TRUCK SERVICE MANUAL
FUEL SYSTEM
1. Fill test oil tank 3/4 full of test oil and maintain
this level or higher during test. Test oil capacity
is approximately five gallons. It is available from
Cummins Engine Company as Part No.
9901168 or Mobil Oil Company No. MCL-41.
2. Fill the hydraulic fluid reservoir to half level in
sight bulb with clean Type A automatic
transmission fluid. Be careful not to allow oil to
enter the standpipe in center of reservoir.
3. Fill cambox with SAE
30 nondetergent
lubricating oil to top of sight glass. Refill when oil
level gets low in sight glass.
4. Plug electrical connection into receptacle
carrying the necessary voltage to operate the
Fig. 6-1-70, F60124. Clamping cylinder and seat
test stand.
Description Of Operation ST790
1. A motor driven shaft and a cam are housed in
the cam box. The cam actuates the vertical
push rod at the bottom of the housing.
2. The push rod is connected to the injector by a
link so the injector plunger will be actuated by
cam action just as it is in the engine. Fig. 6169.
3. Injectors are clamped in the test stand by
hydraulic pressure from the cylinder, piston rod
and injector seat. The injector seat contains a
removable orifice to restrict the metered fuel flow
and cause a back pressure simulating,
compression pressures as found in the engine.
Fig. 6-1-71 F60125. Aligning timing wheel mark
Be sure to use; correct size orifice. Fig. 6170.
4. Before clamping the injector in the test stand, the
cam must be timed by rotating the timing wheel
so the wheel mark and pointer are aligned. Fig.
6171.
5. Shop air pressure regulated by air regulator is
used to apply a balanced force on the hydraulic
system. Fig. 6172. The air gauge at top of
hydraulic reservoir is used as a reference
indicating that pressure has not changed, after
being set using a load test cell during test stand
Fig. 6-1-72, F60209. Air pressure and fuel pressure
gauges.
Fig. 6-1-69, F60208. Link and injector in position
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