(b) Overpriming is first indicated by very weak combustion, followed by
black smoke discharge from the exhaust. Excessive priming is evidence by
wet spark plugs and fuel appearing at the exhaust stacks.
(c) As the prime fuel is injected directly into the intake manifolds of
each cylinder, excess fuel will not be carried off by the supercharge
scroll drain which relieves the scroll housing of excess fuel delivered
only by the discharge nozzle which has opened, either by too high fuel
pressure being wobbled with carburetor manual mixture control out of
IDLE-CUT-OFF position, or by leakage of the discharge nozzle. Check nozzle
for leakage, or holding open due to dirt or foreign material.
(d) Overprining [sic] constitutes a dangerous fire hazard, as well as a
detriment to the oil film lubrication of the pistons, rings, and cylinder
walls of the engine.
(e) Extreme CAUTION should be taken to aboid [sic] overpriming on either a
HOT or COLD engine.
(f) To relieve overpriming, crank engine several revolutions, with switch
in OFF position, throttle wide-open, and carburetor manual mixture control
in IDLE-CUT-OFF position. This can also be accomplished by turning
propellor by hand in direction of rotation.
(g) Loss of compression (check by rotating propellor by hand in direction
of rotation) due to over priming may require lubrication of pistons,
rings, and cylinder walls with oil through the valve ports or spark plug
holes.
NOTE: IT IS RECOMMENDED THAT ALL PERSONNEL BECOME FAMILIAR WITH THE
SUGGESTIONS ON "GROUND TEST" AND "GROUND CHECK" AS DESCRIBED IN ALLISON
TROUBLE SHOOTING AND MAINTENANCE MANUAL RECENTLY RELEASED.
/s/ TYE. M. LETT, JR.
Summary of Contents for P-40 Tomahawk
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