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Your Diesel Questions Asked and Answered

You’ve Got Questions, We’ve Got Answers

Bruce W. Smith
May 9, 2019

Low Fuel Pressure

QUESTION: I purchased a '15 Ford F-350 dualie with 37,000 miles on it. In the service log, the previous owner recorded a low-fuel-pressure issue around 15,000 miles, which the dealership fixed by replacing the stock transfer pump. The problem reoccurred at 43,000 miles. Under hard acceleration, the low-fuel-pressure warning appears on the Driver Information Center screen, and then the engine shuts down a minute later. If I let the truck sit for an hour, the engine starts up and runs fine. I've also noticed the fuel pump is making a whining noise. Is the pump failing again? I am taking it back to the dealer for repair.
Ricky Roberts
Via email
Photo 2/6   |   001 Top Tech Ford Bottle Seal Plugged F Pump
001 Top Tech Ford Bottle Seal Plugged F Pump
  |   001 Top Tech Ford Bottle Seal Plugged F Pump
ANSWER: The whine from the transfer pump and the low-pressure warning appearing only when your truck's 6.7L Power Stroke engine is under heavy throttle suggests the most likely cause is something is restricting the fuel from being picked up by the in-tank pump. On rare occasions, it could be a bad pump. Sometimes it's just a plugged fuel filter. But, more times than not, the typical cause is the cardboard or plastic seal on a container of fuel additive being accidentally dropped into the filler neck. It eventually works its way into the fuel tank, where it's sucked into the fuel pump assembly. Under hard throttle, the fuel pump sucks the seal into the supply tube, restricting or totally blocking fuel flow, which triggers the low-fuel-pressure alarms and subsequent engine shutdown. What a dealership technician will most likely do is drop the tank and pull the fuel pump out to see if there's anything blocking the suction tube or floating around in the plastic housing. They will probably flush the tank while it's out to make sure nothing else is floating around that can restrict fuel flow.

Rocky Mountain High

QUESTION: At 134,000 miles, I had new injectors and a Sinister Pitbull Stage 1 turbocharger installed on my '06 Ford F-250, along with a Banks IQ programmer. Most of my driving is between 5,000 and 11,000 feet (elevation) in Colorado. After the turbo was installed, the engine developed a "jerk" from about 1,800 rpm to about 1,900 rpm while pulling a 30-foot fifth-wheel trailer. The shop where the work was done says it's because I'm lugging the engine. Two other shops tell me the problem is the turbo is too big for high altitude. Who is right? Will raising the power level to Tune 5 or 6 help? Is this the right turbo or is it too big?
Dennis Young
Via email
ANSWER: Sinister Diesel's Pitbull is a drop-in-replacement, variable-geometry turbo with slightly higher flow than the 6.0L Power Stroke engine's stock turbo. It also features an anti-surge design. So, we think it's the right choice for providing the 6.0L with the help it needs to make up for the thin air in high-altitude conditions. However, that turbo shouldn't be causing the problem you're experiencing. You can try adjusting the Banks IQ to Level 5 or 6, which may help. But we think the shop that says you were lugging the engine is on the right track. Whenever a diesel is being worked hard, like when it's towing a big trailer, you need to try and keep rpm slightly above the engine's peak torque output—that's 2,000 rpm for 6.0L Power Strokes.

Cold Blooded Six-Oh

QUESTION: My dad and I have an '05 Ford F-350 with the 6.0L Power Stroke engine. We live in Alaska, and our winter jobs sometime necessitate leaving the truck in a parking lot for about a week in -20-degree (Fahrenheit) temperature. We plug in the block heater. Upon returning to the truck, the engine is very difficult to start. The Power Stroke was rebuilt at 180,000 miles and upgraded with cylinder-head studs and other pieces that constitute making it safe from suffering the typical catastrophic failure that plagues the engines. Oil flow is OK according to the oil pressure gauge, and a mix of white and black smoke comes out of the exhaust, so the FICM is working properly. Could the glow plugs be bad? Or is there something else causing the problem?
Hunter Williamson
Via email
ANSWER: Most mechanics replace the injectors and glow plugs at the same time cylinder-head work is done. But because you don't mention seeing any diagnostic trouble codes, we suspect the glow plugs are in working order. Still, it's best to use a scan tool to double-check for codes indicating bad glow plugs. Is the block heater working? Look at it, as well as the circuit the cord is plugged into. The smoke coming from the tailpipe confirms the engine is getting fuel and there is sufficient oil pressure for activating the injectors. However, FICM voltage must also be analyzed, because, even if it's bad, you will experience smoke from the tailpipe. If the unit doesn't provide enough voltage during cold start (minimum of 45 volts) to activate the injectors on time, the result is smoke and a slow or hard start. "Outside temperatures at -20 degrees only make it worse," says Mark Gotchall at Oregon Fuel Injection. "This is because the spool valves in the injectors move slower in the severe cold. Minimum voltage is 45 volts during cold start. The oil could also be, or contribute to, the problem. Too heavy an oil can cause the injector-spool valves to be slow to respond," Mark adds. According to Ford's Diesel Supplement for that engine, the best oil to use in subzero temperature is a 5W40 synthetic and 15W40 when temps stabilize above 20 degrees above zero.

