Jezza 0 Report post Posted December 27, 2009 Hey there My old 525ee has decided it doesn't want to work anymore and I'm hoping there is someone here who might be able to help me. The 12V feed to the coil on my motor has died and I'm not sure what could be responsible for it. I don't think it's a fuse as this problem has occurred twice now and the car kicked back into life last time. Does anyone have a good understanding of the m20 electrical system and would possibly know why it's lost power at the coil? Cheers Quote Share this post Link to post Share on other sites
turboprop 0 Report post Posted December 27, 2009 Dodgy main relay? Quote Share this post Link to post Share on other sites
BM WORLD 1260 Report post Posted December 27, 2009 Dodgy main relay?yes check that .also the ecu's can develop dry joints in them , around the main output trasistor for the coil etc . also check the crank sensors and plugs from around the gearbox bell housing . Quote Share this post Link to post Share on other sites
Jezza 0 Report post Posted December 29, 2009 Cheers for the input, I will have a stab at it when the weather fines up. Is the main relay found in the fuse box or does it have its own location? Quote Share this post Link to post Share on other sites
Jezza 0 Report post Posted December 30, 2009 I've just had a play around and found that the coil does have 12V at the positive line in, so no power/relay issues. The coil itself has 0.8 ohms across the primary coil and 5600 ohms across the secondary coil which seems alright as well. I also checked the ground for the coil and found something a little suspect. It has around 6000 ohms resistance while the engine is stationary. Is that normal? I thought that was supposed to be a 'clean' ground with 0 ohms resistance until the ecu cuts it temporarily while the spark plug fires. Can anyone verify if the ground line off the coil is supposed to have any resistance? Cheers Quote Share this post Link to post Share on other sites
turboprop 0 Report post Posted December 30, 2009 It wont have any ground until the engine is running, thats how the ECU controls it, by grounding it. If it was grounded while the engine was not running it would overheat and burnout. Quote Share this post Link to post Share on other sites
Jezza 0 Report post Posted December 30, 2009 (edited) Oh OK, seems obvious now. Can I test the ground using a resistor/l.e.d or will the pulse be to fast? Is there any other way of testing it? Edited December 30, 2009 by Junkers Quote Share this post Link to post Share on other sites
BM WORLD 1260 Report post Posted December 30, 2009 coils give very little trouble in these cars . check those crank sensors and also remove the ecu , and open it up and check for dry joints Quote Share this post Link to post Share on other sites
Jezza 0 Report post Posted January 3, 2010 Back with some updates. I have taken the ecu out and have inspected it. No dry joints to be found. Have taken out both crank angle sensors (I can't understand why there are two?) and checked them across pins 1 and 2. Both have around 1000 ohms resistance which sounds fine. Is there anything else I can check or am I going to have to go through the process of elimination? Does anyone one know why there might be two crank angle sensors or maybe what the second sensor is actually for? Thanks Quote Share this post Link to post Share on other sites
Jezza 0 Report post Posted January 3, 2010 (edited) Problem solved! Turns out after a closer inspection that there was a very fine hairline split in the solder joint of one of the transistor connections. Thanks very much for your help! Edited January 3, 2010 by Junkers Quote Share this post Link to post Share on other sites
