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Diesel Tech Questions

You've Got Questions? We've Got Answers!

Jason Sands
Oct 10, 2015
Photographers: Jason Sands
Low-Buck Lift Pump
I have a '95 Dodge Ram, and I believe the lift pump is failing. The engine is hard to start and cranks for quite a while before it actually fires. I want to upgrade to an electric pump anyway, so I've been on the lookout for a budget replacement that flows more than my current engine-driven factory pump. I'm looking for something in the $100 to $200 range that will last me a while and is rated for diesel fuel. Can you help?
Jackson Vossler
-via email
Photo 2/4   |   If you're on a budget, an electric "pusher" pump can be spliced into the stock fuel lines on early Cummins engines with mechanical lift pumps in order to keep fuel pressure where it should be.
Very often, the feed and return lines for the injectors leak and can cause a hard-start situation. A lift pump won't necessarily fix that, but if you're going to upgrade anyway, we can give you some direction regarding what to buy. First of all, lots of pumps will work with diesel fuel, even if they're not rated for it. Simple Holley blue, black, or red pumps are very inexpensive and will run for a while, but usually the diesel will take the pumps out after only a few years.
If you're looking for pumps that are rated specifically for diesel fuel, Walbro and Carter Fuel Systems units are good choices, as each company makes both low- and high-pressure pumps rated for diesel. Many Ford guys run the Walbro 392 on their trucks, and there's really no reason it shouldn't work for a Ram's 12-valve Cummins. While the pressure is a lot higher than that of the factory lift pump, it's not enough to damage the injection pump (although it may be a little hard on the lift pump). Carter also makes low-pressure and high-pressure lift pumps that flow around 100 gph, which is pretty good for a budget unit.
When mounting these pumps, use either a stand-alone or universal fuel filter with lines made to use the stock engine assembly, or splice them between the tank and the factory lift pump, creating a sort of compound-pump setup. We've tried it a couple of different ways over the years, and for a modified diesel, any of the different setups will work- especially in the 300 to 500hp range.
If you keep adding power to your engine, eventually your pick-up in the tank, filter assembly, lines, and pump will all start to become restrictions, which is why companies like FASS, Fuelab, Aeromotive, and AirDog manufacture complete fuel systems for diesels. Using one of these systems can be beneficial, especially in higher-power trucks.
Van Fuel Economy
I just ordered a '16 Ford Transit 350 XLT with the 3.2L I-5 engine, six-speed automatic transmission, and 3.31:1 gears. I am looking at a few ways to increase mileage, keeping cost in mind. I've read a lot about increasing mileage on trucks, but are there any tricks I can use on my van?
George Petri
-via email
Photo 3/4   |   Tire pressure is one of the few easy things one can check to improve fuel economy. Airing low tires up to the high side of normal pressures can be worth 1 to 2 mpg when going down the road.
Since your application isn't a regular 3/4 or 1-ton truck, now seems like the perfect time to introduce the fuel saving tips we've accumulated over years and years of being asked this same question:
1. Drive slowly. Going twice as fast as any given speed causes nearly four times as much drag, so it will greatly affect your fuel mileage. One Ram we tested got 19 mpg at 75 mph, 23 mpg at 65 mph, and 27 mpg at 50 to 55 mph.
2. Keep your vehicle light. Remove any equipment you don't need and limit the amount of junk and trash that accumulate. And if you're not hauling a ladder, remove the ladder rack.
3. Don't believe the lies. When your buddies say they get 35 mpg out of their truck at 80 mph, don't believe them-there's probably a speedometer correction from a different tire size or something else they forgot to factor in. Modern diesels should get between 15 mpg and 25 mpg on the freeway at 65 mph (your van with the 3.2L I-5 might do even better).
4. Electric fans work. While we haven't towed using one, running electric fans while driving around town and on the highway was worth almost a 2-mpg increase in our case, and we've heard similar results elsewhere.
5. Bump timing and increase fuel-rail pressure. You want to create as much cylinder pressure with as little diesel as possible, so raising timing or rail pressure can also increase fuel mileage.
6. Aerodynamics is possibly the most overlooked form of fuel-economy enhancement for diesel-powered vehicles, but it works. A grille block on a '97 Dodge Ram was worth 2 mpg. And that ladder rack we talked about removing earlier? Not only is it heavy, but it causes tons of drag.
7. Gearing can also have a big impact on fuel economy. You've got the 3.31:1 gears, so you're on the right track. If you can, manually shift the transmission into the highest gear possible and try and use overdrive as much as you can if you're not towing.
8. Use your EGT gauge. Exhaust gas temperatures are a good indicator of the amount of fuel you're using, so the lower the temps, the better. We've seen trucks that were set up for mileage (two-wheel drive, camper shell, skinny tires) cruising with an EGT as low as 500 degrees.
9. Don't be afraid to buy another vehicle. If you have a 50-mile, one-way commute, maybe you should be making it in a Volkswagen Golf TDI rather than a Dodge Ram Mega Cab.
10. It may make the ride slightly harsher, but by inflating your tires to a level 3 to 5 psi higher than recommended, you can reduce rolling resistance and save some fuel. Bear in mind, even slight overinflation can cause premature tire wear, different handling characteristics, and, in extreme cases, even tire failure.
Tow Low
I have an '11 GMC Sierra 3500HD four-wheel-drive dualie, and I use it to tow a fifth-wheel trailer. The problem is, the rear of the truck is a few inches higher than the trailer, which makes hooking up a pain. I would like to lower the truck a couple of inches in the rear without losing any towing capacity, but nobody I have talked to so far seems like they can help me.
Bill Gerling
-via email
Photo 4/4   |   Drop shackles are an inexpensive way to lower a truck, without sacrificing its payload carrying or towing capabilities.
There are a few different options to choose from when it comes to lowering a truck. One of the most popular ways of dropping the back of a pickup involves removing leaf springs, which you really can't do with your rig because it will decrease the truck's load capacity.
Fortunately, there are a few solutions that should work for you. One option is to install lowering shackles, which will drop the truck about 2 inches, although they can be adjusted for a bit more drop. The amount shouldn't affect suspension geometry very much.
While it's not definite, you might need to add air springs to keep the rear end from sinking too low once you hook up the trailer.
A second solution involves a big jump in price but also increased capability. If you're looking for a better ride, the ability to raise and lower your truck, and onboard air, a complete air-suspension system might be just what you're looking for. While air suspensions are common on lowered or lifted show trucks, there are very capable kits out there for heavy-duty applications as well. Kelderman Air Suspensions makes a four-link setup designed for '11 GMC Sierra 3500HDs, and Firestone offers a hybrid leaf spring/air suspension that's designed to exceed OEM specifications. While these systems aren't cheap, air suspensions offer instant adjustability while maintaining load capacity and improving unloaded ride quality.