westerbeke 8BTD only runs with preheat on - troubleshooting but can find some sensors

EKM

Active Member
Feb 4, 2007
673
Beach Haven, NJ
Boat Info
2000 420AC
Engines
Cummins 6CTA
2002 8BTD diesel...on a trip, gen runs fine during my 9 hour journey. At anchor will only run with preheat on. Will this do any damage to run w it on?. i have oil pressure, new pump impeller, all the gages are fine (temp at 170, oil pressure at 75psi, 12 volt mtr is off the scale (when off its at 14 volts), exhaust water manifold temp maybe 120 or so). Anyway, at anchor on my annual trip to Block Island RI and Martha's Vineyard and no gen. Life is not good.

It just shut down after running with preheat on and nothing at switch, no clunk, like it has no power at all. Checked the temp switch on the antifreeze size, check the two oil switches (one is normally closed and one is normally open)...both work fine. Without a gen, it tough to be on anchor. Slip rates are crazy here....8.50/ft ($357 per day plus $40 for electric). Need to figure this out!
I have not found the intake water temp sensor or exhaust temp sensor. Any suggestions on where to start...? Not a good start to vacation.

Thanks....
 
Found the exhaust switch....its ok, battery connection ok too. Gen on an Aft Cabin requires the salon carpet to be pulled back an three hatches open to access it.
 
I run my 120V refrig off my bow thruster battery bank and need to run the gen for a few hours each day to keep it running.
 
Have you checked the coolant? The coolant temp switch is at the thermastat housing if I remember correctly.

You mention "with Preheat on". You should have to hold down the preheat button, not just be able to turn it on. Can you clairfy?
 
You are looking where you need to……….the preheat switch on the 8.0 BTD defeats all the safeties (overheat and oil pressure) when it is pressed. This is done so you can crank the generator when it shows no oil pressure.
 
I am guessing one of your high temp or low pressure switches has failed. The preheat switch among other things bypasses all these and will shut the unit down once the switch is released.

Running with the preheat switch on will cause the fuel lift pump and glow plugs to heat continuously, and draw a large amount of current putting a big load on the alternator. Can probably do it for a while, but extra wear and tear. The curious issue is why your volt meter is pegged...you may have damaged the voltage regulator in the process.

The best idea would be to jumper the offending switch(s) and temporarily remove them from the circuit. A little bit of wire and some M/F spade connectors should get you what you need.
 
So the fuse blew on the control panel from running with the preheat switch on....off to find fuses. I had a 7.5amp fuse nd it blew immediately. I found three switches and they all work as they should. The only one that was curious was the oil pressure switches had 2. One normally on (opens when running) and one normally off (makes contact when running).
Exhaust Water jacket - always made on except when too hot.
Antifreeze switch - always made except when too hot.
Oil Pressure - off until started, then one w pressure
Am I missing other ones?
Can I disconnect the glow plugs so they are not always on?
One interesting thing was one of the alternator wires was off....replugged it in and no change.
 
So the fuse blew on the control panel from running with the preheat switch on....off to find fuses. I had a 7.5amp fuse nd it blew immediately. I found three switches and they all work as they should. The only one that was curious was the oil pressure switches had 2. One normally on (opens when running) and one normally off (makes contact when running).
Exhaust Water jacket - always made on except when too hot.
Antifreeze switch - always made except when too hot.
Oil Pressure - off until started, then one w pressure
Am I missing other ones?
Can I disconnect the glow plugs so they are not always on?
One interesting thing was one of the alternator wires was off....replugged it in and no change.
The normally open oil pressure switch is simply a fault signal to the boats System Monitor. It doesn’t affect the operation of the generator in any way. The normally closed switch is the oil pressure failure shutdown switch.

We go through your exact situation here in gory detail. Seems like there is one of these threads every few weeks now. Need to sticky the solution.

http://www.clubsearay.com/index.php?threads/westerbeke-8-0-btda-kicking-my-arse.102186/page-2
 
Replaced the fused and its running again without the preheat on...so far 30 minutes. Such a nice feeling when you don't find the problem. I'll read the other thread...thanks for the reference.
 
Oil level low can shut it down also. As little as 1/2 qt low will do it.
 
so doesn't restart and keeps blowing the fuse. Using a small jumper which was getting hot. Will a bad diode do this?
The temp switches....I checked them out for N.O vs N.C and all appeared to be working. Do these need to be checked to see if they are grounding out?
So trying to give away food yesterday and first boat just happened to have a spare little honda generator.....wired it up to run the refrig and inverter battery charger and laptops. Still hoping to fix this before we move to our next stop. Phone call to Westerbeke tomorrow. Hope they can help!
 
so doesn't restart and keeps blowing the fuse. Using a small jumper which was getting hot. Will a bad diode do this?
The temp switches....I checked them out for N.O vs N.C and all appeared to be working. Do these need to be checked to see if they are grounding out?
So trying to give away food yesterday and first boat just happened to have a spare little honda generator.....wired it up to run the refrig and inverter battery charger and laptops. Still hoping to fix this before we move to our next stop. Phone call to Westerbeke tomorrow. Hope they can help!
Yes, bad diode will allow current to flow where it’s not designed to flow. Will blow the fuse every time you push down the preheat switch. Also, never defeat the fuse unless you want to burn out other components of the circuitry.
 
diode test w voltage regulator....value of 1 on reverse and value of 45 for 2-3 seconds on forward then drops to 1 (no conductivity). so removed the remote station from the equation which requires a jumper from 2-3 or on TB1. Made a jumper for the preheater (one side alligator clip and the other side wired) and then pull the wire of the Solenoid after start up so no juice going to the start circuit. Hot water and charging systems and will worry about his when I get back.
 

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