Checking and adjusting the idle speed

High pressure fuel pump overview

Due to the fact that diesel engines do not have an ignition system, a special tachometer is required. This tachometer is expensive, so buying it is not always justified. In addition to the tachometer, a pin with a diameter of 3 mm is required (drill) and a set of flat templates. In case of regulation, proceed as follows:

Cold start thrust adjustment

Function: the thermocouple is located in the coolant circuit on the thermostat housing and, when the engine is cold, activates the lever on the high pressure fuel pump, and it activates it via the Bowden rod (cold start thrust). Idling at higher RPMs ensures quieter engine operation.

Warm up the engine, the coolant temperature should be 80°C. The coolant temperature indicator should be in the middle of the scale.

Finally, adjust the Bowden rod -9- of the thermocouple, see fig. The fastener must be at a distance of 1-2 mm from the lever of the high pressure fuel pump, otherwise unscrew the fastening bolt on the fastener and move the latter accordingly.

Idle speed test, fast idle test

Check the idle speed and record it. Set speed: 820-850 rpm.

Slide the idle speed adjustment template from Ford 23016 -7- together with a 1 mm thick template between the fuel pump lever -1- and the stop screw -2-. If you do not have a Ford template, then a template or a 4 mm drill bit can be clamped between the fuel pump lever and the idle adjustment screw.

Turn the idle speed lever -6- clockwise and insert a pin with a diameter of 3 mm into the hole. As a result, the idle lever is locked, and the engine is idling at accelerated speeds.

Check the accelerated RPM and note down: Target RPM: 800-1000 RPM.

If the idle speed and fast idle are OK, then check the droop period and correct if necessary.

Idle speed control, fast idle control

The engine must be hot and must be idling.

Place the Ford template 23-016 and the 1 mm thick template between the fuel pump lever -1- and the stop screw -2-. The special tool -7- is mounted on the stop of the adjusting screw, as a result, it is easier to turn it by hand. However, the tool may not be used. If there is no Ford template, then between the fuel pump lever and the idle speed adjusting screw, clamp a flat template or a 4 mm thick drill.

Turn the idle speed lever -6- clockwise and insert a pin with a diameter of 3 mm into the hole. As a result, the idle lever is blocked, the engine idling at a higher speed.

Loosen the locknut and use the stop screw of the fuel pump lever -2- to adjust the idle speed to 900±100 rpm.


Remove template, pin and Ford template. In this case, the lever of the fuel pump is in contact with the adjusting screw.

Loosen the lock nut and turn the screw -3- until the speed is 820-850 rpm.

Finally, check the motor delay time and adjust if necessary.

Regulation of the period of decrease in the number of revolutions of the engine

The downtime period is the time it takes for the engine to go from full throttle again (maximum engine speed) to the idle speed. If the engine speed decreases too quickly, the engine will stall. If the engine speed decreases too slowly, it causes driving problems and increases fuel consumption.

Give full throttle (speed 5150 rpm), release the gas pedal and note the time that will elapse before the engine will again idle. Set time: maximum 5 sec.

Attention! Never give gas for more than three seconds. Do not give gas unnecessarily.

If you cannot get the given value, then do the following:

The speed decreases too slowly: turn the stop screw -2- counterclockwise by 1/4 turn, looking from the end of the pump.

The speed decreases too quickly: Turn the stop screw -2- clockwise by 1/4 turn.

Attention! Screw -2- must not be turned more than 1/4 turn.

Finally, check the idle speed again, higher idle speed, adjust if necessary.

Lock the adjusting screw with a lock nut.