Viking 130 shutdown by shutting off fuel pumps?

I know the normal shutdown involves shutting off power to the ECU by shutting off both batteries and the alternator. But I also read that if the fuel pumps are shut off that the engine will also stop. I haven’t seen any warnings about only shutting off the fuel pumps so I thought I’d ask if there were any reason to not use that method to normally shut down the engine? I don’t know if maybe that would cause any cavitation or other potential issues with the high-pressure fuel pump? Just thinking that shutting the fuel pumps off might be more akin to something like pulling the mixture to lean-cutoff or maybe have a benefit like de-pressurizing the fuel lines at shutdown. 

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  • Another benefit of this approach might be that the master switch can remain on while shutting down, leaving the lights or other ancillary devices on as desired. Also, with the fuel system emptied then maybe there's less danger of inadvertent ignition if the prop is rotated by hand while a battery switch is left on.
    • Starving the GDI mechanical pump for fuel is not good and can make a restart harder

      Shut down the engine by cutting power to it.
    • Well, this wouldn't be starving the "light" pressure pump, it would be starving the high-pressure pump; I think that's what you meant? But I understand - your stance is to shut down the engine by cutting power. On the depressurization of the low-pressure lines (from the pumps to the engine) - I swore I saw a video of your header tank install which shows a line from the manifold back to the header tank to do just what I was asking about - depressurizing that lines after shutdown - but I just can't find that video again. Do you have a description of how to set that up? Or am I remembering wrong?
  • I just saw Jan's response to the "A Neeewwb Question": "The issue in regards to shutting down the engine with the “high” pressure fuel pumps is that you would starve the “higher” pressure mechanical pump and empty the fuel rail of pressure, making it harder to re-start."
    Makes sense, but how much harder? A couple extra seconds of cranking or is it significantly worse? Would there be any concern of testing this approach? Would someone be willing to test that out and report the results? My engine is not running yet (hopefully within the next couple of weeks).
    • Hi Phil, on my 130 engine (during testing of the ECU's ability to recover from low fuel pressure), I remember it taking a full 60+seconds for the engine to finally splutter and stop after switching off the low pressure pumps in the Header Tank - so not a good way to cut the engine. Re-start involved more cranking before it fired into life again.

      The particular ECU (latest software) test, was to see (and you had to be quick switching the pumps back on again) if the engine recovered and continued running (just) as it started spluttering/being starved of fuel. [correct me if I am wrong, Jan]
    • Thanks John. Always good to hear real-life results and experiences. Do you have the bleed-back line from the check valve manifold to the header tank to relieve pressure in the lines after shutdown?
    • Yes, I have the bleed-off line from the check valve going back into the Large Header Tank on my project. Mandatory I think.

      Agreed, electrically killing the engine in flight (for whatever emergency reason) causes EFIS, radio and flaps to go out(my project), before you at least switch one battery back on. This is in my checklists. I’ll start a new thread (here) and post these. Maybe of interest to others.
  • Phil, shutdown of ECU, as my ECU white conductor was labeled "battery power always on" and the white red conductor was labeled " switched ECU power" I wired as noted. The wiring diagram dated 12/12/2018 shows these conductors (W & R/W) wired to the positive bus hard.
    I would like to ask Viking if shutdown is okay by turning off the (R/W switched ECU power), and leaving the contactors and alternator on.
    • All ECU’ should be wired According to the wire diagram. The two ECU wires go to the same spot.
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