97 Caravan 3.0 - NO SPARK!

Tiny
PLOSSER
  • MEMBER
  • 1997 DODGE CARAVAN
  • 165,000 MILES
97 Caravan 3.0 V6 3spd - I have no spark and apparently no power to coil. Here is the full story. I got this van with a blown timing belt. Replaced belt and water pump and test started and it worked. Pulled engine and trans out to repair some other damage. Put it all back in and now no spark. Replaced distributor cap and rotor, all plug wires and spark plugs (and have triple checked for correct connections). HELP, PLEASE!
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Monday, July 11th, 2011 AT 4:07 AM

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Tiny
CARADIODOC
  • EXPERT
Measure the voltage on the dark green / orange wire at the ignition coil, any injector, or either small wire on the back of the alternator. You should see battery voltage there for one second after turning on the ignition switch. What you need to see is if that voltage comes back during engine rotation, (cranking or running).
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Monday, July 11th, 2011 AT 6:18 AM
Tiny
PLOSSER
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I saw that you had replied to another post with a similar issue. I will try this tomorrow. Once I run the voltage check, what would be the next step, assuming I still have no spark? If possible give me a few other specifics to look for so I can do it all at once and in order.
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Monday, July 11th, 2011 AT 7:03 AM
Tiny
CARADIODOC
  • EXPERT
That voltage comes from the automatic shutdown (ASD) relay which is turned on by the Engine Computer. The computer also turns on the fuel pump relay at the same times. That initial one second is to insure fuel pressure is up and ready for starting in case it bled down over a few days or weeks.

After that first one second, the computer turns the ASD relay on again when it gets pulses from the camshaft position sensor and crankshaft position sensor. The purpose of the system is to turn off the fuel pump in the event of a crash that ruptures a fuel line. The engine will stall with no fuel pressure so there won't be any pulses from the cam and crank sensors. With no pulses, the fuel pump is turned off to prevent dumping raw fuel on the ground. This system is WAY more reliable and effective than Ford's inertia switch. The alternator field, injectors, ignition coil(s), and oxygen sensor heaters all get their current from the same source so all of those systems go dead when the ASD relay doesn't turn on.

Since you had stuff apart, be sure both sensors are plugged in. Also, a thick paper spacer must be used to set the air gap of the crank sensor. Without it, the sensor can be pushed in too far where it will hit the flex plate and break. If it's spaced out too far, the pulses will be weak and can cause intermittent stalling. If you reinstall an aftermarket sensor that had a thin plastic rib molded to the end to set the gap, you are to cut the remaining part of that rib off and use a paper spacer.
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Monday, July 11th, 2011 AT 7:23 AM

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