Help! Exasperating Air-in-Fuel Prob's on CD30.

[Geoff Safron]

I've been chasing this demon since I bought the boat: After a few hours of running (1500 RPM or so) air starts to "percolate" up into the primary filter, making the engine rev up now and then with the reduced pressure, until the bubble of air in the top of the Racor makes its way down to the line, eventually stalling the engine. I used to connect this to a half-full or less tank, seas of 3' or higher, and a starboard tack—thinking that the "percolation" was from fuel sloshing around in the tank. BUT, it happened just last weekend, motoring on a completely flat river. The only constant now is time: roughly 3 hours' or more of run-time. All my fittings and clamps seem tight, no fuel leaking; I refitted the tank fitting last summer with plumbers' compound. Could the fuel hose itself have developed pinholes which only open up after a few hours' time? I'm inclined to try to replace every fitting and the hose between tank and primary filter to try to GET this sucker! Any other theories? If swapping out the whole tank-filter line, anyone know sources for proprietary fittings, EG the aluminum tank fitting and down-tube? Please help—I can't count on this engine running when I need to!
Thanks, Geoff



Brainstorm@Unidial.com

[Tad McDonald]

I had a problem similar to this last year (I didn't actually see the air bubbling up but I had difficulty starting the engine. I had to bleed the entire system over and over (injector pump included). While it seemed that all the fuel lines were in perfect condition, air had to be introduced to the system from somewhere. I changed the primary and secondary fuel filters and replaced every fuel line. I haven't had a problem since. Seems pretty drastic but it was effective (and pretty cheap).



tadmcdonald@worldnet.att.net

[Larry DeMers]

I also have been fighting these air leaks until I rebuilt the system. I would caution you to replace..do not reuse any of those "Crushable" washers. I did not, and got a leak under one washer regardless of how tight it was in place. I even left off a washer once, and didn't relaize it until it was too late.

Good Luck,

Larry DeMers
s/v DeLaMer
Cape DOry 30

I had a problem similar to this last year (I didn't actually see the air bubbling up but I had difficulty starting the engine. I had to bleed the entire system over and over (injector pump included). While it seemed that all the fuel lines were in perfect condition, air had to be introduced to the system from somewhere. I changed the primary and secondary fuel filters and replaced every fuel line. I haven't had a problem since. Seems pretty drastic but it was effective (and pretty cheap).

demers@sgi.com

[John]

I also have been fighting these air leaks until I rebuilt the system. I would caution you to replace..do not reuse any of those "Crushable" washers. I did not, and got a leak under one washer regardless of how tight it was in place. I even left off a washer once, and didn't relaize it until it was too late.

Good Luck,

Larry DeMers
s/v DeLaMer

Larry is absolutely correct in his observation regarding washer replacment. The banjo fuel fitting washers are very vulnerable to air leaks if used over again, you must swap them out for new ones after servicing. I have never seen it necessary to replace them if the fuel line is simply cracked open for bleeding. But if the banjo fitting is completely removed from a connection point such as the fuel filter housing or injectors then the washers completely misalign from their previous set and can leak. If a person tries to compensate for the poor refit of the washer by really torqueing down when tightening the hollow fuel nut and shears it off then you've really got a problem. The washers are dirt cheap, stock up on them and replace after service, their replacment can save a lot of heartache.
As far as the air leak goes I'd double check the o-rings on the Racor seperator fittings, sometimes they don't seat properly and get pinched resulting in a air leak. I've also seen problems from fuel line hose barbs where individuals had used a utility knife to cut through stuck hose to remove it and resulted in scoring the barb enough that it allowed air leakage. Are you sure you have a air problem and not a bio-growth problem? The time span sounds just like a mild bio-growth problem gradually clogging the filter.

Cape DOry 30

I had a problem similar to this last year (I didn't actually see the air bubbling up but I had difficulty starting the engine. I had to bleed the entire system over and over (injector pump included). While it seemed that all the fuel lines were in perfect condition, air had to be introduced to the system from somewhere. I changed the primary and secondary fuel filters and replaced every fuel line. I haven't had a problem since. Seems pretty drastic but it was effective (and pretty cheap).

[Marv Birdt]

I also have been fighting these air leaks until I rebuilt the system. I would caution you to replace..do not reuse any of those "Crushable" washers. I did not, and got a leak under one washer regardless of how tight it was in place. I even left off a washer once, and didn't relaize it until it was too late.

Good Luck,

Larry DeMers
s/v DeLaMer

Larry is absolutely correct in his observation regarding washer replacment. The banjo fuel fitting washers are very vulnerable to air leaks if used over again, you must swap them out for new ones after servicing. I have never seen it necessary to replace them if the fuel line is simply cracked open for bleeding. But if the banjo fitting is completely removed from a connection point such as the fuel filter housing or injectors then the washers completely misalign from their previous set and can leak. If a person tries to compensate for the poor refit of the washer by really torqueing down when tightening the hollow fuel nut and shears it off then you've really got a problem. The washers are dirt cheap, stock up on them and replace after service, their replacment can save a lot of heartache.
As far as the air leak goes I'd double check the o-rings on the Racor seperator fittings, sometimes they don't seat properly and get pinched resulting in a air leak. I've also seen problems from fuel line hose barbs where individuals had used a utility knife to cut through stuck hose to remove it and resulted in scoring the barb enough that it allowed air leakage. Are you sure you have a air problem and not a bio-growth problem? The time span sounds just like a mild bio-growth problem gradually clogging the filter.

Cape DOry 30

I had a problem similar to this last year (I didn't actually see the air bubbling up but I had difficulty starting the engine. I had to bleed the entire system over and over (injector pump included). While it seemed that all the fuel lines were in perfect condition, air had to be introduced to the system from somewhere. I changed the primary and secondary fuel filters and replaced every fuel line. I haven't had a problem since. Seems pretty drastic but it was effective (and pretty cheap).

I had a similar problem several years ago. I subscribe to the bio-growth scenerio, particularly if you have a 90 degree fitting on either side of the fuel filter. I'd remove the filter and clean the intake lines and fittings carefully. Good luck....Marv Birdt CD30B CRYSTAL Hull # 358



mbirdt@peganet.com`