Start-Up Surging

QUESTION: The 7.3L Power Stroke engine in my '00 Ford Super Duty surges up and down between idle speed and is dying when it's started cold. If I step down on the throttle and give it some fuel for a few seconds, it eventually straightens out and idles fine. It only does this on first or cold starts. How do I track down what's causing the surging?
Byron Stevens
Via email
Photo 3/6   |   002 Top Tech Startup Surging 7 3l Ford
002 Top Tech Startup Surging 7 3l Ford
  |   Ford 7.3L Power Stroke engines are finicky about the weight of oil in cold weather. If the viscosity is too high, the injectors have a hard time functioning properly, resulting in the "ramping" idle for the first 30 seconds or so until the oil warms up. Using a 5W-40 synthetic oil instead of 15W-40 can make a huge difference in cold starts.
ANSWER: Start diagnosis by checking glow-plug operation, which is easier than most would think even though the plugs are located under the 7.3L Power Stroke engine's valve covers. Begin by checking the glow plug relay, in the center of the engine toward the passenger side to the rear. (The 7.3L has two relays located there, with the one in front controlling the intake-air heater). Use a basic test light. Turn the ignition key to the "On" position but don't start the engine. Both larger posts on the relay should have power with the key in the forward position. If they don't, check the two small posts: If one triggers the test light and the other does not, then replace the relay. If both small posts illuminate the test light, then the PCM isn't commanding the glow plugs to turn on. The next step is to check the glow plugs. Disconnect the wiring-harness from the connectors attached to the valve-cover gaskets. With the test light attached to the positive terminal, touch the outer two pins on both the left and right of each gasket. "Technically, one would want to use a multimeter and check resistance, but a test light will work for a quick check," says Ford diesel expert Kenneth Tripp at Tripp Trucks. "If the test light comes on, the [glow] plugs are fine. If it doesn't, replace the glow plugs." After glow plug operation is checked and assuming all is good, oil quality is the next thing to check out. Ford's 7.3Ls are finicky about the weight of oil in cold weather. If the viscosity is too high, the injectors have a hard time functioning properly, resulting in the "ramping" idle for the first 30 seconds or so until the oil warms up. Using a 5W-40 synthetic oil instead of 15W-40 can make a huge difference in cold starts. If you are already using "winter oil," plug in the block heater overnight (not just a few hours before trying to start it). If the engine magically starts and idles smoothly, then it's time to get the injectors checked. This can be done with a scan tool or manually. The latter involves pulling the valve covers, starting the engine, then disconnecting the injectors one at a time to see which one(s) has no effect on the way it runs. You could also pull all the injectors and have them tested.

