Cam Sensor Voltage

[John Larkin]

With nothing better to do, I decided to get up this morning and set the cam sensor. I'm ready to finish but I can't get the 7.5+ volts no matter what the position. I'm @ 25° ATDC, ready to rock. I've twisted this way and that and volts are either 6.67 or 0. Is this ok?

 

[Black Car]

Morning John,
The way I understand it, you either have voltage or not. The magnetic switch is either made or not. I can be wrong but that is my understanding. So I wouldn't worry about the 6.67 volts.

Gary

 

[salvageV6]

6 to 9 Volts, so sayeth the Manual.

 

[John Larkin]

Thanks guys! Well, sadly it didn't work. I set it where the voltmeter told me to (the moment it went to 0 I tightened it down). Then the car would turn over but then grunt like it was too far advanced. So I had to trial and error it, bumping it back toward the original setting. Got the car started though. So my question now is, does the exact position really matter if the car runs? From gnttype archives, I've read that the cam sensor just tells the ECM which injector to pulse; there may be no benefit to fiddling with it if it's running.

 

[John Larkin]

ttt

 

[S10xGN]

Hey John,

If you find out, let me know. That's what my engine was doing before I gave up on it a month ago well - not really, just put it on hold while working other more pressing jobs. I've done everything possible with my cam sensor except replace the lower part and still get that "high compression" kind of cranking and no start. It's been long enough now that I've forgotten everything that I previously tried and will have to make a fresh start on it WHEN I GET HOME FROM FLORIDA!

 

[Black Car]

John,
I use the ATR tool and not a VM. The mistake I have seen (& done) is to forget to turn PASS when the light (voltage) comes on to when the light goes off. Then turning counterclock wise till the light (voltage) comes on. This is about 1/4" to 1/2".
Stopping when (turning clockwise) the light comes on will make the engine sound like a VERY high compression engine.
My wires are usually pointing somewhere between the drive side headlights and the hood latch.
Getting it right (from 22* to 28*) will make a difference.


Gary

 

[John Larkin]

Without having pictures to describe what I think is going on, here's my best shot: After searching the 'net, it seems that the cam sensor is like a clock (12 segments that are pie-shaped for descriptive purposes only), with every other segment open to the magnetic pickup. I've seen the gear on the bottom only once and can't recall how many teeth are on it but I'm willing to bet there are 12 also.
So if you have 12 "settings" to place the sensor into one will be matched to the correct cylinder/stroke. My other guess is that the sensor is closed to the magnetic pickup for "X" degrees (to allow the coil time to re-energize?) and open for "X" degree that would equate to 6 - 60* pairs of open/closed totalling 360*; I'm assuming EVERYTHING. Hehe.
If the above are all true, then the voltage should only be present on a voltmeter while the window is "open", meaning you can twist the sensor beyond the window in either direction which would indicate the voltage drop. Therefore, the voltage MUST be present to have the sensor aligned properly.
So, when I go to set the cam sensor, I will put the #1 cylinder on TDC compression stroke, turn the crank 25* farther around, then loosen the cam sensor and twist it clockwise as far as it will go, looking at it from the driver fender. Then I will twist it counterclockwise, and expect the voltage to increase (I will be back in the window again when it increases). Then after the voltage drops a second time in my case from 6.67 to .42 when it leaves the window, then slightly twist it back clockwise until the voltage pops back up to 6.67. At that point, I am on the cusp of the window opening to the magnetic sensor and life should be good.
Is this correct?

 

[TurboTR]

Well don't forget that the cam sensor is also what allows the coil module to sync up. Without the cam pulse every 720 deg there's no way to determine where the engine is in the firing order on the BUICK DIS system.

TurboTR