Distribution and Regularity of Injection From a Multicylinder Fuel-Injection Pump

A six-cylinder commercial fuel-injection pump was adjusted to give uniform fuel distribution among the cylinders at a throttle setting of 0.00038 pound per injection and a pump speed of 750 revolutions per minute. The throttle setting and pump speed were then varied through the operating range to determine the uniformity of distribution and regularity of injection.

The variation in distribution among the cylinders reached a maximum of ±17 percent at low pump speeds and one-tenth throttle setting. Above one-half throttle the variation was not more than ±3.0 percent. No effect on the distribution was produced by a change in the type of injection valve or injection-valve spring. As the vale-opening pressure or the residual pressure in the injection tube was reduced to a very low value the regularity of injection increased. The distribution was little affected. A stiffer injection-valve spring also produced more regular injections. Poor seating of the injection-valve stem caused a variation in the residual pressure in the injection tube.