Defender 90 300tdi air leak back to tank

Replaced the lift pump with Delphi and clear fuel line from tank to lift pump and clear line from injection pump back to tank.

Engine struggles to start when left overnight. The diesel is draining away from lift pump heading back toward tank but engine fires as soon as diesel hits lift pump.

Leak of pipes have new washers and pipes, bleed screw on top of filter has new washer and fuel filter has been replaced.

I havent yet replaced the other lines with clear from lift pump to filter to injection pump and washers.

Is it possible the injection pump could leak air overnight?
I have been told there is a one way valve in injection pump?

fit a clear plastic pipe between filter and front banjo fitting on pump you will see if its actually drawing air ,front banjo is also best place to bleed system when changing filter etc,

Ok will give that a go. Its gonna be hard to get clear pipe and clip on banjo fitting to seal unless I can find clear hard plastic line heat it up and slide over barbed pipe. I been using flexible pipe 8mm almost like garden hose which cant be heated. Might change the banjo fitting to match the return banjo fitting on pump, no barb if that makes any sense.

its a good idea to fit pipe well and leave it in place, i often get clear pipe same size as original and use two push fit connectors to put a piece 2-3 inches long in the line