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GM3.1L no spark



 
 
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  #1  
Old December 30th 04, 09:22 PM
boardjunkie
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Default GM3.1L no spark

As per sublect line.....no spark. Verified crank sensor working (.7v
pulses), swapped ignition module with a known good one, and have 12v at
the module input. I know from past experience that a bad coil van
completely knock out the spark on the rest of the coils....tried using
1 coil at a time with all 3.....no dice.
Does the ECM control the generation of coil pulses at cranking or just
after it gets out of open loop operation? Haven't checked for the pulse
input and output at ECM yet...that's next. BTW...the voltages and
grounds at ECM are OK. Need to check for the 5v reference for the
sensors that use it to verify the 5v regulator in the ECM is ok.
Any thoughts?

Travis.

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  #2  
Old December 30th 04, 09:42 PM
Shep
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Try and get it on a scanner and see if the pcm is getting an rpm signal/
"boardjunkie" > wrote in message
oups.com...
> As per sublect line.....no spark. Verified crank sensor working (.7v
> pulses), swapped ignition module with a known good one, and have 12v at
> the module input. I know from past experience that a bad coil van
> completely knock out the spark on the rest of the coils....tried using
> 1 coil at a time with all 3.....no dice.
> Does the ECM control the generation of coil pulses at cranking or just
> after it gets out of open loop operation? Haven't checked for the pulse
> input and output at ECM yet...that's next. BTW...the voltages and
> grounds at ECM are OK. Need to check for the 5v reference for the
> sensors that use it to verify the 5v regulator in the ECM is ok.
> Any thoughts?
>
> Travis.
>



  #3  
Old December 31st 04, 02:44 AM
« Paul »
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boardjunkie wrote:
>
> As per sublect line.....no spark. Verified crank sensor working (.7v
> pulses), swapped ignition module with a known good one, and have 12v at
> the module input. I know from past experience that a bad coil van
> completely knock out the spark on the rest of the coils....tried using
> 1 coil at a time with all 3.....no dice.
> Does the ECM control the generation of coil pulses at cranking or just
> after it gets out of open loop operation? Haven't checked for the pulse
> input and output at ECM yet...that's next. BTW...the voltages and
> grounds at ECM are OK. Need to check for the 5v reference for the
> sensors that use it to verify the 5v regulator in the ECM is ok.
> Any thoughts?
>
> Travis.


Perhaps this article will be of help:
http://www.motorage.com/motorage/art...l.jsp?id=20037
  #4  
Old December 31st 04, 08:25 PM
boardjunkie
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That article was a good overview on the theory of how est operates, but
it wasn't engine specific.

Now I have checked the 5v output on the ECM...its there. When checking
for the ref pulse in (ref HI, ref Low) I didn't see much going on.
There was some activity, but super low level. Seems to me it should be
a little closer to the signal coming off the crank sensor, or even
close to logic level for the ECM to use as a digital input.

Speaking of the crank sensor, I read on this group someone's post
describing the crank sensor "kicking the ignition module in the nuts
until it collapses". I ask.....can the output pulse from the crank
sensor be too high a voltage and damage the input circuit of the
module?
Some poster said the output of this type crank sensor should be ~300mv.
Mine is putting out 700mv, whick doesn't sound like it should cause
problems, but I could be wrong here. Possible for a cr. sensor to take
out an ignition module?

So here's where I am as of now.
If the module is doing its job properly, I assume the ECM has failed.
This wouldn't surprise me too much...I've already replaced it twice.

Any takers?

Travis




> Perhaps this article will be of help:
> http://www.motorage.com/motorage/art...l.jsp?id=20037


  #5  
Old January 1st 05, 02:13 AM
« Paul »
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Some wave forms: (with volts)
http://www.picotech.com/auto/wavefor...ft_sensor.html
http://www.interro.com/wav.htm#28
  #6  
Old January 1st 05, 08:28 AM
aarcuda69062
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In article >,
"<< Paul >>" <" > wrote:

> Some wave forms: (with volts)


Good job Paul!

