Early in the development it became quite evident that cold starting was a problem. This was finally worked out by Packard through the use of glow plugs and speeding up the injectors during the cranking period. It had been felt that during the slow cranking process we were not vaporizing the fuel through the nozzles and that if we could speed up the injection pumps during this period of cranking a better vaporization could be obtained. Our tests showed that we were right, and that the engine could be started quite easily at minus 10 deg. F through the use of glow plugs. The method used for speeding up the injection pumps was accomplished by utilizing a crankshaft cam during the cranking period. The starter would shift the running cam out of position allowing the crankshaft cam to take over. After the engine fired, the starter was disengaged and the running injector pump cam would assume its original position. The starting cam would be run at engine speed during cranking, and the running cam at 1/8 reverse engine speed during engine operation. The shifting was accomplished by a pin-in-slot and spring arrangement to change the indexing of the cams to starting position and return. An Eclipse electric starter with an oversized flywheel was used.... This was powered by a double-sized battery. Development Air Shutters: The first engines had no provision for throttling the intake air. This allowed the engine to run on its own lubricating oil when the throttle was in idle position. As a result the engine idled too fast, thereby causing either excessive taxiing speeds or rapid brake wear. This inability to idle slowly also caused high landing speeds since the propeller did not turn slowly enough to act as an airbrake. Figure 1 shows the first model. Note that the tubular air intakes on top of the cylinders have no valves. Figure 32 shows a later model. Note the butterfly valves in the U-shaped air intakes. Here they are shown fully opened. When the throttle was placed in idle position these valves automatically closed and prevented air from flowing past them. Air could then only enter from the back of the intakes. Since less air could flow into the cylinders, the force of their explosions was reduced, which, in turn, lowered the idling revolutions per minute. Figure 28 shows a cylinder from a more advanced model. Note the circular opening between the air intake and the intake/exhaust housing. A barrel type of valve fitted into this opening. One of these valves can be seen just below and to the left of the cylinder. When the throttle was placed in idle position this valve rotated to a position which cut off almost all of the airflow into its cylinder. This increased the vacuum formed toward the end of the intake stroke, thereby causing more resistance, which reduced the idling rpm to that of a gasoline engine.[16]