valve grinding compound. Leave the valve stem in the housing to act as a guide for the valve, then
insert a screwdriver in the slot and move it back and forth. After both the upper and the lower seats have
been ground, the valve housing, the stem, and the valve should be thoroughly cleaned, reassembled, and
connected to 90 psi air pressure. If, after considerable grinding, either seat still leaks, the valve seat is so
damaged that a new needle valve, a stem, and a seat assembly are necessary. Check both the needle
valve and the valve stem for damage.
c. Valve stem seats improperly. If a valve blows through the exhaust port when the coil is
energized, the valve stein is not seating properly. This may be caused by any one of the following, listed
(1) Dirt on valve seat.
(2) A weak battery or low voltage applied to the coil. This will sometimes give a sufficient
pull to unseat the lower valve but not enough to close the exhaust.
(3) Dirt under the pole plate.
(4) Valve stem worn down so that pole plate strikes the core before the valve seats. This
rarely occurs until after the equipment has been in service for several years. If the stem is found to be
too short, it can be slightly stretched by peening the shank. However, it is recommended that a new
assembly be installed.
Proper maintenance will prolong the life of the battery. Since batteries are ruggedly built, the
basic problem is mainly one of paying careful attention to a few important rules. These are given in the
subparagraphs that follow.
a. Keep the battery compartment ventilated to dissipate heat. Screen openings to keep out dirt.
Leave drains in the bottom of the battery compartment so that washing solution or drain water won't mar
the paint or superstructure.
b. Block the battery to prevent movement. Cables should not be subject to crushing or rubbing,
which will destroy insulation.