Lancashire 207 and 167 for 4 (Jennings 80*, Bell 30*) lead Essex 219 (Critchley 78, Anderson 4-70) by 155 runs
Keaton Jennings held together Lancashire's second innings with a patient half-century on a truncated day's cricket at Chelmsford.
The Lancashire captain batted throughout the 36 overs possible before rain returned at tea leading to a premature end to the day. By that time Jennings, the leading LV= Insurance County Championship run-scorer last season, had racked up 80 runs from 170 balls.
Lancashire lost three quick wickets before 20-year-old wicketkeeper George Bell joined Jennings for an unbeaten fifth-wicket stand of 56 in 23 overs.
When play was finally called off at 4.45pm, Lancashire were 167 for 4 with a lead of 155 going into the final day. Bell was unbeaten on 30 from 78 balls.
Heavy overnight rain had left puddles in the outfield and the umpires required two morning inspections before deciding play could resume after an early lunch.
There was an immediate surprise as Jamie Porter and Sam Cook switched from their more familiar bowling ends. Porter quickly acquainted himself with the River End and with the fourth ball of the day had Josh Bohannon playing down the wrong line and losing his off-stump.
The change did not inconvenience Cook either and in his third over he found the edge of Steven Croft's bat with Dan Lawrence taking a smart diving catch to his right at third slip.
Dane Vilas showed attacking intent with a straight drive, a flick off the legs and a hook for boundaries before he miscued a massive heave and skied Doug Bracewell to mid-on.
The sun made a welcome appearance during the afternoon to turn it into a one-sweater day; even Simon Harmer had dispensed with the snood he had worn for the first two days.
After losing three wickets inside six overs, Jennings and Bell bedded down into a preservation-mode partnership that was enlivened by a perfectly-timed straight drive off Porter by Jennings and a rare boundary off Harmer through the covers from Bell.
Essex had an injury scare when Cook limped off mid-over as a precaution after landing awkwardly. They were already reduced to fielding Michael Pepper as replacement wicketkeeper after Adam Rossington damaged his hand.
Anthony McGrath, the Essex head coach, said it was too early to know the extent of Cook's problem but described his exit from the field as "precautionary".
"Sam Cook was forced off because he's just felt his hamstring a little bit," McGrath said. "The ground is really heavy and it's been tough for everyone, particularly the bowlers. At this stage of the season, we didn't want to take any risks with him but we'll know more about the injury after the game."
