In Reply to: Fuel Shut off valve leak -53 Jubilee posted by Roadrunner on November 28, 2017 at 15:41:49:
Leaking Sediment Bulb Assemblies usually are due to the internal seal on the valve stem being worn. The seal is the major ‘wear’ part on the assembly, all others being strictly mechanical. The only other possible leaking issue would be if the fuel line threads are boogered up/cross threaded. They are a special thread size, 7/16-24”, and once the fuel line outlet port or the valve stem inlet port on the bulb assembly gets cross-threaded, it will never seal right and thus leak. Causes of cross-threading can be from overtightening, forcing the line fitting in when starting it and causing the action, or attempting to ‘re-thread’ the port with the wrong size tap or the line fitting with the wrong size thread die. Always start the line fitting and valve stem by hand to ensure they are correctly aligned. Thread them in as far as possible by hand before tightening with a wrench. There is no need to replace the entire sediment bulb unless either of these threads is cross-threaded. Once cross-threaded there is no way to correct them even if you have the right size tap or die. The Valve Stem Assembly, p/n APN9191, can be purchased new for about $6 at the right place. It comes with a new knurled ON/OFF knob as well. This knob is fastened onto the valve stem with an 8-32 screw. Most all new ones will often fail in the field from vibration causing the knob to work itself off the stem and is lost forever. To correct this from occurring, I always apply a dab of thread sealant on it when replacing the valve stem on a sediment bulb. There is never going to be a need to ever remove it until the next time you need a new valve stem and the new stem kit contains a new knob and screw. Some folks think using Teflon Tape is the solution, but I avoid using Teflon Tape on these old N fuel systems. I’ve worked on many carburetors with pieces of Teflon Tape obstructing the sediment bulb and/or the carb fuel filter brass inlet elbow screen. Besides, the tape is only a temporary band-aid fix anyway. It would be OK in a pinch when you absolutely need to get the field plowed or hay mowed, but don’t rely on it for a permanent fix. Leaking fuel systems are a safety hazard. Do It Right The First Time, Dr. Demmings’ 1st law, has been my mantra since studying his manufacturing practices.
FORD TRACTOR EARLY 9N BRASS SEDIMENT BULB:
2N-9155-B SEDIMENT BULB ASSEMBLY; 39-54:
APN9194 VALVE STEM & KNOB:
WORN VALVE STEM SEALS: