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Diesel Tech Questions

Top Tech

Bruce W. Smith
Jun 6, 2017
Photographers: Bruce W. Smith

Cooler Waters

I am having some overheating issues with the 6.7L Cummins engine in my ’14 Ram 3500 when towing a 15,000-pound toy hauler over the Oregon Cascades. The truck has more than 67,000 miles on its odometer. Mechanically, everything appears to check out fine with no codes. Do you have any suggestions on how to bring down the coolant temperature or what the problem might be?
Phil Blake
Bend, Oregon
Photo 2/5   |   Stock water pumps on some 6.7L Cummins engines experience water-bearing failure or their plastic impellers breaking away from the shafts at less than 70,000 miles. A good fix is replacing the pump with Cardone Industries’ version (PN 5531412), which uses roller bearings and a cast seven-blade impeller. The same water pump can be used on 5.9L powerplants as well.
Did you check for water seeping around the water-pump housing? Our first thought is the stock water pump isn’t doing its job. It’s not unusual for the composite seven-blade impeller used on those pumps to fail before reaching 75,000 miles. Sometimes the plastic impeller breaks away from the shaft, sometimes the bearing fails. When the pump finally does let go, it usually takes the belt with it, leaving you without power steering or brakes.
The good news is the technicians at both Mobile Diesel Service and Dunks Performance say they swap the stock 6.7L water pumps with Cardone Industries’ pump (PN 5531412), which uses roller bearings and a cast seven-blade impeller instead of a plastic one.
Cummins just happens to use the same water-pump casting on both the 5.9L and 6.7L, with identical drive pulleys, mounting bolt holes, impeller depths, and O-rings. The only difference between the pumps is the ’89-to-’07 models use a five-blade impeller, whereas the ’08-and-up use the seven-blade, according to our sources. While they are totally interchangeable, we wouldn’t put a 5.9L five-blade on a 6.7L.

Blast Away

I have an ’83 Dodge restoration in the works, with a 12-valve Cummins and five-speed-manual transmission swap. I plan to build a downdraft room of sorts for painting and sandblasting. Have you seen/done this and do you have any tips? I’m considering using either steel grate or drilled plywood for the floor and then building a frame, but I haven't worked out exactly how I want to collect the used blasting media and how pressurized the tent must be. My current thought is to use two or four box fans, sealed together, filtered, and framed into the structure on top of the tent, to push air down and maintain a pressurized, clean environment inside. Which sandblast media do you advise for the body and frame? I have heard great things about plastic bead and how it is easy to control, reusable, and doesn't heat up as much, but it is hard to come by in my area for some reason. I currently have glass beads to start with but would appreciate input on which media you have used and what their pros/cons are.
Tyler Johnson
via Facebook
Photo 3/5   |   Cleaning old parts during a restoration or rebuild can be done in just about any enclosure. Proper ventilation and protective clothing are the key factors for protecting the person doing the media-blasting from inhaling the dust.
We have been around many automotive restoration shops over the years. The first concern when media blasting is whether the person doing the work is wearing a pressurized helmet and/or suit, as the dust that’s generated is killer on the lungs. You’ll also need a big air compressor to supply you with fresh air—and to supply the gun.
Several body shop owners we spoke with say a makeshift workspace is at its best when air is drawn in one end and vented where the fans are located. During the blasting process, the media, rust, body filler, paint, and such falls to the floor. Covering the floor with plastic will simplify gathering the media when blasting is complete.
Glass beads and plastic abrasives are your best bet if recyclability is important, with glass having the highest hardness and quicker working speed, according to Kramer Industries (kramerindustriesonline.com), a supplier of such products. Another medium to consider is the dustless system (dustlessblasting.com) that uses water to carry the media, which is usually recycled bottle glass. A rust inhibitor is added to the water, and there’s little chance of warping, as the heat generated during the stripping process is negligible.

Hot Saloon

Hi from the U.K. I have an Audi A8 with a blown V-8 engine and want to outfit it with a big diesel from a fairly new American truck. Of the 6.7L Cummins, 6.5L Detroit Diesel, and 6.4L Power Stroke, which is the easiest engine to get 600hp reliability from?
Ian Neal
via email
All three diesel engines you mention can be pumped up to make 600 hp and turn your Audi A8 into a tire-roasting super sedan. However, we recommend you scratch the 215hp 6.5L Detroit Diesel from your potential donor list and replace it with a 6.6L Duramax, like the third-generation (’06-to-’07) LBZ, which makes 360 hp. The 6.6L only needs a small step up in injectors, a slightly larger turbocharger, and a mild ECM “tune” to bring it to a reliable 600 hp.
The 6.4L Power Stroke can be modified to produce 600 hp in much the same way. But our first choice from Ford’s stable would be opting for the newer and more refined 400hp 6.7L Power Stroke engine. Because of its length (41.7 inches) and height (37.8 inches), fitting the 6.7L Cummins into the Audi’s V-8 engine bay is an issue.
Regardless of which direction you take, all the above engines have been in production long enough to: 1) be easily sourced at reasonable prices, and 2) have the bugs worked out of the early generations. As you know from reading Diesel Power, there’s no shortage of aftermarket performance parts for all three brands!

