Diesel Tech Questions
Idle Thoughts?QUESTION: I inherited an ’01 Ford F-250 with 238,000 miles on it. The truck was used primarily to tow cattle and hay trailers. The 7.3L Power Stroke engine runs pretty good despite its fair share of little oil leaks. I don’t know the service history other than the previous owner is said to be meticulous about taking care of his equipment. After driving the truck for a couple of months, I noticed the engine runs quieter when it’s cold than it does when it’s warmed up. And when the engine is warm, it sometimes starts making an odd knock at idle and the rpm fluctuates. It starts fine in warm or cold temperature but puts out some bluish smoke, which goes away after a minute or so. I’ve changed the fuel filter, which didn’t appear to be dirty, and changed the oil. A neighbor performed an ECM scan, but it didn’t produce any codes.
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ANSWER: We covered a Ford 7.3L top-end “reseal” in our September 2017 issue in which the truck’s engine had some of the same idle symptoms you describe—in addition to a pile of annoying little oil leaks around the valley. When the injectors were removed, we found two of the eight had split lower O-rings. That could very well be the case in your farm truck, based on the fact you don’t mention any oil contamination in the fuel bowl. Typically, if the upper injector O-ring, which seals the fuel gallery from the oil gallery, is leaking, some of the oil from the high-pressure oil pump is forced into the fuel gallery and makes its way back into the fuel filter bowl, turning the filter black. The same holds true with the middle O-ring. However, if the lower O-ring fails, there are usually no obvious signs. Since the cylinder isn’t getting a good burn, some blue-white smoke occurs. There are multiple reasons why injector O-rings fail, the most obvious being age and normal wear if they have never been changed. O-rings wear out from heat and pressure. If the injectors have been replaced, the problem could stem from improper torque, which seats it against a copper sealing washer. Poor positioning can allow combustion heat/pressure to damage the lower O-ring. Damage can also occur while pushing the injector into the fuel rail if the O-rings aren’t lubricated properly, or the installation isn’t done with some care.
Variable-Vane Turbo WoesQUESTION: Our ’07 Chevrolet Silverado 2500HD displays a check-engine light associated with diagnostic trouble code P003A. We've been told this means the engine has a stuck variable-vane turbocharger. Is there a fix I can do myself? I would appreciate any help you can offer. We are 100 miles from the nearest city with reputable diesel mechanics, so I do most all repairs.
ANSWER: You are correct. A P003A diagnostic trouble code means there’s a problem at the turbocharger. It could be either a vane-position sensor has failed or the vanes and actuator inside the turbo are gunked up with carbon deposits, unburned oil, and rust (probably on the unison ring they ride on). Either of these scenarios prevents the variable vanes from functioning properly. (More information on how the variable vanes work: toxicdiesel.blogspot.com/2014/06/duramax-turbocharger-vane-position.html.) If you can’t afford to buy a replacement turbo, a do-it-yourself, temporary fix is to remove the turbo from your truck and bench-clean it. Take the unit apart, clean off the rust and carbon (soot) from the unison ring and vanes, replace the vane-position sensor, and bolt it back together. Depending on your skill level and tools, this can take anywhere from 7 to 15 hours. We’ve published several related articles on variable-vane turbos and their repair, including this one on the Ford 6.0L Power Stroke engine’s turbo, which is very similar to the ’charger on your rig’s Duramax: trucktrend.com/how-to/engine/1507-how-to-fix-a-stuck-turbo-for-2003-2007-ford-6-0l-diesel/. This PDF from Kennedy Diesel may also be of help: kennedydiesel.com/docs/Garrett%20VVT%20unison%20ring%20sticking.pdf. A note of caution on DIY bench- and on-the-engine cleanings: Most shops don’t "clean" Duramax turbos because of the labor involved with removing and reinstalling them, and if the bench-cleaning isn't successful, there’s a lot of money lost in labor to replace it. The same goes for the on-engine cleaning, during which a special solution, available from the dealer, is injected into the hot turbo. These “cleanings” don’t have a very high success rate as long-term remedies, according to several of our sources that are faced with these types of situations every month. There have also been multiple part-number changes for product improvements, so the newest replacement turbos are apt to provide longer, better service than the stock equipment you are trying to fix.
“Another issue is that the Duramax MAF sensor is somewhat finicky, and turbo issues will also set MAF-related codes,” cautions Oregon Fuel Injection’s Mark Gotchall. “If the unison ring is even the least bit sticky and the MAF is slightly out of range, then the ECM will still end up triggering codes. It’s best to bite the bullet and replace the turbo.”
