Diesel Tech Questions
Erratic Fuel PressureQUESTION: First of all, I love your magazine! Second, what could cause erratic fuel pressure at the inlet of a Cummins VP44 injection pump? The fuel pressure on my ’01 Dodge Ram is erratic. (I use an Auto Meter Competition Instruments electric gauge with the correct snubber). The fluctuating pressure started out slowly: The needle would just flicker, and now there is an almost constant variation between 10 and 17 psi. In that time, I have checked multiple points for fuel pressure, unplugged the Edge Products control box, had the Auto Meter gauge checked at a shop (tested OK), replaced the bypass valve in the pump, tried multiple power locations, and checked voltage stability—all with no lasting effect of more than a few minutes. Six months ago, the FASS Fuel Systems lift pump ate a bearing, so I had it rebuilt at the factory, and I installed a new fuel line and a bottom fuel sump. You could hear the returning fuel pulsate into the tank, so I stretched the return spring and shortened it by half an inch. This fixed the gauge fluctuation for about four months. However, the problem has started again. You can hear pulsating fuel enter the tank, which correlates with the gauge movement. If you squeeze the return line, it slows the pulsating and the gauge stabilizes. Does the VP44 cause the lift pump to load/unload that dramatically? Or does a failing VP do this? There are no driveability issues or diagnostic trouble codes. My truck has 268,000 miles on it, and I believe the turbocharger and injection pump are original.
ANSWER: We talked to several of our Cummins experts, and here’s what we learned: Bounce, i.e. erratic fuel pressure readings, is typically a result of not using a snubber and/or a needle valve in the line feeding the gauge, or having it installed at the pump instead of as close to the gauge as practical. The needle valve/snubber restricts the flow from the VP44 to the gauge, cushioning the pulsation. “We see that bounce on the gauge frequently,” says Source Automotive’s Bill Allen. “It’s typically caused by the rotational force coming from the VP44 when it’s supplying fuel to the engine. Once a needle valve is installed properly, the issue will disappear.”
Allen says the installation procedure is to have the valve closed, start the truck, and then slowly open valve until the gauge reads pressure. The valve only needs to be open enough for the gauge to read, which can be one-eighth of a turn or less. If the valve is open any more than that, damage to the sensor may occur.
“I assume the ‘bypass valve’ that was replaced in the VP44 is the Bosch overflow return valve (PN 1467445003), and the sensor for the gauge is still the original from four years ago,” Bill says. Use a mechanical gauge to test the VP44 and see if the bounce is still there. If needle bounce is gone, replace the electronic gauge’s sending unit with Auto Meter Competition Instruments’ PN 2239. If the bounce is still there, we suspect there’s an issue with the VP44 return circuit or the transfer pump.
One other thought on the overflow valve:’98½-to-’02 Dodge Rams with 5.9L Cummins engines that still use a Carter lift pump should be fitted with an adjustable overflow valve like that offered by Tork Technology (PN OFV080), which allows easy fuel-pressure adjustment with the twist of a wrench—and it can be taken apart and repaired in less than a minute. The ball and seat in this valve is also considerably beefier than the stock unit. Mark Gotchall at Oregon Fuel Injection says his technicians have seen erratic fuel-supply pressure that’s also caused by the pressure-regulating ball getting stuck in the regulating spring of some FASS Fuel Systems lift pumps.
“Assuming it is a Titanium series, you may have to bend the coil closest to the ball inward and then trim the spring to drop the pressure,” Mark says. “The spring will sometimes drag in the bore of the housing if the ball is pushing into it and cause a pressure surge.” Mark also says the overflow valve in the pump could be getting weak,“but that usually results in low pressure not a surge.”
Diesel Fuel EconomyQUESTION: I have a ’17 Ford F-350. The truck has 13,000 miles on it. I see 14.3 mpg in town at 6,200 feet elevation. On the highway in California, it gets 16 to 17 mpg. I hear reports of much more than that. Am I getting the mileage I should with a 6.7L Cummins engine? Is there any modification I can do to improve mileage? The numbers are for the truck empty with driver and one passenger.
