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PostPosted: Sat Jun 27, 2009 2:30 am 
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crash93ssei wrote:
AFAIK, a bad cam sensor or magnet falling off the cam gear will not cause a no run / no start problem. On the Series ! engine anyways.

I believe the camshaft position sensor is used for injector timing only and if it is bad you will have a 1 in 6 chance of the injector timing being correct while running. I know of several members here who have ran for a while on their cars with the magnet not on the cam gear. They might not run perfect, or get great mileage, but it should run.


No Crash, you are wrong on many levels and seem to be confused. Your thinking the Crank sensor, the crank sensor has the magnet, and the metal fins on the back side of the harmonic balancer run through the grooves on the crank sensor to give it a reading. Also their is no magnet on the cam gear. And YES, a bad CAM sensor will and can cause a no start, no run problem. The magnet falling off the Crank sensor will cause the car to not be able to read timing. There are a variety of different types of crankshaft position sensors. One is a Hall effect crank position sensor that reads a notched metal "interrupter" ring on the back of the harmonic balancer. This was first used on the early GM 3.8L V6 Buick Sequential Fuel Injection (SFI) engines (and turbos) with distributorless Computer Controlled Coil Ignition (C3I). The crank position sensor provides an on-off signal to the Powertrain Control Module (PCM) that the computer uses to monitor engine rpm and crank position. The system also uses a separate cam position sensor in place of the original distributor to inform the PCM about valve timing. This enables the PCM to determine the correct firing sequence which it then uses to control both injector and ignition timing. =D>

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Last edited by crash93ssei on Sat Jun 27, 2009 8:00 am, edited 1 time in total.

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PostPosted: Sat Jun 27, 2009 2:32 am 
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J Wikoff wrote:
I don't know what nada means, but I agree with Crash. My magnet went awol and I didn't get in to replace it for a couple weeks. Ran a little crappy most of the time.


Nada means he's wrong. But I provided the correct info in the post above. :bow: :hail: :beerchug: :banana:

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PostPosted: Sat Jun 27, 2009 5:22 am 
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SCD88GA wrote:
No Crash, you are wrong on many levels and seem to be confused. Your thinking the Crank sensor, the crank sensor has the magnet, and the metal fins on the back side of the harmonic balancer run through the grooves on the crank sensor to give it a reading. Also their is no magnet on the cam gear. And YES, a bad CAM sensor will and can cause a no start, no run problem. The magnet falling off the Crank sensor will cause the car to not be able to read timing. There are a variety of different types of crankshaft position sensors. One is a Hall effect crank position sensor that reads a notched metal "interrupter" ring on the back of the harmonic balancer. This was first used on the early GM 3.8L V6 Buick Sequential Fuel Injection (SFI) engines (and turbos) with distributorless Computer Controlled Coil Ignition (C3I). The crank position sensor provides an on-off signal to the Powertrain Control Module (PCM) that the computer uses to monitor engine rpm and crank position. The system also uses a separate cam position sensor in place of the original distributor to inform the PCM about valve timing. This enables the PCM to determine the correct firing sequence which it then uses to control both injector and ignition timing. =D>


Yes, there is a magnet (called the interrupter) on the cam sprocket. As it passes the cam position sensor, it "interrupts" the sensor.

Just did mine on my LN3 not too long ago http://pontiacbonnevilleclub.com/forum/viewtopic.php?f=20&t=851 and my 2k when I did the cam swap http://pontiacbonnevilleclub.com/forum/viewtopic.php?f=9&t=10061&hilit=mini+meet

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PostPosted: Sat Jun 27, 2009 8:20 am 
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Didn't want to completely hijack the wanted thread, so this was split out....


SCD88GA wrote:
crash93ssei wrote:
AFAIK, a bad cam sensor or magnet falling off the cam gear will not cause a no run / no start problem. On the Series ! engine anyways.

I believe the camshaft position sensor is used for injector timing only and if it is bad you will have a 1 in 6 chance of the injector timing being correct while running. I know of several members here who have ran for a while on their cars with the magnet not on the cam gear. They might not run perfect, or get great mileage, but it should run.


No Crash, you are wrong on many levels and seem to be confused. Your thinking the Crank sensor, the crank sensor has the magnet, and the metal fins on the back side of the harmonic balancer run through the grooves on the crank sensor to give it a reading. Also their is no magnet on the cam gear. And YES, a bad CAM sensor will and can cause a no start, no run problem. The magnet falling off the Crank sensor will cause the car to not be able to read timing. There are a variety of different types of crankshaft position sensors. One is a Hall effect crank position sensor that reads a notched metal "interrupter" ring on the back of the harmonic balancer. This was first used on the early GM 3.8L V6 Buick Sequential Fuel Injection (SFI) engines (and turbos) with distributorless Computer Controlled Coil Ignition (C3I). The crank position sensor provides an on-off signal to the Powertrain Control Module (PCM) that the computer uses to monitor engine rpm and crank position. The system also uses a separate cam position sensor in place of the original distributor to inform the PCM about valve timing. This enables the PCM to determine the correct firing sequence which it then uses to control both injector and ignition timing. =D>



Before you come in here and say that someone is wrong on so many levels, you need to get the facts right. Yes, there IS a magnet on the cam gear. I know this because I had my timing chain, gears, and magnet replaced on my '89 Bonneville SE many years ago, AND also had my engine tore down last year and replaced the timing chain and gears in my '93 SSEi.