Hard-Starting LB7QUESTION: My ’03 Chevrolet Silverado 2500HD’s engine is becoming increasingly difficult to start, taking 15 to 20 seconds before she fires up. There aren’t any check-engine lights, it’s just darned hard to start. When I changed the fuel filter to make sure nothing was amiss there, I noticed a little fuel on the filter assembly. I retightened everything, but there’s still a little fuel seeping from around the primer button. The previous owner says the only issue he ever had with the truck was injectors, which the dealer took care of under warranty a couple of years after he bought it.
ANSWER: The Duramax fuel system doesn’t use a low-pressure fuel pump to push fuel to the injection pump—the injection pump does all the work. With that being said, any air leaks between the fuel tank and the injection pump will cause hard-start issues. Air leaks (aka fuel leaks) can be at fuel-line fittings or at the fuel filter assembly.
“Nine times out of ten, the LB7 hard-start issues are in the fuel filter head,” says John Anderson at the Little Power Shop in Bradford, Pennsylvania. “They are known to deteriorate and can cause hard-start issues. If the fuel is seeping out, no doubt the issue is there and the engine is probably starting to lose prime, causing the long crank.”
To make that repair easier, Merchant Automotive offers a GM Duramax Fuel Filter Head Rebuild kit (PN 10192) for less than $20. The company also has a great how-to video on the rebuild: xtremediesel.com/merchant-automotive-10192-fuel-filter-head-rebuild-kit.aspx. As a side note, if an ECM scan produces a P0380 diagnostic trouble code, that indicates there’s a problem with the glow-plug system. The glow-plug relay (inside the black box on the driver side, near the firewall) could be bad. If it’s good, the other issues are the metal strip that connects the glow plugs on each bank. They are known to corrode and break, connections work loose, and glow plugs burn out. Check the connecting strips to make sure they are OK. Also, check for loose wires going to the glow plugs, as sometimes the connecting nuts work loose. Finally, check the glow plugs. The easiest way to see if they’re working is to physically check each one with a test light. The process is easy: Remove the wire to each glow plug. Connect the lead of your test light to the Positive (+) battery terminal, and then touch the test light to the threaded top of each glow plug. (In this test, the glow plugs are already grounded through the block.) Glow plugs that light up the test light are good. No light, no good.
M300 LockersQUESTION: I just bought a ’17 Ford F-450. After driving it in some less than optimal conditions, I’d like to get an electric or air locker installed. I understand these new Ford dualies use a Dana M300 rear differential. Who makes a replacement locker for it?
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ANSWER: Congrats on the new truck! Ford made some significant rear axle upgrades with the ’17 F-350/F-450s: A 10.8-inch, 36-spline Spicer M275 is found under the single-rear-wheel F-350s, while dual-rear-wheel F-350s and the F-450s get the 37-spline Spicer M300 that has a massive 11.8-inch ring gear. The M300s are available with the option of a Ford Trac-Lok limited-slip differential in the F-350s, while the Trac-Lok is standard in the F-450s. Dana actually revealed the Spicer M300 in 2012 at the IAA Commercial Vehicle show in Hannover, Germany. It has just taken the new differential a few years to be put into Ford’s production. Spicer says its M300 has a gross combined weight rating of 40,000 pounds. “Spicer axles with AdvanTEK gearing are designed to provide increased power density and efficiency in a smaller package than competing axles. The wide gear face improves gearing strength, tapered roller bearings increase fuel efficiency by reducing friction in the axle, and the overall design is optimized for low NVH (noise, vibration, and harshness),” according to a company press release. The bad news is, we don’t know of any company other than Dana that offers parts for the M300, let alone aftermarket limited-slip or locker units. You’ll have to be content running the stock limited-slip. As a service note, the big differential requires Ford’s Additive Friction Modifier XL-3 (or equivalent additive meeting Ford Specification EST-M2C118-A) be added to the lube when the limited-slip is serviced or lube changed out.
Converting Old Iron to DieselQUESTION: I have a ’69 Ford F-250 with a 300ci I-6 gas engine. I want to change it to a diesel. I was thinking of a 5.9L Cummins or a 7.3L Power Stroke. Do you have any suggestions or recommendations as to what diesel to use? Does anyone produce a kit or parts to make the swap easier? I want to use a five- or six-speed manual transmission, too. I’m not looking for a 1,000hp engine—just a reliable stock or mildly tuned engine.
