Page 282 - CTS - Mechanic Diesel - TP

MECHANIC DIESEL - CITS

Starting delivery. (minimum)

7 Governor cutting-in vacuum Connect vacuum pipe.
Run pump at 500 rpm. Operate the vacuum pump till the control rack just starts to move back and note the
vacuum on “U” be manometer. The vacuum should be as specified

Mounting of pump with pneumatic governor on engine
Though pneumatic governor pumps are calibrated on fuel injection test bench by simulating engine manifold
vacuum conditions with the help of a vacuum pump, finer adjustments of governor, in conjunction with engine
venturi settings are essential so as to obtain the desired idling, full load and flyup (maximum no load) speeds.

By exercising due care at the time of mounting the pneumatic governor pumps on the engine.customer
complaints viz. engine hunting, surging. erratic running etc which are normally associated with governor and
venturi adjustments can be minimised.
Normally idling position and maximum speed setting screws of the venturi unit are sealed/set by the engine
manufacturer after adjusting idling. full load and no load maximum speed on the dynamometer. While mounting
the pump, the original setting of maximum speed stop screw. should not be tampered with. We are giving.
hereunder the recommended procedure for the various adjustments necessary.
• Mount fuel injection pump on engine and warm up the engine.

Adjust spring stopper (on governor cover) till engine idles 50-100 rpm below the specified idling speed
(recommended by the engine manufacturers). In this condition, the engine would hunt.
Screw-in the spring stopper (on governor cover) gradually till stable idling speed is obtained. Do not screw-in the
idling stop screw too much as it would increase the no load maximumspeed (fly-up speed).
If the stable idling speed obtained is not as specified by the engine manufacturer adjuststop screw to get specified
idling speed.
• Check maximum no load (fly-up) speed. If the speed is more than that specified, adjust idling stop screw on
the governor cover and re-check the idling speed as well as fly-up speed to obtain both the values within
limits. This is applicable where maximum speed stop screw of venturi, has not been tampered with and engine
manufacturers’ seal is intact.

In case the maximum speed stop screw of venturi is found to have been tampered with, proceed as follows:
• Adjust idling speed as detailed above with the help of governor spring stopper and venturi.
• Check maximum no load speed. If necessary, adjust the venturi maximum speed stop screw to obtain the
specified no load speed. How- ever, this is not an accurate method because full load speed is not assured.

Note: As long as stable idling speed and no load speed, as specified are obtainable, it is not
necessary to check the stability of engine rpm at no load speeds in the intermediate speed ranges.It
is mainly because such conditions are normally not encountered during actual operation of engine.

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CITS : Automotive - Mechanic Diesel - Exercise 15.4