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Old 23-08-2017, 14:13   #1
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Join Date: Sep 2007
Location: Delray Beach, Fl
Boat: 1998 Rosborough 246 LSV
Posts: 563
Generator stops when key on for engine

Hi,

I have a 2010 Ranger 2 tug with a Yanmar 4BY2 engine and a Mace 2.6 generator.

About a month ago, the B+ wire from the engine control module to the helm key apparently corroded at a connection and the key power became intermittent causing the engine to periodically fail. I traced the power from the ECM to a non-accessible area under the sole where it changed color and stopped transmitting power to the key. The symptoms went away when I bridged a fused wire from the house panel to the key to supply 12 volts to the key. The engine has been fine since then -- although I know this isn't a permanent fix.

But, around the same time (not proven to be related), the generator began to cut out when the engine was running. Eventually, I determined the generator would cut out at no-load if I turned on the key switch to the engine - even if I did not start it.

I'm guessing that generator was fuel starved when the engine fuel pump turned on to prime the engine. I checked the generator fuel line and found a slight vacuum between the generator fuel pump and the generator injection pump - supporting the starvation theory.

So, I removed all the various filters and ensured the fuel was free to flow - same problem. I replaced the filters - ran the generator but not the engine for 30 minutes with the a/c on - all was golden.

Turned on the engine key and the generator quit.

Tried the same experiment with the engine fuel line crimped after it splits off from the common fuel line to the tank (foolish idea). The generator ran even with the engine key on - but with no fuel flowing. I could only do this for a short time because of potential engine fuel pump damage.

I can't believe I have 2 bad fuel pumps!

I can't find any air leaks, but there may be a leak that only develops when both fuel pumps are running?

Any ideas, please.
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Rosborough 246 LSV Shearwater V
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Old 25-08-2017, 10:45   #2
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Join Date: Nov 2016
Posts: 138
Re: Generator stops when key on for engine

Hello,

My first thought was that the bad wire you bypassed may have supplied power to another wire that runs to your generator. You write these by-passed wires are hidden so the only way to eliminate this possibility is to find the wiring diagram for your system.

But after reading your 4th from end paragraph, it seems the problem is fuel related. If I read correctly, either fuel pump will supply enough fuel as long as that pump is operating alone. I would guess it could be both pumps are bad but that is not likely.

More likely would be some constriction before the fuel splits off to both pumps. If each pumps uses 5 units of fuel, the pipe before the split must supply at least 10. If it is partially blocked and can only supply 7, then that is enough for one pump but not two.

The above is just a guess. What seems most strange to me is that the generator dies immediately when you turn on the ignition. Even if not enough fuel were to reach the generator pump, I would think the generator would run for at least a little while.

I would check for good fuel flow from tank until the split. I would also try to get the wiring diagram to at least eliminate the electronic side.

Good luck
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Old 25-08-2017, 19:01   #3
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Join Date: Sep 2007
Location: Delray Beach, Fl
Boat: 1998 Rosborough 246 LSV
Posts: 563
Re: Generator stops when key on for engine

The strainer on the tube that picks up fuel from the tank was partially clogged.

The inlet fitting to the generator fuel pump was leaking air when the engine was on.

I found 2 corroded connections on the generator ground.

Runs great now! Thank you
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