MCU Check for Constant Delivery
A fuel distribution reference unit (FDRU) is used for testing the fuel distributor. The FDRU measures the individual amounts of fuel which the fuel distributor dispenses to the injection valves. Measurements are made with engine stopped. Operating conditions (idle, partial or full load) are simulated and set on air flow sensor by means of an adjusting device.
- Set up FDRU (KDJE-P 300) horizontally adjacent to vehicle (tool or tester carriage). Remove air cleaner. Unscrew injection lines on fuel distributor and loosen at injection valves, unscrew, if required.
- Connect lines of FDRU to fuel distributor and plug fuel return line into filler neck of fuel tank. See Fig 1 .
- Clamp adjusting device (KDJE-W 100) for locating air flow sensor plate to stop bracket of air funnel. Pull-off fuel pump relay and bridge the 2 terminals 7 and 8. This will connect fuel pump to voltage.
- Deflect air flow sensor plate and push buttons 1 to 4 for venting unit individually for a short moment. Keep 1 button pushed, deflect air flow sensor plate with adjusting device and locate at a flow rate 6 cc per minute (cc/min.) at idle.
- Push remaining buttons, read individual flow rates. (Max. dispersion: at idle .6 cc/min).
- Calculate difference between lowest and highest flow rate and compare with tolerance value. Adjust air flow sensor plate for 30 cc/min. at partial load and 100 cc/min. for full load. Then calculate difference between lowest and highest flow rate and compare with tolerance value. The max. fuel dispersion is: Partial load 4.0 cc/min. and full load is 10.0 cc/min.
- If the dispersion is outside of tolerance, exchange fuel distributor. Run engine and check all fuel connections for leaks. Adjust idle speed.