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Old 05-08-2013, 09:12 PM   #1
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Default 3.1 cranks won't start

I have a 95 Cutlass Supreme 3.1. A couple of days ago I was driving along and it started to cough & sputter, losing power. I stepped on the gas and it took off just fine. No CEL came on. The next day I was driving again & it died. Now it cranks, but won't start. I was able to get it pushed home and started checking it out. There is pressure in the fuel rail and spark to at least one spark plug (I only checked it at one wire so far). I sounds like it has compression while cranking, but it cranks and comes close to starting, then it bogs down like a spark coming at the wrong time, then it goes back to an almost start condition.

I don't have a scan tool. I have been leaning toward the crank or cam sensor acting up telling the computer false info on timing, but I could be way off on that. I don't want to just start throwing parts on it based on just my educated guess as there is no return on electrical parts after you've put them on.

Anyone else experience this or have suggestions on this or other causes?
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Old 05-09-2013, 07:40 AM   #2
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i would say you are on track, the crank sensor is a pretty common failure if there is spark and fuel. i think i would check the actual pressure of the fuel make sure its within spec first
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Old 05-09-2013, 10:34 AM   #3
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If the crank sensor failed you would have no spark, and it would not cough and sputter ... it would shut down like you fipped a switch. Is your car OBD1 or OBD2? 94/95 was the transition, but I think you are OBD2. Get the car scanned for trouble codes (free at Autozone), and get the fuel pressure checked. When was the last time you changed the fuel filter? You can also see if it is a fuel related issue by giving it a shot of starting fluid while trying to start the car. If it fires up and then dies with the starting fluid, you have a fuel issue.

You can also test the ignition control module. Here is a good write up on how:

Part 2 -Ignition Module & Crank Sensor Test: GM 3.1L, 3.4L.

Start with a scan if you can.
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Old 05-09-2013, 10:49 AM   #4
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it does sound more like a fuel pump or something but the crank sensor can be bad with spark at the plugs. if its intermittent or the connector is bad or wiring it will cause it to be off timing wise
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Old 05-09-2013, 11:26 AM   #5
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Originally Posted by jwfirebird View Post
it does sound more like a fuel pump or something but the crank sensor can be bad with spark at the plugs. if its intermittent or the connector is bad or wiring it will cause it to be off timing wise
I don't agree. If he has spark the problem is not the CPS.
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Old 05-09-2013, 12:06 PM   #6
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I have tried starting fluid while cranking and it didn't start, as a matter of fact, cranking seemed to be hindered by it like it may have been firing at the wrong time, working against the starter. Based on that I ruled out fuel issues.

I think it'* OBD2, but I have no way of getting it to AutoZone or anywhere else w/o a tow as it doesn't start/run. That would have been my first option (getting it scanned).

Based on what people are indicating here, It sounds like the computer relies on the crank sensor for timing the spark, what role does the cam sensor play and might it be the problem?
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Old 05-09-2013, 12:08 PM   #7
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on most gm cars the cam sensor is a back-up for the pcm to determine advance or crank position problem
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Old 05-09-2013, 12:39 PM   #8
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So chances are the cam sensor is not the problem as it is redundant to the crank sensor. It should run fine with a bad cam sensor if everything else is okay?
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Old 05-09-2013, 01:18 PM   #9
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Test the ignition control module.
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Old 05-09-2013, 01:48 PM   #10
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Quote:
Originally Posted by 2kg4u View Post
Test the ignition control module.
I was just looking at the link you provided for testing the ignition control module, and it says if I have any spark from any coil, both the module & crank sensor are okay. I was thinking the crank sensor might be sending intermittent signals or somehow wrong timing in the signal if that'* possible. I know the general conscience is that a crank sensor is either good or bad, but what about going bad...
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