MPG Accuracy

How accurate is the mpg readout on our trucks? My ’17 Ford F-250’s digital display says it’s getting 19 mpg. But when I calculate the number of miles and number of gallons to fill it up, it comes out to 17.9.
Justin LaBelle
via the Internet
Photo 4/5   |   Fuel economy numbers typically don’t match up between what is indicated on the driver information center and what we figure doing our own hand mpg calculations. That’s because the indicated mpg is derived from a computer algorithm and not by measuring actual fuel used against miles driven.
What we have seen during our own road tests is that the manufacturers’ computer-generated mpg displays are slightly on the “happy” side. By that we mean 1 to 2 mpg higher than what our hand-calculated figures show. It should be noted the truck’s system doesn’t monitor actual fuel flow, but rather algorithms based around the length of time the injectors are open, the amount of fuel they are delivering at any point in time, engine rpm, and the odometer readout.
Usually, where big mpg discrepancies occur is when we change tires, which affects the odometer reading and, consequently, the onboard mpg readings. So, if a lift and taller tires are installed on your truck, be sure to have the odometer recalibrated. Taller tires and lift kits cut down on fuel economy because of more wind resistance on both tires and the body and heavier weight of the rolling mass.
Onboard mpg readings can also be skewed because the filling-station pump may not be delivering the exact amount of fuel it indicates. It’s entirely possible for the pump to show you are getting a little more fuel than you are receiving, hence reducing your own mileage calculations. Fuel-station pumps are typically inspected once a year. Sometimes it could be two years between regulatory calibration checks.
Note the state inspection sticker on the pump you are using to see if it’s had a recent inspection. It’s also good to fill up at the same station and use the same pump.

Cold-Start Issue

I've got a 7.3L-powered ’00 Ford F-350 with 200,000 miles and no block heater. This winter in Texas, she experienced hard starts and rough idle for the first time. The “Wait to Start” light goes out as usual, but the “Check Engine” light stays on and sometimes it takes three attempts to get the engine to idle. The CEL goes out if I wait a couple of minutes with the ignition switch in the On position without starting the engine. Once the CEL light goes out, the 7.3L starts and runs fine. My technician thinks it might be an ECM problem, but I'm thinking weak glow plugs. It is obviously ambient temperature–related to some extent.
D. Scott
Granbury, Texas
Are you sure there’s no block heater? Check between the foglights in the bumper (behind the license plate), which is where the factory tucks the block heater’s power cord. If for some reason the cord is missing, it can be purchased.
Kenneth Tripp at Tripp Trucks says he’s willing to bet your truck has an injector-drive module diagnostic trouble code (P1316) stored. If it does, he says you need to run a buzz test to pull the codes from the injector driver module. Unless it has California emissions or is an Excursion, the ECM doesn't monitor glow-plug operation on the 7.3L and won’t show a check-engine light.
Kenneth says when Super Dutys roll into the shop with a cold-start issue, technicians check the glow plugs’ operation with a simple test light. “The glow plug relay is the relay closest to the firewall on top of the engine. Power should be present at all times on the big post closest to the passenger fender. When the glow plugs are commanded ‘‘On” by the ECM, the other big post should go hot.
“Next, we put the test light on the positive battery post disconnect valve-cover harness connections,” Kenneth says. “On the outer two posts on each end are the glow plug circuits. Touching each of these should light the test, indicating a good circuit as the glow plug is the ground.”

