Andy I 0 Posted January 26, 2014 Just checked voltage at the coil with the ignition on (not cracking) there is 12, whill cranking it drops to 9 and when running it's at 9 Quote Share this post Link to post Share on other sites
RT 1006 137 Posted January 26, 2014 Just checked voltage at the coil with the ignition on (not cracking) there is 12, whill cranking it drops to 9 and when running it's at 9 Hmm, that's odd :headscratch: you should have around 9v with ignition on, 12v whilst cranking and 9v running. I'll have a think about this one, I'll also have a look at my car and get back to you later. Quote Share this post Link to post Share on other sites
Andy I 0 Posted January 26, 2014 That would be great thanks, might end up with a relay Quote Share this post Link to post Share on other sites
Andy I 0 Posted January 26, 2014 This was at the + side of the coil, or should I have been on the -iv side? Quote Share this post Link to post Share on other sites
Ford1975 2 Posted January 26, 2014 9 or 12v on cranking?? the purpose of the coil is to give higher voltage on cranking 30-40k volt momentary inline with points opening :headscratch: Quote Share this post Link to post Share on other sites
RT 1006 137 Posted January 26, 2014 Just checked voltage at the coil with the ignition on (not cracking) there is 12, whill cranking it drops to 9 and when running it's at 9 Right, I've had a look and I've had a think. The only way I can explain the readings you got is if you had one meter lead on the coil negative and the other lead on the battery positive? or one meter lead on battery positive and the other on the coil positive and the leads on the coil are the wrong way round. If this was the case then with ignition on (not cranking) you would be measuring battery voltage which would explain the 12v. When cranking the battery voltage drops due to the very high demand upon it by the starter motor which explains the 9v. With the engine running what you will be measuring now is the negative pulses to the primary side of the coil via the points. This will effectively be a 'chopped up' DC voltage. The average multimeter cannot measure a pulsed DC accurately hence the 9v reading. My advice would be to double check that you have the leads on the coil the right way round as I think you may have them reversed which is why you got the readings above. The lead from the points/distributer should go to the coil negative. Check and see how you get on. Incidentally I've just checked my car, the battery is a bit flat but this is what I measured so it should give you an idea. Ignition on 6v, cranking 9v, and running 6.5v. You should get about the same with a bit of variation depending on how good your battery is. Quote Share this post Link to post Share on other sites
RT 1006 137 Posted January 26, 2014 9 or 12v on cranking?? the purpose of the coil is to give higher voltage on cranking 30-40k volt momentary inline with points opening :headscratch: What he means is 9v on the coil primary Quote Share this post Link to post Share on other sites
RT 1006 137 Posted January 26, 2014 This was at the + side of the coil, or should I have been on the -iv side? No that's correct, measure from the positive side but ensure the coil leads are the right way round Quote Share this post Link to post Share on other sites
Ford1975 2 Posted January 26, 2014 What he means is 9v on the coil primary On the primary side of the coil it always going to be BATTERY voltage which is going to tell you nothing only the condition of the battery, If your are trying to fault find a problem you need to check the coil for ( resistance ) THAT WILL TELL you if the coil is operating or not... Quote Share this post Link to post Share on other sites
RT 1006 137 Posted January 26, 2014 On the primary side of the coil it always going to be BATTERY voltage which is going to tell you nothing only the condition of the battery, Not if it's got a ballast resistor in series with it (which the Mk5 has) hence the 6-9v at the coil when running. Quote Share this post Link to post Share on other sites
Ford1975 2 Posted January 26, 2014 Yes so there's 12v at coil so it getting its feed. ANDY said it starts if he gives it a squirt in the filter box so either weak coil giving weak spark or low fuel pressure not allowing enough fuel into the cylinder. Good luck Andy. :thumbup: Quote Share this post Link to post Share on other sites
sierra3dr 36 Posted January 26, 2014 (edited) Which area are you from Andy? Manchester? Edited January 26, 2014 by sierra3dr Quote Share this post Link to post Share on other sites
mk4ste 43 Posted January 26, 2014 Which area are you from Andy? Manchester? i think he's cumbria, lakes Quote Share this post Link to post Share on other sites
sierra3dr 36 Posted January 26, 2014 Too far to help Quote Share this post Link to post Share on other sites
