I am working on a pair of 200HP HPDI's 2001. It all started with bad gas in the tank. I cleaned tank and all fuel filters, VST, injectors, Etc.... They both ran allright after that. Then they stopped running. I got the starboard engine running again by taking the high pressure mechanical pump apart, cleaned the small screens in that pump. After reassembly the starboard motor now runs better, still not perfect. Now to the big problem, the port engine has good fuel pressure (measured at the VST (50psi) & at the fuel pressure sensor at the high pressure pump), The symptom is the spark is erratic ( only 1, 2 or 3 cylinders are firing intermittently) on the port engine. I have tested each sensor at least twice and have changed each sensor from the starboard engine and still get the same symptom. I have tested the "lighting coil and get a good reading, also, I have tested the pulser coils and all put out the correct peak voltage reading. Also, I have checked the continuity of all wires going to the ECM. Also, I swithched the known good ECM & Injector driver from the starboard engine to the port and still get exactly the same symptom. All of this is history, now to my direct question. Each coil has a red/yellow wire coming from the fuse/relay holder, I get battery voltage (DC) at these coil terminals with the ignition key on (measured with a standard volt meter) then when I try to start the motor, I get 140-200 peak volts on the few firing coils (read using my Stevens peak voltage meter). I don't understand if the 140-200 volts is AC or DC & how it boosts up to that amount. At this point it appers to be the ECM, but I have switched them out and the starboard engine runs on all 6 cylinders with the ECM from the port (problem) motor, hence, I feel that it is not the ECM. I am not getting any continuity between the white wire (at the key switch) and the black ground wire at the key. I have bought the "blinky light' tester YB-06795 and get no codes. I have just ordered the Yamaha software and cable for a PC (had to order it from Australia), it should be here in a week. My next step is going to be to disconnect the main harness to the key and plug the keyswitch directly to the harness on the motor to isolate the harness from the key to the motor. I am looking to see if there is something feeding back a bad signal to the engine. I need a Yamaha expert to shed some light on this problem. HELP!!!!! I have been working on this problem for the last 50 hours, so I have been trying to be very thorough, but, feel that I am overlooking somthing. Any help will be deeply appreciated.
