I have an onan microquiet 4000, model 4kyfa26100k, that wont start. This unit is on a horse trailer that we just purchased. The people we got it from assumed it ran out of gas. So seeing as we got a good deal, we bought it. Its not out of gas. Has good fuel pressure, has spark, I changed the oil, air filter, removed carb and inspected and I even tried to fire it off of ether. It just cranks. Anyone have any ideas on this. I would rather fix it myself but dont want to throw money at it. Thanks

 

When you say it ran out of gas, do you mean gasoline or propane? If it is propane, push the start button down firmly instead of up. It will crank and prime it simultaneously. Don't crank continuously more than 10 seconds. Let it cool, then try again. Might take four, five or my tries. If it is gasoline, all mine had a prime lever or button on them to push while trying to start. This can happen if it has not been started for a while.
Bob

 

It is a gas engine. The fuel pumps work fine when it is primed and there is plenty of fuel pressure at the carberator.

 

try changing the plug some times a bad plug wont fire under compression . you can pull it out and see it spark out side the cylinder but could still be bad . cheep place to start

 

I must have forgot to metion that i did change the spark plug. That was one of the first things i did.

 

Have you checked the gas and made sure the carb has no water in it?

 

yep. did that too. actually took carb off and made sure it was clean and open. Didnt find any water.

 

Ok, if it has spark, as you claim, and it won't fire using ether, it doesn't have spark with the plug installed. Either that, or the ether isn't getting to the cylinder, suggesting a blockage in the air intake tract.

Since you have covered most of the bases, check the valves and actuators. and do a compression test. I am thinking that perhaps the intake valve is not opening, therefore not allowing mixture to the cylinders. All the fuel, spark, and compression in the world won't make any difference at that point.

The other side of the coin, how is the exhaust? is it perhaps partially blocked or otherwise horribly restricted? Not allowing airflow through the engine, causing it to not start.

Check it out

 

Thats a good idea. As far as the exhaust, I did pull the plugs out and then crank it over. It seems fine. I dont think there is any blockage there. I know there is a low oil pressure switch, and a control circuit board. Either one of them could be bad also. Just wanna pinpoint it a little better. I will check the valves and make sure they are functioning. I dont think I cant get a compression guage on it considering where the plug is at.

 

There could be a secondary on/off switch for the ignition that is in the off position.

 

Not sure if you fixed your problem yet but mine was just having the same problem. Pulled the carb apart and found the float in the fuel bowl had a small hole and was filling with gas. Replace the float and solved the problem.

Swyped from my Nexus 7 using Tapatalk 2.

 

wow, forgot i posted on here about the onan. I finally got the unit running, ended up working on valves and replaced fuel shutoff solenoid. It was kinda messed up. Anyway the last few times i have started it in will only run for 5 to 7 minutes. Runs like a top for that time though even under load. Oil level is good. Friend thinks its the cpu but thats a $350 guess. Any ideas? I am ready to be done with this project.

 

Coil or condenser get hot and stop working.an exhaust valve could be sticking ;they will do that.It is a good idea to run mmo in your gas to keep the valve from sticking.Might be a good Idea to put in a new head gasket and decarbon the cylinder and exhaust valve.BTDT

A good carbon test is to run it half wot and spray in a water mist into the carb.if you get lots of witesh smoke you have a bunch of carbon. Use a good spray and flood the engine and let it stop. waite a few minutes and do it again till the smoke clears . I have done that on a few engines and it make a big difference in how they run.

 

Thanks for the info. I ran it again this morning and it ran for 7 1/2 minutes and then died. It will not restart after it dies. Oil level is fine. I felt that it was overheating just didnt know what to look at. So I will try the coil/condenser and see what happens. Good idea on the mmo also, havent used that stuff in a while. Thanks for the info.

 

One thing you should look at is the vent for the gas tank. Make sure it is working.