Could this be the problem?

[zackc]

In working on my gen set. A Westerbrake 7.6Kw which is on my 3870 the on, off, start knob broke off. I suppose as old as it was I should not be surprised. I took off all the wires and removed the switch and made a slot in the stub that remained sticking up. This way a small flat head screw driver works like a key and works just fine until I can find that part of the switch and replace it. When I wired it back up I may have made a mistake and if so would this keep the gen set from starting. In the on position I have power going to the fuel solenoid and pump, in the start position there is power to starter and it turns with plenty of rpm to start. Now here is where I could have a problem, but I am not sure. The switch has room for four sets of wires. In the off position I can pull down the spring loaded pre-heat switch and I can hear it engage at the gen set. In the on position it will not function. Would this cause the gen set not to start or should it start any way?

[David M]

Do you have any pictures? The fact that the preheat switch does not work in the run position should not prevent it from running. The preheat switch does not need to be working after the genset is running on its own.

[Pblais]

Now here is where I could have a problem, but I am not sure. The switch has room for four sets of wires.

With 4 wires you could connect them 6 different ways with 8 it's something like 33 ways. Asssuming two colors it's only 12 ways. There really is only one way that would be correct.

There is also the problem that the switch could be broken.

[David M]

Trace the wires to their origin so you know with certainty what wire does what and then "flag" them with white electrical tape and a Sharpee. Separate the key switch from the wires and test the individual terminals on the key switch for continuity with the key in all its positions. Draw it all out on paper. Go to the dealer and ask for an electrical schematic or where you might find one online. The original owners manual probably had an electrical schematic...check Ebay. Google the model number of your generator to find more information. Ask the dealer where you can purchase a replacement switch or its equivalent if the switch is bad. It should all make sense then and save you the cost of sending someone out at $95 per hour to move one wire from terminal A to terminal C.

[Beausoleil]

Bill,

Worth a look: check the fuse on the right side of the control box. I have a problem with our 7.6BTD. I don't have the wiring drawings with me (I'm at work), but our problem is that the genset will run for a few minutes, and then blow the fuse. It seems (from memory, anyway) that the engine cut-off solenoid is tied into the same pre-heat circuit somehow. For whatever reason, as the engine warmed up, some current was being shunted through the fuse. If I remember right, if the fuse is blown, trying to start it gives the same symptoms you're seeing - turns over fine but never starts. You might have accidentally blown the fuse while re-attaching the wiring.

Rather than have an electrician troubleshoot my problem(even though it's under warranty), since we're replacing the whole electrical system on the boat, I thought I'd just wait for the ratty wiring with breaking-down insulation to be replaced...

Wiring drawings are available here.

[never monday]

are we discussing the rotary switch on the lower helm station?

[zackc]

Thanks for all the info. Yes I am refering to the lower helm station.

[spencer53]

You most likely have an oil pressure safety switch. It will cut off the fuel if oil pressure drops low. When starting, the preheat switch will override the oil pressure safety switch allowing fuel to the injectors. Once the engine starts, the oil pressure build allowing the preheat override to be released. Find that circuit and confirm that it is wired correctly and I am confident your problem will be solved.

[zackc]

So, from what I am gathering here is that when the rotary switch for the gen set is in the on position the pre-heat circuit should be working, right?

[never monday]

I had to go reread your post.
Yes, the preheat should work in the on position. The on position powers the pre-heat switch.
You should also get the solid clunk from the fuel cut solenoid in the on position.

Don't start chasing problems on the engine....you didn't mess with it to cause this problem.
Go to the Westerbeke (note spelling) site and download the wiring diagram for your unit. There are some weird special mandated circuits you need to be aware of.