Blackwood was particularly strong after the Penguins pulled Murray for an extra attacker with 1:07 remaining and the Devils holding a 2-1 lead. He made two saves on Guentzel in a span of six seconds, and another on Evgeni Malkin with 16 seconds left.
The Devils blocked 20 shots, three by Jesper Bratt.
"Everyone was battling out there, guys were getting into shot lanes, blocking shots and getting their sticks in lanes," Blackwood said. "There was kind of a little bit of mayhem in the end, but we were able to hold that one down and get the two points."
Coleman scored his first goal in 11 games after collecting his own rebound low in the left face-off circle and beating Murray on a backhand at 19:55 of the second period for a 2-0 lead.
"I kind of surprised myself," Coleman said. "It's been an emphasis to get to the net a little more and get more chances. I know I'm capable of getting more offense. Sometimes you get an ugly one to get you back."
Johnson scored his first goal in 92 games, a wrist shot from the left face-off circle 8:00 into the third period to pull the Penguins within 2-1.
"I thought we played a strong game, start to finish," Penguins coach Mike Sullivan said. "Both (New Jersey) goals were fluky goals. We generated a fair amount of quality scoring chances and defended hard. I thought our guys played smart, but we just didn't find the back of the net enough."
Zajac scored his first goal in 16 games off a wrist shot from the slot to give the Devils a 1-0 lead 6:59 into the first period.