B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 005-052   Throttle Body Assembly

Check for free-throttle operation.

Make sure all connections are tight.

Restricted throttle travel can cause low power.

Check for full-throttle travel in both directions from idle (1) to wide-open position (2).

Be sure the throttle cable is parallel to the throttle body centerline.

WARNING  To reduce the possibility of severe personal injury or death when working on the fuel system, turn off the fuel supply at the vehicle’s main fuel shutoff valve before removing any component.

WARNING  Liquefied petroleum gas is normally treated with an odor-producing chemical, so that users will be able to smell fuel leaks. Always be alert for the smell of fuel. If you enter a room or approach a vehicle and a smell of fuel is present, immediately shut off all engines and ignition sources and avoid sparks, arcing switches and equipment, cigarettes, pilot lights, flames, and other sources of ignition in the area and in areas with common ventilation. Provide extra ventilation to the area and do not start the equipment or nearby equipment until the leak is corrected and the area is ventilated. Avoid leaving liquefied petroleum gas-fueled equipment in unvented rooms overnight or for extended periods. Store and service liquefied petroleum gas-fueled equipment in large, well-ventilated areas or outside.

WARNING  Liquefied petroleum gas is heavier than air and can accumulate near the floor, in sumps, and in low-lying areas.

Turn off the vehicle’s main fuel valve.

Operate the engine at low idle until the engine dies or bleed the fuel from the fuel filter.

WARNING  The pressure of the fuel in the line is sufficient to penetrate the skin and cause serious personal injury. Wear gloves and protective clothing.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

Remove the fuel jumper hose.

Remove the charge air cooler hose from the inlet elbow.

Remove the wastegate signal line from the intake elbow fitting.

Disconnect the following:

• Wastegate control valve
• Mixer inlet pressure sensor
• Fuel control valve
• Humidity Sensor (Gas Plus only)
• Fuel pressure/temperature, secondary (Gas Plus only).

Remove the two capscrews and fuel control valve.

Remove the fuel control valve o-ring and discard.

Remove the three capscrews, inlet elbow, and o-ring seal.

Disconnect the following:

• Throttle connection linkage
• Idle speed control valve connector
• Throttle position sensor connector.

Hold the throttle body in place while removing the air/fuel mixer.

Remove the four nuts and air/fuel mixer from the throttle body.

Remove the four mounting spacers, throttle body, and mounting gasket.

Discard the mounting gasket.

Disconnect the following electrical connectors:

• Throttle actuator
• Exhaust back pressure sensor.

Hold the throttle actuator in place while removing the air/fuel mixer.

Remove the four nuts and air/fuel mixer from the throttle actuator.

Remove the three capscrews and the throttle support bracket.

Remove the throttle actuator.

Discard all o-rings.

To replace the throttle break-over lever, remove the retaining ring and break-over throttle lever.

Inspect the throttle break-over lever pivot shaft for excessive wear.

Replace the throttle body assembly if excessive wear is found.

Install the throttle break-over lever with the springs positioned over the fixed lever.

Install the retaining ring.

Check the break-over lever travel.

Install the new mounting gasket, new rectangular seals, throttle body, and four mounting spacers.

Lubricate the throttle body sealing ring with Lubriplate™.

Install the mixer and four nuts.

Connect the following:

• Throttle position sensor
• Idle speed control valve
• Throttle linkage.

Adjust the throttle linkage.

Use new o-rings when installing the fuel control valve.

Lubricate the new o-rings with Lubriplate™.

Install the fuel control valve and two capscrews.

Install the inlet elbow o-ring seal, inlet elbow, and three capscrews.

Install the wastegate signal line to the inlet elbow fitting.

Connect the following:

• Wastegate control valve
• Mixer inlet pressure sensor
• Fuel control valve
• Humidity sensor (Gas Plus only)
• Fuel pressure/temperature, secondary (Gas Plus only).

