Engine

Page 16

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Volvo Bus Service and Maintenance Manual

 Throttle control
19 Check that the accelerator pedal does not stick, that there is full throttle at the injection pump and that the pedal returns to low idle when released.
 Speed limiter
  Check the tamperproof seals, electrical connections, linkage, springs and also clearance/adjustment according to below.
 
 Air throttle system
20 Check the accelerator pedal and the dust boot.
 
 Overhauling accelerator pedal valve, air throttle system
21 Carry out an overhaul check.
 

Mechanical throttle control

Check return springs, mounting and condition. The accelerator pedal should return to low idle when released. Replace binding cable controls, and lubricate the linkage and lever control if stiff. Levers and ball joints should be free from play.

Kickdown position

On buses with the ZF or Voith automatic transmissions, there should be full throttle at the injection pump with the switch in the kick-down position. This means that when the accelerator pedal is at full throttle, there must be a distance of 2-3 cm between the throttle arm and the high idle stop.

On the late product type, with the inductive-sensor kickdown contact, check that the "kick-down" relay is activated when about 2 mm pedal travel remains and before the accelerator pedal reaches its stop position.

Air throttle system, function check

Check level pivot points for excessive wear and corrosion. With the control cylinder fully extended, check for leakage around the dust boot. In the event of leakage, replace the seals. When the accelerator pedal is depressed, the control cylinder should operate smoothly and not bind. When the pedal is released, the throttle lever should return quickly to low idle.

Overhauling air throttle system accelerator pedal

Remove the accelerator pedal valve pivot pin and lift off the pedal. Remove the actuating roller.

Clean. Lubricate the roller and pivot pin with a dry spray lubricant. Lift off the dust boot and remove the plunger. Clean the plunger seat in the valve and re-fit the plunger dry without lubrication. If necessary, replace the dust boot.

Accelerator pedal adjustment

Speed limiter

Check the tamperproof seals at the joints according to the illustration. The tamperproof sealing must be renewed if the system has been serviced, e.g., control unit replacement or stall motor.

Switch on the feed switch. Check to make sure there is a clearance of approx. 0.5 to max. 2.0 mm between the stop boss and the upper lever when the control is in the idle position. If not, adjust the pull rod as follows: bend loose the ball dish where the damper cylinder is attached to the outer lever.

Push back the lever so that there is contact against the low idle speed stop screw. Adjust the length of the damper cylinder control rod so that the ball dish fits on to the stud. If necessary, also adjust the throttle wire length.

Anti-tamper seal points

Anti-tamper seal points

1.Electrical connection, stall motor
2.Control unit ("9011")
3.Fusebox
4.Attachment nut, circuit card, electrical centre
5.Electrical connection, speedometer