How to fit a non-return valve to your diesel car.
What Does a non-return valve do?
A non-return valve is a one-way valve that will only let the fuel flow
in the direction of the injector pump. If it was
to try to flow backwards it would close and stop the fuel in the
Why you might need a non-return valve.
Non-return valves can be used for a multitude of problems, mainly where the fuel has drained back to the fuel tank due to the system drawing in air
overnight. This could be caused by a leaking fuel line or a bad seal
on the injector pump.
You don’t necessarily have to have a fuel leak to have a leaking fuel
line because the diesel system sucks the fuel if any of the joins are
unsealed they will draw in air bubbles.
Diesel cars rely on a sealed fuel system to ensure the fuel stays primed but
if it isn’t the fuel lines will empty over a matter of hours. Come the
morning and the engine is turning over….. and over….. on the ignition key.
Fitting a non-return valve is not a repair but it will lessen the symptoms of
the fault until you can find the problem(this is often easier said than done).
How to install a Non-Return Valve on your Vehicle.
Fitting a non-return valve is usually a very simple job.
First, you need to work out what size you need by the internal diameter of
your fuel line. Commonly these are between 6mm up to 13mm in larger
Once you have your valve we need to identify which is your feed fuel line.
In a common setup, this will come from the fuel filter.
Now we have established which line it is you need to cut the line ready
to fit your new non-return valve. The valve should have some type of
parking to indicate which way the flow is intended to go, ensure you
get this right otherwise your engine will not run.
The first start might be tricky since we have broken the seal on the fuel line.
But if your reading this its probably something you have tackled
If your engine has a prime bulb give it a few squeezes to get fuel back
into the fuel lines.
If not a few cranks of the engine should see it fire into life.