put the thermostat on the inlet side and install a switch on the dash or console so the fan can be turned On and Off manually. An auxiliary transmission-cooling setup is also an excellent way to extend the automatic's service timeframe for trucks with tall tires that are driven off-road in sand or mud.
 
OEM Air Suspension
QUESTION: I'm finalizing my plans for trading in my '14 Ram 2500 for a '19 Ram 3500 dualie so I can tow a 40-foot fifth-wheel toy hauler during the summer months. The rest of the time it will be used to tow much smaller, lighter trailers around the ranch—or be driven empty. What's your opinion on getting the Ram air suspension package? Is it worth the cost? Will it make the truck ride like concrete when I'm not towing?
Shawn Hollister
via email
Photo 4/6   |   Image Courtesy of Ram MediaAftermarket air suspensions for Ram heavy-duty rigs cost less money than the air suspension option offered by the manufacturer. But you won't be getting the integrated electronics that can lower the rear of the truck with a touch of the infotainment screen to ease loading/unloading trailers, a trouble-free onboard air system that self-levels the truck according to the load, a "lower" axle ratio that provides better towing performance, or a factory warranty that covers all the above.
ANSWER: Ram Truck's optional Auto Level Rear Air Suspension (Code SEB) is included in the Max Tow package (Code AJL), which also includes Mopar's 30,000-pound direct-mount fifth-wheel Hitch option (Code XNH). The Max Tow Package also sets the truck up with a 4.10 gear ratio and a gross vehicle weight rating of 14,000 pounds. By ordering the Max Tow option package, you will be all set to pull that 40-foot toy hauler—and probably any other fifth-wheel trailer. Sure, you can get an aftermarket fifth-wheel hitch and rear auxiliary air suspension for a lot less money. But you won't be getting the integrated electronics that can lower the rear of the truck with a touch of the infotainment screen to ease loading or unloading trailers, a trouble-free onboard air system that self-levels the truck according to the load, a "lower" axle ratio that provides better towing performance, or a factory warranty that covers all those components. As for ride quality, the air suspension is supplemental to the rear leaf springs, so the truck shouldn't ride any firmer when it's empty than an identical model that didn't have the auto-level rear suspension system.
 
Pulling Its Weight
QUESTION: My tow vehicle is a '14 Chevrolet 2500 with 3.73 gears and AirLift 5000 airbags. I'm looking at buying a 41-foot Heartland Gateway fifth-wheel RV trailer that has a dry weight of 13,000 pounds, GVWR of 15,500 pounds, and a dry hitch weight of 2,020 pounds. I was wondering how legal I am by weight and if my truck is good to go when it comes to towing such a trailer?
Scott Sheldon
via email
 
ANSWER: You're good to go, but by the smallest of margins. The 2014 Chevrolet Trailering Guide shows your model has a maximum fifth-wheel/gooseneck trailer towing capacity of 15,800 pounds. That model Gateway has a maximum load capacity of 2,500 pounds, which you'd probably never exceed. Rear air springs are definitely a good addition to help keep the truck level and give it better stability in turns. You will also find that installing aftermarket sway bars front and rear will make a significant improvement in reducing body lean when you're trailering or hauling near maximum capacity. We've employed Hellwig Products Big Wig sway bars in the past and found them to be a welcome addition in setting up a pickup for heavy hauling or towing.
 
