Difference between revisions of "Engine start CB-Oct2010-outline"

Latest revision as of 22:46, 13 December 2010

Engine Starting random failure

In October 2010, the engine would not crank sometimes. We probably had some problems earlier, but it became obvious as the month went on. We finally had a case where we couldn't reset a circuit breaker to fix it. We were able to start it using a maintainer's way of cranking the engine over.

30 Oct 2010
See description of functional testing, observations, and some thoughts while under way and experiencing the problem.

02-03 Nov 2010
See report of testing and analysis of some possible failure modes. (Unfortunately, no problems were found, and engine started fine after our two days of testing!)

06 Nov 2010
We have no test/work report yet (as of eve 06Nov); however, we have a verbal report:

• The CB was replaced by the new one with "wrong" form factor temporarily.
  See photos and discussion and/or report status email
• Since CB is the prime suspect at this time, it must be eliminated as culprit before going forward on other analysis. Also, most workers think the CB is indeed a likely failure point.
  

07 Nov 2010

• Main battery upper switch knob crumbled when we turned it on; switch became unusable.
  • We moved some of the wires so that bottom switch now selects battery #1 and/or #2 or none.
  • Top switch is still in position. (Only used as a terminal block to distribute switched power to non-engine systems.)
  • See sketch and discussion of this fix.
    NOTE that this fix isn't actually associated with the failing CB problem.
  • With above fix, we changed the wiring such that we may have less voltage drop produced for the 12-volt circuits.
• Test sailed the new CB: fairly stiff winds, some seaway to shake the boat around a bit. Performed the "glow-plug" test several times on both tacks: CB never tripped.
• (Unfortunately, we're not sailing Nevermore regularly these waning days of the season to REALLY test the temporary CB thence validating our conclusion that the old CB WAS the problem!)
  

18 Nov 2010
No more sailing available to test out the temporary CB and wiring: new owner will be taking the boat. Discussions centered on what new owner needs to know and our thoughts of whether the current CB and separate terminal block is sufficient, or whether to recommend the new switch we have located but did not order.
Ted's email below gives our best thoughts about what to do. (The temporary terminal-block issue was not known by most of us.)

I would categorize our breaker installation as "temporary".  We
fabricated a terminal block out of wood and some machine screws.  
If it fails (it had started to crack) the connection will not be
reliable.  I had intended to replace it with something like this
(if we did not find the correct breaker to reinstall on the engine):

     http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=WM5803-ND

Ted

TO DO: (informal project list 'til we get organized)

• Locate replacement CB in case we find it's failing
  • Have electrically equiv one from West Marine - very different form-factor from original
    • Installed it temporarily 06Nov
    • results: test-sailed with temp fix 06Nov (o.k.), 07Nov (o.k.)
  • Torresen has located one that appears to fit in current location on engine
    "Volvo Penta p/n 841178, descript. FUSE, $45.79"
    • Ask Torresen:
      • why does it says "FUSE"; check p/n with picture info they sent
        • REPLY: mistake in catalog; IS a ckt breaker
      • ask Torrensen how wires are connected (are they compatible with old CB?)
        • REPLY: yes, they have the same screw-terminals as the old CB.
    • If p/n o.k., ORDER CB from Torreson/Volvo
      • NOT DONE: will suggest this to new owner
• When new CB is permanently installed, re-trim wire-bundles out of way of dipstick access
• Get proper version of engine wiring diagram on wiki (only have camera copy of the good one that came with N'more, wwhich is in the hardcopy engine tech manual), and a nonsense one (still by Westerbeke) from another version of the engine manual.
  • believe this was done but not sure (ThomS @ 14Dec10)
• Purge our referenes to the bad version of tech manual "Edition two" and make sure we're only using info from "Edition one"
  • not doing any more work like this, now that boat (and manual hard-cover document) are gone