The tip-off

At best, water in the fuel is an awkward inconvenience. But it could cause engine failure at a crucial time.

Water in fuel

Water in your diesel fuel tank is bad news. If it finds its way to the injectors, you’ll experience erratic idling and performance. The engine may even cut out momentarily, especially during acceleration.

A pressure indicator will reveal variations in the common rail system – if you have one of those. You’ll also see black or white smoke during engine operation. These are reliable symptoms of water in the fuel.

The issue can be avoided if your engine’s fuel filters have water-sensing senders. These are common but not fitted to all engines.

Follow the fuel from the filler and tank and you’ll come to the primary filter. This filter isn’t usually fitted with water alarm sensors, but it is the first place that water will be seen.

It’s good practice to examine the filter before you set of out to sea. Most people do this while checking the oil level. You should see clean diesel inside the clear plastic filter bowl.

There may be some particles of dirt in the bottom. Small amounts can be accepted, but I’d recommend stripping and cleaning the bowl to begin monitoring. If the dirt returns after one trip, there’s probably dirt in your fuel tank and/ or the filter needs replacing.

If you see water under the fuel, drain it off immediately. Run the engine afterwards to see if more water appears. If so, the problem needs to be addressed.

Water in the primary filter will pass through the low-pressure pump that takes the fuel to the engine. The water enters the secondary filter (mounted on the engine). If your engine has a water sensor, it will be on this filter. The alarm comes on and the engine goes into self-protection mode.

BNZ