Fuel issue kad42b

[baily]

Hi all looking for help I have an issue with air getting into the fuel line having to bleed the engine to start it.
So up to now I have changed the primary fuel filter o rings, new fuel filter on engine, new fuel line from filter housing to fuel pump and new copper washers on fuel line to fuel pump and bleed screw.
I would be great full if anybody can give me any ideas what to look for or a way to test where the air is getting into the system please.

 

[BruceK]

Fuel taps is one. Often the tap (I come from a metric system so forgive me) may have NPT thread and the tails BSP thread. I think I got them the right way round. Any way with NPT, the peaks and valleys of the threads are flat. In BSP, they are rounded. This is enough to allow air in but not fuel out. Check there is PFT tape or similar sealing. Corrosion on the lift pipe where it exits the tank or in the tank. Copper joints work hardened.

About the only way to narrow it down is by using a jerry can and plumbing it in at various stages to see where the leaks start. Can be a bid of a sod but easy in principle.

 

[spannerman]

They can also leak at the lift pump, have changed a few because of this.

 

[bluejasper2]

try checking the fuel line connections we had similar happen to us took fuel lines of cut off 1" refitted solved our problems these were the flixible fuel lines from fuel tank. they were not leaking but were letting air in.

 

[fred247]

check any flexible hoses,
we had the same issue, one of the rubber hoses was pulling in air, but not leaking.

 

[oldgit]

When did it start doing it, had you replaced any primery/secondary fuel filters or done any recent work.
Worth checking for any weeps.
On my boat a smear of fuel was visible on one of the ribs.It turned out to be tiny crack in the copper piping to the lift pump.

 

[baily]

This issue started after a trip to Lymington went to start the engine and had to bleed the fuel system to get it to start and I have not found the issue have replaced the primary fuel o rings new engine fuel filter new fuel pipe from primary fuel filter to the fuel pump and replaced copper washers on fuel line to pump and bleed screw on filter housing still not found how air is getting inti the line?

 

[spannerman]

Simplest way to find out is fit some clear hose between the lift pump and fuel line, if you see air bubbles its upstream, if none then its from the pump onwards.