FP Generator Issue - Any Suggestions?

HMBJack

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I have a 2006 330 Express with a Fischer Panda (FP) 4200 diesel generator with 400 hours on it.

My FP starts and runs fine, but it has a weird thing going on. Here's my situation:

After about a hour of running perfectly with or without load, the RPM's drop down to ~10% then the RPM's go back up to ~80% then it drops again to ~10% RPM's and the process repeats up and down though never stalling.

It seems like it is running out of fuel - which I don't think is the issue because I have replaced the fuel pump, fuel filter, have a full tank of fresh diesel, swapped the Fuel pump relay several times with new ones, checked voltage to the fuel solenoid and the issue still persists. I also loosened my fuel cap to allow more air ventilation in the tank but that too did not fix my issue. Alan over at Fischer Panda Tech Support is also stumped.

It seems like my issue is temperature related since the FP runs great for an hour or so then starts to act up.

Really not sure what to do next. Test or replace a temp sensor somewhere? Test the fuel pressure? I'm stumped...

Any ideas or suggestions?

Thanks,
Jack
 

Fishtales

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I have heard of generators that have a load/no load switch where the generator runs and if the switch is in the no load position, the rpms drop significantly I believe to save on fuel. Could there be some type of circuit in the FP unit that is normally in the load position and maybe after something heats up it is alternating between the two? Just a WAG.
I would call the service department for FP and see what they have to say. I called them when I changed out the starter on my unit and they were super helpful. Post if you need contact info.
 

HMBJack

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I agree, the FP Tech Support is excellent though they can't solve all issues over the phone. I pretty much have them stumped unfortunately.

I ran the boat and generator today and it ran perfectly, with a medium load of 15 amps, for 2.5 hours - then - it did that RPM's up and down thing - again without stalling. I then turned the generator off and opened the sound proofing clam shell and let it sit off for about 5 minutes. Started it up again and it ran flawless until I returned to the dock 1.5 hours later. So it might be a temperature thing or air flow issue into the generator's engine - not sure.

So, I may be sort of okay now. This morning, before I went out, I switched the fuel pump relay again and maybe this one is better. It still failed me after 2.5 hours but that is better than nothing.

Still searching for the ROOT Cause of my issue. I will report back if, and when, I find it.
 

wspitler

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Could be an intermittent temp (thermistor) switch for either the exhaust temp, coolant temp, oil pressure, or generator windings. They close the fuel solenoid and if one was intermittent it might cause surging. Just a thought? Do you see a red light on the panel when it happens? The only switch that doesn't indicate on the panel is the windings switch. I'd check all of them for corrosion. I think that they all provide a ground for the solenoid and while you are at it check all of the ground wires between the engine and the battery buss.
 

HMBJack

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Thank you Bill. Good idea on the intermittent issue on the ground wires to temp sensors. I will check them all.
 

HMBJack

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Okay, I think I located my issue.

Thanks to Bill (above), I closely examined all connections at the thermo switches and temp sensors. What I found was a disconnected ground wire at the cylinder head (called a thermo-switch). It is a little spade type connector that came off and would be hard to see if you weren't looking for it. Since it is up high near the top of the generator, it probably came off when re-attaching the sound proof clam shell.

So, with that ground re-connected, my generator ran flawlessly the whole time on a today's Dungeness crab trip (about 3 hours). I think I'm in the clear for the time being. Yay!

Many thanks to all who made suggestions here with a special thanks to Bill who got me looking at the right spot.