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Fuel for the ignition

There's little doubt that many cold, blustery days lie ahead of us before leaves re-appear on the trees. And from the standpoint of fuel systems, it is imperative to ensure that all components are win...



There’s little doubt that many cold, blustery days lie ahead of us before leaves re-appear on the trees. And from the standpoint of fuel systems, it is imperative to ensure that all components are winterized. (That is to say, such work should already be complete. But it’s better late than never.)

The inspection

Primary and secondary filters and fuel filter/water separators should be replaced, and fuel tanks should be drained and flushed at least once a year on long-haul vehicles.

Fuel lines and fittings also need to be inspected. Look at the state of clips and plastic ties that hold lines in place, and watch for kinks in the fuel line. Spongy flexible lines can indicate swelling or internal line restrictions, or leaking fuel on the pressure side of the fuel system.

The built-in fuel heater within the fuel filter/water separator also needs to be functioning correctly. With the separator, you should watch for any signs of fuel leaks, the excess accumulation of water in the clear plastic bowl, air bubbles and other telltale signs of electrical or mechanical damage.

After all, water is one of the diesel engine’s biggest enemies.

Diesel fuel tends to absorb and hold water because of its high vaporization temperature, and this water can freeze and plug fuel lines in cold weather.

Even if you use a fuel filter/water separator, water that still gathers in the fuel tank and pick-up line can lead to microbial growth and plug the filter.

(An additive such as Biobor JF or an equivalent can help here.)

You can determine microbial activity with a commercially available test kit.

Waxing problems

But that isn’t the only thing that can plug your fuel filter.

A diesel fuel’s “cloud point” is the temperature at which wax crystals will settle in the fuel. These wax crystals form from the paraffin base of crude oil, from which diesel fuel is distilled.

The resulting deposit typically looks like candle wax, and it clogs porous material in your fuel filter. This prevents the flowing of fuel and, even when the engine is cranking fast enough, it can keep your engine from starting.

The grade of the fuel you select will determine the temperature at which “waxing” will occur.

Quite simply, the pumps will be labeled to indicate the grade of fuel, and the No.1 D that is less prone to waxing is usually more expensive than its No.2 D counterpart.

But few long-haul truckers like to use the No.1 D grade because – all things being equal – it could cost you five to 10 per cent in fuel economy. It tends instead to be favored by city bus drivers that see a lot of stop-and-go driving, particularly with vehicles powered by two-stroke Detroit Diesel engines.

Those who mention “summer diesel” are referring to the No.2 D variety, which has a distillation point about 38 to 66 Celsius (100 to 150 F) higher than No.1 D. You can still use it throughout the year, but an additive is in order if you want to avoid waxing in colder climes.

It’s best in cold weather to use a low-sulfur No. 2 D fuel with a cloud point temperature that falls 6 C (10 F) below the lowest expected ambient air temperature, to prevent the clogging of your filters.

Mixing problems

Some fleets will blend in-yard supplies of diesel fuels, mixing both a No.1-D and No.2-D fuel to lower the cloud point, rather than using a traditional additive. Others will add kerosene.

Typically, such blending will affect the ignition delay characteristic of the fuel, leading to a dense exhaust smoke. That’s particularly troublesome in regions such as Ontario and B.C. that actively check such things.

And when 10 per cent of your fuel volume consists of No.1 D, you’re lowering the cloud point by only 3 F. If you wanted to lower the cloud point by 10 F, about 30 per cent of the fuel would have to consist of No.1 D, with the remainder being the No.2 variety.

And there are some other important differences between the grades that need to be considered before running to the No.1 D pump because of cold weather:

CETANE NUMBER (ignition quality), which is a measure of the time delay between the beginning of injection and the actual start of combustion. Usually a minimum cetane number of 45 is recommended for best engine performance. But No.1D fuel may be one to two points below that of its No.2 D counterpart.

HEAT CONTENT of No.1 D fuel is a few per cent lower than No.2 D fuel. That means a slight drop in fuel efficiency when you operate with No. 1 D.

THE VISCOSITY of No.1 D fuel (lighter viscosity) is likely to be slightly lower than No.2 D fuel. This is unlikely to be low enough to cause a catastrophic failure, but a steady diet of No.1 D in engines designed for No.2 D fuel may lead to greater long-term wear in the fuel injection system.

Diesel fuel also oxidizes in the presence of air, heat, and water – even more so if the fuel contains cracked products such as kerosene that are relatively unstable. This can lead to undesirable gums and black sediment that can lead to plugged filters, deposits in the combustion chambers, and gummed or lacquered injection system components that can reduce engine performance and fuel economy.

Additives

Diesel fuel from major OEMs seldom needs supplemental additives. But if your rigs operate in cold weather for extended periods of time, you might still want to consider a low-temperature performance additive. A number of such products are readily available, both from fuel OEMs and as aftermarket products. Chevron Zerolene, for example, helps engines operate below a fuel’s cloud point temperature. Designed for use with No.2-D fuel, it improves filtering at low temperatures, and slows the freezing of the fuel line. A one-gallon bottle (4.5 litres) treats up to 300 gallons (1,350 litres) of No.2 D diesel fuel.

Basically, a product like Zerolene changes the size and shape of wax crystals and allows the waxes that are formed below the cloud point to form a porous wax cake on the fuel filter, to allow an adequate flow of fuel during your engine’s critical warm-up phase.

To maintain clean injectors, a number of liquid additives are commercially available. These concentrated cleaners are specifically designed to clean up the injectors in all heavy-duty, direct-injected diesel engines.

Synthetic Diesel Fuel

Now for the future:

Synthetic lube oils are already widely available and in use in many heavy-duty rigs. But several companies are also testing and researching the use of a synthetic diesel fuel.

One such fuel is known as Syntroleum and is a shared venture between DaimlerChrysler and Syntroleum based in Tulsa, Okla. Dodge trucks, equipped with the Cummins 5.9-litre, six-cylinder B engine, are widely used by DaimlerChrysler.

With a 7.2-litre diesel, the test engine ran nearly 20 times cleaner than a comparable diesel from the late 1980s.

The synthetic fuel is made from natural gas and can run in today’s vehicles without modifications. Syntroleum is crystal clear, just like water, and it contains no aromatics (and theoretically sees no smoke at the exhaust stack), no sulfur and no heavy metals. With no sulfur, you can run it in a diesel engine and add an exhaust catalytic converter – ala gasoline automotive engines – and further clean up NOx (nitrous oxides) and other emissions.

This fuel will be readily available for diesel engines by 2004. n

– Bob Brady is the president of Hi-Tech Consulting in Burnaby, B.C.


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