Another Westerbeke Post - but with some narrowing down

Island Time Buffalo

Island Time Buffalo

Active Member
Aug 19, 2014
240
Grand Island, NY
Boat Info
380 Sundancer 1999.
Engines
7.4 Horizons
1999 7.2 BCGTC: The classic problem: the unit will only run with the PreHeat button depressed.

My mechanic has spent some time on this, who is a certified regional field engineer for GM and a lifelong boater (I only mention that because this diagnosis is not coming from a hack like me, but from a very capable troubleshooter), and here's what we did:

We eliminated all the usual suspects, the sensors (oil pressure, water temp, exhaust temp, and overspeed). We individually and in toto bypassed or jumped them all. And the fuel pump is performing perfectly, oil pressure is perfect.

What he discovered was that the circuit board, which is supposed to "take over" command" of the unit when the preheat is released, would not send power to the fuel pump circuit, but it would power the ignition circuit (or possibly the other way around, I didn't write it down). According to the schematics, those two circuits are the ones that kill power when one of the aforementioned relays reports a condition. So, one appears to be working, the other not. I'm not sure how he did it, but he manually powered the circuit and the genny ran without the preheat.

So we're thinking circuit board took a crap. Still waiting to hear from Westerbeke, but has anyone encountered anything like this?
 
Island Time Buffalo said:
1999 7.2 BCGTC: The classic problem: the unit will only run with the PreHeat button depressed.

My mechanic has spent some time on this, who is a certified regional field engineer for GM and a lifelong boater (I only mention that because this diagnosis is not coming from a hack like me, but from a very capable troubleshooter), and here's what we did:

We eliminated all the usual suspects, the sensors (oil pressure, water temp, exhaust temp, and overspeed). We individually and in toto bypassed or jumped them all. And the fuel pump is performing perfectly, oil pressure is perfect.

What he discovered was that the circuit board, which is supposed to "take over" command" of the unit when the preheat is released, would not send power to the fuel pump circuit, but it would power the ignition circuit (or possibly the other way around, I didn't write it down). According to the schematics, those two circuits are the ones that kill power when one of the aforementioned relays reports a condition. So, one appears to be working, the other not. I'm not sure how he did it, but he manually powered the circuit and the genny ran without the preheat.

So we're thinking circuit board took a crap. Still waiting to hear from Westerbeke, but has anyone encountered anything like this?
Click to expand...
Yes, many of us have. The “cutout” path after starting goes through the three switches you already bypassed and then a “K2 Run Relay”. That run relay may be stuck open. When you press the preheat before you press start, you should hear the run relay click. It’s pretty easy to hear.

ah, nevermind. If the run relay were bad it would turn off as soon as you released the start switch. The preheat bypasses the three shutdown switches but it doesn’t bypass the run relay. So I was all wet on my original analysis.
 
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A possibility is there is a broken wire along the daisy chain of the three shutdown switches. They are wired in series so any wire break along that path will shut it down once the preheat is released.
 
ZZ13 said:
A possibility is there is a broken wire along the daisy chain of the three shutdown switches. They are wired in series so any wire break along that path will shut it down once the preheat is released.
Click to expand...
Good possibility, but at one point we bypassed the whole circuit with all 3 switches, so that wouldn't be it in this case.
 
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After looking more carefully at the schematic, there is a 4th switch that doesn't get the same mention on the forums as the other 3 that are in series. It's the oil temperature switch, it sits on a separate circuit from the other 3 switches, and it sits between the fuel solenoid and the choke solenoid and also has the fuel pump in the circuit, which might explain why we get power to the ignition, but not the fuel. In the pic below I traced the circuit in red and blue, the switch is at the top of the diagram.
Oil Temp Switch.JPG


The unit is also a bit hidden, under the belt cover on the pulley side of the unit, so it wasn't obvious. We are going to try jumping this one and see what we get.
 
Good find! My diesel doesn’t have that switch. Hope that’s it.
 
OK, some progress! The remote rocker switch (in the cabin) "Preheat/On" is most definitely 'effed up .... and possibly the "Start/Run" switch as well. Just ordered the replacements from FlounderPounder Marine.

We were able to get the genny running intermittently just by tapping the switches in various combinations. I suppose this may not be the whole problem, but it definitely is one of them. Crossing the 'ol fingers that this will do it.
 
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