> http://www.picotech.com/auto/wavefor...ft_sensor.html


Inductive crankshaft sensor, 2 volts peak to peak on the AC scale.
(there's a clue)

> http://www.interro.com/wav.htm#28


Second batch down, under "Channel lab scope", the top wave form
again is an inductive crank sensor, shows 8 volts peak to peak AC
volts (suspect it's a running engine).

700mv isn't indicative of a good crank sensor.
  #7  
Old January 1st 05, 01:56 PM
Lawrence Glickman
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On Sat, 01 Jan 2005 07:28:20 GMT, aarcuda69062
> wrote:

>In article >,
> "<< Paul >>" <" > wrote:
>
>> Some wave forms: (with volts)

>
>Good job Paul!
>
>> http://www.picotech.com/auto/wavefor...ft_sensor.html

>
>Inductive crankshaft sensor, 2 volts peak to peak on the AC scale.
>(there's a clue)
>
>> http://www.interro.com/wav.htm#28

>
>Second batch down, under "Channel lab scope", the top wave form
>again is an inductive crank sensor, shows 8 volts peak to peak AC
>volts (suspect it's a running engine).


5 volts on a scale of 8

>
>700mv isn't indicative of a good crank sensor.


in a 5 volt logic circuit, 0.7 volts would be considered a logic low

Lg

  #8  
Old January 1st 05, 04:21 PM
aarcuda69062
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Default

In article >,
Lawrence Glickman > wrote:

> >Second batch down, under "Channel lab scope", the top wave form
> >again is an inductive crank sensor, shows 8 volts peak to peak AC
> >volts (suspect it's a running engine).

>
> 5 volts on a scale of 8


Okay, 5 volts, that makes 10 volts AC peak to peak.
(waveform tagged "YLO")

> >
> >700mv isn't indicative of a good crank sensor.

>
> in a 5 volt logic circuit, 0.7 volts would be considered a logic low


Given the two examples posted, his crank sensor is not capable of
achieving the voltage level that is characteristic of that type
of crank sensor, IOWs, it's kaput.
  #9  
Old January 1st 05, 05:53 PM
Lawrence Glickman
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Default

On Sat, 01 Jan 2005 15:21:28 GMT, aarcuda69062
> wrote:

>In article >,
> Lawrence Glickman > wrote:
>
>> >Second batch down, under "Channel lab scope", the top wave form
>> >again is an inductive crank sensor, shows 8 volts peak to peak AC
>> >volts (suspect it's a running engine).

>>
>> 5 volts on a scale of 8

>
>Okay, 5 volts, that makes 10 volts AC peak to peak.
>(waveform tagged "YLO")
>
>> >
>> >700mv isn't indicative of a good crank sensor.

>>
>> in a 5 volt logic circuit, 0.7 volts would be considered a logic low

>
>Given the two examples posted, his crank sensor is not capable of
>achieving the voltage level that is characteristic of that type
>of crank sensor, IOWs, it's kaput.


If he can buy a new one at a dealer and install it himself...that is
the magic question. He needs that 5 volt output, or darn close to it.

I would call anything less than 3.8 or 4 volts not good enough.

Lg

  #10  
Old January 1st 05, 06:41 PM
duck
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Default


boardjunkie wrote:
> As per sublect line.....no spark. Verified crank sensor working (.7v
> pulses), swapped ignition module with a known good one, and have 12v

at
> the module input. I know from past experience that a bad coil van
> completely knock out the spark on the rest of the coils....tried

using
> 1 coil at a time with all 3.....no dice.
> Does the ECM control the generation of coil pulses at cranking or

just
> after it gets out of open loop operation? Haven't checked for the

pulse
> input and output at ECM yet...that's next. BTW...the voltages and
> grounds at ECM are OK. Need to check for the 5v reference for the
> sensors that use it to verify the 5v regulator in the ECM is ok.
> Any thoughts?
>
> Travis.


 




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