I have a Generac 4000EXL that I cannot get to run properly. Its about 7 years old and has not had its wheels ran off. It has had regular maintenance done as well.

Just recently it has started to run on half choke, full idle (hope Im describing that correctly). It will not run if the choke is off.

My husband is a mechanic and he removed the carburator twice and cleaned it thoroughly and did not find any gunk, gum or junk it it. We also drained the gas tank and replaced the fuel with fresh 100% gas, no ethanol. It still refuses to run on anything but half choke.

I need some suggestions and ideas on what to check next. I have heard that there is some sort of sensor somewhere that could be bad that is making it run like this??

Thanks

We are getting adequate fuel to and through the carb. There are no blockages in the carb. The screen at the fuel switch/sediment bowl have been cleaned out several times.

Could a week motor be causing this? What about a vacume leak??

Half choke means the carb is set to deliver a rich gas/air mix.

Some thoughts;

You have a vacuum leak that is letting in air after the carb.

The carb is not delivering enough fuel through the main jet.

you have a dirty/clogged air intake/filter that is leaning out the mix using the main fuel jet.  The engine will start and run but not run to a full load. 

The 4000exl has a solenoid to run the engine at half speed when there is no demand.  Is this working correctly?  If it is stuck in the half speed position it might be throttling the engine.

Yes, it was immersed in carb cleaner. All the passages was blown out and the main jet was cleaned out with a small wire.

Where else could a chunk of gunk be hiding that could lean it out so badly?

THe intake gasket hasnt been checked yet. That is next on my hubby's list.

Air filter is not missing and not clogged.

Thanks

The solenoid is working properly per my hubby.

This gen has worked on a load running at half choke. I ran it for several hours running my A/C, lights and water pump and did not realize it till after several hours. This only occured last year and it has ran fine until now. We ran it for 4 days last December during the ice storm when we lost power, it ran like a champ, but when we got it out this spring to run on the LQ, it was running on half choke. I havent really needed it until now.

I will not use it untill it is running properly.

Sounds like it is sucking air somewhere - you will have to check the gasgets to make sure thery are in good shape. Another possable problem could be a burnt exhaust valve. If the exh valve is leaking it sends some of the exhaust fumes back into the combustion chamber, thus leaning out the mixture (that's why it runns on 1/2 choke). I would sugest doing a compression test on the motor... that will tell you if the valves are still ok.

Good luck

Barfly - Sunny South Africa

Check the needle and seat and the be sure the float's not hanging up.... getting caught on the side of the housing or a catching a gasket. If the float's not dropping down, then the needle's not dropping off the seat.....Maybe a little but not by much... Poor gas flow into the bowl.

 Runs at low idle, runs with choke on at high idle, starves for fuel and shuts off when load applied?

Check the fuel shuttoff valve for restrictions. Blow out with high pressure air stream.

The fuel shut off valve has been checked and is clear.

Doesnt run at low RPM/low idle. Only runs at half choke/high RPMs. This is with or without a load.

debugging this on the internet is difficult...:D

IF you eliminate air leaks et cetera

Then as a last ditch before taking it to a small engine mechanic...run a tank with this thru it...

http://www.webbikeworld.com/sea-foam/

UPDATE~~~~~~~~~~

We have had the carb off again. The main jet is clear as are all the passages. The gaskets are good and not drawing air. Getting good air flow into the carb and getting good fuel flow as well. There are no adjustments that can be made to this carb.

My husband was messing around with it last night and discovered with putting the idle control ON and then manually messing with the choke, he could get it to idle down and not run on half choke, but it still refuses to run on no choke.

I called Generac and told them all I have done, they dont have any answers as we have done everything that they would have suggested.

They refered me to a dealer for repair, its 2.5 hrs away (one way)

My husband got to thinking that maybe the spark plug could be the issue? Is it possible for the gap to be too wide causing it to not run unless its on half choke? He is thinking that a half choke would mean more fuel and easier for the spark to ignite, no choke would be a lean mix and a wide gap would not be able to ignite?

Could this be possible?

You have ignition as proven by the fact it's running when it has enough gas. A weak ignition system would result in a low rpm and power, and as additional fuel was added with the choke, the motor would slow and smoke by burning excessively rich with the unspent fuel. It would also be very hard to start.

One thing you can consider is the ignition timing. If your motor has points and a condenser type of ignition system, instead of the newer solid state units, it is subject to wear. Very few people grease the cam on the point's rubbing block. As it wears, the point gap and dwell will change, retarding the ignition, with a loss in power and engine smoothness.

Another problem is when condensers age, they loose the capacity to properly charge the primary circuit when the points are opened. This  results in a reduced power or even a no start. The points will burn, and once again the dwell and timing are affected.

As many previous posters have stated, they believe its a clogged jet or a limited fuel supply, because it will run using the choke.

On some carbs, there are metering jets installed in the drilled passages behind core plugs. If these plugs are not drilled and removed, you cannot gain access to the jets, either for cleaning or removal. Your carb should have at least two jets, one being an idle circuit, the other a main metering jet. Most engines that are run at a continuous RPM, don't have a third jet that are typically used at midrange, during the acceleration cycle. If there is a core plug in the carb body that was not removed, it may contain a jet that was not cleaned of spoiled fuel and varnish.

Another fuel problem may be one of supply. You mentioned that there was gas coming from the line. Was it an adequate supply? Did you have a flow limited by the fuel line diameter, or was there some dripping from the end? Some fuel systems have filters on the pickup lines inside the tank. If your fuel system was not treated with a gas stabilizer last fall, these filters can be subject to gunk and varnish and plug up as well.

Another problem to check is the age hardening of the rubber fuel lines. Depending on the quality of the rubber line and its age, fuel lines can become crushed inside and close up, while not being visible on the outside. Again the fuel flow from the open line will determine if this is a concern. If a rubber line has aged, it can crack, especially at the fittings. This may cause a loss of fluid, or allow air to enter, depending on its usage.

Another consideration is the air inlet. Any restriction here, will result in the type of symptoms your engine exhibits. This can be found in an air filter, a filter housing, a preheater from the exhaust manifold, a crushed fresh air inlet hose, anything that limits the amount of air your engine needs to run at full throttle.

Just some thoughts   Gard

I feel your pain with the Generac. I had a built in one on my last LQ trailer that only had 400 hours on it and was the biggest piece of junk I've ever owned. I spent countless hours working on it and many hundreds of dollars at the nearest RV reapir shop and even at the Generac dealer and service shop in Evansville, In.

If I had kept that trailer, my next step would have been to take the thing out and toss it in the Ohio River and then put an Onan in it's place. I had already priced that option at $2700 installed.

A guy made me an offer on the trailer before I could get that job done. I loved that trailer, the only reason I got rid of it was because of the darn Generac and all the trouble it caused.

I have a friend with the same generator in his trailer, he is going to take it out and put in an Onan.

Just take it as a life lesson learned and chuck the thing. You'll sleep better.

I think that is what we are going to do. I found one at www.jackssmallengines.com for about $38.00. They have all the gaskets and new air filters as well. Im going to have my husband order all that from them, hopefully tomorrow.

I hate to hear you had so many problems. This is the only problem we have had with it and it started last year and was intermittant. Its been a good generator for our use. If I was going and staying in the trailer every weekend or so, I would have a better generator.

We bought this years ago before an ice storm and before I had a LQ trailer, but bought it large enough for when I did get a small LQ.

I hope we get this one working till I can save up the money for a good one.