David Jenkins
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 posted on 28/6/07 at 05:53 PM |
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A question about EDIS...
Just something that occurred to me today...
I have Megajolt with all the usual EDIS bits. If I leave my ignition switched on with the engine stopped, am I frying my coil? Or don't the
coils get charged when the engine isn't running?
In the bad old days of contact breakers & coil, if the ignition was on and the points were closed, the current through the coil would eventually
cook it to death.
The reason for asking is that I'm playing around with my electrics, or putting new maps in the MJ unit and so on, and the ignition is sometimes
on for quite a few minutes. It would be nice to know if I need to be cautious.
cheers,
David
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matt_claydon
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| posted on 28/6/07 at 06:07 PM |
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No, the coil won't be energised, the EDIS doesn't know where the engine is if it's not turning (unlike points) so will not energise
the coil without a continuous signal from the crank sensor.
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hearbear
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| posted on 28/6/07 at 06:09 PM |
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My understanding is the megajolt or ecu have to switch the coil on and off to give the spark so with the ignition on nothing will happen.
3.9Ltr SSC Stylus should be fun
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MikeRJ
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| posted on 28/6/07 at 06:22 PM |
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quote:
Originally posted by hearbear
My understanding is the megajolt or ecu have to switch the coil on and off to give the spark so with the ignition on nothing will happen.
Points also have to switch the coil on and off to give sparks 
Most OEM electronic igntions (inc. EDIS) will power down the coil to stop it frying if they sense the engine isn't running.
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rusty
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| posted on 28/6/07 at 06:31 PM |
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To test jsut put a volt tester / meter on the coil
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David Jenkins
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| posted on 28/6/07 at 06:50 PM |
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That's what I thought/expected.
Rusty - fair comment! I was thinking that as I was out hooning around this evening... might get the meter out, just to be 100% sure (but I expect
there to be no power).
cheers,
David
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COREdevelopments
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| posted on 28/6/07 at 06:53 PM |
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i like your avartar rusty.
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COREdevelopments
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| posted on 28/6/07 at 06:55 PM |
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oh also, not meaning to hijack thread. but has any one got a map for megajolt on a 4age? im running twin40 dellortos. anyone
Rob
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David Jenkins
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| posted on 28/6/07 at 07:27 PM |
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quote:
Originally posted by rusty
To test jsut put a volt tester / meter on the coil
Hmm - put a meter on the coil connector; +12v appears on the centre connector when the ignition's on. The other 2 connectors are 0v, but
I'm not going to risk my meter on the resistance setting with live volts around to find out whether that's true 0v or open-circuit!
However they are connected to chassis when the ignition's off.
I'll have to go and check up on the EDIS circuit description to see what it's supposed to be doing...
UPDATE: 12v on the centre terminal is entirely correct, according to Ford's EDIS description. Now I need to find out what happens on the other
2 terminals... 
[Edited on 28/6/07 by David Jenkins]
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scottc
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| posted on 28/6/07 at 07:59 PM |
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the other two terminals (1 and 3) get 12v when charging the coil I think? then get grounded when they should spark? I think.
Don't sound too sure do I
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David Jenkins
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| posted on 28/6/07 at 08:02 PM |
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I would expect it to work like a normal coil - the terminal gets grounded until the spark is required, building up a magnetic field, at which point
the circuit is broken and the collapsing magnetic field induces the HT in the secondary.
...but I don't know for certain what the EDIS does, either! 
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paulf
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| posted on 28/6/07 at 08:05 PM |
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Never checked this myself but if the coil is supplied with 12v to the centre then if the other end is indicating 0v it must be connected to neutral, a
meter would show 12v if it was open circuit.Maybe it would be worthwhile putting an ammeter in line to see how much current is flowing as the edis
probably limits it to a safe value when not running.Ive never had a problem leaving the ignition on whilst working on mine .
Paul.
quote:
Originally posted by David Jenkins
quote:
Originally posted by rusty
To test jsut put a volt tester / meter on the coil
Hmm - put a meter on the coil connector; +12v appears on the centre connector when the ignition's on. The other 2 connectors are 0v, but
I'm not going to risk my meter on the resistance setting with live volts around to find out whether that's true 0v or open-circuit!
However they are connected to chassis when the ignition's off.
I'll have to go and check up on the EDIS circuit description to see what it's supposed to be doing...
UPDATE: 12v on the centre terminal is entirely correct, according to Ford's EDIS description. Now I need to find out what happens on the other
2 terminals...
[Edited on 28/6/07 by David Jenkins]
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David Jenkins
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| posted on 28/6/07 at 08:10 PM |
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quote:
Originally posted by paulf
Never checked this myself but if the coil is supplied with 12v to the centre then if the other end is indicating 0v it must be connected to neutral, a
meter would show 12v if it was open circuit.
I had my meter on the connector, looking back at the MJ & EDIS - I probably forgot to mention that I had unplugged it from the coil!
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MikeRJ
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| posted on 4/7/07 at 07:57 PM |
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quote:
Originally posted by David Jenkins
quote:
Originally posted by paulf
Never checked this myself but if the coil is supplied with 12v to the centre then if the other end is indicating 0v it must be connected to neutral, a
meter would show 12v if it was open circuit.
I had my meter on the connector, looking back at the MJ & EDIS - I probably forgot to mention that I had unplugged it from the coil!
In that case I would expect to see zero volts on the two outer connections as there will be nothing to pull itnup to 12v. Tryin it again with the
coil connectors and all three terminals should be at 12v with the engine stopped.
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