Camshaft Position Sensor

  • Thread starter Thread starter Joe
  • Start date Start date
....sometimes simple is good, eh?

BANDIT2941 said:
Yes, they all use the waste spark system. Thats why they don't even really need
a cam sensor. If they didn't have waste spark, it would have to know where the
cam is(to dictate where top dead center on the firing stroke is) but since its
the waste spark system, it just fires the plug every time the piston is at top
dead center. So once its firing, next its exhaust, ignition system doesn't know
the difference, it fires all the time. They boast this as a feature, but its
really just an easier thing to do.
Click to expand...
 
Um,

If it doesn't know there the cam shaft is, how does the computer know when
to inject the fuel?
 
There are two reasons the cam position sensing capability is there:

-Sequential fuel injection requires knowing which cylinder of the pair is on
the firing stroke. If the cam position input is lost, the system will revert
to a mode where injectors for both paired cylinders are fired at the same
time (i.e. not SFI anymore).

-OBD II misfire diagnostics also need to know which cylinder is on the
firing stroke, since the diagnostics must have the ability to identify the
specific cylinder that is misfiring.
 
Um,
If it doesn't know there the cam shaft is, how does the computer know when
to inject the fuel?
Click to expand...

Um,

It seems as though the OBDI cars have multiport fuel injection as opposed to
sequential, so they don't need to know where the cam is. Besides, tell me how
the computer in an OBD1 car locates the position of the cam and I'll be the
first one to admit I'm wrong. But that might have to wait a week since I'm
leaving for vacation in FL at noon today :)
 
-Sequential fuel injection requires knowing which cylinder of the pair is on
the firing stroke. If the cam position input is lost, the system will revert
to a mode where injectors for both paired cylinders are fired at the same
time (i.e. not SFI anymore).

-OBD II misfire diagnostics also need to know which cylinder is on the
firing stroke, since the diagnostics must have the ability to identify the
specific cylinder that is misfiring.
Click to expand...

I shouldn't have worded the post the way I did. On OBD1 cars it seems they have
multi port fuel injection as opposed to sequential, so they don't need to
locate the cam. On OBDII cars, when they lose input from the "cam sensor" as
you said, they would revert to multi port non sequential injection.

Again, as I said to Kirk, to my knowledge the OBDI cars have no way to locate
the cam. I've had my engine out of my 95 twice and pretty much gone over it top
to bottom, inside and out, no cam sensor to be found.
 
Buster said:
My '96 SL-1 gave the same error. After replacing the plugs and plug
wires (just because they were old), the error code never reappeared.
Buster
Click to expand...
I'll back you up on that. I had the same error with my 96 SL1. It went
away with aftermarket plugs & wires, then came back. The problem went
away for good with Saturn OEM plugs & wires.

Jim
Ohio
 
My 96 SL2 uses both cam sensor and coil pack to determine cam position.
Cam sensor is located up on top and behind the starter
about $22:00 for a new one at the dealer.
 
The cam position sensor on the OBDII cars is embedded in the coil pack.
There are (apparently) different characteristics that result from putting a
spark through a highly-compressed air-fuel mixture and non-compressed
exhaust. As I understand it, there is a capacitive coupling in the coil pack
to the ignition wires that permits the computer to determine which cylinder
fired.

So you probably wouldn't see something that looks overtly like a camshaft
position sensor.
 
That sensor is a crankshaft position sensor, not a camshaft position sensor.
It tells the engine very precisely where the crankshaft is. That
information, plus simply knowing which cylinder fires, lets the computer
know precisely where the camshaft is.
 
They boast this as a feature, but its
really just an easier thing to do.
Click to expand...

Wow, and Harley boasted when they got rid of the wasted spark setup...

I always suspected GM used wasted spark on the Saturn motor because of
the way the coils are on it.

There is no camshaft sensor on the OBDI cars, they fire all 4 injectors
at the same time (cheap GM...) and have wasted spark, so they don't need
one..
 
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