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Engine fails to start on slow turning failure. Checked for any liquid in cylinders thru the spark plugs and cylinder pressure sensors – no liquid. A couple times we did a manual slow turn and tried the engine and it started up. A couple times we just did the turning gear a couple rotations and it started up. It had a couple wierd electrical alarms and tried changing out the MCM since it does everything including the slow turning signal. Had some communication issues so he put the old MCM back on and the engine started up a couple times like brand new. It sat over the weekend and now has the slow turning failure and it wont rotate when manually trying the slow turn. Swapped out the main starting valve still nothing. Ideas?
When you have a slow turn failure, does the engine actually turn? This can be seen by trending engine speed during the failed start. If it is slow-turning, but never getting to the next sequence…starting, it is likely a failed speed sensor (ST173). We have had this happen several times. The two speed sensors on the cam gear (ST173 & ST174) are treated as primary & secondary, respectively. If the primary fails, you will not get an alarm…it just will not get past slow turn. The easiest way to troubleshoot this is to have eyes on the ESM while a start is initiated, and watch the lights to see if there is a pulse from the sensor. These sensors can work intermittently, which may explain why it starts some of the time and not others. Even better is to put an oscilloscope on both sensors and compare the signals. This will sometimes show a weak signal (smaller square wave), even when the sensor is working.
If you find a bad primary sensor and want to start quickly, just swap the wires with the secondary and use it for starting…then change the sensor when it is convenient.
Agree with Stephen, there is also a bulletin regarding to a bad sensor batch, you can find it in the wartsila portal and check if you have this badge of sensors onsite. We have had several situation even do replacing the sensor for a new one, works couple of days then start failing again, we went to the point to videoscope the sensor adjustment from one port to see the sensing distance properly adjusted.
Thanks for the response. We haven’t watched the engine when starting but I dont think it is even turning when the failure occurs. Yesterday when trying do the slow turning locally out on the engine we couldnt get it to rotate. We pulled the spark plug on A1 and had air blowing out, put it back in, pushed the slow turning solenoid in, heard air flowing but no rotating of the engine was happening. We had swapped out the main starting valve just to eliminate it, didn’t help.
Have you checked if you have an air leak in the start air lines?
We had one of the lines that broke and was causing trouble with slow turning occasionally, check in your cylinder connections for the start air valve if there is a broken line.
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