Again, don't fall into the trap of thinking "fuel sync" provides the exact timing for the fuel injectors, it just tells the PCM which cylinders are up next. Timing is derived from the notches in the flywheel via the crank position sensor. The cam sensor only changes signal once per crank revolution, that would not provide exact timing info.

Plus/minus 8 degrees from 0 registers as "in-sync" in the PCM. The "window" is there to account for slack in the timing chain and the distributor drive gear. When setting fuel sync with the proper scan tool the engine idle raises to 1000 rpm to take the slack out (more speed = more friction). If fuel sync is off too far the PCM will fire the wrong injectors.

I think what trucklover referred to was that the rotor isn't close to the inside contact of the respective plug wire when the PCM fires the coil. That's an interesting question that might be worth exploring. Unlike older points designs turning the distributor does not change the ignition timing, that comes from the flywheel notches.

 

That is what I was trying to say about the rotor...thanks for clarifying!

So like you are saying setting the fuel sync at +4 does nothing in reality, you are just getting the injector within the target range, but setting it to zero would be the best situation to insure the injectors fires with the cylinder correctly. The factory service manual also tells you to set it to zero as well. I am glad we are having this conversation. My cam lobe wiped out on the 210x cam due to a stuck lifter; not sure why the lifter stuck. I have only put 45k miles on the truck in 10 years so maybe I let it sit too much! Anyway I pulled the engine and have tore it completely down to clean everything and also am replacing the bearings and rings while I have it apart. I am going back with the Hypotek HPT206SPT @ 110 LSA single pattern cam to get more bottom end power out of the truck, the 210x is a little too big for a heavy 4x4 truck in my experience. When I set the fuel sync I will shoot for around 0 on the scanner.

 

I agree!

 

I think, in a way, this is just horribly named.
But another way, your spark HAS to be synced to the piston position - CrankPS.
And the injectors HAVE to be synced to the (open) valves - DistPS.

So, thought that's it ultimate job, it's name would be more logical as Crank/Dist timing mismatch.

That said, I will be moving my cam, etc.
But before, I would like to find a way to check sync.
Is there anything in alfa?
Is there a DTC I could split? (CEL at 6.1 ret, reset, CEL at 6.1 adv, split the dif?)

 

Need a pretty high-zoot scanner to read fuel sync.

 

AlphaOBD2 doesn't work with these truck