CLAS B.LINE AC 0550BL Mode D'emploi page 15

HU 0014BL
Step 1. Run the engine until normal operating
temperature is reached and then shut the engine
off .
Step 2. Locate and connect the vacuum gauge to
a port directly on the manifold (fi g.2) or on the
carburetor/throttle body below the throttle valve.
Step 3. Start and idle the engine observing the
gauge reading. Refer to the gauge examples on
the following pages to indicate possible problems
and their possible causes.
1. READING: 16 - 21inHG
DIAGNOSIS: NORMAL
4. Reading of a weak but steady
measurement. DIAGNOSIS: Ignition
delay. Confi rm with the timing light
and reset to factory specifi cations.
METAL TRANSFER PUMP
2. When the accelerator is suddenly
opened and released, the needle
should drop below 5 inHg and
then bounce back to about 25
inHg before returning to the initial
reading.
DIAGNOSIS: NORMAL
5. Slightly low and slowly
fl uctuating reading. DIAGNOSIS:
Mixture too lean or too rich.
Check and reset according to
manufacturer's specifi cations.
3. Extremely low but constant
reading. DIAGNOSIS: Leaking intake
manifold system, defective manifold
or carburetor base gasket, cracked
vacuum hose, seized open EGR
valve.
6. Smooth fl uctuation between
normal and low. DIAGNOSIS: Blown
cylinder head gasket between
two adjacent cylinders. Perform a
cylinder leak test.