Fuel Pumping System and Oiler Repair

Part two in a three-part series: Restoring a 4?HP Charter-Mietz oil engine

| August 2006

I took a look at the camshaft arrangement for the pumps. There are two ratchet assemblies, one mounted on the fuel tank. This ratchet has a camshaft mounted on top that stops in four positions. The second ratchet is mounted on the rear end of the transfer port cover. It is spring-loaded, with a wedge-shaped tooth that engages a spider wheel on the camshaft. It ensures that the camshaft reel turns only in one direction. The camshaft reel itself has three sets of camshafts: two having four lug-type camshafts set 90 degrees apart, and each camshaft set itself was 45 degrees from its neighbor. The third set is the spider wheel, which has eight angular lugs that engaged both timing ratchets at various times. As the crankshaft turns, the ratchet assembly, when engaged, advances the camshaft assembly at the rate set by the adjustable ratchet. This can be from no movement of the camshaft, 1/8 turn, 1/4 turn and to approximately 1/3 turn. Each setting provides a different camshaft action on the pumps.

"I was astounded to find the bugger (the flywheel) weighed 351 pounds with the governor attached!"

On the first setting, with no movement, the setting maintains a simple stroke of the camshaft, maintaining the pump selected, whether it be on the primary or secondary pump. On the 1/8 turn setting, the camshaft is allowed to trigger both pumps on an alternating basis. For each revolution of the crankshaft, one pump or the other is triggered. I should note here that the secondary pump has the provision to alter the stroke of the pump itself by means of a threaded camshaft pushpin and jamb nut - for adjustment of stroke as required by the use of different fuels.

For the third setting, the position allows the camshaft to advance 1/4 turn, activating the pump selected at every revolution of the crankshaft. I believe this position is a set up position for the fourth setting. This last setting is triggered on the primary pump injection stroke only. The 1/3 turn allows the primary injector pump to be triggered only every other revolution of the crank. The engine double-strokes during this setting. If the engine were to be run constantly, and have long periods of no load, speed could be maintained during the no-load cycle with this setting at the savings of half the fuel normally used.

The entire camshaft assembly is mounted on a rocker arm, activated off an eccentric camshaft on the governor side flywheel. With the governor at rest, this eccentric has maximum throw, about 1-inch total, which translates to about 2-1/2 inches of throw at the fuel end of the camshaft assembly. As the engine speed increases, the eccentric is spun in its axis and at full-governed speed, the eccentric barely moves the rocker arm. The ratchet assemblies turn the camshaft assembly no matter what the rocker stroke may be, but the length of stroke the camshafts give to the fuel pumps may vary from nearly 1-1/2 inches down to no movement of the pump drive pistons at all.

The rocker also has a pivot pin opposite the camshaft assembly that drives the oiler. As engine speed increases, the pump stroke is shortened, maintaining a constant flow of oil to the piston and its bearings, but cutting back on volume as the load lightens. Luckily, the fuel camshaft assembly and both ratchet assemblies were not stuck. The governor was free as well, and only needed a cleaning and oiling. I did have to remove the governor side flywheel though, so I could place some needed thrust washers on several shafts to take out end thrust that was excessive.


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