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Diesel Tech Questions

Top Tech: You've Got Questions? We've Got Answers!

Bruce W. Smith
Dec 7, 2016
Photographers: Bruce W. Smith

Leaky 6.2L

I have a Chevrolet 1¼-ton military pickup configured with a 6.2L diesel engine. It’s in good condition and only has 66,133 actual miles on the clock. There’s a constant oil leak under the engine. Everyone tells me this is something I just need to put up with because it's characteristic of the 6.2L. However, I'm not the kind of guy who likes to just put up with stuff that doesn't work right. Can you folks help me understand how I can get this truck to stop leaking engine oil?
Joe Tinnerello
Via email
Tracking down the cause of mysterious oil leaks is nearly as bad as getting to the bottom of mysterious electrical problems. Oil leaks can usually be easily traced to their source with a visual inspection—if the engine is clean. For the oil leak on your 6.2L powerplant, a friend who just retired after spending 20 years as a diesel technician for both the Air Force and Sea Bees says nine times out of ten the culprit is the rear main seal. The oil-pan gasket is another major leaker. Military trucks can sit for long periods of time without being used, so seals and gaskets tend to dry out, crack, and leak.
But before you dig out the tools, clean the engine. The military’s mechanics attack such issues the same way the guys at Mobile Diesel Service (mobildiesel.co) do: “We solvent-wash the engine, blow it completely dry, run it, and watch for the leak,” says MDS owner Shawn Smalley. “You just waste time by speculating. We learned years ago that there’s no use tearing anything apart until you see where the leak originates. If the engine is clean, you’ll see where the oil is coming from and be able to make the necessary repairs.”
Although keeping an engine and engine compartment clean may seem a bit obsessive-compulsive to some folks, it really is a part of preventive maintenance, allowing you to see potential trouble before a small oil, fluid, or fuel leak turns into a much bigger problem.

Gallons Gone

I have a ’95 Ford F-350 that’s been my daily driver for more than 15 years, and I hope to drive it for another 40. The odometer shows 185,000 miles. What could cause a sudden drop in fuel economy? The truck is a dualie with a 7.3L Power Stroke engine that’s set up with a Banks Power PowerPack system. Its E4OD four-speed automatic transmission is rebuilt. Around town, fuel mileage has always averaged 13.5 mpg. Then I saw it drop to about 12.25 mpg, with no noticeable change in performance. I checked mpg over several tanks, and the new lower mileage is as consistent as the higher fuel economy was before. I removed the chip from the computer and saw no change, so no apparent malfunction there. I’ve had the ECM checked, and there are no diagnostic trouble codes. Do you have any suggestions? I also wanted to tell you I love the magazine, but I sure would like to see more OBS Ford articles!
Charles Renes
Tustin, California
There are a multitude of possibilities for fuel economy loss without noticeable drops in normal performance. You have to go down the checklist until you find the mileage-sucking culprit. A change in tires or tire size, traffic flow or driving conditions, weather, or fuel with lower cetane all have a negative effect on fuel economy.
Mechanically, the injectors may be partially clogged, which will definitely affect fuel economy without a noticeable difference in power until you’re trying to tow a heavy load. It would be wise to check the condition of the turbocharger up-pipes; even the smallest leak will reduce turbo efficiency and drop mpg. The same goes for the charge-air pipes. Also, check the mass-air-pressure sensor and the tube that feeds it.
Alec Hembury at Industrial Injection (industrialinjection.com) says, “I have seen a few things cause it. A vacuum leak, brakes dragging somewhere, I even had one where the water pump was starting to go out and load down the engine, causing bad fuel economy. It could even be that the warm-up valve behind the turbo is having issues.”
As for no diagnostic trouble codes being triggered, our friend Mark Gotchall at Oregon Fuel Injection says the ’94-to-’97 Power Stroke engine’s ECM “is not very good at codes when there is a problem. You often have to drive the truck with a scan tool hooked up in order to see what PIDs (parameter IDs) are out of ‘normal’ range.” He also adds the exhaust backpressure sensor could be out of range or the fuel supply pressure not at the level it should be.

Moving Backward

I am currently in the middle of swapping a ’96 7.3L Ford Power Stroke engine into a 7.3L IDI-powered ’94 truck. I’ve got the computer and engine harness from the donor truck. What other wiring do I need to change?
Nate Kimball
via email
Upgrading an older truck with an engine and transmission from a newer model, even if there’s only a couple of years’ difference between the two, isn’t as easy as one might expect. You have to move all the newer technology into the older rig. So you are on the right track by using the newer 7.3L’s wiring harness and computer.
Diesel experts we talked with, including Aden McDonnell at GOS Performance (gosperformance.com), say you’ll actually need everything electrical from your donor truck to make the swap work properly. That means in addition to the engine harness and ECM, you’ll need the injector drivers, as well as the dash wiring harness and instrument cluster if you want everything to function in the older truck as it would in a newer one.

