Injection pumps have two provisions for synchronizing fuel delivery with piston movement. Time marks on the journey gears establish the an easy relationship. Elongated mounting-bolt holes, which permit the pump body to be rotated a couple of degrees, administer the fine adjustment. Reference marks stamped on the pump body and mounting flange enable the adjustment to be replicated (Fig. 5-14).

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Before remove a pump, bar the engine over until both valves ~ above No. 1 cylinder close and also the timing mark on the harmonic balancer or flywheel aligns through its pointer. This procedure indexes pump-gear timing marks for straightforward assembly. If the very same pump is reinstalled, the reference marks ~ above the pump body and also flange have to be valid. Substituting an additional pump put the marks right into question and also the engine need to be retimed, either statically or dynamically.

Static timing steps vary enormously, however the purpose of the exercise is come synchronize the onset of fuel distribution with the piston in No. 1 cylinder. Relying on engine make, model, and application, fuel should start to flow all over from 8–220 btdc together the flywheel is barred over by hand.

Flywheels for tiny utility engines typically have 2 marks enrolled on their rims: one representing tdc and also the other, constantly in advance of the first, indicating once fuel should start to circulation from No. 1 shipment valve. A convenient means to screen fuel flow is to consist of an adapter out of a size of clear plastic tubing and a delivery-valve fitting, as presented in Fig. 5-15. The mechanic progressively bars the engine over, while watching for the slightest rise in the fuel level. The beginning of fuel movement should take place at the minute the timing mark aligns through its pointer. If tdc is passed and the plunger retreats, the flywheel must be turned ago 15 degree or so come absorb equipment lash, and also the operation repeated.

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

Timing specifications because that distributor pumps are often expressed in thousandths that an customs of plunger movement from bdc. Number 5-16 illustrates the dial-indicator adapter that replaces the central bolt in the distributor head. Locating bdc—the specific moment when the plunger pauses at the bottom the its stroke—requires patience. As soon as bdc is found, the mechanic zeros the gauge and bars the engine over in the typical direction of rotation come the suitable crankshaft or harmonic-balancer mark. He then rotates the pump human body as essential to match lift through the released specification.

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Dynamic timing, made v a strobe irradiate while the engine ticks over at slow idle, compensates because that pump-gear wear and other variables. It is the only way that van and also other inaccessible engines can be timed.

The sunlight timing irradiate draws strength from a wall outlet or, if equipped v an inverter, indigenous the engine’s 12-V or 24-V battery (Fig. 5-17). A transducer clamps over No. 1 fuel heat to cause the strobe as soon as the injector opens and also the suddenly drop in fuel push contracts the line. The instrument likewise tracks how numerous crankshaft degrees the timing breakthroughs as engine rate increases.

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