Hard Brake Pedal

QUESTION: My '05 Chevrolet Silverado 3500HD has a brake issue. She's got about 168,000 miles and is well maintained. I mostly use her to make 900- to 1,200-mile trips to work in the oil fields here in Alberta, Canada. During the last two years, applying more and more force on the brake pedal is necessary for stopping. After consulting a local shop that specializes in GMs, I flushed the power-steering system and had the brake rotors and pads replaced—all with no improvement. Since then, I have flushed the power steering three more times. Every time the fluid starts coming out quite dark (but see-through) and is completely clear by the end of the flush. The pedal force hasn't reduced after the last two flushes. I've checked for fluid leaks, and none are visible. I have no trouble exerting enough force to get the truck stopped so there is obviously still some brake boosting left. But something isn't right here. Do I need to replace the power-steering pump or the master cylinder? Or something else?
Jim Roth
Via email
Photo 4/6   |   003 Top Techduramax Ps Pump
003 Top Techduramax Ps Pump
  |   Braking issues on 6.6L Duramax-powered GMs can be attributed to many causes, one of which is a bad or failing power-steering pump, which is the heart of the braking system because it supplies the hydraulic "boost" to the brakes.
Photo 5/6   |   004 Top Tech Hydratech Brakes
004 Top Tech Hydratech Brakes
  |   Braking issues on older heavy-duty diesels can be alleviated by replacing the factory hydroboost and factory steering pump with new components or with an upgraded hydroboost kit like this from Hydratech Braking Systems.
ANSWER: The power-steering pump is the hydraulic power source for this type of braking system, so if it's starting to get tired, it won't be providing the correct levels of available hydraulic power to the brake-assist unit. But, with that being said, it would also not supply enough power to the steering gear, which would have a noticeable effect on the steering. First, let's explain the relationship between the brake and steering: The hydroboost pump supplies pressurized fluid to the brake master cylinder. From there, it returns to the hydroboost reservoir and to the power-steering gearbox. Do a quick braking/steering test to see if there's any noticeable lack of power steering when the truck is warmed up and put it through a tight parking lot turn (or sitting still steering lock-to-lock). If the steering effort improves by raising engine rpm, this indicates the power-steering pump is getting tired. If there are no noticeable problems with the power-steering system, then we can somewhat rule that aspect out of the discussion and focus more on the hydroboost system. "I have found that flushing a power-steering system is similar to flushing a high-mileage transmission," says Paul M. Clark, owner of Hydratech Braking Systems, when asked about the color of the brake fluid during flushings. "You can push 16 to 18 quarts of new fluid through a professional transmission-flush machine and then find the fluid dark in color again in about 500 miles. Similar to an oil change in a high-mileage vehicle—it's going to go dark again not too long after it is changed." Paul suggests an additive, such as Lubegard 20404, is the quickest and least-expensive way to "tickle it" to see if there is any response. Sometimes these additives have incredible results in less than 50 miles of use, freeing up sticking/varnished-up components, breathing new life back into a steering gear and/or a hydroboost unit. Applying the brakes firmly will load the engine down just about the same as cranking the wheel lock-to-lock. This would be noticeable enough know if the hydroboost is the culprit. Likewise, if braking effort is OK when the engine is cold but gets worse as the engine and ambient temperatures rise, it usually points toward a failing or worn-out power-steering pump. Paul also passes this tip along: An advanced trick that sometimes helps to free up a sticking spool valve inside a steering unit is to apply the brakes firmly a few times with the engine off. That will force the valve through its full range of travel, which it wouldn't typically do during normal use. "Cycling this valve all the way in and all the way out of the bore it operates in may help knock some varnish loose to free up this valve, subsequently resulting in more braking assist for a given amount of brake pedal apply pressure," Paul adds.

Controlling Body Roll

QUESTION: My wife and I ditched our big toy hauler for a new Lance 1062 cab-over, slide-in camper. Our '15 Ford F-350, which has a little more than 60,000 miles, tows the trailer with ease. But I'm very disappointed in how it handles with the camper. There's lot of body "lean," and that's disconcerting when traveling country roads and twisty highways. What can be done to make our truck feel more stable?
Verne Wentworth
Via email
Photo 6/6   |   005 Top Tech Ford Sway Bar
005 Top Tech Ford Sway Bar
  |   Replacing the stock rear sway bar with a thicker aftermarket version will greatly improve the handling on pickups carrying slide-in campers, including late-model Ford F-350s. Replacing the stock hydraulic shocks with gas dampers will also help ride and handling whether hauling a camper or towing a trailer.
ANSWER: The transition from towing a gooseneck or fifth-wheel trailer to hauling a slide-in camper is the most dramatic change a driver will ever experience when it comes to a vehicle's handling dynamics. The fifth-wheel's hauler distributes the weight of the trailer somewhat equally between the front and rear axles, while keeping the truck's center of gravity low. So, handling with and without the trailer remains pretty much unchanged when it comes to cornering.
However, a slide-in camper, especially a cab-over, raises the truck's center-of-gravity (COG) a couple feet or more. That change in COG makes the truck/camper package considerably more "top heavy," which creates significantly more body lean or body roll when cornering. Such campers, which can weigh more than 4,000 pounds when loaded, can also change the fore and aft COG, placing more weight over the rear axle than on the front, and contribute to drivers being uncomfortable. Our suggestion to vastly improve handling, especially in reducing body roll, is to upgrade the front and rear stock sway bars for heavy-duty versions such as the Big Wig sway bars from Hellwig Products. Replacing sway bars is something you can do in your driveway with basic handtools, and it's the most cost-effective way to reduce body lean on any pickup fitted with a slide-in camper. When the truck enters a corner, the weight transfer to the outside pushes that end of the sway bar downward. At the same time, the other end of the bar, which is also attached to the frame, resists that twisting, helping reduce the lean. Aftermarket sway bars are thicker than stock pieces, so they place more resistive force against the body leaning in corners. If installing thicker sway bars doesn't provide the level of handling you want, the next step is to install air-helper springs over the rear axle. "Airbags," as some people call them, can be inflated to whatever level you need to provide additional support to the leaf springs under your Super Duty. Hellwig, Air Lift, and Firestone Ride-Rite all offer great kits. The combination of helper springs and heavy-duty, antisway bars should put you at ease behind the wheel when that camper is in the bed.



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