iDRY Vacuum Kilns

Sponsors:

my LT 40 idles fine, quits when cutting

Started by chassawyers, February 28, 2006, 07:43:08 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

chassawyers

My first post!  Been cutting since 97 and made a few boards in that time.  I have been having problems with excessive fuel use and smoke and so had the mill checked out  by the local Onan service rep.  He say I need a new carb - 375 bucks please.  I get it home and it purrs like a kitten (his words).  Pull the lever to start cutting and the Onan dies with a bang!  Repeat performance many times.  Return to dealer and he say needs new plugs - 47 bucks please. ( I had done all the fuel system checks prior).  Get it home and saw for a few hours and it starts quitting again. 

I would think a jet effecting high speed operation, he say bad plugs, or maybe carbon on the heads.  Compression good.  Fuel good.  Never had problem before new carb.  It did run after new plugs!  Soooooo, do I need new plugs again, after about 6 hrs operation time?  I put in Lucas UCL to remove carbon.  What yall think??

Tom

I think that if it is carbon, the only way to get rid of it is to pull the heads off of the jugs and scrape the stuff out.

Water in the fuell will act like that too.

Even if water isn't a problem, you will benefit by installing a glass sediment bowl, or the like, somewhere in the fuel line where you can see it.

Minnesota_boy

That sounds like an accelerator pump problem or a jet that is plugged.  Can you increase the throttle slowly with no load and have the engine rev up?
I eat a high-fiber diet.  Lots of sawdust!

Pete J

If I were to guess. See if your fuel tank is venting properly. If it idles fine but then really needs to suck fuel to cut, it might be starving. Same thing can be said of your carb vent hose. Check that it's not plugged.

isassi

If it's got gas and it's got fire, it's bound to run. Simple words, but oh so true in gas motors. After checking what was mentioned above, it leads back to insufficient fuel flow for the load or fuel starvation, period. Not plugs or wires or points...just fuel. It sawed ok for 4 hours, then a repeat of the previous problem...you had a condition change within the fuel system. Might have some water in the fuel tank that finally got to the carb. But I would guess you had some debris shake loose and lodge in a main jet or in the needle valve, affecting the float height....to me that fast that it ran ok for a few hours means the Onan guy installed the new carb correctly, but something else is now affecting your fuel flow. It isn't unheard of to have casting sand in the carb break loose after awhile and cause that problem. Good luck

getoverit

I had a car once that did the very same thing as you are describing... it drove me nuts for weeks. I got so mad one day that I threw a ball peen hammer at it, hit the coil when it hit, and it started right up. Seems the coil opens up when it gets hot while running??

replaced the coil and never had any more problems.

By the way, someone gave me their onan engine off of a woodmizer... its a T260G (24hp)engine... I went to onan (the only people you can buy parts from for it) and told them I wanted it rebuilt. They told me it's cheaper to buy a short block... got a price on the short block of $2,750 (not installed, just the parts)... no thanks, I'll buy another engine, and you can bet your sweet a&& it wont be an onan!
I'm a lumberjack and I'm ok, I work all night and sleep all day

Minnesota_boy

www.smallenginewarehouse.com has good prices on some engines.  I got the Linamar (Onan) from them to replace the engine on my mill.  Give them a call and ask about the availability of Onan parts.  They may become your new Onan service center.
I eat a high-fiber diet.  Lots of sawdust!

isawlogs

 Have you called your WoodMizer rep about the trouble you are having , I have called them a few times with head scratchers and they have come trough with answers to the problem . Actually they are the first I call when something comes up on my mill that I cant figure out .
A man does not always grow wise as he grows old , but he always grows old as he grows wise .

   Marcel

KnotBB

It sounds like a car with a bad fuel filter.
Try changing the fuel filter if it has one (and as stated before, add one if it doesn't).  If there's water in the system it should have stopped there.  Check for kinks in the fuel line that might be causing a restriction of fuel flow.   Might try running some "Heet" with the gas to clean out any water present.  Might try changing the fuel line.  They can deteriorate and act like a flapper valve. 
Steve

To forget one's purpose is the commonest form of stupidity.

logwalker

Am I missing something or did you say $47 for plugs. They are a $3 item and you need two.

