B737 Next Generation Undifferentiated
Human-Machine Interface; Confusion; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft; Procedure
During engine start with right ignition selected; the right engine started normally but the left engine did not light off. We followed the QRH and aborted the start. We then referred to the MEL for guidance. We both felt sure that there was the possibility to start the engine with the left ignition. While referring to the MEL we applied the procedure for the left ignition inoperative instead of the right ignition inoperative. The left engine was started with the left igniter and then the switch was moved to both. During cruise flight; when filling out the logbook; we reviewed the procedures we had followed and recognized [we had made an] error. We spoke with a mechanic at our next stopover to make sure he understood what system did not work and followed up with a call to Maintenance Control. Although we took our time; we should have been more thorough in our review of the MEL. Perhaps we were both so sure we were doing the correct procedure and just read what we were sure was correct. We did not question ourselves enough. I think the MEL could use some bold letters or highlighting to help with this particular situation. But as I look at the MEL now; it seams clear enough. In the heat of battle things sometimes look different.
Inflight the Captain and I questioned our call on which MEL item was [appropriate] for our abnormal start. ...we consulted with Maintenance Control who stated that all procedures we had followed were proper. MEL procedures for faulty ignition are a bit confusing which is why I submitted this report.
When their left engine failed to start the flight crew of a B737NG consulted the MEL and utilized a procedure therein and successfully started the engine.  While enroute they determined they may have used an inappropriate procedure for the situation.  After landing maintenance advised their chosen procedures were; in fact; appropriate.