If your fuel system leaks, it can be expensive and dangerous – but it’s easy to maintain.




The most basic fuel systems consist of a pipeline running from the fuel tank through to the engine. Modern vehicles also incorporate return lines, fuel coolers and pressure regulators. This adds to the number of connections and components that can leak, making occasional checks even more worthwhile.
There are two main causes of a leak in a fuel system. First, a cracked or corroded pipe, or a loose connector, can allow fuel to escape. That’s an expensive waste, but it’s also a danger because of the fire and explosion risk from petrol, while diesel fuel leaking onto the road becomes a slippery hazard for motorcyclists.
Second, depending on the fuel system’s design, tiny gaps in connectors and pinholes in the pipework can draw air into the system, causing worrying engine symptoms, such as starting issues, misfiring and rough running.
These can both be avoided by checking under the vehicle for signs of fuel drips, ensuring connectors on fuel lines are tight and that metal pipes are free of corrosion.


Fuel pipes

Newer vehicles have [tl:gallery index=1 size=215×129]plastic fuel lines, but these can split with age and, like metal pipes, can chafe at the point where they contact and vibrate against the sharp edges of the ’van’s structure and components. Therefore it’s important to check the pipes are firmly secured by their clips and are prevented from vibrating too close to other parts.
Treat rusty fuel pipes with care, though. Trying to remove rust from a pipe might produce a pinhole through which fuel could spurt, especially on pressurised sections, so always wear eye protection. And though risking a pinhole leak while cleaning the pipes may seem counterproductive, it’s better to discover these potential leaks in your workshop rather than to discover one when you’re on the road.
Keeping fuel lines clean is the first step to preserving them. A build up of road dirt leads to moisture being held around the pipes, which then leads to rust forming. If kept clean, their original anti-corrosion treatment will do its job, although a smear of preserving grease, liquid wax or oil will help.
Once you know where the fuel lines are underneath the vehicle, it’s a quick job at the car wash to aim the water jet underneath to keep them clean. The water will dry off after a few miles of driving.
Clean the pipe connections, plus the bolted and screwed fixings and supports, then apply penetrating oil. When dry, give them a squirt of liquid grease from an aerosol. This helps individual sections of the fuel system to come apart easily for maintenance and repair, reducing garage bills for both labour and parts.
Check that no fuel pipes are loose or hanging down where they might become snagged if ground clearance is low, too.
Rubber pipes can be flexed with the fingers to reveal cracks in the outer casing. If the braiding is showing in the cracks, it’s time to renew the pipe. Fit only automotive fuel piping that’s rated to suit your vehicle’s system and use new securing clips.


Engine pipes
There’s unlikely to be [tl:gallery index=2 size=215×129]any corrosion here, but if you smell fuel look for leaks at the connections. Due to the high pressure of fuel reaching the injectors, repair in this area should be entrusted to a professional.

Fuel tank

Modern fuel tanks are plastic, [tl:gallery index=3 size=215×129]but still keep an eye on the metal brackets and straps that hold them in place. Use a non-metallic tool to poke away the accumulated dirt, then brush the area clean and apply rust convertor, followed by a liquid wax or oil. Check along the seams of steel fuel tanks.


Filler cap

Check the hose between the filler [tl:gallery index=4 size=215×129]neck and the tank and, if there’s a vent hose here, ensure it is kept clear.





The wrong fuel

1. Putting petrol into a diesel tank

Accidentally filling a [tl:gallery index=5 size=215×129]diesel ’van with petrol can cause serious and expensive damage. Diesel components rely on the lubricating qualities of the fuel, which aren’t present in petrol. So if petrol goes through the system, it will rapidly cause wear and surface damage to precision components in the fuel pump and injectors.
Ideally, don’t start the engine, or even turn the ignition on. Draining the tank and refilling with diesel should get you going again.
If you have turned the ignition on, vehicles with an electric fuel pump will have started pumping petrol through the pipework, though draining and flushing the system should rectify the problem. If the engine has been started, the complete system may need to be removed for cleaning or replacement of parts.
If the vehicle has been started or driven, a garage might want to replace all the engine fuel components because it has a responsibility to ensure that everything is in order. However, some engines will perform normally once the fuel is replaced.


2. Putting diesel into a petrol tank

There will be a loss of [tl:gallery index=6 size=215×129]performance and exhaust smoke, and a modern engine management system will soon object via the dashboard warnings. However, if you drain the tank and fill up with diesel, all should be well after the smoke clears.



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