ANSWER: We receive plenty of questions related to fuel economy on diesels because there’s not yet an EPA requirement to list mpg for heavy-duty (10,000-pounds-and-up GVWR) pickups. From our experience driving Fords and in doing comparison tests against GM and Ram pickups in the same segment, your mileage is on par with the expected fuel economy for that type of vehicle. All the newest ¾- and 1-ton trucks we’ve driven get between 18 and 19 mpg on the open road (at 60 to 65 mph), 14 to 15 mpg in combined driving, and 12 to 13 mpg in actual stop-and-go city traffic. We test pump to pump, filling up at the same fuel pump, topping off the tank, and then figuring actual mpg instead of using OBD II data. Remember, driving at speeds more than 60 mph has a negative effect on fuel economy. Aerodynamic drag increases with the square of velocity, and with pickups, the effect of drag really shows itself at speeds more than 60 mph. Fuel mileage can drop 10 percent driving 65 mph instead of 55 mph. Lift kits and taller tires also increase drag as well as add weight, which also affects fuel economy. In addition to drag, engine rpm contributes to fuel economy: Higher driving speed and engine rpm yield lower fuel economy. Easing into and out of the throttle will give the best mileage. There are a lot of variables. However, the zero-cost way to improve mpg numbers is to slow down on the highway and regulate the modulation of the right foot.
More Lift Pump WoesQUESTION: I’ve been dealing with lift pump problems on my ’02 Dodge Ram 3500 for several months and have reached a high level of frustration with “factory” replacement parts. My truck is stock and pushing 350,000 miles. I baby it and make sure everything is serviced on a regular basis. In 2017, I replaced the factory Carter lift pump (for the third time) when the fuel pressure started fluctuating a lot—sometimes dropping down to 5 psi when she was under load—and it never seemed to deliver more than 10 psi. The same thing is happening again with this new pump. I don’t want to spend a lot of money on a fancy high-performance lift pump, because this is just a farm truck. But I’m fed up with wasting money on the “stock” replacement stuff, and I don’t want to end up having to buy a VP44. Suggestions?
ANSWER: We imagine 35 percent of ’98½-to-’02 Dodge Ram trucks with 5.9L 24-valve Cummins engines are still running Carter lift pumps, and it’s safe to say they all have the same repeated failure issues, even in stock applications. It’s just something that’s to be expected when you have a diaphragm-type lift pump that was designed to push fuel rather than suck it all the way from the fuel tank to the VP44 injection pump. We have covered the change from the Carter to other, more robust and worthy lift pumps in numerous articles over the years. Spend the extra bucks and buy a FASS Fuel Systems or AirDog replacement. Each will provide the steady fuel flow the engine needs to run properly without killing itself in the process.
Oil Cooler RemoteQUESTION: Seeking your advice on the oil cooler in my ’10 Ford Super Duty. The service writer at my local Ford dealership says it’s not flowing/cooling like it should and needs to be replaced. Should I bite the bullet and spend the extra money to have a remote kit installed when they do the work? This makes the second time in 240,000 miles the cooler problem has been addressed. The first replacement was at 152,000 miles. I bought the truck new and plan on keeping it for at least another 10 years. But with all the labor involved to have the stock oil cooler replaced, shelling out $2,400 every time this has to be done is tough.
ANSWER: This comes up in a lot of casual conversations about 6.0L/6.4L Power Stroke engines. You have to look at the return on investment: Does it make monetary sense for you to fork out $1,500 to $1,800 on a remote oil-cooler kit that moves the cooler and filter to the firewall just to save the labor (14 to 16 hours to remove and replace the oil cooler) once every 150,000 miles? You will still have $300 for a new stock cooler the next time. Granted, a remote kit does more than save a ton of labor costs when the next replacement comes around; it also improves the capacity to cool the oil better than having it running through a cooler buried deep in the engine’s valley and makes it easy to change filters. Speaking of changing filters, your last oil cooler’s life seems a little short-lived from the norm. Preventive maintenance is a huge part of owning a diesel pickup and keeping big-ticket repairs at bay.
“The trucks I typically see that go many years without oil-cooler issues tend to be really well maintained,” says Kenneth Tripp, owner of Tripp Trucks in South Carolina and a former Ford Power Stroke development engineer. “Some will argue it is the coolant Ford uses that causes the issues, which I would argue isn't the cause. It’s poor maintenance.”
