Mikef
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| posted on 30/1/16 at 12:53 PM |
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Possible faulty coil pack
I am using a Ford coil pack Mk1,driven by an Emerald K6, I only have the engine running on 2 cylinders I have checked every thing you can think of,
inc Compression test just in case. 1&4 are the cylinders that are not running. Which would seem to point to the coil pack as it is wasted spark,
and this would be the 2 that should fire together. I have checked for a spark at the plug,which is a bit difficult on my own, however I seem to get a
bit of a spark which does look very weak and possibly intermittent , bit yellow. I suppose my question is has anybody experienced this. I can
understand NO spark, and that would be an easy fix. Any thoughts gratefully received as always.
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ian locostzx9rc2
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| posted on 30/1/16 at 01:01 PM |
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Sounds like a coil pack new coils are only about £20/£25 so worth getting a new one
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britishtrident
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| posted on 30/1/16 at 01:25 PM |
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Almost certainly the coilpack, with a pile of equipment they are not so easy to diagnose as the old stuff but the two companion cylinders being down
makes almost 100% certain.
When replacing any coil which has plug leads I always either do resistance and leakage tests on the plug lead or replace them as a matter of course
and always pull the spark plug out and check the condition and gap.
Modern engines because of the very high voltage requirements of the very wide plug gaps now specified place huge demands on insulation of coils and
plug leads, if the gap is too wide or the plug lead has excessive resistance the coil insulation gets damaged by arcing.
[Edited on 30/1/16 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 30/1/16 at 02:07 PM |
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This might help NGK guide to testing
leads
I should add 99 percent probability of coil fault the other 1 percent probability is an injector driver fault if you have injectors 1 & 4
sharing a bank and 3 & 4 on a different bank.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Mikef
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| posted on 30/1/16 at 02:42 PM |
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Many thanks for this. As you say I am coming down on the side of faulty coil. I have made up a test rig so that I can clip the pug to it and earth.
Would appears that I am still getting a spark at 4 but seems very intermittent, and an occasional very weak spark on 1 , 2/3 are ok . Will check all
the leads but they are not very old magnacor, have some spares so will double check. Out of interest I am using a standard Ford ( not cheap no name)
coil pack and revving it to 7.5k. I have mounted it in the engine compartment at one end of the block, I reckon it must get pretty hot. I was thinking
of moving it ? As the apparently faulty coil is only one season old and has not done much work. Do you know of any high quality coil packs that might
last a bit longer ?
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britishtrident
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| posted on 30/1/16 at 03:33 PM |
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If you on your test rig cut the side electrode off an old spark plug just leaving a little stub you will get a better test more representative of
the much higher spark voltage required under compression -- in ambient air the spark should be able to jump well over 25mm. The bigger gap forces
the spark voltage up to more realistic in cylinder levels.
By the sound of it the insulation on on the high voltage side of the oil is more likely to be the cause than damage to the low voltage winding through
overheating.
Found elsewhere on the net
"Ford originally specified a plug gap of 1.3mm for the Zetec engine. However, this gap was found in practice to cause problems with coil pack
and lead failures. As a result, Ford issued a TSB on this and reduced the gap from 1.3mm to 1.0mm, which appears to have solved the problems which
were occurring"
I know from experience on Rover K EU3 engines with COP coil packs that the official Rover plug gap of 1.1mm seems to cause coil pack failures at low
mileage but when the gap is reduced to the 0.8mm used on the previous generation MG-Rover system the coils don't fail and there is no
difference in the running or emissions of the engine.
[Edited on 30/1/16 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Mikef
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| posted on 30/1/16 at 05:00 PM |
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What can I say. Really big thanks, top tip re cutting off the side electrode. I have a feeling the plug gap may be some of the issue I am using a std
1.3 possible bigger gap, will knock them back when I get the new coil.
Thanks again.
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