Fuel Injection Mixer Replacement

Throttle Body (Injection Mixer) Components:

REMOVAL
1. Remove the hose clamp, air hose and intake pipe.
2. Disconnect the accelerator cable connection.
3. Disconnect and remove the water hose.
4. Remove the vacuum lines, noting each location to assist in proper installation.
5. Disconnect all electrical connectors.
6. Disconnect the fuel supply and return lines.
CAUTION: Relieve pressure of the high pressure fuel line prior to removing the high pressure fuel line connector. Refer to FUEL PUMP in DIAGNOSIS AND TESTING.
7. Remove the four mounting bolts and remove the throttle body/mixing chamber assembly.

DISASSEMBLY
The following items are not recommended for removal during throttle body service unless they are being replaced.
Throttle position sensor
Injector holder screen
Fuel return nipple
Throttle valve
ISC servo assembly

Throttle Position Sensor (TPS) Mounting:

1. Remove the throttle position sensor and connector joint (only if replacing).
2. Remove the two mounting screws for the injector holder.
3. Wiggle loose and remove the injector holder.
4. Remove the retaining screws for the pulsation damper cover and remove the cover with its O-ring, spring and the pulsation damper diaphragm. Discard the pulsation damper cover O-ring, it is NOT reusable.

Removal Of Injector:

5. Wiggle loose and remove the injectors by hand, one at a time.
NOTE: Do not attempt to remove an injector using a pliers or similar tool.
6. After removal of an injector, close the fuel inlet by sealing it with tape, etc. to prevent entry of foreign matter. Remove and discard the O-ring and the collar from each injector, they are NOT reusable.
7. Remove and discard the injector seal rings, they are NOT reusable.
8. remove the three nuts and washers for the fuel pressure regulator and remove the regulator. Remove and discard the two O-rings, they are NOT reusable.
9. Remove the throttle cable bracket, damper spring and the return spring.

Removal Of ISC Servo Assembly:

10. Remove the ISC mounting screws and remove the ISC servo assembly (only if replacing).
NOTE: Do not disassemble the ISC servo assembly.
11. Remove the connector brackets.
12. Remove the two remaining screws that secure the mixing chamber to the throttle body. Separate the mixing chamber and throttle body, remove and discard the seal ring.
13. Remove the throttle valve set screw (fixed SAS).
14. Remove the nut securing the return lever, remove the lever with the adjusting screw.
15. Remove the free lever, throttle lever and the two return springs.

INSPECTION
1. Check operation of the throttle valve shaft. If it does not operate smoothly and with light resistance, clean thoroughly and lubricate with a light machine oil.
2. Clean all components using detergent, except the throttle position sensor and the ISC servo. These two components will be damaged by immersion in detergent, wipe with cloth only.
3. Use compressed air to clean and check the individual vacuum and fuel passages.
4. While cleaning the injectors and fuel pressure regulator, ensure that seals remain tight on inlets and outlets.
5. Before reassembly, electrically test the following items to determine there serviceability.

INJECTORS

Injector Resistance Test:

Measure the resistance of the injector coils using an ohmmeter.
Resistance: 2-3 ohm @ 68°F (20°C)

ISC SERVO

ISC Continuity Check:

Measure the resistance of the ISC servo between terminals 1 and 4.
Resistance: 3-35 ohm @ 68°F (20°C)

ISC Operational Inspection:

Connect a 6 VDC power supply across terminals 1 and 4 of the connector and check for smooth operation of the servo motor both extending and retracting.

THROTTLE POSITION SENSOR

TPS Connector Terminal Identification:

Measure the resistance of the TPS between terminals 1 and 3.
Resistance: 3.5-6.5 K-ohm

Check the sensor for cracks or other visible damage.

ASSEMBLY
Assemble in the reverse order of disassembly taking note of the following special points:

Mixer Body Seal Ring Installation:

1. While mating the mixing chamber and the throttle body, make sure that the seal ring does not protrude from the groove.

Injector Seal Ring Installation:

2. When installing the injector seal rings, make sure that the flat side faces up.

Injector Installation:

3. Ensure that the injectors are installed in the correct position by color.
4. On installation , fit a new O-ring and collar to each injector.
5. Set each injector on the mixing chamber at its correct position and angle, press down with a finger until it is seated.

Fuel Pressure Regulator O-ring Installation:

6. Install new O-rings on the fuel pressure regulator before installation.

Diaphragm Installation:

7. While installing the pulsation damper diaphragm, ensure that correct side is installed facing as in the accompanying image.

Injector Holder Filters:

8. Before installation, check the injector filter and replace if necessary.

Installation Of Injector Holder:

9. On installation of the injector holder, set the holder in place and press down firmly. Tighten the two mounting screws alternately until the holder is seated.

TPS Installation:

10. If the throttle position sensor was replaced, ensure that joint A and joint B are properly aligned on reassembly. Do not tighten the mounting screws until final assembly.

TPS Installation Check:

11. Check for correct installation of the throttle position sensor. Using an ohmmeter check that resistance between terminals 1 and 2 or 2 and 3 show a smooth change while moving the throttle lever open and closed, full sweep.

AT COMPLETION OF ASSEMBLY
Using an ohmmeter, inspect the idle switch as follows:
1. Check to ensure there is continuity between the body and terminal 2 with the throttle valve in the full open position.
2. Check to ensure there is NO continuity between the body and terminal 2 with the throttle valve in the full closed position.
3. If the idle switch does not pass the continuity tests, replace the ISC servo as an assembly.

INSTALLATION
1. Install the throttle body/mixing chamber assembly, the four mounting bolts and torque in a cross-pattern, to 10.8-14.5 lb-ft (15-20 Nm).
2. Connect the fuel supply and return lines.
3. Connect all electrical connectors.
4. Install the vacuum lines, taking care to place as noted in disassembly.
6. Connect the accelerator cable.
7. Install the hose clamp, air hose and intake pipe.