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Old 06-26-2015, 04:28 PM   #1
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Default No spark Buick 3.8

Hello everyone,

I'm chasing down a no start issue with a '95 Regal 3.8 V6. Recently it threw and shredded the serpentine belt while driving. I found that the water pump pulley shaft had worn to the point where it let the pulley wobble pretty severely. I replaced the water pump which fixed the belt issue but now the car will not start.

I tested for spark with an in-line spark tester and discovered that there is no spark at all to any of the cylinders. This led me to believe there is something going on with the ignition control module or the crank position sensor, so I tested them using this write-up: https://www.gmforum.com/trouble-shoo...m-test-299761/

I verified that the ICM was getting both power and ground in the proper terminals. However, the N terminal, which supplies power the the cam and crank sensors, was only showing 4.4 volts instead of 12. I replaced the ICM with one from another car and am getting the same no start condition with the same 4.4 volt reading. After a little research I found another site that says 4 to 5 volts from the N wire is normal, is this the case? I went ahead and tested the 18x and 3x signal wires from the crank sensors. The 3x test pulsed from 0 volts to 6.7 volts as it should. The 18x wire stayed at 6.7 volts with no pulses at all while turning the crankshaft.

Any help with this situation would be greatly appreciated. At this point I really don't know what is going on. Tomorrow I intend to pull the harmonic balancer/crank pulley to inspect the crank position sensor for any damage from the belt coming apart. I already checked the wiring in the area as best as I could for damage and found nothing, but I could've missed something.

Thanks in advance for the help.
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Old 06-27-2015, 11:06 PM   #2
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The ICM test states:

NO- If you have no pulses, recheck all connections. Try again. If you still have no pulses the 18X CKP Signal from Crankshaft Position Sensor is not being received. Without this Signal the ICM will not spark the Coils. The Crankshaft Position Sensor is bad. Replace it.

If the harness(wires and connectors) from the crank sensor to the ICM are ok, and the blades on the back of the harmonic balancer are ok, it'* the sensor....probably damaged by the belt....
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Old 06-28-2015, 12:49 AM   #3
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You're right. After pulling the balancer off, I found that the crank sensor was actually broken by the belt. I replaced it, put everything back together, and it fired right up.

This is what I originally suspected, but when my icm test readings came out different than specified (4.4 volts from n terminal instead of 10-12) I went in that direction.

Thanks for the help. I'm glad to get the car out of the garage and back on the road.
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Old 06-28-2015, 09:02 AM   #4
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Forgot to mention, the ICM Test states the 18X AND 3X signal should be 5-6 volts, not 12 volts....your'* may have been a little lower than 5-6 volts because the battery was weak...
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