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Parker Engine Mobile OE: Racor Products Blog & Information - North America

Clogged Filter: Filter or Fuel Problem?

Without warning! Your fuel filter plugs, and your diesel engine sputters to a stop. Dead in the water. Stuck on the side of the road. Half-way through plowing a field. 10 minutes after the emergency power kicks in. The severity of the situation can range from highly irritating to downright dangerous.

Whenever it happens it's always at the worst possible time. It's easy, and maybe natural, to blame the fuel filter for "pre-maturely" plugging. But what does that even mean?

Fuel filters don't plug "pre-maturely". They plug exactly when they are supposed to-- at the moment when your engine needs the most protection from highly contaminated diesel fuel.

So remember, when fuel filters plug quickly, they save your engine. Always keep element spares with you, and buy your fuel from trusted sources. An onboard diesel fuel filter’s job is to remove fine particulates and water in reasonable amounts. They can’t magically make really bad fuel good again. However, they are very cheap insurance against catastrophic contamination of your fuel system, which could happen with your very next load of diesel fuel.

Which brings us to prevention. The problem wasn’t the diesel fuel filter in the first place. The blame falls squarely on the cleanliness of the fuel tank and the diesel fuel that was dispensed into it. If the fuel tank is rusting inside and usually half full, that will cause trouble. Normal tank temperature cycles promote water condensation on the walls. Soil bacteria love the interface between the diesel and water. Dead bacteria plug filters. If this is you, get your fuel tank cleaned.

What else can you do? Again, carry spares. Be aware of your diesel fuel supply. If you actually own the fuel supply, use a large dispensing filter when transferring fuel to equipment. There’s no reason to transfer dirty fuel from a storage tank to your equipment if you don’t have to. Consider a filter polishing loop system on the fuel storage tank, or even onboard the equipment.

More? Keep diesel fuel tanks topped off to avoid water condensation. Buy a vacuum/pressure gauge and change filter elements when differential reaches 8 inHg above starting value. Above 8 inHg, water removal efficiency slides and plugging really starts. Pinching pennies at this point is asking for trouble.

Extra credit: Cut open a used filter now and then, and look for wet contamination and black sludge. A used filter may have a thin coat of brown to black contamination, with a little bit of sheen. That’s normal. But finding wet globs of stuff (like the accompanying picture) is cause for concern.

In short, to survive a plugged filter shutdown and avoid future problems:

1. Always carry spares. 2. Find fuel supplies you trust are clean and their tanks maintained. 3. Look for big (maintained) dispensing filters at the pump. 4. Don’t ignore repeated “water-in-fuel” warnings. 5. Check the onboard fuel tank for rust and water regularly. 6. Keep your diesel fuel tank topped off when possible. 7. Cut open a used filter now and then for inspection. 8. Buy a gauge and monitor filter pressure drop.


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