Starting with chapter 9 for this question is a bit interesting, because I wouldn't say that Phillip helps Timothy out at all in this chapter. Chapter 9 begins with Timothy setting out some ropes to make navigating the island easier for Phillip. Timothy then asks Phillip to make some sleeping mats, and Phillip gets mean.
"You ugly black man! I won't do it! You're stupid, you can't even spell."
Timothy responds by smacking Phillip's face. Phillip is utterly shocked that Timothy would do such a thing, but it humbles Phillip. By the end of the chapter, Phillip requests Timothy's friendship.
Chapter 10 is similar in that Phillip doesn't actually do much to help Timothy out. Timothy's request during this chapter is that Phillip climb a tree in order to get some coconuts down. Phillip is too scared to do it. Much of the chapter is conversation and focused on their growing relationship.
Chapter 11 is the chapter that has Phillip very worried that Timothy killed Stew Cat.
Chapter 12 finally sees Phillip doing things for Timothy. Phillip wakes up to hear Timothy's ragged breathing. Timothy is in a bad way with fever and overall weakness, and readers learn that he is suffering from malaria. Timothy is quite delirious during this chapter, and he wanders down to the water at one point. Phillip listens for him, but all Phillip hears is a splash and then silence. Phillip makes his way to the shore and drags Timothy onto the beach. He then covers Timothy with grape leaves and brings him water from the hut in an attempt to make him comfortable and nurse him back to health. The fever eventually breaks, and Phillip helps Timothy return to the hut.