I am leaning toward a carb running to rich. If this was the case the plugs should be very dark to black (soot). That would explain why the engine runs for several hours after changing them. 

Did you check your air cleaner in the beginning? A dirty one would cause the original symtoms.

I would go back to dealer and seriously kick some tail. The first carb was possibly good. The first plugs were likely fouled by the new carb and then he had the gall to charge you $47 bucks to do it again.
You seem to be charged a lot of money with very poor results. Who is this guy so I can avoid him.
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

jpgreen

Just a note..

Onan's becoming a dieing breed in IMO. You can't buy a new one in the USA anymore because they are non EPA compliant. 

With that in mind, soon parts are going to dry up also, may take some time but it will happen.
-95 Wood-Mizer LT40HD 27 Hp Kawasaki water cooled engine-

scsmith42

I concur with Logwalker.

1 - check to see what your plugs look like.  If they are black, then your problem is probably that it's running too rich.  This could be a clogged air filter, or sediment from the fuel line that is blocking the needle valve.

Rather than replacing the plugs, bead blast them and reuse them.

If the plugs are not black, but are white, then I'd agree with KnottBB's suggestion about fuel starvation.

Carbon on the heads can be cleaned off by pouring water SLOWLY into the carb at high idle or fast speed.  Run a few gallons through over the course of an hour or so.  One easy way to do this is to install a small orfice (say around .050) into the end of a piece of rubber tubing, and then place this in the carb inlet.  Run the hose to a 2 - 5 gallon tank and gravity feed it after the engine starts.  The water will turn to steam and do a super job cleaning the inside of the motor.  It won't hurt it as long as you don't go too quickly; water injection is commonly used on racing motors and it keeps them super clean.  I seriously doubt that your problem is excessive carbon though.

If you have dark plugs, there is a chance that you have a weak spark, and it's blowing out at higher speeds when the combustion pressure is higher.  This is a typical sympton of a weak coil.  Onan's have a bad reputation for coil failure, so one other option is to replace the coil.

Good luck, and let us know how the troubleshooting goes.

Scott

Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

Danny_S

that sounds like a guy I know from school, idles fine but when he starts to work he quits.... :D  :D  :D
Plasma cutting at Craig Manufacturing

highpockets

I'd sure look at coil problems.  Another thing I have found out is non resistive plugs seem to do better than some of this other stuff.   My guess is that the onan guy went through the fuel system, rusty tank, clogged filter, etc.   
Louisiana Country boy
homemade mill, 20 h.p. Honda & 4 h.p. for hydraulics.  8 hydraulic circuits, loads, clamps, rotates, etc.

Slabs

Do you have the marine-type fuel line to tank couplers?  I have seen the seals in the coupler go bad and the fuel pump pulls in air and starves the engine under load.  I have also had some success in replacing the seals(O-rings).
Slabs  : Offloader, slab and sawdust Mexican, mill mechanic and electrician, general flunky.  Woodshop, metal woorking shop and electronics shop.

D._Frederick

Make sure that the vacuum operated fuel pump is operating correcty. May be the hose to it is bad or the seal on the tip-stick is gone.

woodmills1

my Onan has 3400 hours.

Carbon build up caused a symptom that sounded just like a rod knock untill I localized the sound as higher up in the case using a hose like a stethescope.  Did the water trick by dribbling it out of a soda cap while motor was on high revs.  Please remove the blade if you do this :o :o. that was at 800 hours.  around 1000 I got a can of onan decaronizer and used it according to directions.  So much smoke and particles came out of the exhaust on restart that my wife actually left for work early thinking I had blown the motor and would be a bear for the rest of the day. :D :D.  Have used mid grade gas since the 1000 hr mark with out a repeat need to remove the carbon.

