Install pressure gauge, Part No. ST-1273, to the
fitting in the turbocharger outlet.
Install another pressure gauge, Part No. ST-1273, in
the intake manifold.
Operate the engine at rated RPM and load. Record
the readings on the two gauges.
If the differential pressure is greater than 21 kPa [3
psi], check the charge air cooler for plugging. Clean
or replace if necessary.
Install a temperature gauge in the intake manifold.
Lock the fan drive in the ON mode to prevent erratic
test results. This can be done by installing a jumper
across the temperature switch or supplying shop air
to the fan. Refer to the fan drive manufacturer for
Some trucks have a manual switch that will
lock on the fan.