Generator lurching/chugging

[Depewtee]

Hi All -

I have an Isuzu 3-cylinder diesel 15KW genset (the generator is a Mecca Alte).  It has 500 hours on it and has to date not given me any troubles.  The last time I used it, several weeks ago, it had been running fine for about five minutes.  I turned both roof airs and went inside to wait for the bus to cool down.  When I returned outside about 15 minutes later the generator was still running, but it was lurching/chugging and not producing much power (I have not measured the output yet, but it barely lights a 40 watt incandescent bulb).  Over the last couple of weeks I have started it several times, and  every time it starts immediately and immediately starts the lurching/chugging.  I thought the fuel tank might be too low on fuel to supply the generator properly, but tonight I removed the supply line and ran it directly into a five gallon container full of fresh diesel.  The genset still lurched/chugged (interestingly enough, the supply line from the fuel tank kept flowing fuel so I had to cap it off).  Bottom line, I think fuel is getting to the engine.  I pulled the fuel filter and it looked brand new.  I will buy a replacement fuel filter tomorrow and see if that makes a difference.  I did a search of the board and the consensus was that problems with gensets are nearly always a loose or broken wire somewhere.  There are no obvious loose or broken wires, but I have yet to have time to research this further.  Another thought, this happened after I had washed/scrubbed the roof of the bus really well.  Is it possible water went into the exhaust (exhaust exits through the roof).  This is not likely, but I guess a possibility.

Tonight I shot a video of the genset lurching/chugging.  Any thoughts?  (sorry for the poor video quality, but it was dark outside.  The audio is really good though)

Genset lurching/chugging

Brian S.

[Len Silva]

It sounds like it might be sucking air.  Pull the return line and run it into a container to look for air bubbles.

If that's not the problem, then it could be a problem with the governor, sounds like it's hunting.

[Brassman]

Don't know if this has anything to do with your situation, but the engine sounds exactly like an improperly set electronic governor. Just from distant recall, but gain set to high can cause a barking hunt. If it is electronically governed  unplug and replug all electronic connectors (with all power supplies secured). Also, check the face of the speed sensor, clean, reset to proper distance from flywheel. My experience is with larger industrial machines, so none of the above may apply.

[Joe Camper]

I have a Kabota that WILL NOT BURN the ultra low sulfer fuel without lucas or some such additive.

Mine was doing the same thing and the only thing I did that worked was additive.

[TomC]

It is lurching at a relatively constant rate.  And since you said it isn't lighting a 40watt light, it sounds like a relay or circuit breaker in the alternator is clicking in and out. Try turning off all circuit breakers and see it that does anything.  That lurching isn't that bad-but of course it shouldn't be doing it.  Try running a gallon can with additive in it like Joe said.  Good Luck, TomC

[robertglines1]

bleed injectors?

[James77MCI8]

Check the air filter and the fuel filter. Is it smoking(black)during the lurching and chugging?

[Sean]

I went over to Brian's place this afternoon to look at the genny.

Unfortunately, I do not think is is as simple as a fuel delivery or air induction issue.  I am hearing metal-on-metal clanking deep inside the engine.

I believe the slapping is coming from the injection system.  Isuzu uses individual mechanical unit injectors operated by a rack, and the rack is controlled by an electric solenoid.  With the solenoid power off completely, I can rotate the crankshaft through 960° by wrench (which should be all four strokes on all three cylinders) without encountering any mechanical obstructions or clunking.  So I do not think the crank, pistons, or valves are hitting anything.

I did not have time to apply power to the actuator while turning the crank, which might provide some additional insight.  That would have to be done with the fuel supply disconnected.

Neither did I think to disconnect the actuator power, then crank the engine around with the starter, which might also have provided some insight.

Does anyone here know the intimate details of Isuzu's rack system and injector pistons?  I spent quite a while hunting for them on line, with no success.

-Sean
http"//ourodyssey.blogspot.com

[robertglines1]

after listening to video...it doesn't sound like engine noise the rpm and noise don't match.surging could be engine coming under uneven load..like a coupler engaging and dis engaging. don't know your set up between engine and generator...a sheared key or slipping elect clutch could be making sporadic engagement..Sean has the advantage of being there...but listen and see what you think about engine rpm and noise sequence..please post final outcome...only a stab in dark..good luck      Bob  Post thought?starter still engaged???

[junkman42]

Brian, try cracking each injector line at the injector's one at a time with the unit running.  The result should tell You which cylinder or fuel pump is causing trouble.  If no difference between cylinders only the shadow knows but isolating the cylinder will help!  The washing of the roof and the malfunctioning genny may not be a coincidence.  Try checking each injector and report, if You would like to talk call Me I live north of You in Laurel Hill.  eight50 six five 2 2800.  John L

[Depewtee]

Thanks for all of the replies.  There is a definite metal on metal sound coming from within the engine.  It sounds like it is coming from the "front" of then engine - the end furthest from the generator.  I called the closest Isuzu authorized service center (located in Mobile, AL) and they "may" have someone coming through this area within the next two weeks. I am awaiting a call back to confirm.  If not, my other option is make the 2 1/2 hour trip to Mobile.  The service manager seemed reasonably familiar with the engine, but admitted they have not worked on many of them.  He quoted a shop rate of $85.00 an hour with a likely 2 hour time frame for diagnosis.  No word yet on how much the service call charge would be if they come here.  I will keep everyone posted.  If anyone is familiar with this engine and these symptoms please chime in.

Brian S.

[Len Silva]

Not much help here but I did find they have a 5000 hour/5 year warranty.
http://www.isuzuengines.com/

[Depewtee]

Len,

I saw that some engines have the 5 year, 5,000 hour warranty, but all of my paperwork states that mine has the 2 year warranty.  Original purchase date on the genset was January 2006.

Brian S.

[robertglines1]

Brian,where your at there are a lot of marine repair places..A lot of boats have simular units..might be worth a ck..Would be better if it were warranty!

[James77MCI8]

Is the crank and camshaft coupled via gear train or chain. If it is chain driven it or the sprockets could be worn. If gear driven the gears cold be worn.