CAUTION  On B5.9G and B5.9LPG engines, be sure to use two wrenches when tightening the hose. Twisting and damage will occur to the fuel jumper hose if only one wrench is used.

Install the fuel jumper hose.

NOTE: The fuel jumper hose used on B5.9G and B5.9LPG engines is different than the one used on B Gas Plus and B LPG Plus engines.

Connect the charge air cooler hose to the inlet elbow.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

Turn on the vehicle’s main fuel supply valve.

WARNING  Keep hands, long hair, jewelry, and loose-fitting or torn clothing away from fan and all moving parts. Serious personal injury can result.

Operate the engine and check the jumper hose for leaks using gas detector, Part Number 3823984.

If leaks are found, close the valve, turn the key to the OFF position, and repair leaks immediately.

Hold the throttle actuator in place while installing the throttle support bracket and air/fuel mixer.

Install new o-rings on the throttle and air/fuel mixer.

Lubricate the o-rings with Lubriplate™.

Install the three throttle support bracket capscrews.

Install the mixer and four nuts.

Connect the following:

• Throttle actuator
• Exhaust back pressure sensor.

Use new o-rings when installing the fuel control valve.

Lubricate the new o-rings with Lubriplate™.

Install the fuel control valve and two capscrews.

Install the inlet elbow o-ring seal, inlet elbow, and three capscrews.

Install the wastegate signal line to the inlet elbow fitting.

Connect the following:

• Wastegate control valve
• Mixer inlet pressure sensor
• Fuel control valve
• Humidity sensor (Gas Plus only)
• Fuel pressure/temperature, secondary (Gas Plus only).

CAUTION  On B5.9G and B5.9LPG engines, be sure to use two wrenches when tightening the hose. Twisting and damage will occur to the fuel jumper hose if only one wrench is used.

Install the fuel jumper hose.

Connect the charge air cooler hose to the inlet elbow.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

Turn on the vehicle’s main fuel supply valve.

NOTE: The fuel jumper hose used on B5.9G and B5.9LPG engines is different than the one used on B Gas Plus and B LPG Plus engines.

WARNING  Keep hands, long hair, jewelry, and loose-fitting or torn clothing away from fan and all moving parts. Serious personal injury can result.

Operate the engine and check the jumper hose for leaks using gas detector, Part Number 3823984.

If leaks are found, close the valve, turn the key to the OFF position, and repair leaks immediately.

When connecting the linkage to the throttle control lever, adjust the length so the lever has minimum stop-to-stop movement from idle (1) to wide-open throttle (2).

The break-over spring, second spring on the lever (1), is to make sure that the throttle linkage does not break from overextension. The break-over spring will actually close down the throttle plate if it is overengaged.

Do not exceed break-over spring travel by more than 10 degrees past wide-open throttle stop.

With the throttle pedal fully depressed, verify on INSITE™ that the throttle percent reading on the INSITE™ monitor screen is greater than 85 percent. If the INSITE™ reading is not 85 percent, adjust the linkage.

Before making any adjustment, turn off all accessory loads such as air conditioning, wheelchair lifts, and fans.

While making the adjustment, do not turn the steering wheel.

With the engine running, unplug the idle control valve (center picture).

Use INSITE™, not the vehicle tachometer, to check engine speed. INSITE™ is more accurate.

Adjust the idle screw as follows:

• Turn screw clockwise to increase speed.
• Turn screw counterclockwise to decrease speed.

Adjust the setscrew until the engine idles between 600 to 650 rpm.

Verify that at no-throttle pedal INSITE™ reads 0-percent throttle.
(If INSITE™ does not read 0-percent throttle at idle, the ECM will think the throttle pedal is being depressed and will not
use the idle bypass to control idle speed.)

The engine can die when the idle speed control valve is unplugged. Make sure the accessory load is at a minimum.

The setscrew is extremely sensitive. Use quarter turns.

When the base idle adjustment has been completed, reconnect the idle control valve.