Air in fuel system, any help in diagnosing?

[savageseadog]

The OP said "Engine starts and runs well at normal cruising speeds", so a blocked pickup pipe isn't a possibility.

So did mine or I wouldn't have bothered contributing to the thread.

 

[pvb]

So did mine or I wouldn't have bothered contributing to the thread.

You'll have to explain that. If a pickup pipe blockage is sufficient to stop the engine at idle speeds, how can it allow sufficient fuel through for the engine to run normally at cruising speed?

 

[fisherman]

A friend had an ongoing fuel problem, after a lot of head scratching and a complete dismantle, he found a bluebottle in the vertical section of pipe coming up out of the tank, it allowed fuel to flow until it got up to a right angle bend and then stopped. Now that's what you call diesel bug.

 

[ghostlymoron]

I understand that after tightening the through bolts on the sedimenter and filter units, the problem has not re-occurred - yet.

 

[pcatterall]

Yes!! after a long test period and a long run the problem has not re-occurred. Advice from this forum gave me confidence ( and a figure) to torque up the bolts ( I had been concerned about breaking the glass).
Touch wood of course but thanks to all for the advice.

 

[Bilgediver]

I have one of those mystery leaks and would like to know if there is some diagnosis that will help me locate it.

I seem to rrmember from a previous thread that your CAV filter head is used as a junction point so replacing with a Racor might need some thought. The air leak is probably in the CAV filter between the lift pump and fuel tank or the connection at the fuel tank if it is on the tank top. av you ensured the small seal is under the centre bolt head as this may be required on some filters. Check that the seals between head filter bowl and base are all correctly inserted as easy to put a twist in one of these.

Your fuel system possibly does not return the spill fuel to fuel tank but recirculates it at the CAV mixing with fue from the tank. This can allow it to build up especially at low revs. Pressurising with a small electric pump will certainly help and show up the leaks