T540 Impulse issues

[TreeHunter]

I have a Mark 1 T540xp. The saw was originally shelved dirty ad with gas in the tank roughly 5 years ago. The coil was tight against the flywheel. Perhaps the original reason for being shelved in combination with the hot starting issues this saw is known for?

Anyway, I corrected the ignition coil position. I have replaced the recalled tank vent with the new factory assembly. I cleaned the carb as best I could WITHOUT taking the top off where the autotune is attached. I cleaned and went through everything on the saw but I did not pull the cylinder. Looking into exhaust intake and spark plug everything looks clean inside, ring is in okay shape, springy when pressed while visible in exhaust port. I do not have a compression test reading.

The impulse line from the crankcase to the carb is intact and appears in good shape. The primer bulb feels a tad dry and does not feel like fuel is being pushed when the bulb is depressed. The bulb does not fill with any fuel no matter how many times it is pressed but it does create pressure in the fuel tank. Is the primer bulb the fault in the fuel system here? On choke and after ten primes (some priming occurring) the saw fires and will fire and die again with the choke turned off. The saw runs a little longer with a bench prime/pouring some fuel into open carb.

My next step short of a new carburetor is all new fuel lines, impulse line, a new fuel filter and primer bulb assembly to help bring fuel to the carb BUT... I feel like I am missing something. Anyway, Ill keep pluggin at it once I get some parts and can get it back on the bench. Thought I would throw somethin up here for all yalls input and much needed assistance. Cheers and keep the saw in the wood!

 

[Stump Shot]

Best way to diagnose which part has failed is to pressure test each one until you find the leak.
Carburetor Testing Pressure Gauge

 

[Michael Rupley]

Try switching the lines where they attach to the primer bulb and richen up the low speed screw

 

[Merkava_4]

Try switching the lines where they attach to the primer bulb and richen up the low speed screw

I don't think it's going to allow you to manually adjust the idle mixture. It is an electric / electronic carburetor.

I just found out about it a minute ago. It's called Husqvarna "Autotune"

Parts Drawing

 

[TreeHunter]

I don't think it's going to allow you to manually adjust the idle mixture. It is an electric / electronic carburetor.

I just found out about it a minute ago. It's called Husqvarna "Autotune"

Parts Drawing

I hadn't thought about this but yes, absolutely. There are no adjustment screws on this thing. Thinking more about this and considering what Stump Shot said first, I feel like there is an air leak somewhere and I have to track it down.