Injection pumps have actually two provisions because that synchronizing fuel delivery with piston movement. Timing marks top top the journey gears develop the simple relationship. Elongated mounting-bolt holes, which allow the pump human body to it is in rotated a few degrees, carry out the fine adjustment. Recommendation marks stamped on the pump body and also mounting flange allow the mediate to be replicated (Fig. 5-14).

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Before removing a pump, bar the engine over till both valves ~ above No. 1 cylinder close and also the timing mark on the harmonic balancer or flywheel aligns with its pointer. This procedure indexes pump-gear time marks for straightforward assembly. If the exact same pump is reinstalled, the recommendation marks top top the pump body and flange should be valid. Substituting another pump put the marks into question and also the engine have to be retimed, one of two people statically or dynamically.

Static timing actions vary enormously, however the objective of the practice is to synchronize the beginning of fuel delivery with the piston in No. 1 cylinder. Depending on engine make, model, and application, fuel should start to flow everywhere from 8–220 btdc as the flywheel is barred over by hand.

Flywheels for tiny utility engines generally have 2 marks inscribed on their rims: one representing tdc and the other, always in advancement of the first, indicating once fuel should begin to circulation from No. 1 shipment valve. A convenient method to screen fuel circulation is to consist of an adapter the end of a length of clean plastic tubing and also a delivery-valve fitting, as presented in Fig. 5-15. The mechanic gradually bars the engine over, when watching because that the slightest rise in the fuel level. The beginning of fuel movement should occur at the minute the timing mark aligns through its pointer. If tdc is passed and also the plunger retreats, the flywheel need to be turned back 15 degree or so to absorb gear lash, and the operation repeated.


Drive gears because that Navistar (International) DT358 and also its cousins have six timing marks. I beg your pardon one to use depends upon the engine model and also application. In a reversal of timeless practice, details American Bosch pumps time to the end, rather than the onset, of fuel delivery. The shipment valve, which acts as a inspect valve, because that No. 1 plunger need to be disabled prior to timing.

Timing specifications because that distributor pumps are often expressed in thousandths the an customs of plunger motion from bdc. Number 5-16 illustrates the dial-indicator adapter that replaces the main bolt in the distributor head. Locating bdc—the an accurate moment when the plunger pauses in ~ the bottom that its stroke—requires patience. As soon as bdc is found, the mechanic zeros the gauge and also bars the engine end in the normal direction that rotation to the ideal crankshaft or harmonic-balancer mark. He then rotates the pump human body as crucial to enhance lift v the published specification.


Dynamic timing, made with a strobe irradiate while the engine ticks end at slow idle, compensates for pump-gear wear and other variables. It is the only method that van and other inaccessible engines deserve to be timed.

The sun timing irradiate draws power from a wall outlet or, if equipped with an inverter, from the engine’s 12-V or 24-V battery (Fig. 5-17). A transducer clamps over No. 1 fuel heat to create the strobe when the injector opens and also the suddenly drop in fuel press contracts the line. The instrument likewise tracks how numerous crankshaft levels the timing developments as engine rate increases.

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Unit injectors (UIs), which incorporate the pump duty with injection, space timed as explained below.