By Russ and Tiña De Maris
Distraction can lead to disaster. Say you pull your rig into the truck stop fuel island. You’re low on fuel, and your dash warning system says you need DEF (diesel exhaust fluid). It’s been a long day on the road. You pop open the filler lid that hides your fuel cap – and the DEF filler cap.
As you stand in a stupor, your reverie is interrupted when you notice you’ve stuck that DEF nozzle – not in the DEF filler – but in the fuel filler! Now you’ve got DEF in a diesel tank! Sorry to say, but you have just seriously complicated your day.
In line for a disaster
If you’ve got a diesel engine truck or motorhome, and you’re a DEF user, you’ve probably cussed the stuff more than once. Sure, diesel exhaust fluid does reduce the amount of nitrogen oxide your engine kicks out. That’s good for air-breathers like us humans. But it does add an additional layer of fussing, and more money at the pump. But if you accidentally put DEF in your diesel engine fuel system, you put yourself in line for a disaster.
DEF is a mixture of water and urea, that “sort of smells like a barnyard” stuff that’s used in a lot of fertilizers. While it’s not good to get water in your diesel tank, a fuel separator system will usually catch water before it gets too far into your fuel system and cause serious damage. Here’s the problem: Fuel separators aren’t designed for, nor are they good for, separating out DEF. The DEF gets past the separator and into the fuel system.
DEF is extremely corrosive, which is bad for the fuel system itself. And while diesel fuel contains agents to lubricate, DEF works the opposite way – it reduces lubricity. Once in a fuel system, DEF can cause mechanical parts to seize. It will also begin to crystallize, clogging up passageways where fuel needs to move. In short, if you’ve got DEF in your diesel, you’ve got a financial disaster ahead of you.
Don’t touch the starter!
How much of a disaster? Much depends on the action you take the moment you realize that you’ve goofed and put DEF in a diesel tank. Want a small financial disaster? DON’T TOUCH THE STARTER! Instead, call for a tow truck and have your rig towed to a mechanic, pronto. The mechanic will need to take several important steps. Drop the fuel tank and dump the contents. Clean out the fuel tank. Change your fuel filters. Your charges? A red face, and a few hundred dollars. Remember, diesel fuel contaminated with DEF is considered a hazardous waste, and that in itself spells dollar output.
Your second option? Jump in the seat, hit the key, and drive like nothing has happened. Result? The moment the lift pump in your rig begins to push that contaminated fuel, you’ve got problems. It’s highly likely you’ll be looking at replacing your high-pressure fuel pump, your injectors, and a lot of other fuel system goodies. Your charges? Easily SEVERAL THOUSAND dollars. All from having DEF in a diesel tank.
Yes, we’ve heard of folks who, recognizing they’ve goofed, do “alternative” fixes. Drive a little. Crawl under the rig and pull the fuel separator lever and hope that the DEF will miraculously come out. Add various nostrums to the fuel tank to “increase lubricity” like two-cycle engine oil. Repeat all of the above. And maybe some folks have gotten away with it – so far. It may be that the time bomb just hasn’t gone off yet.
Avoiding the problem
How can you prevent the problem from the start? You may be blessed with having a rig where the DEF filler and the fuel ports are far, far away from each other. Some pickup owners cuss when they have to fill up their DEF tanks, because they have to pop the hood and practically crawl in with the engine. That might be enough to help you slow down and think your way out of a problem – before you get into it. And if you need a little reinforcement, watch this video produced by a diesel mechanic that can put the “multi-media fear of god” in you.
Some truck stops have introduced a “DEF mis-fill prevention device” on their bulk DEF pump nozzles. It’s a simple idea: The nozzle is equipped with a magnetically activated system. Until a strong magnetic force comes near the nozzle, you can pull the lever, but no DEF will flow. Equip your DEF port with the appropriate magnetic safety device, the nozzle flows. We’ve heard plenty of griping about these. If you hit a truck stop with the mis-fill preventer and don’t have your rig equipped with the safety device, you’ll have to go in and get one at the fuel desk, sometimes leaving a deposit. Of course, this system won’t stop you from pumping DEF out of a carton or jug into your diesel filler.
Talk to yourself!
If your fuel tank cap and your DEF port are anywhere close to one another, there’s a good chance of a major, expensive goof. So, if that’s the case with your rig, it may be best to slow down and concentrate. Don’t let anyone come chat with you as you fill up. Talk to yourself instead. We know – talking to oneself is generally reserved for folks who’ve had too much ethanol. But, hey. If looking like an idiot can save me potentially thousands of dollars, I’ll talk – and sing – my way through every fill!