Non-running issue

I hope you can help me with my 2002 BMW E39 5-Series 2.2 petrol with the M54 engine and manual transmission. It has done 98,000 miles. The car cranks strongly, but doesn’t start – the engine doesn’t fire at all. The car was driving perfectly the night before it refused to start and there were no signs of anything wrong – engine noises, overheating, etc – and it has always started first time before. When I crank, the rev counter doesn’t move. The engine management light is not illuminated and there are no other warning lights showing on the dash. I’ve put a diagnostic tester on it, but there are no codes logged.

I have checked the battery and it’s showing 11.8 volts. I’ve put a known good battery on it from another car and it still cranks, but won’t start. I fully charged the BMW battery to 12.8V, but it made no difference. I checked the cold cranking with a multimeter and it dropped to 10.72V – does that seem OK?

I don’t think it’s an immobiliser problem, as the car recognises the key when I turn it over. I’ve checked the fuel pressure at the Schrader valve and fuel came out at quite a good pressure. I sprayed some Easy Start into the intake, to no avail.

I can’t hear the fuel pump priming, but can’t be sure. There are two fuses listed for the fuel pump – I’ve checked both and they’re OK. I’ve unplugged the MAF sensor, but that made no difference. I’ve checked for spark on one of the cylinders and there was a good spark showing. I’m thinking it could be the crankshaft position sensor, but I don’t want to replace this sensor needlessly as they are quite expensive. Can the sensor be checked using a multimeter? What sort of resistance should a healthy sensor show?

I’m also hope it’s not the timing chain, but I understand these usually rattle long before they let go. Ian Rimmer From the data I have on your BMW, the immobiliser prevents the starter from operating, so because your vehicle cranks over, this can be discounted.

The fuel system should run at a pressure of 3 Bar and this should be checked using a proper pressure gauge fitted to the Schrader valve. A lower pressure will still produce a spray when the valve is depressed, but it may not be enough to start and run the engine. As you cannot hear the fuel pump operating, I would first check the fuel pump relay, which according to Autodata should be relay number 2 located in the load area.

If the relay is not at fault then I would suspect the crankshaft sensor or possibly the camshaft sensors, but I am slightly confused by the lack of codes. I would expect a pending code to be held somewhere in the system. Although you do not mention which code reader you are using, it may be that you will need an official BMW reader to find the pending codes.

Before testing the sensor, you should check the resistance of the loom between the sensor and the ECU – this should be below 1 ohm. The sensor pins on the ECU should be numbers C21 and C8. This is the central bank of pins on the ECU and the pins are numbered from left to right starting at the lowest row of pins on the ECU.

Testing the actual sensor would require an oscilloscope to check the waveform being produced. This should be a steady and even square wave formed as the sensor passes the pick-up.