Flushed Again

I just changed the oil cooler on my ’06 Ford F-250 with a stock replacement. The truck’s 6.0L Power Stroke engine is upgraded (head studs, SCT programmer, and new ECT/EOT sensors), and when I bought it at 185,000 miles, it had a new radiator. It now has 200,000 miles. Recently, the “wrench light” came on and the data log showed big coolant and oil temperature differences. I drained and flushed the EGR and oil coolers with distilled water. The symptoms still remain: The wrench light comes on after several minutes of driving, and when the oil temperature hits 260 degrees, the water-temperature gauge drops to zero then maxes out with a “check gauges” message. Coolant temperature stays between 185 and 200 degrees. Do you have any suggestions?
Christian Blake
Tampa, Florida
Oil-cooling systems are finicky when it comes to cleaning, and a single water flush doesn’t cut it. It needs to be a chemical flush—not one, but several—followed by a water flush. Then, immediately fill it with the proper coolant afterward.
Anthony Youngblood at Super Duty Service in Grain Valley, Missouri, says, “We use Ford VC-9 coolant cleaner whenever we work on those oil coolers. It’s an iron cleaner. Our flush process uses hot water forced through by compressed air, and we take samples after every flush until it runs clean with no gunk of any type. Then we immediately fill with CAT EC-1 coolant. It’s an all-day deal. We don’t take any chances.”
The last step Super Duty Service technicians do is a good lesson for anyone performing this kind of maintenance: Once the flush starts, get the new coolant into the system ASAP. Never let the water in the coolant passageways sit overnight. It will cause more rust to form, thus negating most of the benefits gained from flushing.
That brings up another thought: Was your truck’s engine ever run with only water in the cooling system? Water without the rust-inhibiting benefits of antifreeze quickly promotes rust. Install a coolant filter for a week. The filter will trap rust and other debris that may still be circulating in your truck’s cooling system. Leaving the filter in place adds a lot of potential leak points you don’t want to deal with down the road. Hence, the reason we suggest it only as a temporary installation.

Icy DEF

I need some 6.7L Cummins engine help. I have a ’14 Ram 2500. The truck’s batteries died. I got the batteries replaced, and now I am getting diagnostic-trouble code “P20B7” along with a message that says, “Service DEF System-See Dealer.” (The check-engine light isn't on). The truck has 49,822 miles on it. It appears there is a 50,000-mile factory warranty on the DEF system. I cleared the code and unhooked the batteries for three minutes to see if the ECM was just being stupid. I think the battery change and the DEF system error are coincidental; I just wanted to see if anyone had more information?
Damon Rivetti
Chatsworth, California
Photo 5/5   |   DEF gets slushy when ambient temperature drops below 12 degress F (-11 deg C). When that happens, it’s tough for the little heater in the DEF tank, and those that might be heating the feed line, to get the fluid warm enough to circulate properly. When the metering system senses a flow issue, codes such as “P20B7” (“Reductant metering unit heater-control circuit low”) tend to pop up, alerting the driver there’s a problem within the SCR/Reductant heater circuit. Such a code may or may not indicate there’s an actual DEF heater or heater circuit failure.
You really need to get your truck to the dealer before the 50,000-mile, five-year DEF warranty expires. A few Ram trucks have been experiencing issues within the DEF system, setting off that code, which is normally only seen in sub-freezing weather. Specifically, P20B7 is “Reductant metering unit heater-control circuit low.” In simpler terms, there’s a problem within the SCR/Reductant heater circuit.
The code tends to be triggered when trucks are parked outside in single-digit or colder conditions, which causes the DEF to crystalize. DEF is a mixture of 32.5-percent urea and 67.5-percent water, and it starts crystalizing/freezing at 12 degrees F (-11 deg C). When that happens, it’s tough for the little heater in the DEF tank, and those heating the lines, to get the fluid warm enough to circulate properly. When the metering system senses a flow issue, those “P20” codes pop.
The owner’s manual says it may require 50 or so miles of driving before the DEF warms up enough to start flowing. (The temperature sensor that controls the heater is in the DEF-pump module.) But there’s really no sure way to tell how long it really takes.
Our sources say this is typically more of an issue in Ford and GM diesels than Ram. Mark Gotchall at Oregon Fuel Injection says he has seen a blown 15-amp fuse that controls the SCR heater relay cause this to happen. If that circuit in your rig is good, then it’ll take further diagnostics checking the SCR/Reductant heater wiring, the heater in the DEF tank/injector line, or possibly the ECM.

Crazy A/C

I have been a subscriber of Diesel Power for many years and love the magazine. Hope you can help me troubleshoot an electrical issue: The A/C, wipers, and seat heater on my ’08 Ford F-250 intermittently decide to not work all at the same time when I start the engine. It doesn’t happen very often—sometimes once every few months, sometimes every day—and never when it’s at the dealership’s service department. When it happens, I can usually turn the engine off and on a couple of times and it fixes the problem. Any ideas what this may be?
Zach Westerfield
via email
Solving such a puzzle takes good electrical diagnostic thinking. You have three systems that fail to turn on with the ignition switch. What is the common denominator between them? The smart junction box under the dash.
The technicians at Tripp Trucks in Charlotte, North Carolina, say they’ve seen this happen. Kenneth Tripp says fuse #45 of the SJB powers the windshield-wiper motor and the blower-motor relay but doesn’t feed either the heated seat circuit or the electronic automatic-temperature-control module. Conversely, the HVAC system, which also plays a role in the operation of the heated seats, has nothing to do with the wiper system.
Kenneth says the common connection is that all three systems get their power from the SJB. The only way to diagnose this case is to perform multiple circuit checks the next time the three systems fail to power up when you turn on the ignition. Just by process of elimination, we think there’s something amiss at the SJB that’s causing the problem.

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