Help! Westerbeke 8kw genny randomly drops RPM. On the hook...

Hey guys, we are currently on the hook and our generator is doing great except it will randomly start dropppmg RPM. Sometimes a little, sometimes a lot. It’s a slow decrease in RPM, not sudden and has no relation to load. Here’s a video I got. Hard to hear with that baby laughing but you can see the frequency dropping. That’s with very little load. It then recovered and I turned the toaster oven on and microwave on. It was just fine. Even running an AC doesn’t bother it. This rpm reduction is random and is doing it every 5-15 minutes. Once the RPM drops, it’ll last for a minute or two before creeping back up. All gauges are in the green. Any ideas? Anything I can check? We aren’t planning on leaving till tomorrow so we really need this thing to hang in there.

This picture was with a load and doing just fine.

https://youtu.be/VqnUW7e_h9E

Sounds like low fuel pressure to injection pump. Saw Hz meter wavering, the Hz (frequency) is proportional to engine rpm. Heard rpm going up and down too.

Got good fuel filters in there? Both primary and secondary?

Is electric lift pump known good? Many trawlers carry a spare pump as they do get weak.

Ski in NC said:

Sounds like low fuel pressure to injection pump. Saw Hz meter wavering, the Hz (frequency) is proportional to engine rpm. Heard rpm going up and down too.

Got good fuel filters in there? Both primary and secondary?

Is electric lift pump known good? Many trawlers carry a spare pump as they do get weak.

Click to expand...

Thanks for the quick response. If it was a fuel issue wouldn’t it not be able to carry a load?

Sometimes low fuel pressure, or air in fuel, shows up at light load more than heavy load. What you said makes sense, but that is not always the case.

The troubleshooting is the same. Verify good fuel pressure and no entrained air.

Check for loose wires, corroded/bad connectors.

2X in the last several years that's all mine was.

That second fuel filter on engine is a great call by Ski. Do you know where "all" the fuel filters are on the 8?
Has anyone worked on the genset recently? Especially around the governor?

If it is problem with the electrical control system, you will see the speed control lever moving. It is the big lever coming out of the side of the timing gear housing and pulled on by the shutdown solenoid. If it is not moving and solenoid stays firmly bottomed, focus then goes to fuel.

Usually the fuel solenoid stays bottomed or releases fully if there is a control electrical issue.

If fuel or air filter(s) are plugged it would not speed back up or carry a load, they will stay plugged but if small amounts of air are being sucked in it may slow the engine periodically until the air is pushed thru. Some engines can't tolerate any air at all while others are ok with small amounts from my experience mostly with farm tractors. Just a thought for what it's worth.

I carry a spare lift pump for my Westerbeke. It's a 12.5 kw, but I believe the pump is the same for the 8. Ski is giving you priceless troubleshooting info. You'll do well to follow! If the lift pump is the round one, they often have a fuel filter in the bottom that's often neglected because it's not easily found. Mine has the square Facet lift pump, if you do some research, you can find an aftermarket Facet pump that meets the OEM spec for a fraction of the cost of the Westerbeke OEM pump. My engine fuel filter is close to the lift pump, it uses a small replaceable cartridge. I use a 2 micron Racor for the genset so the engine filter doesn't require frequent service.



You can test the lift pump by removing the discharge line then holding the preheat button, that should cause the pump to run. Alternatively, just use a jumper to energize the pump from the 12V circuit breaker on the engine. If the pump's working, you should get a good flow, it pulses, if you place a finger on the discharge, it should push fuel past your finger with moderate pressure. IIRC, the pump is spec'd for around 5 psi.

Location of fuel filter is in the manual ...

https://www.westerbeke.com/technical manual/manual_service_35e_44c_8-15 btdc_45100_rev_2.pdf

Hey guys! Just had an awesome day with the family. After my wife’s shower we shut the genny down and didn’t mess with it until after dinner. I giggled the wires going to the preheat and start switches on the engine mounted controls. The switches no longer worked. So I pulled the panel and found someone dicided to just stick the wire into the hole of the switch prongs and used what looked like an epoxy to keep it tight. Wtf. Anyway. I “slightly” improved the connection for now and started her up. Btw, I could hear the lift pump running as I held the preheat switch. She ran perfectly for about 30-45 minutes before I heard the rpm drop, then recover. Then it did it again, this time a big drop. I was determined to see what was causing it. I ran to the engine room and pulled the covers off the generator. The shut off valve was holding tight. I gave it a wiggle and it was solid. But I did notice some fuel leaking from what I think is the lift pump. So maybe you guys are right, might be the lift pump failing.


Here’s a pic.

Steve91T said:

......... The shut off valve was holding tight. I gave it a wiggle and it was solid. But I did notice some fuel leaking from what I think is the lift pump. So maybe you guys are right, might be the lift pump failing.

Click to expand...

Shut off valve... meaning the solenoid? If it's not moving, then I'd suspect the filter or the lift pump. Just because you can hear it running doesn't absolve it of responsibility! The filter could be clogged- the filter is the small can -lower right in photo- with the knurled ring at the top. Back off that ring and the can will drop away leaving the filter cartridge still on the filter assembly. Should be a 30200 cartridge.

Can't discern from the photo if the lift pump has a filter, the older ones which is what's pictured typically have a filter in the housing, the bottom of the lift pump twists off and the filter's inside. That could be the source of your leak.

I think I'd make sure the filters are new, then try again. If the problem persists, then you might want to do further testing on the pump. I'm not sure if the OEM style pump is still available, you may have to use the newer style Facet pump, may be some re-fitting involved.

In addition to finding and fixing the source of any leak, I agree with prior post to check and replace the 30200 filter.

Our boat came with a 2 year old Westerbeke 7.6. Towards the end of last season it was getting hard to start. Once started it ran fine. We have a Racor, the unit also has an 80 micron inlet fuel filter before the electric lift pump which is to be changed every 250 hours or so. Then the on engine 30200 filter. When I pulled the 30200 for changing I found it was covered in crud and had nearly collapsed in upon itself. An easy inexpensive fix that hopefully solves the hard starting. With a smaller 10 or 30 micron Racor not sure i have to get too worried about changing the 80 micron inlet fuel filter.

So this morning I found some generator filters in a box on the boat. So I pulled the cover off the generator while it was running and saw a midt of fuel spraying. So I shut it down will have to add that to my list.

Interesting thing happened this morning as well. My starboard engine quit. I couldn’t get it restarted. I changed the racor and that seemed to solve the problem but it died soon after and won’t start. Acts similar to my last trip when I ran a tank dry and got air in the system. I’m thinking that when I ran the tank dry I clogged the engine mounted filters along with the generator filter. Idk. But seems to be a strange coincidence.

The good news is it getting better at single engine docking!

The filter in the bottom of my cylindrical fuel pump on my old 8BTD looked like it had never been changed in 30 years but it still ran. Black pile of goo.
Fluctuations in speed, go with SKI.

Hey guys. Ok so we are down to either fuel filters or lift pump. Any idea where to buy a lift pump?

Here are some filters I found in the engine room marked gen filter.

Next time I’m at the boat I’ll change the filter and see what happens. I’ll keep you guys posted. Thanks for the help.

I guess I never updated this thread. I’m sorry.

New main and generator fuel filters solved my problems. And a new fuel line fixed my fuel leak. She’s been up and running perfectly now for many hours.

Thanks for everyone help.