Ron Streck and Jim Ahern share third place at 5-under-par 66. Bruce Fleisher, who aced the 16th hole, Graham Marsh, Ed Dougherty and Dick Mast are tied for fifth place at minus-4.
The start of the opening round was delayed close to three hours because a thunderstorm was forecast for the area. It passed over, but tournament officials sent the players off split tees in order to complete the first round.
Sullivan, a Champions Tour rookie, began on the back nine and wasted little time in breaking into red figures. He knocked a pitching-wedge to 12 feet to set up birdie at the 11th, and added one more birdie on his opening nine, a 2-footer at the par-3 15th.
His second nine started with a birdie at the par-5 first and Sullivan collected his second birdie on that side at the next five par. He two-putted from 40 feet at the fourth to reach 4 under for the championship.
Sullivan hit a 7-iron to 6 feet to set up birdie at the sixth. He missed the green with a four-iron at the par-3 eighth, but chipped in from 25 feet out on the fringe.
'For whatever reason, I played well today,' said Sullivan, who admitted he has had problems in the opening rounds of tournaments this season. 'It was a pretty easy 65.'
Jenkins, who finished second last year when this event was held at Glen Oaks Country Club, two-putted from 25 feet for birdie at the first. He drained a 20-foot eagle putt at the fourth, then rolled in a 25-footer for birdie at the fifth.
Jenkins knocked a wedge to 6 feet to set up birdie at the seventh. He three-putted from 45 feet for a bogey at the eighth, but Jenkins still made the turn at 4-under 31.
At the 526-yard, par-5 13th, Jenkins reached the green in two with a 5-wood. He two-putted again for birdie from 50 feet, then joined Sullivan in the lead with a 6-foot birdie putt at the 17th.
Jenkins is on a major roll at the moment. He has finished outside the top-10 once since late March, a tie for 12th at the FedEx Kinko's Classic, and came in fifth last week at the Senior PGA Championship.
'I'm very pleased with the way I'm driving,' said Jenkins, a five-time winner on the Champions Tour. 'It's always nice to win, but I'm out here playing as well as I can. That's never disappointing.'
Pat McDonald, who replaced Craig Stadler in the field when he withdrew Friday morning with a sore elbow, shot a 3-under-par 68. He is tied for ninth place with Keith Fergus, John Bland and Leonard Thompson.
Mike Reid, who captured the Senior PGA at Laurel Valley last week, carded a 2-under-par 69 and is part of a group tied for 13th place.
Defending champion D.A. Weibring dropped four shots in his last six holes en route to an even-par 71. He is tied for 28th place.