Grays, dominant throughout, had stunned the Cumbrians with a well worked free-kick seven minutes into the second half. Fabian Wilnis clipped a free-kick into the box for Jon Ashton who nodded down, allowing skipper Jamie Stuart to turn and volley past the flat footed Ben Williams.
The goal had been coming for the visitors who were without so much as a point away from home all season. Grays' lively striker Andre McCollin should have given his side an early lead when he tricked his way past two defenders, but his powerful shot was smartly blocked by Williams.
The hosts lacked any creative spark which was no surprise in their 12th game without a win. Visiting winger Ishmael Welsh then robbed Evan Horwood and set off on a stunning 60-yard run and was only denied a killer second goal as Williams pulled off a fingertip save.
Moments earlier Carlisle's Simon Hackney had wheeled away in celebration, before the assistant referee ruled his header to be offside from David Raven's cross. By now the home crowd were voicing their frustration at caretaker boss Greg Abbott, as well as the players, as Carlisle were outplayed by their lowly visitors.
Abbott, appointed after John Ward's midweek ousting, would surely have been wondering if he really wanted the job. But the introduction of Madine on the hour gave rise to cheers throughout Brunton Park and he duly responded to nod in his third goal of the season and give his side a replay in Essex.
Marc Bridge-Wilkinson almost snatched an even later winner with a sweetly struck dipping volley, but in truth anything less than a draw would have been very harsh on a determined Grays side who belied their position two leagues below the home side.