Non-starter

There’s an issue with our 2003 BMW 318i 2.0 E46 with the N42B20 engine and Bosch ME9.2 management system. After covering more than 100,000 miles, the engine will now fire when operating the starter, but on releasing the key the engine fails to run. If Easy Start is sprayed into the intake when firing up, the engine will continue to run until spraying is stopped, which suggests it is a fuel supply issue. No fault codes are present.

So far, the fuel pump, fuel filter and integral pressure regulator have been renewed, and the fuel pump fuse and relay have been checked. When the ignition is switched on, the pump does not run to prime the system.

I have studied the wiring diagram in the January 2013 issue of Car Mechanics and it appears that the ECU should provide a ground via pin D10 to energise the pump relay. Before I condemn the ECU, can you advise whether any of the engine sensors are responsible for sending a signal to the ECU that the engine has started turning/running, to tell it to continue activating the pump relay? If this is the case, is there a simple way to deduce which part is at fault? David It could be a security lock-out issue due to a problem with your key or another part of the security system. Check your fault codes and see if codes relating to security are present. I managed to overcome the non-starting/non-running problem and it turned out that I probably caused it myself!

I had renewed the fuel pump and the design of the pump is such that a flexible tube connects it to a separate outlet on the body of the pump carrier. This tube was not making a seal and fuel under pressure was escaping back into the tank. Betterquality hose clips solved the problem.

However, I am now left with the original problem. I have discovered that if I leave the airflow meter unplugged the vehicle will run very well. Presumably the engine is running on default settings. When the meter is reconnected, the performance deteriorates and the car become almost undriveable. The following codes are produced: ‘P1347 – misfire cyl 3 with fuel cut off’ (this is usually the first to appear). ‘P1343 – cyl 1’ ‘P1345 – cyl 2’ ‘P1349 – cyl 4’ ‘P1341 – multiple misfires’ So far, I have replaced the airflow meter, eccentric shaft position sensor, crank position sensor, crankcase vent valve (oil separator) and hoses. The main ECU has been specialist-tested and found to be OK.

The only components I can think of left to consider are the MAP sensor (BMW call it a differential pressure sensor), camshaft position sensors, the Valvetronic module and the Valvetronic motor. Could it be that the Valvetronic system is not activated when running default settings? Or could I have affected the Valvetronic system when I reconnected the airflow meter? David I have checked the continuity of the wiring from the AFM to the ECU and all seems in order. I am using the vehicle with the AFM unplugged as it runs quite well on default settings.

I have discovered that the Valvetronic system only begins to operate when normal running temperature is reached. As the problems only seem to appear after some miles (with the AFM reconnected), I now plan to renew the engine management temperature sensor. David Check the wiring from the AFM to the ECU for both continuity and freedom of shorts to earth, lives or to other wires, since this is the only thing I can see that can account for the fault codes. Alternatively, disconnect the wiring from the AFM and the ECU and rewire with your own wiring.