I have a MF 2615 WHEN THE PTO IS ENGAGED MOTOR STALLS AND DIES

It sounds like you have covered most of the possible issues with the electrical system. A ground issue could be a possibility, but there are other potential causes as well. Here are a few more things to check:

1. Check the wiring, connections, and terminals for the PTO. Verify that there are no loose or corroded connections and no damaged wiring.

2. Inspect the PTO clutch for wear, damage, or signs of shorting. A failing clutch can cause an increased electrical load, which can drain the battery and cause the engine to stall.

3. Check the belt tension and condition for the mower deck. A loose or worn belt can cause excessive load on the PTO and engine, leading to stalling.

Jammed. You're going to have to do a serious review of the PTO.

Check pto and seat safety switches.

I take it to mean that when you engage the PTO drive the extra load to the idleing engine stalls
disconect the slasher and try engaging the PTO drive without load to discount an internal PTO gearbox fault if it doesn't stall check the idle speed fuel delivery system and airfilter any thing that can impact the power output of the engine

I had a similar experience and I had to replace the PTO.
What size motor do you have and what brand is it?

Sounds like a problem with the governor. Start it up. Don't engage the blades. Drive to a hill. Idle all the way down. Try driving up the hill. The motor should pick up when it slows while pulling up the hill. If it doesn't, the governor isn't working right.

its ether the regulator or the stator in the engineas for as the pto killing the engine it might only need a govenor adjustment to take care of that problem

are you sitting in the seat or have you jumped the safety switch under the seat before you engage the PTO I believe our tractors use an electric solenoid to apply hydraulic pressure to a wet clutch inside the trans axle I would think it would be OK with your chipper I have a 450 tiller that was built for the older 400 models 425 445 455 that I now use with my 2210 If I hit a large root or stone when using it with my old 445 it would stall the tractor at full power. Now with the 2210 it will actually slip the clutch on the tiller s PTO shaft I think the correct approach would be to increase your RPM s gradually or start increasing the power just as you trip the PTO switch. You want enough RPM s to create enough hydraulic pressure to run the PTO circuit so that you don t slip the wet clutch anymore than necessary and you want the RPM s low enough so that you don t shock the mechanical systems too severely at start up
Let me know how it works

check the belt as it bound, if you do not think so then take it off(the belt) and engage the PTO if it does not die then it is: the belt, pulley, or blades are/is the reason why it is stalling Tim

Check and adjust your RIO switch{reverse implement option}near the trans if so equipped.What happens when you press forward pedal then engage blades?Would also check the lower bearing on your pto clutch to see if its seized up.