Date: 201210
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight phase: Taxi
ATC / advisory: Tower ZZZ
Aircraft component: Engine Starting System
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Time Pressure; Workload; Communication Breakdown; Distraction; Confusion
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew; Person Maintenance
When detected: Taxi
Result: Flight Crew Returned To Gate; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Company Policy; Human Factors; Logbook Entry; Procedure
Primary problem: Ambiguous

Narrative: The logbook advised us of a placarded Start Valve Light. We understood it to mean that we were to do the procedure. We could start the engine ourselves and do the procedure. The procedure called for normal engine start except after start we had to verify that the pressure had returned to prestart level to indicate that the valve had indeed closed. The engine started normally and we saw the pressure drop back to the prestart level; so we thought the valve had closed and everything was fine. However; the pressure fell to zero after turning the pack on and we returned to the gate and shut down the engine. Maintenance showed up and said they were supposed to start the engine. We had not seen any Maintenance personnel prior to this. After rereading the MEL we discovered we had read the wrong section. We were in 80-1 and the placard was on the next page 80-3. The indications matched for 80-1 so we did not realize this mistake until after shutdown and talking to Maintenance. Maintenance changed the start valve and the engine started and operated normally. There were no other problems. The flight was uneventful.I have several suggestions as a result of this event:  1. More care to ensure that we are indeed on the correct procedure. 2. Have the company fix our aircraft and not have the logbook so full of placards. This aircraft had 5 MEL deferred items on it. Every aircraft has MEL items on it causing extra workload. 3. If maintenance action is required prior to departure; it would help if that were annotated on the flight plan. 4. Better coordination with Maintenance. We did not talk to Maintenance prior to departure. They were nowhere to be seen when we departed; which was about 2 minutes early starting the push and on time starting the engine. 5. Have the company stop blaming pilots for maintenance delays and threatening legal action against us. During this event; passengers were accusing us of breaking the aircraft on purpose. We are being coded with delays for 'additional checks' when there are placards. I was blamed for a delay three days prior to this event. This environment is increasing stress; increasing distractions and compromising safety.


Second narrative: [Narrative 2 contained no additional information.]


Synopsis: The flight crew of a B737-800 inadvertently utilized the wrong MEL placard when dispatched with the left engine start valve deferred. Only after noting zero pneumatic pressure after turning on the left pack did they realize the start valve had never closed. Maintenance replaced the valve.