Carburetor: Testing and Inspection

Carburetor Components:

"A" VACUUM PORT (VRV CONTROL)
Inspection conditions: 185 - 205~F (85 - 95~C)
1. Disconnect the vacuum hose from the carburetor vacuum port "A" and connect a hand vacuum pump to the nipple.

A Port Vacuum Curve:

2. Start and race the engine to make sure that the "A" port vacuum increases gradually with engine speed.
If an abnormal vacuum reading occurs, the passages may be plugged. Clean as necessary. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.

"D" VACUUM PORT (DISTRIBUTOR ADVANCE CONTROL)
Inspection conditions: 185 - 205~F (85 - 95~C)
1. Disconnect the vacuum hose from the carburetor vacuum port "D" and connect a hand vacuum pump to the nipple.

D Vacuum Curve:

2. Start and race the engine to make sure that the "D" port vacuum increases with engine speed.
If an abnormal vacuum reading occurs, the passages may be plugged. Clean as necessary. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.

"E" VACUUM PORT (EGR VALVE CONTROL)
Inspection conditions: 185 - 205~F (85 - 95~C)
1. Disconnect the vacuum hose from the carburetor "E" vacuum port and connect a hand vacuum pump to the nipple.

E Port Vacuum Curve:

2. Start and race the engine to make sure that the "E" port vacuum increases with engine speed.
If an abnormal vacuum reading occurs, the passages may be plugged. Clean as necessary. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.

"F" VACUUM PORT (VACUUM SWITCH CONTROL)
Inspection conditions: 185 - 205~F (85 - 95~C)
1. Disconnect the vacuum hose from the carburetor "F" vacuum port and connect a hand vacuum pump to the nipple.

F Port Vacuum Curve:

2. Start and race the engine to make sure that the "F" port vacuum drops rapidly with engine speed.
If an abnormal vacuum reading occurs, the passages may be plugged. Clean as necessary. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.

CARBURETOR BLEED AIR PASSAGE

Primary Well Bleed Nipple Circuit:

1. Disconnect the vacuum hose from the air nipple and connect a hand vacuum pump to the nipple.
2. Apply vacuum to see that it bleeds off and does not build vacuum inside the carburetor.
3. Disconnect the vacuum hose from the primary well bleed nipple and connect a hand vacuum pump.
4. Apply vacuum to see that it bleeds off and does not build vacuum inside the carburetor.
5. If vacuum builds up on either test, disassemble and inspect the carburetor. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.

SECONDARY WELL BLEED NIPPLE (FEDERAL, HIGH ALTITUDE ONLY)

Secondary Well Bleed Nipple Circuit:

1. Disconnect the vacuum hose from the additional bleed air nipple and connect a hand vacuum pump to the nipple.
2. Apply vacuum to see that it bleeds off and does not build vacuum inside the carburetor.
3. If vacuum builds up on during test, disassemble and inspect the carburetor. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.

JET AIR NIPPLE (FEDERAL, HIGH ALTITUDE ONLY)

Jet Air Nipple Circuit:

1. Disconnect the vacuum hose from the air nipple and connect a hand vacuum pump to the nipple.
2. Apply vacuum to see that it bleeds off and does not build vacuum inside the carburetor.
3. Disconnect the vacuum hose from the jet air nipple and connect a hand vacuum pump.
4. Apply vacuum to see that it bleeds off and does not build vacuum inside the carburetor.
5. If vacuum builds up on either test, disassemble and inspect the carburetor. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.