Recently doing a leak back test on my TD6 I found that I had a lot of fuel come out of the return fuel hose while testing.

About 400ml in a few seconds, the injectors only just released enough fuel to reach the measuring bottles - about 700mm of tube.

All injectors were similar so all good there.

However previously using the same kit and setup i've run the engine for over a minute without coming close to filling the bottle I put the return hose in.

The only change is that ive fitted a new lower milage engine, runs and drives well and no codes generated.

Any idea why i'm now getting so much fuel out of the return hose??

Most of the fuel is returned to the fuel tank its normal

This is coming from the disconnected return line, that would normally be connected to the top of the injectors, I havent traced it but assume its going back to the tank, hence the concern over the amount of fuel coming the "wrong way"

I Believe you are supposed to clamp these return lines when doing the test otherwise fuel spills.