To come in and say that a bad cam sensor WILL cause a not start problem is wrong. It has been proven here by several members that a car can still run with a bad cam sensor or missing magnet. I never said that I am 100% sure that a bad sensor will not cause a no start problem. I will quote my '93 FSM later when I am not so tired.....

I am in no way confused about anything. Remember, AFAIK = as far as I know. That does not mean that what follows is know to be fact, only what the poster understands to be true. If you feel you have information to correct it, that is fine, I am always up to learn something. However, to come back the way you did, trying to prove something, only made you look bad.


Also, the magnet can not "fall" off of the crankshaft sensor, it is actually molded into the sensor. The only way the magnet can be removed from the sensor is for it to be struck by something hard enough to break the sensor. I have a broken one with the magnet exposed as well as a good one that is not broken. I will take pictures for you and post them later.

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PostPosted: Sat Jun 27, 2009 11:52 pm 
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You can unplug our cam sensors and the car will still run.

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PostPosted: Sat Jun 27, 2009 11:54 pm 
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:stupid:

my '88 either lost the magnet or the sensor went bad and i ran it for at least a year like that without any reliability problems.

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PostPosted: Sun Jun 28, 2009 11:46 pm 
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Just to stir this pot a little....A few years ago I purchased a 1988 Olds 88 with a VIN3 3800 engine iirc. I bought it for $250 from an auto repair shop who could not get it to start. The computer had set code 41 (cam position sensor). They had changed the pickup, crank sensor, coils, and ultimately gave up. I towed it home, removed the timing cover and found the interrupter magnet holder broken and missing the interrupter magnet. Unlike the newer, push-in, round plastic-framed magnets, this older engine used an aluminum rectangular shaped magnet holder and a small (6mm?) bolt to hold it in place on the cam gear. I replaced the magnet and the car started right up.

Now, I am aware that newer engines will start and run without the magnet, but I can assure you that this older one would not. I don't know if this was an Oldsmobile PCM quirk, or whether it is true for all the VIN3 engines, but, like everything else in life, you gotta be careful when you say "always..." or " never...."

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PostPosted: Sun Jun 28, 2009 11:54 pm 
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But it is true for the Series I.

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2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights


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PostPosted: Mon Jun 29, 2009 8:50 am 
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J Wikoff wrote:
But it is true for the Series I.


Maybe the "new" plastic magnet holder and starting protocol was all part of the changeover from VIN 3 to VIN C. I don't know my history as well as I should.... My old Chilton's shows that both the VIN 3 and VIN C were used in 1988. So, I'm guessing maybe 1988? I'll go read the great Wikipedia article.....

Wikipedia Article wrote:
...The 3.8 L (3800 cc) LN3 was an engine produced by General Motors' Buick Division. Introduced in 1988, the 3800 LN3, would later be loosely considered the Pre-Series I, although the older 3.8 SFI (LG3) was still available that year in some models. Designated initially by VIN code C, the multiport fuel injected 3800 LN3 was a major redesign, featuring changes such as a balance shaft, on-center bore spacing, use of a 3x/18x crank-trigger system, and other improvements. This generation continued in use in several GM products into the 1990s....


That appears to be the clue as to when the start protocol changed, and it was certainly pre Series I. I was just pointing out (from experience) that I had encountered a no-start situation from a missing cam magnet that indeed can occur in older 3800 engines. It is a good thing to know if you encounter a code 41 no-start with a VIN 3 or older engine.

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PostPosted: Mon Jun 29, 2009 9:08 am 
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So then it appears that a bad cam sensor can cause a no start no run problem, but not necessarily will every time.

This is exactly why I said as far as I know :wink: because I wasn't 100% sure on it.

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PostPosted: Mon Jun 29, 2009 10:36 pm 
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I thought you were confusing the crank and cam sensors because I didn't realize that the cam gear had a magnet, sorry, my bad. But yes, I have seen a bad cam sensor cause a 92/93 supercharged car to die and not restart. Also I have seen a magnet fall out of a crank sensor, but it was on a 3300 engine which is basically the same setup as the 3800. The plastic around the magnet dried out and cracked from age, and the magnet was stuck to the back side of the harmonic balancer. I'm not saying either situation is very likely, but it can happen. I have 3 Series 1 supercharged motors currently and I'm still learning more every day.

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PostPosted: Tue Jun 30, 2009 9:48 am 
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First of all let just remember that every 3800 Made( I mean every single one that came off the production line ) is an SFI engine.. All of the use the Dual Hall Crank sensor.. All of them have a cam sensor.. Some of the early Vin C's will have starting and running issues if it has lost the cam signal.. On the 89- later Vin C's I believe that the ECM program was slightly different.. when a code 41 happens the ECM will run off the last good known fuel sequence... The engine will not always run right, and if it run piss poor you simply shut it off and restart... Chances are you get a better fueling sequence allowing the engine to run better..

90-95 Vin L and 91.5-95 Vin 1 should all run even with a code 41.. May not run good and may have a hard time starting but they should run..

When you look at the old Buick 3.0 and 3.8 they both used different systems as compared to any 3800... If there were any issues they would not run..

The Cam sensor on the 3800 is only there for one reason, and thats Cylinder #1 TDC, The ECM/PCM makes calculations via that #1 TDC pulse and the Crank Position pulse... Being that the ECM/PCM knows where #1 TDC is, the ECM/PCM takes the pulses from the Crank sensor( 18x's ) and with the calculations you then have True SFI... Its part of the very reason these cars can do 30-35 on the open road.. Just about every 3800 made is capable of 30 Mpg..

Just remember some of the early 3800's had issues running with a Code 41... Not all


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