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Testing Coil packs

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  #1  
Old 10-02-2005, 11:25 AM
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Testing Coil packs

Ok I need some help in understanding the proper way to test a coil pack.

I have a 97, 4.6l with the Ei system, 2 packs paired.

The book tells me to probe for secondary res across say number 3 and 5.
For primary resistance check between + and - inputs @the pack.

I searched out this problem on here but found a different way to check it (or at least I dont understand it anyways.

I quote... SVTRobG
Senior Member



You can check the resistence on the coils to see if any are bad.

Specs are...

Primary resistence = 0.55 ohms
Secondary resistence = 5.5 K-ohms

You check the primary by connecting your ohmmeter to the + & - terminals of the coil pack.

You check the secondary by connecting the ohmeter to the + on the terminal and the - on the spark plug side (there's a coil wire inside the boot).

If the coil pack doesn't test out to those specs it's crap !!!

End Quote......


The book tells me to check at the output on the pack 3 and 5 I get 13.26 ohms, the book says 5.500 ohms If I look at the picture in the book the ohm meter that was used shows the same reading as I am getting 13.26.

I have not done the other as I am not sure if it is ment to test between the + input at the pack to the output (wire) or else where. I just want to make sure I am not spending moneys for no reason.

I was gonna switch packs to see if my P0305 code follows but all my packs test the same.
Can some one shead a bit of light on my shaded brain
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Old 10-02-2005, 12:18 PM
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Update,
Checked the primary resistance on both packs, both tested at 0.6 ohms
So thats good.

Wires check out good (they are new) Plugs are good as well. (At least they show no signs of anything wrong) Who designed the plug location ?

I am still worried about the 13.26 ohms across 3 & 5 coil pack.
I know with heat this is going to increase.
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  #3  
Old 10-02-2005, 01:50 PM
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best method to check is with the ford computer WDS...
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Old 10-02-2005, 02:06 PM
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Yes I will prolly have to take to the dealer,

I just took it back out for another run,
After getting it up to temp, I really loaded it down, using a steep grade and the A/C I was able to set a mis in the engine with out a code setting for quite some time.
Once the code came back I read it and found my P0305 was now a P0304 So my problem just changed cyl.

I can clear it out and the truck misses badly at idle, much worse than before.
Upon takeing a slow trip up a large hill I heard what sounded like a exhaust leak on the left side. I did find a smalll leak at teh gasket from the manifold to the pipe so I am not to worried about that atm.

But it does take a long time for the code to reset itsseslf after being cleared tho the engine still misses bad.

What ever it is I think its related to heat.
I am letting it cool down before trying it again just so I got information to work with.
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  #5  
Old 10-02-2005, 04:09 PM
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Be advised that a coil pack or coil may ohm out okay, but that doesn't necessarily mean it's good. A coil stress test and/or power balance test as Faster150 mentioned is the most accurate way of checking the ignition system.
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  #6  
Old 10-02-2005, 09:38 PM
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Emonster - sounds like your problem is the exact same problem that I'm having with my '98 5.4L. I've changed the plugs, visually inspected the coils, changed the fuel filter but the problem still persists. As soon as the truck warms up she starts missing pretty good under load - although I'm not convince that it's an ignition miss - could be even related to fuel. Driving at 55 km'h with the truck in 3rd gear, app 1200 rpm, (o/d turned off), the minute you touch the gas the truck hits 1400 rpm and it starts bucking. My idle is actually pretty decent - only shows about 550rpm on the tach but it's not labouring up and down at all - there's a slight miss at idle but it's hardly noticeable.

Whatever my problem is, I know that it's heat related, just wish I could figure it out.
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Old 03-31-2006, 05:28 PM
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So what ever happened? Emonster, Myersc99?
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  #8  
Old 03-31-2006, 06:22 PM
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Quote:
Originally Posted by Emonster
Ok I need some help in understanding the proper way to test a coil pack.

I have a 97, 4.6l with the Ei system, 2 packs paired.

The book tells me to probe for secondary res across say number 3 and 5.
For primary resistance check between + and - inputs @the pack.

I searched out this problem on here but found a different way to check it (or at least I dont understand it anyways.

You are confusing a COP spec with a coil pack spec.

EI Systems coil pack.

Primary resistance .3 to 1.0 ohms
Secondary resistance 6.5 to 11.5 K-ohms

For a 4.6L engine you check 7/4, 8/2, 1/6 and 3/5.

Last edited by temp1; 03-31-2006 at 06:26 PM.
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