1994 BMW 740i does not start

One morning, started my car - it coughed and sputtered and finally died. No check engine light. I tried to get codes from computer using the gas pedal/stomp method and got nothing. More attempts at starting eventually resulted in complete failure of ignition, ie. it will crank but not start. New fuel pump relay. Fuel pressure is good. Battery is new. I tested crank position sensor and got a steady .6 -.8 VAC. I tested the cam position sensor and got a measurement cycling between .6VAC and 0VAC. Could this be the culprit? or is it normal for cam sensor to go to zero during cranking? HELP! No money! No car!


Problem solved. Well, after months of debating whether I should buy one sensor or another, knowing they are non-returnable, I finally just measured the resistance of the crank position sensor and found it to be way out of spec, which should be ~540 ohms ±10%. Ordered the part and replaced the sensor in about 15 minutes. I had to use a long t-handle allen wrench since the sensor is tucked in front of the dipstick tube and under the lower radiator hose, neither of which I wanted to remove.
Hope this helps somebody in the future. Unfortunately, I never got any help from this forum. I still love Car Talk!

Glad to hear you got it fixed. Maybe the next time something happens we can help you out.

Congratulations. You might want to join one (or more) of the BMW forums, for questions like this you’ll have a lot better chance of finding a person that had the same or similar problem there. The problem with a general discussion like here is that there could be dozens of reasons it didn’t start, but only a few of them might apply to your model/year 7er. And given its age, you’ll want to be hooked into a forum with lots of owners like you.

nhoskins…are there 2 sensors located in the front? i own the same car and suddenly did not turn on, cranks over but that’s it. i ordered the crank sensor but removed it and the sensor does not fit due to the oil filter tube. i now read your comment and went outside and do see another sensor under the radiator hose. the sensor i just removed was just under the air filter duct.

Nice work…you actually DIAGNOSED and repaired an issue that could cost others several hundreds of bucks to fix…by throwing parts at it. Nicely done. Bravo.

Hey jerbarr740i, sorry I didn’t see your post until recently. If you haven’t figured it out already, the sensor under the air filter is the cam position sensor. The lower one, tucked conveniently between the oil filler tube and the lower radiator hose, is the crank position sensor. That is the one I changed. You do not need to remove anything -but you will need a long t-handle allen wrench. Shouldn’t take more than 10-15 minutes. Good luck.

To all the other guys who posted, thanks for the praise and support. My earlier post was a little harsh, mainly due to frustration. Take care, N