Had the bad carburetor problems that showed the symptoms of uneven running just like a surge.  The the think would not stay at constant rpm with the governer trying to stablize rpm but moving in and out causing a fluctuation in rpm at idle and speed.  Had the carb rebuilt by a local shop for less than the kit cost from woodmizer.  3 days after rebuid it started again so I took off the top of the carb and found massive amounts of small rust particles in the bowl.  used paper towl to get most out then blew clean with air.  Flused the entire fuel system and started with fresh gass in empty buckets with no problem since.   No longer use any metal gas cans, all plastic now thinking they were the source of my problems since 2 of the chain saws were showing fuel contamination problems also.
James Mills,Lovely wife,collect old tools,vacuuming fool,36 bdft/hr,oak paper cutter,ebonic yooper rapper nauga seller, Blue Ox? its not fast, 2 cat family, LT70,edger, 375 bd ft/hr, we like Bob,free heat,no oil 12 years,big splitter, baked stuffed lobster, still cuttin the logs dere IAM

chassawyers

I dont know if it would be Kosher to point my angry misused finger at PCS Power in Bosier City, Lousiana about his charging to fix work already fixed, ie, $47 to replace plugs, even though it was my third trip towing the mill 140miles round trip($50 gas/trip).  I guess I should not mention Rock specifically as I already did that in a three page letter to Onan regional.  So I will not.

I did not mention I cut wood for 5 hours just before taking it to be serviced?  I sprayed a bit of wd40 into the intake and that seemed to help?!?!?  I have turned a wernch more than a few times and this Onan is more than a bit strange.  I get you all when you suggest I consider a different brand on replacement.  I did all the fuel system checks stuff.

You guys are great!  Thanks for the time and ideas.  I was turned on to this site by Denis of Orange, tx and it is excellent because of you all.  Thanks...charlie  (and the water trick is my next move).

Fla._Deadheader


I've used a spray bottle, like a Windex bottle, to mist the water into the carb. Too much water MIGHT hydraulic the piston and bend a rod. Just be careful.
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

logwalker

The only real good clue is she ran fine for five hours after plug change. That eliminates the fuel system. But not  the coil. Pull those plugs and tell us how they look. They should be a nice light chocolate. I always used the plugs as my first diagnostic tool.
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

SPIKER

Lots of good replys the water trick works best when engine is warm (cold water on the hot carbon causes it to crack off & be blown out.)   now I agree with one posted who said that the fuel HOSES can cause similar symptoms especially the going out with a bang under load.   as it needs MORE fuel it sucks open a tear in the hose side and that causes a small flap of hose to pull out aginst the other side and it is basically6 sucked shut.   braded hose helps prevent this but teflon is much better.   fuel filters can cause it to run fine while ideling and run afor a bit then die usually it will surge or reve up faster as it get leaner, ...  check the plugs for sure right after it does this if HOT & WHITE then it is goig lean on stoping.

check for leaks around base of carb @ gasskets using WD40 to spray on them which acts as a temp seal.


not sure if I acn add anything more to what others said other than ouch for the prices you have to pay to that guy who was susposed to FIX it.

Mark M
I'm looking for help all the shrinks have given up on me :o

wiam

I have been told not to bead blast plugs for small engines by my small engine guy.  He  says that any blast left in the plug can destroy a small engine quickly.

Will

chassawyers

As a guy that  types like a pirate looks dancing with two wooden legs, I really appreciate all your time and key pokin.  Thanks everybody.

I spent the day making sure all the fuel lines are suckin only gas.  Did the water thing with a mister bottle.  Put Lucas YCL in the gas.  Let er run about 3-5 minutes and she will die after 5-15 seconds every time.  I think it is coil time.  I have a spare and will swap it out tomorow. 

scsmith42

Re bead blasting the plugs, it's ok to do as long as you use high pressure air to blow out the beads that get caught between the insulator and the steel body of the plug. 
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

GlennG

My stump grinder did this last summer, turned out to be a cloged fuel filter. I removed the filter and flushed it out with a water hose. Lots a black crud came out.

Mine would idle fine then die under load , it would restart after a 1 minute rest.

good luck
Glenn

Thank You Sponsors!