Cummins QSC starts but then quickly dies? Thoughts?

[John]

Thanks in advance for any help.

’05 QSC 540 – 2 weekends ago started her up, ran 15 secs, died. Odd, never happened before, never even a hiccup before then. Started up again, fine all day with several start and stops and long runs.

This past weekend, fired her up in the morning to warm up for an oil change, ran fine, idled 10 mins or so, no problems. Shut her down to start oil change.

Changed oil, fired her up as usual. Ran fine for 30 seconds to a minute while I look at oil pressure, etc. and then the SmartCraft displays goes blank and motor dies at same time again, just like the previous weekend.

Let her rest for a few mins while I look around the engine room for anything super obvious…nothing. Try to start her again a couple mins later….took a bit longer to start (4 seconds instead of the usual 2) but started and ran fine for a couple mins but then died again.

That was it. Didn’t try anything else. Figure I’d start some research as to what could be the cause.

I hear the pump when flipping ignition on, no codes or alarms in the SmartCraft display. Just crapped out and display goes blank. The constant power is on at the posts (12.5v) by the ECM. Will trace those back to see if anything can interrupt it which might produce same results if the power is killed.

Boat has FireBoy system and a Glendinning.

At a loss. Any thoughts on what to check or start replacing?

Thanks again,

J

Topic

[Corey Schmidt]

When the displays go off with the engine, you’re losing direct ECM IGN power…

Check the ECM power stud circuits thoroughly… make sure that the wires are run DIRECT to the batteries un-switched and the wires are fused and that the fuses are in good shape. Then, if those circuits look 100% I would look at the FireBoy as your main suspect… bypass it if possible and see if your problems go away…

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John

[Andre Huizing]

Hello John, we had the same problem on a 2006 (Smartcrap era) QSC 2 years ago. It would suddenly and inexplainably die. Very long (half a year) story short: in our case it was a flacky 24V/12V converter that Cummins uses to convert between our 24V installation and the 12V Smartcrap stuff on the dashboards. The engine would think the ignition was just shut off.
Now I understand from your post you have a 12V installation so there will be no converter. However I’m pretty sure it’s somewhere in this circuit. I think your engine also thinks it’s getting shut off. I eliminated every possible source by shortcutting everything that can stop the engine the stopbuttons, the fireboy system and some other stuff. My problem was also that after it had stopped it would typically immediately be able to start again. I got lucky when after one random shut off it would not start again and I could trace it back to this converter.
In general: the electronics on our vintage are of an extremely poor design electronically and physically. It’s like an aftertought on a basically good engine.
Lots of luck, André

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