Why did Jensen not kill Strunk according to their pact?

Strunk actually asked Jenson not to kill him..... he asked more than once. As for Jensen, when it came down to killing his friend..... he never could have done it.

Lee Strunk seemed groggy and confused. He lay still for a second and then motioned toward his leg. "Really, it's not so bad, Not terrible. Hey, really—they can sew it back on—really."

"Right, I'll bet they can."

"You think?"

"Sure I do." Strunk frowned at the sky. He passed out again, then woke up and said, "Don't kill me."

"I won't," Jensen said.

"I'm serious."

"Sure."

"But you got to promise. Swear it to me—swear you won't kill me."

Jensen nodded and said, "I swear," and then a little later we carried Strunk to the dustoff chopper. Jensen reached out and touched the good leg. "Go on now," he said. Later we heard that Strunk died somewhere over Chu Lai, which seemed to relieve Dave Jensen of an enormous weight.
Christine