Patent ID: 8733673

Claim:
An electronic unit injector having a spray tip with an internal valve seat, a needle valve in the spray tip, a spring cage surrounding a compression spring biasing the needle valve closed against the spray tip seat, a plunger operating in a chamber remote from the spring cage, a wall forming an end of the plunger chamber with a passage leading to an interior of the spray tip through passages in the spring cage and spray tip, wall receiving pins that laterally locate the wall, a plate type check valve adjacent an end of the wall passage allowing forward fuel flow from the plunger chamber through the wall passage to the spray tip cavity when open and stopping reverse flow into the wall passage when closed, an electrically operated control valve for selectively spilling fuel being displaced by the plunger at intervals between injection events, a ratio of the wall passage length to a cross section dimension of the wall passage being about 3 or less, whereby a fluid hammer effect of fuel in the wall passage on the check valve when the control valve opens to spill fuel in the plunger chamber is relatively small.