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Thread: Air in Racor

  1. #1

    Air in Racor

    Leaving for a short cruise last Friday, I fired the engines up about 1/2 hr before planned departure. After 5-10 minutes, I walked to the stern to check water flow. Both sides OK, but as I was looking at the port tube, the engine coughed, then quit. Cranked engine, no start. Pulled top off Racor, can half empty (or half full, depending on your outlook on life). Filter looked clean, changed it just because, filled can, primed with manual pump, good flow out of injector pump bleed. Tried to start, cranked for 5 seconds, nothing. Cranked again, advanced throttle quickly to full, fired up, idled smooth. Ran 10 minutes or so, coughed and died. Checked Racor, half empty. Just because it’s easy to do, switched port supply and return over to keel tank. Filled Racor, etc, cranked 5 sec, no start. Cranked and advanced throttle, fired up, ran smooth. Half hour later, still running. Decided to proceed with weekend anchor-out, ran 2 hrs to destination, no issues. On Sunday afternoon, stbd engine started right up, port cranked, no start. Cranked again, advanced throttle, started up, ran smooth, ran about 3 hrs to home with no incident. I’m thinking I have an air leak somewhere between the main tank port side pick-up and the manifold valve, and have no explanation for the new need to advance the throttle to start. First thing I’ll check is the pick-up tube, although I don’t think that’s the problem. I think all the line between the tank and manifold is copper (to be confirmed), so the manifold valve itself might be the most likely culprit. I’ll report back after inspecting the pick-up tube, piping and manifold valve. Meantime, any suggestions or ideas are welcome. TIA
    Mike Peters, 1985 43MY, Cat 3208T, Blue Bayou; 2011 Key West 246BR, F250, Baby Blue; Punta Gorda FL

  2. #2

    Re: Air in Racor

    Could be a weak seal on the cap of the unit. I had a leak from the drain at the bottom of the bowl. No fuel came out but air was being sucked in and you could see the bubbles. Turned out the bowl had a crack at the bottom next to the drain. Good luck.
    SEVEN
    1979 53' MY Hull #563
    Antioch, California

  3. #3

    Re: Air in Racor

    Quote Originally Posted by SEVEN View Post
    Could be a weak seal on the cap of the unit. I had a leak from the drain at the bottom of the bowl. No fuel came out but air was being sucked in and you could see the bubbles. Turned out the bowl had a crack at the bottom next to the drain. Good luck.
    I just changed my Racor filters last weekend and a couple of the gaskets looked a little questionable. Of course, I changed them with the ones which come with a new filter, but a little donk in the top of the housing could have easily caused a leak.

    That tiny o-ring looking gasket on the threaded cap screw could be out of place or broken as well.

  4. #4

    Re: Air in Racor

    Yep, that little red o-ring has bitten me before - I think I posted about it a couple of years ago. Since the engine operated fine on the keel tank pulling through the same Racor, I’ve eliminated everything downstream of the manifold. Tried to pull the pick-up tubes this afternoon, but stalled at the elbows that thread into the plate. Surprised, as the fittings on the shutoff valves came right apart. I soaked them in penetrant and left them to marinate for the night.
    Mike Peters, 1985 43MY, Cat 3208T, Blue Bayou; 2011 Key West 246BR, F250, Baby Blue; Punta Gorda FL

  5. #5

    Re: Air in Racor

    If you have an electric fuel pump, hook it up and at the racor and run it with a clear hose returning to the tank thru the hole for the gauge and check for air. Or hook it up to suck from the tank thru the racor and back to the pick up tube. That may clear whatever in the pick up tube. You could also turnoff the selector valve which would slightly pressurize the racor and valve and check for leaks.
    Pascal
    Miami, FL
    1970 53 MY #325 Cummins 6CTAs
    2014 26' gaff rigged sloop
    2007 Sandbarhopper 13
    12' Westphal Cat boat

  6. #6

    Re: Air in Racor

    You did not mention the secondary filter.
    If it is restricted, the lift pump may not be able to draw from a further away tank.
    Just a thought.

  7. #7

    Re: Air in Racor

    In similar cases, it has been a leaking Racor, a loose secondary spin-on, or a weak lift pump.

  8. #8

    Re: Air in Racor

    Just an update. Pickup tube was clear. Thinking of Capt Ralph’s suggestion, I decided to do the next easiest thing and change the secondary fuel filter. Couldn’t budge the filter, and instead of warming up the engine, I got a bigger wrench...and snapped off the filter mount. New filter mount arrives at Kelly Tractor on Wed. While playing with the filter, I spun the top off the Racor...and found the can half full, same as the failure condition with the aft tank. Was the engine minutes from failing on the keel tank? Don’t know, but as long as I’ve got the filter mount off, I ordered a new secondary filter-to-pump fuel line as the next most likely restriction - it runs across the top of the engine, so leads a hard life. If that doesn’t do it, the priming pump-to-Racor and Racor-to secondary soft lines are the next candidates.
    Mike Peters, 1985 43MY, Cat 3208T, Blue Bayou; 2011 Key West 246BR, F250, Baby Blue; Punta Gorda FL

  9. #9

    Re: Air in Racor

    Replaced the filter base, complicated by Cat having renumbered the part, presumably when the 3208 went out of production. Replaced both Racor o-rings, and installed new secondary filter. Engine started up on aft tank with application of throttle, and ran an hour without a stumble; Racor vacuum was steady at just below 4 mm Hg. Opened the Racor and found fuel level down several inches. Tomorrow I’ll switch Racor tops just to eliminate one more thing. After that, I’ll get a couple of fittings to back pressure the lines and look for leaks.
    Mike Peters, 1985 43MY, Cat 3208T, Blue Bayou; 2011 Key West 246BR, F250, Baby Blue; Punta Gorda FL

  10. #10

    Re: Air in Racor

    How much is several inches? 2-3” down is normal ops.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

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