A Mechanic reports on the numerous efforts to troubleshoot the cause of a right center fuel boost pump low pressure light illumination and EICAS message on a B757-200. The Universal Fault Interrupter (UFI) was replaced; but Mechanic did not notice an operational check was required.

Narrative

Right Center Boost Pump Low Pressure light illuminated. EICAS message Center Right Fuel Pump displayed. Deferred by Mr. X. MEL replaced center right fuel pump. No help; needs further troubleshooting. Removed and replaced (R&Red) low pressure switch S10011 per Aircraft Maintenance Manual 28-42-01; no help. Found 3 phase power at CB in cockpit; but no 3 phase power on 1ABC at relay K10012 on P37 panel and no power at pump. Need to find problem between P6 and P37 panels. Right-hand center fuel pump GFI relay open. Reference figure; removed and replaced GFI relay K10012; no help. Removed and replaced Universal Fault Interrupter (UFI) assembly acc'd boost pump operations check; operations test of the hydraulic motor generator. Per Aircraft Maintenance Manual 24-25-00; operations test of pump reverser per Aircraft Maintenance Manual 28-22-00. All checks test satisfactory. Removed from MEL 28-22-02A. When I returned to work in March 2009; I always review previous aircraft that I have worked to see if any more problems have occurred. I noticed an entry by another shift co-worker referencing my signoff and performing an operations check of the UFI. When I was troubleshooting this discrepancy; there aren't any wiring prints to include this modification. The only prints I could find were in the Engineering Order that installed this modification. The FIM includes this UFI and I referenced the required Aircraft Maintenance Manual operations test that was listed in the Engineering Order. My co-worker that worked the aircraft on the RON shift entered an operations check required per the doc. The only place this Engineering Order is referenced is in the description and operation; which I did not catch. If in the Table of Contents the UFI Relay Adapter Module; etc. was listed in R&R; I feel I wouldn't have missed it. My intent was when coming back to work I was going to contact engineering; but they were the ones that caught it on the following shift; after I clocked out.