We know fuel nozzles get contaminated, but how does this occur? After all, there are several screens in the fuel system that are designed to prevent this. There’s the fuel strainer (part of the airframe), there’s a screen in the fuel injection control assembly, and there’s also a screen in the flow divider (spider) on the top of the engine. Generally, these defenses should combine to prevent any contamination of your nozzles – but it can still happen. Some sources of contamination include:
- a disintegrating rubber hose;
- a small shard of metal resulting from corrosion in a wet wing fuel tank;
- a small particle of sealant from work on the fuel system;
- the disintegration of the diaphragm in the flow divider itself, which misses all of the screens.
As we can see, despite the various screens, contamination happens, and when it does, it’s nearly impossible to fix using the method of cleaning employed by most mechanics. In fact, soaking the nozzle in solvent also serves to loosen up any deposits, which can actually add to the total amount of contamination in the nozzle.