Chrysler RAM TRUCK 2500 1994 Service Manual page 166

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SERVICE BRAKE DIAGNOSIS § - 7
SHORT
CONNECTING CHECK
VACUUM
GAUGE
J9005-81
Fig. 3 Booster Vacuum Test Connections
TESTING DIESEL ENGINE VACUUM PUMP OUTPUT
On models with a Cummins turbo diesel engine, a
low vacuum condition i n the brake booster will cause
the brake warning light to illuminate.
The following test checks output and condition of
the vacuum pump and interconnecting hoses. How­
ever, a more comprehensive testing procedure is pro­
vided i n the Power Brake Booster-Brake Pedal-
Vacuum Pump section. Refer to the procedure for
"Diagnosing A Low Vacuum Condition" i n that sec­
tion.
(1) Check pump vacuum and booster hoses and
connections. Make sure hoses are i n good condition
and securely attached. Run engine and check for vac­
uum leaks. Replace leaking hoses before proceeding.
(2) Disconnect vacuum hose at booster and connect
vacuum gauge to hose end.
(3) Run engine at curb idle speed and note vacuum
reading. Then run engine at 1/2 to 3/4 throttle and
note vacuum reading again.
(4) Vacuum should range from 8.5 to 25 inches vac­
uum at various throttle openings. Vacuum should
hold steady and not drop below 8.5 inches.
(5) I f vacuum output is OK, check booster and
check valve as described i n this section. However, i f
vacuum is low, or does not hold steady, vacuum hoses
or pump components are faulty.