Westerbeke 8.0 BTDA kicking my arse

Discussion in 'Electrical Stuff' started by ZZ13, Dec 11, 2020.

  1. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    All of the years and hours on the generators and? I would think that the manuf. has considered all of these issues wouldn't you? However, if the WB relay has a typical suppression diode integrated and someone installed a relay without then I could see the issue being real. The Only device on that diode is one small relay.
     
  2. km1125

    km1125 Active Member

    222
    May 5, 2021
    470
    Cummins QSB6.7
    Well, it worked just fine for ~1200 hrs, so I think the manuf did something right!!

    How do you explain both the diode failing and the fuse blowing?
     
  3. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    Yea that's a good question. Unless something did a dead short on the relay side of the diode and as a component of the diode failure the fuse let go I don't know. And they could be completely independent issues also....
     
  4. ZZ13

    ZZ13 Well-Known Member

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    We lost power on the dock. Dock transformer box was left open in the rain. Everything wet. So I need my generator. Replacement parts haven’t arrived. Decided just to try to start it with the preheat solenoid disconnected. Started right up. I was surprised. Thought I’d have to find a way to heat the intake air.
     
    dtfeld likes this.
  5. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    The big thing pressing the preheat button does is getting fuel pressure up and energizing the fuel solenoid to get the thing running until the oil pressure is up. In very cold weather the fuel needs to be heated which is the glow plugs and pre-heat solenoid.
     
  6. ZZ13

    ZZ13 Well-Known Member

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    Air temp in the engine room was about 70. Ran great for several hours. The dock master plugged the blow dryer into my boat to dry out the wet breakers in the dock electrical panel. Everything is dry and back on shore power.
     
    The Bill Collector likes this.
  7. ZZ13

    ZZ13 Well-Known Member

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    So I studied the schematic 1000 times to try to figure out what happened. As part of that it appears to me that with the positive wire to the preheat solenoid disconnected, the diode is serving no protection purpose. It could be a direct connection from the preheat switch to the run relay in that case. It seems the purpose of the diode is to prevent the preheat solenoid from getting energized via a path through the shutdown switches when preheat is released after starting.
     
  8. km1125

    km1125 Active Member

    222
    May 5, 2021
    470
    Cummins QSB6.7
    Yes, that's the purpose, but it's not from the shutdown switches, it's from the path that provides power to the fuel solenoid. This gets power through several SAFETY switches which are designed to cut power to the fuel solenoid if any of the conditions put the genset at risk... high engine temp, low oil, or high exhaust temp. The shutdown switches do provide power to that circuit though.

    Now, that diode is there really for one-button convenience. You could add a push-button to supply power directly to the preheat solenoid and just hold that down prior to starting the genset too.
     
  9. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    Not quite, it still will not start. That preheat button not only closes the glow plug solenoid but more importantly also provides +12VDC through the diode to the K2 relay coil until oil pressure is up and THEN +12VDC is routed through the safety switches to keep relay K2 energized when the preheat switch is released. The crux of all this is that Oil Pressure switch is open until the generator is running. The K2 relay must be energized closed at all times when starting and when running.
    The K2 relay contacts provides +12VDC from the 20 amp circuit breaker to:
    • Fuel Pump
    • Fuel Solenoid
    • Alternator Field
    • Gauge power
    So, if that diode was replaced with a length of wire then the glow plugs would be activated all of the time the generator is being started and when it is running which would not be too good.
     
    Last edited: Jan 11, 2022
  10. km1125

    km1125 Active Member

    222
    May 5, 2021
    470
    Cummins QSB6.7
    Maybe I wasn't as clear as I thought. You could remove the diode and have a separate (momentary) switch that JUST powered the glowplug circuit. You'd have to hold that one down for a few seconds prior to pushing the START switch which would provide power to the K2 relay. The start switch would be wired to where the diode connected to the K2 coil.
     
  11. ZZ13

    ZZ13 Well-Known Member

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    Roger. And I wasn’t clear I meant “safety shutdown switches” when I wrote “shutdown switches”.
     
  12. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    But then the starter would run all of the time once the OP switch closed right?. Maybe I'm not getting the issue with the diode??
    Plus it takes time to build the fuel pressure so to expect the fuel pump to initialize when cranking would take time. The last thing you want any generator to do is to excessively crank; water ends up in the cylinders.
     
    Last edited: Jan 11, 2022
  13. ZZ13

    ZZ13 Well-Known Member

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    My last post on this (until the next failure). My diode failed closed (I tested it after I removed it). So it end up acting just like a wire. Thus, it became a path for the preheat solenoid to constantly be energized when the generator was running. It could have been like that for a long time. Who knows. Eventually the solenoid started acting up and drawing more than the 8 amp limit, blowing the fuse. So disconnecting the wire from the solenoid eliminates this situation. Since I don’t really need the preheat to start the generator in the climate I boat, I may never reconnect that wire to take the diode out of play. I’ve seen that diode fail too many times on multiple generators.
     
  14. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    Bill - I would try and talk you out of this action - Yes that will enable the generator to start but the starter motor switch then remains active when the unit is running and if accidently pressed will damage the starter motor and/or the ring gear.
     
  15. km1125

    km1125 Active Member

    222
    May 5, 2021
    470
    Cummins QSB6.7
    OK, so now I see the flaw in my 'plan'! The diode isolates the preheat solenoid AND the start solenoid from the 'run' circuit, so you'd either still need the diode in place to isolate the start solenoid (for one-button) operation, or you'd have to do something else (like add a another button for the starter). Adding a separate "preheat" button but retaining the diode to isolate the start circuit might be worth considering, especially when you might rarely need the preheat function. You'd only push that button when the temps were low enough that the engine might need that boost to start.

    I think you could solve the diode-reliability problem just up up-rating it to a size larger than the fuse. I don't really see a downside to that. Much easier to source fuses than it is diodes when you're on a trip.
     
  16. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    https://www.amazon.com/MCIGICM-Rect...ywords=rectifier+diodes&qid=1642005763&sr=8-1
     
  17. ZZ13

    ZZ13 Well-Known Member

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    I still have the functioning diode in there. I’m not removing it. I’m just removing the connection to the preheat solenoid. But you are right. Might be kinda pointless to do that. I’d eliminate one item to signal me that that diode might be sick. A fault light on the anode side of the diode would have been nice. If it lit up with the engine running, time to replace the diode.
     
    Last edited: Jan 12, 2022
  18. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    I think you would always know the diode is functional as when you press the Preheat button the fuel pump will run and you should hear the fuel solenoid click. If the diode was open (fried) then nothing but the preheat solenoid would operate with the preheat button pressed.
     
    ZZ13 likes this.
  19. The Bill Collector

    The Bill Collector Well-Known Member GOLD Sponsor

    Jun 2, 2008
    Tacoma, WA
    1998 450 Sundancer, Achilles dinghy w/15hp
    3126 Cat's
    Good news today... Gen oil analysis.

    MARK: No problems stand out for this generator. Universal averages show typical wear after about 100 hours of oil use, and these results look great after a 160-hour run. Your generator actually produced less metal overall, which is always good news. There isn't any sign of trouble in this data, and there isn't any fuel, water, or coolant contamination to point out. Low silicon and insolubles show the air and oil filters are both working well. Just check back to start building trends. All is well from our end at 1,009 total hours!
     

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