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Unread 07-12-2010, 04:52 PM   #1
headstrong50
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1993 YJ Wrangler 
 
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coil getting constant voltage instead of pulsating

i recently put my drive train back into my 93 yj after getting everything rebuilt. the jeep fired fine before, but when we went to turn it over, it wouldnt. i bought a new coil because i wasnt getting any spark, but that didnt help anything, so i tested the volts and instead of it pulsating at 12 volts, it was constant. what does this mean? or am i way off?

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Unread 07-12-2010, 05:16 PM   #2
laybackman
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Quote:
Originally Posted by headstrong50 View Post
i recently put my drive train back into my 93 yj after getting everything rebuilt. the jeep fired fine before, but when we went to turn it over, it wouldnt. i bought a new coil because i wasnt getting any spark, but that didnt help anything, so i tested the volts and instead of it pulsating at 12 volts, it was constant. what does this mean? or am i way off?
Was this a complete disassembly/rebuild of the engine?

"turn it over" does that mean the starter turns the engine but it does not fire?

Do you have fuel pressure at the fuel rail? Do you have gas? I ask becasue I have done a bunch of rebuilds and I am quite meticulous YET one time I spent an entire 12 hour day chasing a problem....yep no fuel!

If you have no fuel pressure at the fuel rail or high voltage or any spark at all coming out if the distributer you may have a problem with the ECM. Does your CEL come on when you turn the ignition switch to the ON position?
If not then you have an ECM problem.

IF the CEL does go on and you have fuel opressure at the rail but it will not fire up I would suspect the crank sensor first.

The coil input is always 12v when starting/running. It is the output voltage to the distibuter cap that is important. That voltage depends on the coil output. But if the crank sensor or the vss sensor 'sees' no movement of the turning asssembly you get no spark of fuel after a second or so of cranking.

EDIT if the sensor in the distributer sees no mevement the same thing happens I beleive.
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Unread 07-12-2010, 08:19 PM   #3
ctm
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for the coil it is the ground connection that is pulsed by the ignition module on the trigger signal from the distributor
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Unread 07-13-2010, 12:15 AM   #4
headstrong50
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the engine cranks, just does not run. i checked the fuel rail and i have pressure.
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Unread 07-13-2010, 01:51 AM   #5
Douglas S.
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Have you checked for codes?
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Unread 07-13-2010, 03:32 AM   #6
Mark05059
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sounding like a crank sensor issue.
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