ANSWER: There’s good news, and there’s bad news. The good news is, it’s fairly easy to convert old gas-burning iron to diesel. Although we don’t know of a full-on swap kit for that specific model, there are several shops around the U.S. that could be good sources for motor mounts and related adapters to replace the I-6 powerplant with a diesel. Give Diesel Conversion Specialists (406-755-8878), CPP Diesel (724-785-4022), and GOS Performance (800-620-4467) a call, and check out 4btswaps.com and forddieselpower.com forums related to specific transplant questions. The bad news, according to Ford/Cummins conversion expert Aden McDonnel at GOS Performance, is the ’69 F-250’s engine bay is rather short between the firewall and radiator support. That means some heavy modifications to the firewall need to be made in order to mount a 5.9L Cummins rearward enough to leave room for an intercooler. He also recommends using a ’94-to-’98 5.9L 12-valve Cummins for simplicity’s sake: “Three wires run the whole engine, while the 24-valve Cummins and 7.3L Ford Power Stroke require a lot of wiring. As far as a transmission is concerned, we recommend the Ford’s transmission and transfer case (if the truck is four-wheel drive) to make the 4x4 linkage easier to deal with,” Aden says. “Also, if this is a 4x4, we recommend using a Dana 60 high-pinion rearend to ensure the front-driveshaft angle is correct.”
Painless Performance offers a complete wiring harness that works with a manual transmission, which may help if you don’t have a donor truck with all the wiring and choose to run an ’03-to-’05 5.9L 24-valve engine. If you don’t already have a Cummins engine, checking out ACD Engines might be worth your while: acdengines.com. The 5.9L Cummins is easy to hop-up with a few minor turbocharger and injector upgrades. (Check out our three-part series on converting from a 7.3L Power Stroke to a Cummins 5.9L 24-engine: trucktrend.com/how-to/engine/1702-part-2-cumminsallison-swap-into-2001-f-250-super-duty/.) Should you decide to stay with Ford, the 7.3L IDI (pre-’94½) has the least wiring to contend with. But the engine is a slug compared to the Power Stroke diesel that replaced it. Another item to consider is weight: A 7.3L IDI weighs about 900 pounds, while the Cummins 5.9L is close to 1,100 pounds. Ford’s 300 straight-six weighs around 600 pounds. Those differences in engine weights might require addressing the frame strength and beefing up the front springs.
VW TDI XJQUESTION: My neighbor’s ’05 Volkswagen Jetta was squashed by a tree during Hurricane Irma, and he made me a deal for the car that I couldn’t refuse. My goal is to have the VW’s 1.9L diesel swapped into my ’01 Jeep Cherokee to replace its 4.0L I-6 engine that is long in the tooth. The Jeep has been well cared for over the years and survived being the vehicle our two kids learned to drive in, so it has a lot of sentimental value. Now it’s going to be the knock-around daily driver for the wife and myself here in South Florida. Are there conversion kits for this? Or somewhere I can find information on what’s needed?
ANSWER: You’re in luck. First, you landed a complete donor car, which is great because you have the entire wiring loom, ECM, plumbing, and intercooler to go with the engine. Second, that engine is well-suited for being under the hood of a Jeep. That era’s Volkswagen TDI engine made 100 hp at 4,000 rpm and 177 lb-ft of torque at 1,800 rpm. It accelerates like cold molasses, but its saving grace, which you’ll find advantageous for daily driving, is that the engine runs as smooth as silk and delivers 33 mpg in city driving. Owners typically see mpg in the mid- to high-40s on the interstates, at speeds of 70-plus mph. The OBD II-compliant 1.9L TDI can easily be tuned up to make around 160 hp and 265 lb-ft of torque with software, according to the folks at Coty Built (cotybuilt.com), a good source for your Jeep-to-VW diesel conversion parts—and all the tuning/performance goodies that are needed for making the TDI fly. That kind of extra power will be of great benefit to the XJ, because the engine is pushing more weight than that of the VW sedans. Coty Built’s basic TDI conversion kit (for Jeep XJ, YJ, and TJ models) is listed at $5,495 and includes everything needed for a Jeep’s gauge cluster to remain functional, along with many of the Jeep components under the hood, using a special trussmember designed for the TDI installation. This kit gives the transplant a factory appearance. TD Conversions (gastodiesel.tdconversions.com) in British Columbia, Canada, is another good source if you are on a tighter budget. Randy Holmquist, the owner of TDC, drives an ’01 XJ “TDI” as his daily driver. TDC offers the adapter plate (for manual-transmission XJs only) and motor mounts to make the physical aspect of placing the engine under the hood of a Jeep XJ rather easy. Figuring out all the plumbing and wiring logistics is on your shoulders. “You can acquire the hard parts to make the swap for about $1,400,” Randy says. “The time-consuming job is the wiring. Every wire has two ends. It’s figuring out which end goes where that takes the most time with this conversion.” He suggests labeling every end when the harness and ECM are removed from the donor car to save a lot of time and potential headaches when interfacing with the Jeep wiring. Here is one word of caution about the TDI conversion using ’05 and ’06 engines: Pull the valve cover and check the camshaft, as TDIs of this vintage are notorious for eating up camshafts and followers. We actually recommend pulling the timing belt, cam, and followers, and replacing all with high-quality parts.