Still No Luck

Still no luck.  I bought four new spark plugs and a new engine coil, none of which made the least difference in how the engine runs.  I did, however, finally manage to prove to myself pretty definitively that it’s only running on three cylinders, and that the fourth (back) cylinder is not firing.  I fiddled for a while, and finally managed to get the engine to start again.  I let it warm up a bit, then removed the back coil entirely.  I got it started again, and it ran precisely the same.  Assuming the engine won’t run on two cylinders (probably a safe bet), it seems safe to assume the back cylinder is dead.  I guess it doesn’t rule out the fuel injector entirely, but given how the engine backfires when it runs, and given the wet spark plug in the back cylinder, I think it’s safe to assume the fuel injector is working.  I’ve asked again for Viking to give me a pinout of the ECU cable so I can go through and check the wiring harness with an ohmmeter.  If that fails, I’m not sure what to try next.  Fingers crossed…

Update:    I just got home and checked all four fuel injectors one at a time.  All four click when energized, ruling out injector wiring and complete injector failure (though not ruling out a clogged injector).  I’m going to do a compression check next, just to rule out possible failure with rings and/or valves.  I want a baseline for annual compression checks, anyway, since that’s good practice for the annual inspection.  Assuming the compression checks are good, I’ll try a continuity check for each coil wire back to the ECU connector.  I’m assuming I can puzzle out which wire is which (unless one is broken, in which case I’ll only be able to find three of the four and will know I have a wiring harness problem).  I’m hoping that’s what it is, even though it’s unlikely, because that’s something I can easily fix.

Failing that, I guess I’ll pull the injector(s) and make a visit to the junkyard for some parts to swap in.

Jan’s got good troubleshooting advice.  I’m sure it’s something simple and that we’ll nail it down shortly.  I still think it’s likely it’s something trivial like a broken wire or a clogged injector.  Just doesn’t seem likely that it’s anything substantial.  Which of course doesn’t make the process any less difficult.

Update:  Did a compression test on the questionable cylinder, and it was 120+ PSI without bothering to warm the engine first.  That was so good that I didn’t bother to check the other three yet (since I’m not worried about them).  I pulled the injector rail, cleaned it, then pulled all four injectors and cleaned them.  Reassembled everything and started the engine.  Ran like crap, wanted to vibrate off the front of the plane.  Shut it down quickly.  No change.  Sent an e-mail to Viking, I suspect the next step is to replace injector(s), but will await word from on high.


11 thoughts on “Still No Luck

  1. Hi Jeff
    Have you tried to verify if a spark is generated by the back plug?
    Also I would be checking the compression in the cylinders.
    Hope you figure it out soon, be a big help for me when my engine arrives.

    • I haven’t verified that a spark is generated. Haven’t figured out how to do that easily without the risk of damaging the coil. At the moment, I’m sitting in my kitchen waiting for the local auto parts store to open so I can run over and buy a compression tester. Assuming I have good compression, Viking suggested that I test the injectors. That’s unexplored territory for me, but I’ll figure it out. Viking seems fully committed to nailing this down. It’s frustrating, but I can’t complain about the help I’m getting.

  2. Hi Jeff, Bummer but good to know the thing will run on three cylinders, I guess. The obvious thing now seems to be to replace the plug wire, but I suspect you have already covered that base. Also good to hear Jan is helping you out. Do you have many varmints that might have chewed through something? Trying to imagine what could happen from two weeks of sitting.

    • I checked pretty carefully for varmint chewing (I have seen mice in my shop before). No sign whatsoever (and the signs are usually pretty obvious). On this engine, each spark plug has it’s own coil, so there are no spark plug wires in the traditional sense. There is, however, a wire to each coil to trigger it. It’s this wire that I need to check very carefully all the way back to the ECU. I just don’t have a pinout of the ECU connector, so I don’t know where it’s supposed to attach (and it’s a friggen’ huge connector – something like 50 pins). Jan is definitely helping, and has supplied some great advice. He believes it’s likely a fuel injector. I don’t disagree, but I’m going to test compression and wiring first, since that’s much easier than sourcing some of the parts I need to test from junk yards given the lack of time I have to work on this right now. If the compression test is fine (which I expect it to be) and the wiring checks out ok (which, honestly, is what I suspect is the problem), then I’ll move on to the fuel injectors and the pressure rail.

  3. I had been trying to post, with no luck. It has been my feeling that an injector (maybe just some ice from your reported temps)
    Something else I did not see mentioned, did you ever try the backup switch? That could eliminate some of the items, If no change, then look closely at the injector(s)

    • Good thought; yes I tried both the backup fuel pump and the backup ECU. No change whatsoever. I thought of ice, but it just doesn’t seem likely to have persisted for a week. It’s cold and wet here, but not cold enough for ice to stay frozen throughout the day (it’s been in the 40s in the day time). I’m afraid I’m going to have to pull the injectors and have a look. Maybe later this afternoon.

    • Good call. I wasn’t aware of the screen, but that seems very reasonable. Will do after lunch (well, and some necessary Christmas errands), then report back.

  4. Maybe try swapping a working coil/plug/wire from a firing cylinder. If it doesn’t work and you switch them back and they work on the original, you can at least rule those three components out. Or swap the stuff from the back to a working one. Either way?

    It’s rather concerning that this problem just developed on its own.


    • The parts are easy enough to swap. What’s hard is figuring out which cylinder isn’t firing once things get moved around.

      I’m not too worried about how the problem developed at this point. I’m still assuming it’s something simple and that I just haven’t identified it yet. At this point, I’m betting on a bad injector. But until I obtain a spare to try swapping in, there’s no good/easy way to prove that. Maybe I can find an unlocked Honda Fit in a parking lot somewhere… 😀

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