Dual Fuel Solenoid or VHP Solenoid on Cat 3306 engine.

[3rdGenDslWrench]

I'm working on our 970F Material Handler and its the first time I've been around a dual horsepower solenoid. I read the book and it briefly explains its purpose and how it works and I understand it fine. The operator was complaining of spitting and sputtering and "snatching" (mind you he sounds just like Boonhauer from King of the Hill). I cleaned the primary filter out and changed the secondary filter and took it for a ride out to one of our salt piles.
According to the book, in 1st gear only the transmission controller operates in 1 of 2 horsepower modes depending on engine RPMs. What I found was that if I went into a hard dig and curled the bucket back the engine would shuttle between 2000 and 1800 RPMs. When the engine got up to 2000RPM it would kick down to 1800 RPM then back to 2000RPM until you got off the throttle.
My question is should it constantly shuttle like that or once your RPMs drop to 1800 it kicks up to 2000 RPMs or higher and hold it there?

 

[rare ss]

i'd be checking the transfer pump pressure, I've had a simliar issue on a D7HXR and had under 5psi but would still run ok (as the fuel tank sat higher) but under load it'd cough and pop, should have around 32psi

 

[Nige]

If it's anything like the bigger machines with engine, powertrain, and hydraulics all electronically controlled it should reduce engine RPM when it hits the pile. The theory is that at higher RPM the engine is producing less torque than its maximum. You need torque for both the powertrain and the implements. So if the machine is in 1st gear forward with the bucket on the ground (or almost) and ground speed is less than like 1mph then the transmission control commands the engine to reduce RPM in order to produce more torque. Either way though the RPM should not go up and down, it should go down and stay there basically until you hit reverse and which point it will go up again.