Cam Angle Sensors 92 SVX OBD I
 

Doing a poll... How common is it for a cam angle sensor (s) to become weak and cause hard cold (or even warm) starting? And does anyone have test procedure that can be done with an digital VOM? Thanks in advance...

Norm

Re: Cam Angle Sensors 92 SVX OBD I
 

Gid'ay Norm, the book does not give an ohm reading for the cam sensor, you may want to check it with the ohm meter to check for a open circuit. It does say it should get an AC voltage reading, when turning the engine over, of at least 0.1 V or 100ma.

As you probable know it is a magnetic pick-up, and the field does become weaker with age.

Harvey.;)

The problem with using a VOM is that it can't display fast enough, no matter what its sampling rate may be.

Thanks for the info. Any input as to why the field would weaken over time? Resistance change in the coil? Magnet on the cam gear loosing its flux?

Norm

Yes Norm, its the magnetic field that becomes weaker over time. Heat and vibration are the things, that cause the field to weaken. The magnet is in the pick-up, with the winding wound around it. the cam gear just has a tooth that bridges the magnetic gap as it passes by.

In some other engines that use this type of magnetic pick-up, the flux gap around the magnet core, becomes bridged by metal filings. this shorts some of the magnetic flux out, at the case, reducing the flux across the pick-up gap, and hence the signal.

The output of these sensors depends on the strengh of the field and the speed of rotation. This why they can give so much trouble when starting, when the speed is slow, and its ok when running, due to the speed.

Harvey. ;)

Another consideration is that some manufacturers won't allow the fuel to enable until a specific voltage threshold is reached. This is done in order to help prevent flooding when trying to start a slow spinning engine.

Is this the error code you received?