I've used that line a few times when people were wondering if fuel sync is causing the issues with their truck. While the name suggests that it provides some critical timing for the fuel injectors, it merely helps the computer to figure out which cylinders are getting fuel and which cylinders are firing. 98+ trucks use the cam sensor only at start-up, I think older ones are a little more picky about the cam sensor working.

Here's a demonstration on a 2002 2500 (only 1500s went 3rd gen in 2002):
Grrrr, the jump to the relevant part isn't working. See 23:45 into the video.

 

I would love to see someplace where that is documented...... Digging thru the service manual for a 98, it doesn't say anything about it not being used once the engine is running.

I would expect the engine would be able to 'limp' if it lost the signal while it was running, but, without the cam sensor signal, it simply will never start.

 

The only thing I noticed in my beast when I set the fuel sync (96 5.2/NV3500) was that it seems like it "jumps 2 life" after only a couple'o turns of the crank, instead of several rotations, especially on a cold morning after sitting out all nite. Other than that, no perceptible difference while driving.

 

According to the service manual the pcm needs to see at least one complete rotation of the crank before it can start. If you look at crank sensor and how it works(you can see it in the video) it will give the pcm a signal for only four cylinders(4 on,4 off). "run all day" with out a crank signal ??? I would like to see how it reacts with a(or multiple) misfires or really low rpm like when the iac is going out.

 

I don't think it will run at all without crank signal. Now, cam signal? Maybe. Be a simple matter to test it, just unplug the sensor with the engine running.... see what happens.

 

Duh ! That's exactly what the video shows...

 

I didn't watch the whole video.....

I am sure the PCM can compensate for loss of cam sensor signal, at least, if the engine is already running, but, that does not imply that the PCM DOESN'T pay attention to that sensor when it is working.......

 

Just jump forward to 23:45 in the video, I posted the link with the time marker but it didn't work.

The PCM pays attention as so far as it throws a DTC when the cam signal goes away which is useful when trying to figure out why it doesn't start anymore .

 

The FSM doesn't have that info. Below is a snippet from the factory training for a different 90s Dodge vehicle that switched from SBEC to JTEC PCM just like the Ram trucks.

"The PCM determines crankshaft position from the inputs provided by the Camshaft and Crankshaft Position Sensors. Once the crankshaft position is determined the PCM can synchronize fuel injection and cylinder identification.
In order for the vehicle to start, both the CMP and CKP sensor signals must be present. On 1992–1996 vehicles, both CMP and CKP sensor signals are necessary for continued engine operation. On 1997 and later vehicles, once the engine is running, the CMP sensor signal is not needed for continued engine operation."

 

Interesting. Still and all, you need it to work to start the truck. Which implies that it works all the time. Strange that it changed for 97 model year..... same computer as the 96 uses, isn't it? Just different programming?