Kenneth recommends changing the coolant every 30,000 miles, even though the owner’s manual says 100,000 miles/6 years initial service, with subsequent service at 50,000-mile/3-year intervals. “The reason owner’s manuals are so forgiving on maintenance intervals is for sales reasons.” Kenneth tells all of his Power Stroke customers that it’s cheap insurance to be over-zealous on preventive maintenance and using the proper fluids and filters. If a Super Duty owner wants to maximize a 6.0L/6.4L engine’s oil-cooler’s life, service the cooling system frequently and go a step farther when draining the coolant—drain the engine block, too. Flush the entire system. That type of preventive maintenance really pays off.
Broken Bolt ExtractionQUESTION: What is the recommended method for removing broken exhaust-manifold bolts? I’ve been hearing a funny whine from my ’08 Ford F-250’s 6.7L Power Stroke engine and finally tracked it down to exhaust leaking from the driver-side exhaust manifold, where both bolts at the rear port sheared off. Are there any fix-it tips? I’m praying there’s a way to get them out without the expense of taking the head off and having a machine shop do the repairs.
ANSWER: Broken exhaust-manifold bolts are common on 6.0L/6.4L Ford Power Stroke engines. We suspect the bolts on the rear exhaust ports shear off because of heat cycling, as those locations are where the highest manifold temperatures are reached. We’ve watched the technicians at Mobile Diesel Service tackle broken exhaust bolts several times. Their method is pretty straightforward: Remove the exhaust manifold, use a sharp center punch to dimple the exact center of the broken bolt, then drill a small pilot hole through the broken fastener using a premium drill bit designed to tackle the stock stainless steel bolts. Drilling the bolt has to be precise and perpendicular to prevent damaging the thread during the final step. If you are not able to get the punch in the dead center of the broken bolt, make (or find) a bushing that’s the same outside diameter as the size of the hole in the exhaust flange, with an 1/8-inch inside diameter. The bushing centers the pilot drill bit. After the hole is drilled through the broken bolt, a healthy shot of lubricant is sprayed through the hole, which is then allowed to sit for an hour so the penetrating lubricant can work. Then, step up to a bit that’s slightly smaller than the bolt to facilitate using the biggest EZ-Out or similar bolt extractor. Some technicians will use a left-handed drill bit in place of a dedicated bolt extractor, because as the reverse-rotation bit bites and heats up the broken bolt, it also helps back the bolt out. Using either method, it’s slow, tedious work. Getting a broken exhaust bolt out can take a couple of minutes to a few hours. Once the broken bolt is removed, the hole should be tapped to make sure the threads are clean and not damaged, or, if the threads have been galled, the hole will need to be drilled and tapped so a Heli-Coil can be installed. Ford recommends installing new manifold bolts and gaskets, as does Mobile Diesel Service.
Sloppy SteeringQUESTION: The steering on my ’01 Dodge Ram 2500 is finally at the point where dealing with the play in the steering wheel is wearing me out on longer trips. The tie-rod ends and ball joints have been replaced, and the alignment is spot-on. I know the power steering box is leaking a little, and I’m sure a lot of the play is related to it wearing out. I can turn the steering wheel about 1½ inches before the tires move. Any suggestion regarding the best replacement?
ANSWER: We have driven trucks that had the steering boxes replaced with inexpensive aftermarket rebuilt units, and we’re not overly impressed by the results. That’s why when it was time to replace the stock power steering box in one of our own trucks, we installed a Redhead version (redheadsteeringgears.com; 800-808-1148). The steering improvement was like driving a new truck with zero play in the steering wheel and the perfect amount of “weight” in the actual steering feel. Not everyone is willing to spend the money on a premium power-steering box—until they feel the difference. One of the biggest differences internally, from what we’ve been told, is Redhead takes the time to install the correct-size ball bearings in the worm-and-piston assembly. Most rebuilders take the worn-out bearings and replace them with the stock size. This takes into account that the bearings wear down, but it doesn’t compensate for the fact that bearing channels wear down as well. Hand-fitting the internals and installing oversized recirculating ball bearings removes that looseness entirely. Another thing Redhead does is test its steering boxes under 1,200 psi of air pressure to make sure there’s no leaking, play, or lash. All final adjustments are done under pressure. We suggest you check and/or replace the intermediate steering shaft at the same time. Borgeson (borgeson.com; 860-482-8283) makes a good replacement, especially for older trucks that use a stock “rag joint.” The rubber in those joints deteriorates over time, contributing to some of that sloppiness in the steering wheel. Borgeson’s universal shafts use billet steel universal joints.