View Full Version : No start, no spark...........
12-01-2008, 08:16 PM
My 1992 525i won't start all of a sudden. I pulled out a spark plug and there wasn't any spark when I tried to start it. I've read that the crankshaft sensor could be responsible. The Bentleys manual said to test the ohms on it (which should read 1280) to see if it is faulty. My question is: how the hell do I get it out to test it? It has a 5mm hex nut on it that I just can't get any leverage on. And there isn't much room to work with because of the fan blades. Any suggestions are appreciated.
12-01-2008, 08:20 PM
I don't know if this will make sence, but if you take two open ended wrenches and put the 5mm closed end around the bolt and then put a second one (of any size) on the open ended side of the first one you can get plenty of leverage. I wish I had a picture to show you what im talking about.
The hole on the second one locks into the open side of the first on (only works with the angle on the hole on a certain side). The hole on the first one goes on the nut.
bimmer dot info
12-02-2008, 09:09 AM
You need an allen key to remove it. If you can not get enough leverage with an allen key you can try an allen socket. You might need to remove the fan too.
12-02-2008, 12:26 PM
you can get enough leverage on an allen the same way. Put the hole through the allen and it will give you more leverage. I had to do it to get the stupid bolts off the swaybar bushings.
12-02-2008, 08:59 PM
Well I finally got the sensor out and tested it. Unfortunately the ohms read the same as the new one I just bought, which was around 500. I don't understand this because the bentleys manual said it should read 1280. So now I am back at the beginning, clueless and frustrated.
bimmer dot info
12-03-2008, 07:13 AM
I tested a new one when I was having some problems. I think it came in at 480 ohms.
When you were checking for spark did you have the plugs body grounded?
Was the car sitting for any length of time before the problem started?
12-03-2008, 11:37 AM
Actually my car sat for about 4 and a half days. When I got home sunday night it started right up and sounded good (only ran it for a minute). But then I went out the next day and it wouldn't start at all. It will turn over as if it is about to start, but just doesn't get there. As far as having the plugs body grounded, I'm not exactly sure what that means.
bimmer dot info
12-03-2008, 12:33 PM
Did you remove the plug and hold it in the air and then try to start the car? If so you might have damaged that coil. If you are going to check for spark you need to provide a path for the current to flow. The threaded part of the plug should be touching a grounded part of the engine (make sure there is no gas or other flamables in the area).
Have you tried charging the battery or jump starting it since sunday?
12-03-2008, 07:30 PM
There's an error in the ohm specs in the Bentley manual...sacrilegious I know, but I went through the same thing on my old car. I can't remember if it was for the crank sensor or the cam sensor, but I checked one of them and the measurement was way off but it DID match the spec for one of the other sensors listed (on that same page IIRC). Went to a part store and checked a new one before I even bought it and it was the same as the one in the car.
That car it wound up being the computer was bad. No spark or fuel when it was cranking and the crank/cam sensors all checked out. Also my code reader wouldn't talk to the car either...just errored out.
edit...did you check the fuel supply yet? make sure you've got power back there and pressure at the rail? At least have someone turn the key to RUN (not necessarily START) and listen for the fuel pump at the back of the car. No noise = no fuel pump
03-13-2009, 09:32 PM
Sorry for the late response. Unfortunately I was testing for spark all wrong. I had pulled the plug and simply laid it on the manifold which didn't give it any path for a current (as mentioned above). :tsk: In the end it was the fuel pump (which is very exciting to change in 10 degree weather). Thanks for all the help, I just wanted to provide some closure for this thread.
04-24-2009, 03:35 PM
How did you determine that the fuel pump was the problem? I am currently sorting through the same type of problem right now. I can jumper the relay fuse and get my fuel pump to work but it will not run when I try to start the engine.
04-27-2009, 07:52 PM
These fuel pump failures can be tricky. I had a 540 that acted like it was running out of gas at speed. Then it began to happen at lower demand moments, too. When I jumpered the relay, the pump turned on all nice and buzzy. Electrical ciurcuit to pump was fine. When I pulled the hose to check for fuel volume, the pump shot a spray across the engine compartment with great verve. "Fuel pump must be good" says I. No it wasn't. That pump has to deliver enough pressure to overcome the check valves in the pump and at the fuel pressure regulator. I replaced the pump at the top of the Cajon Pass on I-15 at a Chevron staion. Problem solved.
(p.s. jumpering the relay tells you that the pump works. You need to track down the relay instruction circuit, i.e. 85/86 )
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