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Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 22903
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My BMW wont start. It has recently had an extensive service

Customer Question

My BMW wont start. It has recently had an extensive service and the fault codes have been sorted out, but it doesnt start. Or better still it takes forever to start. Once it does its fine.
Submitted: 4 years ago.
Category: BMW
Expert:  Matt replied 4 years ago.

can you tell me what the fault codes were?

also this is the petrol engine 318 not the deisel?
Customer: replied 4 years ago.

Initially, the EML light came on. I was told my camshaft sensor might be the problem as it was very dirty, this was cleaned and the fault codes reset. However, it still had problems starting, so much so that after about 2-3 weeks, the car stopped starting. I took it to another garrage where I had a full service done, the 2 cam shaft sensors and crankshaft sensors have been changed, the oil filter changed, the plugs all changed. Its still having the same problem. I picked up the car on Wednesday, yesterday, it took three tries to start it up. Today it wont start, I dont know the technical way to say it but it turns but wont catch if you get my drift.

Expert:  Matt replied 4 years ago.

1st check for spark by removing one of the spark plugs and plug it back into its coil ( secure with ty-wraps) and rest it on the metal of the engine ( DO NOT hold it on place by hand) then have your assistant turn the engine over whilst you watch the plug. It should give a fat blue spark at regular intervals.

If not then check that there's power to the coil pack using a meter. If there’s 12V at the pack but no spark then check the ECU power supply (fuse and relay) and also the connections to the crankshaft speed sensor.

If there is a spark and its still not starting then its likely that the ECU isn't opening the fuel injectors, if the injectors are working you can hear them click - its difficult to hear them with background noise so use a long screwdriver like a stethoscope, placing the handle end in your ear and the metal tip against the body of the injector whilst your assistant turns the engine over.

If you can't hear anything check the ECU power is present by measuring voltage at the fusebox and on its relay socket if OK then check the connections to the crank speed sensor and consider replacing this sensor if the wiring / connections look OK

If the car will start using a squirt of quick/ easi start into the intake then this confirms the problem is lack of fuel

Also its worth checking that the electric pump that feeds the injectors is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If you remove the filler cap to the fuel tank and listen inside while your assistant flicks the ignition you should hear it clearly