Loanee Alfie McCalmont grabbed the only goal to end Carlisle’s three-match winless run against Colchester.
The Blues had been beaten in their last two Brunton Park encounters but bounced back to winning ways by the narrowest of margins.
Allied to Northampton’s home defeat by Grimsby it strengthened their grip on the third automatic promotion place.
The goal came after just four minutes when Colchester’s Connor Wood tried to head back towards his own goal but it was short and McCalmont was there first to steer his shot beyond keeper Kieran O’Hara, from just inside the box.
Paul Simpson’s side had a great opportunity to double their lead after 24 minutes but Jon Mellish was woefully wide from a great position after Omari Patrick had found him unmarked in the area.
Fiacre Kelleher was close for the visitors but his header off a corner was over the op and then McCalmont was close to a second just before the break but saw his snap drive whistle just wide.
Colchester, looking for a club record fifth straight away win, made three changes early in the second half and one of the new arrivals Matt Jay just cleared the bar when trying his luck from the edge of the area.
Carlisle’s top scorer Kristian Dennis, on as a substitute, could have sealed the win late on but he was guilty of a glaring miss when he shot over the target.
