If your diesel engine misfires or stops, or your diesel heater starts smoking, you may need to know how to fix water in diesel fuel. How to stop it happening is probably your first thought though. Read on.

Water in diesel fuel can become a nightmare. It can stop your engine dead in its tracks. If you happen to be in your boat at the mercy of a tidal river it can be extremely dangerous. At the very least water in diesel fuel is inconvenient at best.

Water has adverse effects on many things. I only have to look at the bottom of our boat when she come out for periodical checks and antifouling to know that. Also of course, mixing water and electricity are a dangerous partnership. Having mentioned our boat reminds me of my reasons for writing this article.

It is a fact that water in diesel fuel can cause all sorts of mischief. If you have a diesel heater sharing your fuel tank, water can begin to accumulate in the pipes and inevitably get into the heater itself. This will stop your heater from working and can cause damage.

If water gets into your engines fuel pipework it will build up and travel into your fuel filters. Water is heavier than diesel, so diesel will float on the water. This means that your engine will continue to run until a little after the fuel filter is full of water. Beyond that point, the water will replace your diesel and end up in your engine’s injector pump. Your engine will stop when the last of the diesel has been injected. Hopefully without damage. Not everyone is this lucky, particularly if they continue to crank the engine. The injector pump is now only pumping water, and water is not compressible. This could now become a major and very expensive problem.

Imagine the image above is your water trap or fuel filter. The fuel comes from the pump into the top of the trap or filter. Because water in the fuel is heavier than the diesel it sinks to the bottom of the water trap or fuel filter. Eventually the water will fill the item and instead of fuel being pushed to the engine, a mix of fuel and water will end up in the engine. Possible disaster. Just to be clear. The fuel in the jar above is red diesel, commonly used in boats, Never to be used in any road vehicles apart from those classed as ‘plant’.

Don’t let this happen to you. Water in diesel fuel is preventable without breaking the bank.

The trick is to prevent the water from reaching your very expensive equipment by installing a water trap in the fuel line. The picture below shows a very simple, but incredibly successful water trap. It is made by CAV but there are many more types available. This one is on my own boat and what you can’t see is the CAV fuel filter to the right of the trap. You will find many water traps that have a fuel filter inside the same unit, above the water trap. This is okay and does work. However, I prefer to remove the water before it gets to the filter, just my preference.

When you fit a water trap it needs to be fitted after the lift pump but before the first fuel filter

Something important, as far as I’m concerned, is that my water trap is above the engine compartment, not inside it. When we are cruising, the water trap is in full view. In fact, because my water trap has a glass bowl, it is illegal for it to be placed in the engine bay, likewise, I believe with clear plastic bowls too. I believe that Racor are an exception to this rule.

There are many boats that have water traps tucked away in the bilge that are all metal cased. The big problem with these is that they often get overlooked and can go years between servicing. A water trap that is full of water has done its job but is no longer a water trap!

If you have diesel heating, such as Eberspacher or Webasto, whether they heat the air or water, and they have their own separate fuel tank, they also need a water trap. Diesel heaters hate water. Not only will water stop the heater from working, it can also cause internal damage. More expense….

Do yourself a big favour. Carefully check your fuel supply lines to see if there are traps or filters in the line. They are very easy to service, so do it. If you can’t find a water trap, get one fitted, preferably a trap with a drain tap at the bottom. If at all possible, fit it somewhere that you can easily see the fuel in the trap. You’ll soon recognise water if it appears, and be able to drain it before it can cause damage.

Before I go it may help you if you know how water can get into your fuel system.

Condensation is a major factor that cannot be ignored. There are a range of pour in products that can treat this problem once the mass of water is removed from the system. Air in your tank will almost inevitably have a level of humidity, and any moisture in the air will condense when it gets cold, or meets something cold. It’s also the good reason given for keeping a full fuel tank over the winter months.

Sometimes, water may have contaminated the fuel before you buy it and go into your tank without being seen.

Finally. What about your fuel tank lid? Make sure it is tight and that any seal it has is in good shape. Oh, and by the way… Make sure you do not get distracted… Make sure you actually put the fuel tank lid back on!

If you are concerned or want more information about water in fuel, click the link below. As well as being able to read part two of this article there is a seperate link to a very useful unbiased article from Wikipedia

 

The Menace of the diesel bug.

As well as the running problems that are caused by water pollution, there is also the danger of diesel bug existing if there is water in your diesel fuel. In the second half of this article called ‘Diesel Bug Cause Effect and Cure’ you’ll find lots of information about how to sort out the problem.