Coil Pack Check
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New User
Joined: Oct 2007
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Coil Pack Check
1999 250 Sd with 5.4, need to know internal resistance of the coil pack and what points on the pack to test it on. Thanks.
Or how else to check it without buying $500 software package. 
Or how else to check it without buying $500 software package.
Post Fiend
Joined: May 2006
Posts: 10,007
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From: Central Florida
There are two coils in each pack, the low voltage and high voltage. Testing the resistance doesn't give you great information. A scan tool that reads the coils is going to be the easiest method. By theory though, if you are having a miss, the cylinder that is missing will have a colder exhaust manifold inlet. You can use an IR probe or a spray bottle of water to find the cooler tube.
Posting Guru
Joined: Jul 2007
Posts: 1,433
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From: Spring Lake
There are two coils in each pack, the low voltage and high voltage. Testing the resistance doesn't give you great information. A scan tool that reads the coils is going to be the easiest method. By theory though, if you are having a miss, the cylinder that is missing will have a colder exhaust manifold inlet. You can use an IR probe or a spray bottle of water to find the cooler tube.
If the coil pack is fine the other two parts of it are the connection and corrosion can be removed relatively easily with WD-40, wire brush, or dialectric grease to ensure a good connection. Is there a critical piece of the coil I am missing?
Elder User
Joined: Jan 2002
Posts: 780
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Wrong way to test coil.
You cannot accurately test a coil with a VOM. You need to look at the waveform with a scope or use something that checks the resonance frequency (ring test). A good scanner does a pretty good job of picking up the cylinder that has the miss, but does not confirm whether it is the coil pack, injector, or some other problem. Many times subbing the suspected coil pack with a know good one is the easiest and most reliable test.
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