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Old 10-27-2008, 06:41 PM
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318 ignition spark mystery(help!)

I replaced the timing chain
went to start the engine I had spark all was well.
then my spark went away...so in the process of figuring this out I have replaced the ecu or ecm, ign coil, starter relay and the ign resistor.
Whats wierd is this-holding the ignition coil wire off the block while cranking the engine no spark turn the key to off and a spark occurs
I can turn the key from accessory to off and get a spark every time but while engine is cranking(start position) no spark
what am I missing?

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Old 10-27-2008, 09:21 PM
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we really need some more info, what year & model is the car, auto or standard trans, 2 or 4 barrel carb.

if its an older model year, check for power at the positive side of the coil while cranking.
i know in 75 on the Plymouth Fury Mopar had a relay over on the passenger side inner fender and a bad connection or if the relay went bad it could cause a no spark.
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Old 10-27-2008, 10:15 PM
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it's a big ol' piece with the Winnebago body
the vehicle is 1 ton van 73' 2-barrel
electronic ignition, with one pickup coil in the distributor, automatic trans.
everything seems original or at least has not been messed with too bad.

Last edited by androopa; 10-27-2008 at 10:17 PM. Reason: forgot info
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Old 10-30-2008, 02:11 AM
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i don't have a book that goes back that far, so i the specs i have for the pickup coil may not be right so i won't post them.
if you have a book with the tests and the specs, check it out.
Mopar pickup coils were pretty good and lasted a long time, but they did go out. replacing it if you haven't already probably wouldn't hurt.

if power checks good at the hot side of the coil while cranking, with one end the test light hooked to battery positive hook the other end to the negative side of the coil and check to see if the light flashes while cranking.
if it does flash and you have no fire from the coil, you have coil problems.
if it doesn't flash, check the wiring out for any damage.
if you don't find any problems, the ignition module may be bad.
check for good power and ground at the module while cranking.
some modules were grounded thru the wiring, some weren't. so make sure the module has a good ground thru the bolts too.
i usually recommend replacing the ignition coil any time the module has gone out.
it may take a few modules before you get a good one that will last.
i've replaced them only to have it go out in a few minutes or a few days.
if the module makes thru the first 2~3000 miles, normally it will last for years.
once your sure you have a good one, buy a second one for a spare.
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Old 10-30-2008, 07:36 AM
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I think I would check the ballist resistor, a common problem with old chryslers.
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Old 10-30-2008, 11:46 AM
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Ground?

I had this proble once when the ECM wasn't grounded good enough. Drove me nuts!
Pat
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Old 10-30-2008, 04:29 PM
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I would check the pickup. When you turn the key on then off it is simulation the pickup making and breaking the coil circuit through the module. If when cranking there is power at the plus side of the coil and none at the minus side then either the module or the pickup is bad. Where you just had the engine apart I would take a hard look for a pinched wire between the coil and the distributor or module. If the negative side was being held at ground all the time you will get spark when the key is turned off because the field in the coil will collapse generating the spark.
Check the obvious first, look for a pinched or broken wire.

Chet
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Old 10-30-2008, 10:26 PM
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The ECU checked out bad, as did the RESISTOR and pickup coil. So I went with the flow of it all and replaced the starter relay , ignition coil. and I found a voltage regulator unused laying around here.
Testing the wiring with a volt/ohm meter I found no spark between the ECU(4 point plug) and the coil. Checking the wire though I had no breaks(continuity). Thinking about it I remembered that the Ignition switch layed with in that wire run and checking it out I found that power was not leaving the switch. Duh...
I felt like a big dummy... Yes the engine was turning over but the switch also completes the circuit between the ECU and coil. Which that particular feed on the switch was not opening up preventing the complete circuit.
Alright enough said...thanks for the advice you all gave for I was definitely looking for the answer.
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Old 10-30-2008, 11:07 PM
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I have an old Dodge trick van that the same thing happened to it.
On that one, it was just the ign switch that went bad.
It was supposed to be putting voltage to the resistor before the coil but it wasn't.
I just checked the wire color code on the resistor and found it on the ign switch, jumped it and she fired right up.
I got another ign switch and the problem went away.

Oh, the van is 1976 so not all the new electronics, just electric ignition, no points.
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