Pictures of your twin filter installation please

[a64pilot]

I think many engines, especially larger ones, again especially if pressure fed with a pump will just eat the bubbles, may stumble, but then will go on.
I know my 4JHE will just pass the bubbles through the return fuel line and drive on, as long as it gets enough fuel to run.
However many engines are finicky about air bubbles in fuel and won’t self bleed.
I think a lot depends on if your motor can just pass the air on down through the return or if it causes problems.

[capn jlp]

I saw your post about dual fuel filters and wanted to send you a diagram of the system we use on our Morgan 41. The diagram was on another computer at another location so please excuse the delay.

[Tillsbury]

Lovely, thanks for that. I see now why you have two separate valves rather than a selector to choose the filter.

Two questions:

Why do you have a valve V5 rather than a selector on the vacuum gauge? The way you have it you can’t read the vacuum gauge for the engine when the generator is on.

And is it ok to join the return lines like that? If the engine is on and generator off could there be a problem with pumping fuel into the return of the generator or vice versa?

[capn jlp]

"Why do you have a valve V5 rather than a selector on the vacuum gauge? The way you have it you can’t read the vacuum gauge for the engine when the generator is on.

And is it ok to join the return lines like that? If the engine is on and generator off could there be a problem with pumping fuel into the return of the generator or vice versa?"

We've never had the engine on when the generator was running, nor vice versa, hence the VG is always telling us the condition of the filter that is serving whichever is running.

It's apparently OK! We've had this setup for years now with no issues. Would suggest that it's a matter of the fuel returning via the path of least resistance.

[Tillsbury]

Handy to know, thanks! Do you have a pump for priming at all?

[capn jlp]

On the Perkins there's a priming pump with a manually-activated backup function, but I've rarely had to use it. The auxiliary fuel tank is located physically at a higher level than the engine so gravity provides substantial positive pressure.

Years ago I discovered that by accident. That fuel pump failed, and I was able to keep the engine running by switching to the auxiliary tank. When sourcing from the main tank (located below the engine) the engine would stop after a few minutes from lack of fuel. Going back to the aux tank, I was able to restart!

"If all else fails, try logic..."