fail to start, HELP

A pal of mine has a UK '96 1800cc E180. It ran fine until it just failed to start about two weeks ago. A local "expert" has dismantled half the car,
changed the crank sensor and says that there is fuel and a spark and has bypassed the immobiliser. The engine cranks but does not fire. Is there a common problem I can start at to try and help out? Any suggestions gratefully received. Thanx for any help here.
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