[Gmecm] erratic 3.8L Cam sensor alarms

[David Allen]

IIRC the magnet IS indeed replacable.  In fact I have replaced several; working throug the sensor hole wihtout engine disassembly.
David


----- Original Message ----- 
From: "Ron Drew" <rjdrew at adelphia.net>
To: <gmecm at diy-efi.org>
Sent: Sunday, October 08, 2006 3:44 PM
Subject: Re: [Gmecm] erratic 3.8L Cam sensor alarms


> Many thanks Scott; I think that you have led me to the problem. I understand 
> that the magnet is not replaceable; so I'm planning to replace the timing 
> set.
> 
> Ron
> 
> ----- Original Message ----- 
> From: "Scott Feaver" <sfeaver at magma.ca>
> To: <gmecm at diy-efi.org>
> Sent: Sunday, October 08, 2006 10:52 AM
> Subject: Re: [Gmecm] erratic 3.8L Cam sensor alarms
> 
> 
>>I had my magnet come out of the sproket at about 130k miles.   Its held in 
>>a plastic retainer and it disintegrated.    Maybe its starting in your 
>>case, and its position drifts slightly back where the sensor wont pick it 
>>up..
>>
>> Scott
>> ----- Original Message ----- 
>> From: "Ron Drew" <rjdrew at adelphia.net>
>> To: <gmecm at diy-efi.org>
>> Sent: Sunday, October 08, 2006 10:09 AM
>> Subject: [Gmecm] erratic 3.8L Cam sensor alarms
>>
>>
>>> Has anyone experienced problems with a GM 3.8L (1989 with 122K miles) 
>>> missing cam position pulses? More specifically, the pulses generally 
>>> begin to miss when the car has been driven for a while on warmer days; 
>>> and it only seems to trigger the alarm at lower speeds.
>>>
>>> This what I have done:
>>> - I replaced the ECM with a known good spare which did not help.
>>> - I've tried a couple of different brands of sensors, which did not help 
>>> (they all behave the same).
>>> - The crank sensor works flawlessly; the cam sensor shares the same '+ 
>>> volts' & 'ground' with the crank sensor, so any problems with the '+ 
>>> volts' and 'ground' would need to exist on a very short run of wiring 
>>> between the Crank and cam position sensors.
>>> - I have not yet scoped the sensor line going back to the ECM.
>>>
>>> I suspect the problem may be with the position indicator mounted on the 
>>> cam sprocket. I don't know if this is a permament magnet or a normal 
>>> piece of metal. As far as I can tell there is no magnetism in the 
>>> position indicator. BTW I may go weeks and not see an alarm, so the 
>>> problem can be very erratic.
>>>
>>> I thought I'd check here and see if nayone has experienced this or has 
>>> any ideas.
>>>
>>> Thanks
>>> Ron
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>>>
>>
>>
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