IDI E4OD
QUESTION: My grandfather just handed me the keys to his '94 Ford F-250. My grandparents only used it to tow their travel trailer, and the truck was always garaged and well maintained. The odometer reads 235,000 miles. The7.3L Power Stroke engine purrs, but the E4OD four-speed automatic transmission feels like it's a little sluggish when it shifts, especially going into Fourth gear. I plan to have it rebuilt. Will installing a shift kit help? I would like to keep the truck pretty much stock for towing my RZR.
Bradley Abrams
va email
Photo 5/6   |   E4OD four-speed automatic transmissions were used in Ford trucks from 1989 to 1997. During that time, they went through many internal design changes, especially in the latter years, to accommodate the first 7.3L Power Stroke engines. E4ODs evolved into the 4R100, which makes it easy to rebuild an early F-250 or 350's transmission into a very strong hybrid E4OD/4R100.
ANSWER: Those early E4ODs, used in Ford trucks and Broncos from 1989 to 1997, went through several internal-design changes, especially in the latter years. The transmissions from '94 models and into mid-'97s saw the biggest modifications, because they had to handle the torque of the turbocharged Power Stroke diesel engines. Those modifications finally led to the E4OD evolving into the 4R100. According to Phil Mitchell, the lead technician and E4OD/4R100 rebuilder at Geezers Garage in Coburg, Oregon, it's easy to rebuild your early E4OD into a very strong hybrid E4OD/4R100. He's rebuilt more than 1,000 of those generation Ford automatics during a couple of decades working for AAMCO, and now at Geezers Garage. Phil suggests using a mix of "like-new" used '97 Power Stroke E4OD and '98 4R100 components to replace some of the weaker parts common to the '89-to-'95 F-150/F-250/Bronco transmissions. One of the most critical upgrades on any pre-'95 E4OD is replacing the center support and center shaft with parts from a '97 E4OD or any 4R100. Another critical upgrade is replacing the stock E4OD aluminum planetary gears found in those early E4ODs with steel versions found in 4R100s and Super Duty E4ODs. He also suggests using high-performance 4R100 Alto PowerPacks that have Red Eagle frictions and Kolene steels for all the clutches, along with installing a good shift kit like the "Tugger" from TransGo. Installing an F8 pump and TransGo 4R100 LU boost valve, replacing the three-friction E4OD direct drum with a four-friction version from a V-10 4R100 transmission, and replacing the two overdrive clutch steels and frictions with four thin ones make a world of difference. Doing this kind of hybrid rebuild will give you a stout '97 Power Stroke E4OD/'98 Super Duty 4R100. Along with the rebuild, you should look into installing a matched torque converter. TCI Automotive's "E4OD Maximizer" might be a good option for this particular application. Make sure you use Mercon/Dextron III ATF, too, as using the wrong transmission fluid will quickly destroy the clutch frictions.
 
7.3L Hiccup
QUESTION: I have an '02 Ford F-250 with 131,000 miles on it. The Check Engine light comes on when the engine is started and it runs rough—almost as if it has a problem with the injectors. I had the diagnostic trouble code (P1316/injector module) cleared, but it keeps coming back. If I drive 15 to 20 miles, the engine smooths out and the Check Engine light goes away. This is very puzzling. Could something be amiss with the wiring harness for the injectors or the injector drive module?
Jason Robbins
via email
Photo 6/6   |   A common trouble issue with 7.3L Power Stroke engines is loose connections at or in the under valve cover harness that controls the injectors and glow plugs. A scan tool is the best way to check the integrity of the UVCH. But an ohm-meter can also be used. If the two outer pins read 0.8 to 2 ohms, it's good. The next two toward the center pin should read less than 5.0 ohms.
ANSWER: The P1316 diagnostic trouble code just lets you know there are additional codes stored in the injector drive module. "You need a scan tool capable of performing an injector electrical test (buzz test)," says Kenneth Tripp of Tripp Trucks. "When you run the buzz test, it will display codes stored in the IDM. Only then can you properly diagnose the problems." Kenneth says a last-resort test sans the proper scan tool is disconnecting each harness plugging into the valve cover gasket and checking the pins with an ohm-meter or test light. With the test light lead connected to the Positive post (+), touch each of the outer two pins both on the left and right sides of the valve cover gasket itself. Doing so checks the injectors-to-glow-plugs connection. If the connection is completely broken, the test light shouldn't light. Kenneth warns that if the truck is of higher mileage and it has faulty glow plugs, this way of testing could send you on a diagnostic goose chase. The integrity of the under valve cover harness can also be checked with an ohm-meter. Use the meter to check the two outer pins on each side as noted above. They should read 0.8 to 2 ohms. The next two toward the center pin should read <5.0 ohms. If no test light or ohm-meter is available, remove the driver-side valve cover and inspect the injector-to-glow-plug harness and its connection with the valve-cover gasket. The '99-and-up harnesses, although redesigned to one single connector to "fix" the '94 -to-'97 7.3L engines, are prone to melting the connectors and gaskets and becoming disconnected under the valve cover. If this is the case, Ford sells a retainer clip kit to fix this (2C3Z-14A163-AB). Kenneth says "No, you don't have to replace the gasket and injector harness. Just install the new retainer clip kit." If the harness is bad, use the OEM replacement, not an aftermarket version, because Ford's has the locking clip and provisions to keep the valve cover from damaging the harness when it's bolted back on. While you are looking at the valve cover and connections, make sure the bolt-together connection, where the harness goes directly over the driver-side valve cover, isn't rubbing on the cover, creating an intermittent short. Obviously, a harness connection concern isn't the only possibility of what is causing your engine's issues. It could also be a faulty IDM, wiring harness, or injector coils. (Check out our 7.3L "Top-End Reseal" article on this topic: trucktrend.com/how-to/engine/1706-tips-to-make-ford-7-3l-top-end-re-sealtune-up-easier/).

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