1Combine juice, vinegar and soy sauce in a shallow dish or ziplock freezer bag and add pork tenderloin. Cover or seal and chill 1 hour.
2Cook orange marmalade in a small saucepan over medium heat until melted. Remove and reserve 1/4 cup for basting. keep the rest warm in pan.
3Remove pork from marinade. Throw out the marinade. Grill pork, cover with grill lid, over medium high heat. (350-400) 25 minutes, baste with reserved marmalade last 5 minutes. Serve with remaining warm marmalade.