B757 Captain discovered during engine start that a MEL procedure for a failed generator had not been accomplished by Maintenance. The aircraft had flown three legs since the original deferral.

Narrative

During preflight review of logbook I noted that the right generator had failed the day before. The generator repair had been deferred under MEL 24-1. MEL 24-1 requires in part that the Integrated Drive Generator (IDG) be disconnected per MPM 24-1. During pushback; we started the right engine first and noted that the IDG 'DRIVE' light extinguished during engine start (this light should remain illuminated if the drive is disconnected) and that after engine start; EICAS did not display the R GEN DRIVE and R GEN OFF messages that should have been displayed if the IDG were disconnected.We shut down the engine and were towed back to the gate. Maintenance was called and accomplished the IDG disconnect. Maintenance also complied with my request to verify that the other MEL requirements were re-accomplished. During this re-accomplishment; I commented to the Supervisor present on the fact that none of the mechanics performing the work (there were three) had in their possession a copy of MPM 24-1 and were accomplishing their tasks from reference to the MEL and memory. The aircraft had flown three legs between the time the MEL deferral was accomplished and our flight.Following the maintenance action at the gate; all indications after engine start were consistent with a disconnected IDG (drive light remained illuminated and R GEN DRIVE and R GEN OFF EICAS messages displayed).The log book indicated that this aircraft had completed a Heavy C check in September and had suffered a left pack failure; right generator failure; AFT CARGO DET 1 failure; and other systems issues in the two weeks following completion of the check.