Checking the injectors
Block ignition.
To check if fuel is getting to the injector, loosen the fuel line bolt on the cold start valve.
Keep a rag ready in case you spill gasoline. If gasoline does not splash out, have an assistant turn the starter.
If fuel comes out, remove the injector.
Keep a vessel or rag ready.
Remove the large air hose between the mixture adjuster and the throttle body to expose the air plate.
In the central mounting block, pull out the fuel pump relay and bridge contacts 3 and 87 on the block with a piece of wire. The fuel pump should start working.
Raise the measuring plate for the air in the distributor by hand. The injector must throw out a cone-shaped jet.
If this is not the case, lift the plate up to the stop. Repeat check.
Similarly, the difference in the amount of injected fuel for individual cylinders should be measured.
Each injector should be lowered into its measuring vessel so as not to damage the injectors.
Slightly raise the air measuring plate (about 2 mm).
The aforementioned wire jumper must be kept inserted by an assistant until 2 ml of fuel is poured into the first cup.
Compare the volumes of fuel in different cups. The deviation from each other should not exceed 3 cm3.
With a larger deviation, the injectors with the highest and lowest performance should be swapped. Repeat check.
If the performance has also changed, then the corresponding injectors need to be replaced.
If the result does not change during the second check, the pipeline to the injector may be narrowed or the dispenser is faulty.
Injector tightness test: If the fuel pump is turned off after two minutes of operation with the air gauge plate up, no fuel should seep through the injectors.
Installation of the injector is described below.
Checking the cold start valve
On the side of the intake pipe of the engine, with a power of more than 10 kW, there is a cold start valve (2). Here you can see the fuel supply line (1) and plug (3).
Block ignition.
Unscrew the cold start valve, disconnect the plug, leaving the fuel line connected. Run the starter briefly to pressurize the fuel pump.
Lower the valve into the vessel, connect two pieces of wire of sufficient length to the valve contacts.
Connect the free ends of the wires to the positive and negative poles of the battery.
The valve should spray a stream of gasoline in the shape of a cone.
To check the tightness, disconnect the wires.
Operate the starter again briefly so that the fuel pump builds up pressure.
Wipe valve dry. Within one minute, gasoline should not leak.
Checking the fuel dispenser
1 Diaphragm pressure regulator
2 Pressure regulator
3 Fuel dispenser
4 Throttle valve potentiometer
not for long (about 1 second) start the engine or crank the starter to pressurize the fuel.
Loosen the tie-down bands on the thick air hose between the mixture adjuster and the throttle body, disconnect the hose.
Remove the air filter cover with the mixture adjuster screwed to it.
Raise the air measuring plate that has shown up completely. The resistance of the plate must be the same all the way.
When pressing the plate back quickly, no resistance should be felt. If it is, it is necessary to replace the air quantity meter (flow meter).
If the plate goes up tight, and down - easily, then the distribution piston in the dispenser is stuck. The fuel dispenser needs to be replaced.
Checking the air quantity meter
Warm up the engine or let the warm engine run for about 1 second before testing.
Remove the air supply hose between the mixture adjuster and the throttle body after loosening the tie-down bands.
Measuring plate position for air
Check measuring plate for air. It must be in a certain position on the side facing the high pressure fuel lines.
The plate should be 1.9-3 mm below the top edge.
If the position of the plate is not correct, it can be lifted up and by bending the retaining brackets, correct its position. The flat spring cannot be bent.
Check if the plate touches the walls.
If so, loosen the central mounting bolt and center the plate.
After this adjustment, the idle speed and CO content should be checked.
Check of stabilization of turns of idling
Idle speed control valve (4) with disconnected plug (5)
Turn on the ignition. You should feel the valve work.
Otherwise, the control valve or temperature sensor is faulty.
Checking the switch on the throttle shaft
Disconnect the plug from the switch on the throttle valve connection. By connecting an ohmmeter to the switch contacts, measure the resistance.
The resistance should be zero when the throttle is closed, and infinite when the throttle is open.
To check the adjustment of the switch, slowly open and close the throttle.
When the distance from the throttle lever to the stop is 0.15 mm (measure with a flat feeler), the switch must clearly click, in which case the adjustment will be correct.
Throttle Shaft Switch Adjustment
Loosen the switch holder on the throttle shaft.
Insert a 0.1 mm thick feeler gauge between stop and lever.
Slide the switch towards the throttle lever until it clicks into place.
Tighten the switch in this position and check the adjustment again.
Checking the Temperature Sensor
coolant temperature sensor (2) located on the left end side of the cylinder head below the coolant pipe (1). The picture shows the plug (3) shown disconnected.
Disconnect the plug at the sensor on the left side of the cylinder head.
Connect an ohmmeter to both contacts of the sensor, measure the resistance.
Check that the resistance value matches the coolant temperature.
If the values correspond to the temperature of the coolant, then the sensor is in order.
Lambda control test
To carry out the check, the idle speed must be correctly adjusted, you need to make sure that there are no leaks in the exhaust system and that the temperature sensor is working.
To check the operation of the lambda probe heating, disconnect the plug on the probe.
Using a test lamp, check if there is voltage between the contact of the red / white wire and "weight".
If not, find a broken wire in the wiring diagram.
Then you should poll the memory of the self-diagnosis system.
For the measurement described below, a special cable is used in the workshop, with which you can connect to the pressure regulator wires with the plug inserted.
Connect measuring cable between pressure regulator and plug, connect ammeter.
1 Black wire to control box
2 Plug to mounting block
3 Plug for lambda probe with black/white and brown wires.
Start a warm engine and let it idle for at least 2 minutes.
Read and write the current value.
Clamp off the crankcase ventilation hose. The current must then drop.
If not, disconnect the lambda probe plug.
The black conductor going to the control unit should be shorted to ground for about 2 seconds.
If at the same time the current value changes, then the lambda probe is faulty.
If the current remains unchanged, there may be a malfunction in the Motronic control unit. It is tested in the workshop.
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