City were held to a draw at the LNER Stadium after a late strike in the first half cancelled out Freddie Draper's opener.
Imps head coach Michael Skubala made three changes from the side that earned a point on the road at Wigan Athletic last Saturday.
Fresh off of signing a new deal at the Imps, Freddie Draper was re-introduced into the starting XI, along with Conor McGrandles and Reeco Hackett.
On ten minutes, Freddie Draper met the cross of Sean Roughan, and managed to get a strong strike away while on the floor, which was equalled by visiting goalkeeper Nathan Bishop.
City kept the pressure on and Draper's persistence was rewarded as he opened the scoring seven minutes later. Following a corner the ball found the striker, and while his first attempt was blocked, he made no mistake with the rebound.
A long ball over the top found Tendayi Darikwa advancing into the penalty area, but his cross was just too far in front of an arriving James Collins at the back post.
Just after the half hour mark, a teasing Sean Roughan cross caused chaos into the Cambridge penalty area, with goalkeeper Bishop nearly parrying the ball into his own net. He was bailed out by a sliding defender on the line, with two City attackers closing in.
Three minutes before the break, United equalised through James Gibbons. His left-footed curling effort from inside the box took a deflection before nestling in the bottom corner.
In added time, a swift counter-attack from the visitors saw Imps goalkeeper Zach Jeacock called into action, getting a hand to a header from close range, just before the half time break.
Four minutes into the second half, City forward Collins was the one to leap highest, but could not direct his effort from a Tom Bayliss corner on target.
Gibbons had another effort from inside the penalty area on 57 minutes. His effort was deflected into the side netting at the near post and out for a corner.
After 72 minutes, another Roughan cross picked out Collins. His first effort was blocked at the back post, but his rebound from close range was fired over the bar.
Two minutes later, Imps captain Paudie O'Connor had a golden chance roll wide of the post after Hackett's free-kick found the defender free at the back post. His header rolled across the face of goal and wide for a goal kick.
Cambridge went up the other with Josh Stokes testing Jeacock with an effort from distance.
City were reduced to ten men when substitute Joe Gardner was dismissed for a challenge in front of the Cambridge bench on 86 minutes.
Despite five minutes of added time, neither side could find a winner and both teams had to settlenfor a point.
Imps: Jeacock, Darikwa (Jefferies 78'), Jackson, O'Connor, Roughan, Hackett, McGrandles, Hamilton (House 78'), Bayliss, Draper (Makama 67'), Collins (Gardner 82') Unused subs: Wickens, Montsma Clucas,
U's: Bishop, Andrew, Morrison, Watts, Brophy, Kachunga (Ballard 69'), Okedina, Loft (Stevenson 79'), Stokes, Cousins, Gibbons (Digby 85') Unused subs: Stevens, Bennett, Barton, Longelo
Attendance: 8,606
