Blinking check engine light 5.4L
Posting Guru
Joined: Oct 2005
Posts: 2,209
Likes: 1
From: Louisville, Kentucky
Originally Posted by Johnny Langton
I've got a friend with a '97 Expy...and it likes to leak water down on that #4 every time it rains,and we can't find out where it's coming from. Usually we can just pull the COP off,and blow all of the watrer out,and it's good to go again until the next rainstorm.
JL
JL
Post Fiend
Joined: Jun 2005
Posts: 7,047
Likes: 2
From: North west La
I have a 97 with the 5.4. It lost the number 4 cop due to the heater hose leaking on it. I replaced the hose clamps & the coil & plug. I've had1 more cop fail since then. I may replace all my cops with the ones Troyer performance offers that are higher voltage on my next tuneup.
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
Originally Posted by lariat97
I have a 97 with the 5.4. It lost the number 4 cop due to the heater hose leaking on it. I replaced the hose clamps & the coil & plug. I've had1 more cop fail since then. I may replace all my cops with the ones Troyer performance offers that are higher voltage on my next tuneup.
The coil will only continue generating a stepped-up voltage until the plug fires.
No more, no less.
And a new fine-wire plug will fire at a LOWER voltage than an old, worn out one.
Steve
Last edited by projectSHO89; Mar 19, 2007 at 07:22 PM.
Cargo Master
Joined: Oct 2003
Posts: 2,833
Likes: 4
From: Jefferson, Iowa
just looking at the plug thing from an electricians point of veiw ( my profession of choice ) if you have more windings on the secondary side of the transformer you will bump up your output voltage ie your higher voltage coil. now the coil will not build electrically for no more than the period of time between o vdc and 12 vdc or the capacitive input amount, because straight dc voltage does not work in a transformer for steping to different voltages. the instant your voltage goes from 0 to 12 vdc that is the same as 1/4 of an ac sign wave creating a split second of essentually ac power, producing your 35k plus ignition. that is why your car coil will only arc once on an old points system. you do have a point of the worn plug requires more voltage potenial to arc, but transformers work in the world of power ( watts ) not necessarly just voltage, so if ohm's law tells us anything a watt is the voltage multiplied by the amperage. Amperage is what creates the heat and ignites our fuel. So with a smaller gap less actual voltage is required thus leaving a little more amperage to create heat in the arc.
Postmaster
Joined: Oct 2006
Posts: 4,171
Likes: 12
From: SE Texas
Originally Posted by 78fordman
just looking at the plug thing from an electricians point of veiw ( my profession of choice ) if you have more windings on the secondary side of the transformer you will bump up your output voltage ie your higher voltage coil. now the coil will not build electrically for no more than the period of time between o vdc and 12 vdc or the capacitive input amount, because straight dc voltage does not work in a transformer for steping to different voltages. the instant your voltage goes from 0 to 12 vdc that is the same as 1/4 of an ac sign wave creating a split second of essentually ac power, producing your 35k plus ignition. that is why your car coil will only arc once on an old points system. you do have a point of the worn plug requires more voltage potenial to arc, but transformers work in the world of power ( watts ) not necessarly just voltage, so if ohm's law tells us anything a watt is the voltage multiplied by the amperage. Amperage is what creates the heat and ignites our fuel. So with a smaller gap less actual voltage is required thus leaving a little more amperage to create heat in the arc.
JL
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Your both wrong about when the plug fires and at what voltage level.
Usually the plug will spark jump at about 7 to 9000 volts in a good trouble free system.
The rest of the voltage (35k to 40k minus about 7k) is waisted and in reserve as the plug deteriorates and need more reserve to fire. The voltage used, goes up to cover the difficult spark jump conditions.
The most difficult times the plugs experiennce is under open EGR when the fuel is cut back to a lean condition and the ignition timing is advanced.
There is more science to this than meets the eye. It's not just only simple ohms law.
The resistance in the spark gap due to the A/F charges changing with throttle opening, calculated fuel injection amounts, plug conditions, leakages etc change all the time as the engine is running and needs the large reserve volrage available to keep the engine running over a long length of time or you would be servicing the ignition all the time.
Usually the plug will spark jump at about 7 to 9000 volts in a good trouble free system.
The rest of the voltage (35k to 40k minus about 7k) is waisted and in reserve as the plug deteriorates and need more reserve to fire. The voltage used, goes up to cover the difficult spark jump conditions.
The most difficult times the plugs experiennce is under open EGR when the fuel is cut back to a lean condition and the ignition timing is advanced.
There is more science to this than meets the eye. It's not just only simple ohms law.
The resistance in the spark gap due to the A/F charges changing with throttle opening, calculated fuel injection amounts, plug conditions, leakages etc change all the time as the engine is running and needs the large reserve volrage available to keep the engine running over a long length of time or you would be servicing the ignition all the time.
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