Mystery Power Loss

I have an ’03 Dodge Ram 3500 with the six-speed manual transmission. The engine seems to have lost quite a bit of power, even though it has a FASS fuel system, S&B cold-air intake, Southbend clutch, straight-pipe exhaust, and new turbocharger installed. Do you have any ideas on what could be causing the loss of power?
via email
Photo 2/4   |   A number of readers ask about their older trucks’ engines losing power and how to solve the problem. Being able to diagnose this issue requires answering a long list of if/then-type questions, as there are many, many forks in the diagnostic road. The more specific details you provide us, the more likely we can point you in the right direction to a solution.
There are way too many variables for us to be able to point at one cause for your truck’s 5.9L Cummins engine’s power loss. Have any diagnostic trouble codes been triggered? Did the power loss come immediately after the fuel system upgrade was done or months later? What is the cetane rating of the fuel you’re using? Is the turbocharger making the proper amount of boost? Is the fuel-rail pressure within specifications? How many miles are on the engine? Are the injectors in good shape? Being able to diagnose such an issue requires answering a long list of “if/then” questions. There are many, many forks in the diagnostic road.

Off the Grid

The grid-heater light on my ’04 Dodge Ram 2500 continues to appear after a factory re-flash of the ECM. Since then, the truck has been to our local Ram dealer four times and the problem is not corrected. I have work orders totaling $2,500 without any results. Pulling our 30-foot trailer is the only thing we use this truck for. We really need a cure. Please help!
Larry Busbee
Flagstaff, Arizona
Do the seatbelt chime and grid-heater light come on at the same time? Did the dealership technician use a diagnostic trouble code scan tool and provide you with any error information? Which parts have been replaced thus far? That information will be helpful for diagnosing the problem.
Mark Gotchall at Oregon Fuel Injection (oregonfuelinjection.com) says, “There is most likely a cure. But we would need more detailed information before being able to pinpoint the cause of the problem. Our best guess, without knowing more specific details, is a loss of rail pressure at higher rail-pressure demands. It’s a common problem with that era engine.”

Six-Liter Performance

I just read the September 2016 issue and the article on water-methanol on the ’12 Ford F-250. Would water-methanol be a good add for my ’04 F-250? I tow a 14,000-pound trailer and need more power. My truck is a work in progress, and I am always interested in any aftermarket power-adders. The 6.0L engine has 130,000 miles, it’s studded, and the ECM is flashed with a performance tune. I’m also contemplating a new turbocharger, but I don't want to make this a race truck. Which turbo do you recommend with the stock injectors? Which tuner do you recommend? My goal is to make more power while keeping it dependable.
Buddy McKenzie
via email
Photo 3/4   |   Ford’s 6.0L diesel engines have their issues. However, when those concerns are addressed, the engine is a very strong runner.
Making more power and keeping your engine “dependable” is a very tough tightrope to walk. More power brings with it more internal stress. Your question about upgraded turbochargers and programmers is a lot like asking someone which manufacturer builds the best diesel truck. Everyone has an opinion.
For example, Ford Super Duty Service (sdutys.com) performs a lot of Garrett PowerMax Stage 1 turbocharger and SCT X4 programmer upgrades on 6.0L engines according to shop owner Anthony Youngblood. “A PowerMax can be bolted on and run as-is. But a custom ECM calibration that includes tuning the PHP FICM can help maximize the full potential of any upgrades. The majority of the engine’s power is gained through tuning—not by adding aftermarket parts. While the bolt-on pieces are effective, at what point do we lose reliability? I always ask customers whether they want to ‘use’ their truck, or ‘play’ with their truck. The ‘players’ are OK with turning a wrench every week or two. The ‘users’ generally just want to do routine maintenance.”
Mike Dunks at Dunks Performance (dunksperformance.com) also likes Garrett’s turbo and the SCT programmer, along with the addition of a 4-inch exhaust. “If this was one of my towing customers, I’d also highly encourage him or her to run an Edge Insight with EGT probe for engine monitoring,” says Mike.

Muscle Up a 12-Valve

I have a stock ’95 Dodge Ram 2500 with a 5.9L Cummins engine and automatic transmission. What would be the list of parts needed to make 350 to 400 hp while towing and daily driving?
Randy Loewen
via email
Photo 4/4   |   Doubling the power from 12-valve 5.9L Cummins engines takes little more than a bigger turbocharger to flow more air and fatter injectors to bump up the fuel. Adding freer-flowing intake and exhaust manifolds also increases its breathing and gain in power.
That’s a relatively easy goal to achieve, and a story in our August ’16 issue (“12-Valve Rebirth”) details an engine rebuild that brings the kind of performance you want. We suggest installing 60hp injectors, a rebuilt P-pump, a slightly larger turbocharger such as a BD Diesel Performance Super B, and a new intake manifold and downpipe. We also recommend using ARP head studs. Those upgrades should put your truck’s 5.9L into the 350 to400hp range. Increasing airflow, fuel, and boost, plus getting the exhaust out faster, all contribute to improving power and reliability.
Brian Roth, the owner of BD Diesel Performance (bddieselperformance.com), suggests replacing the exhaust manifold, because “it’s likely on its last legs and should be changed, rather than waiting for it to crack from the higher EGT that will be generated by the new power level.” He also recommends upgrading both the torque converter and transmission to support the higher torque levels that come with more horsepower.



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