If your Generator has surging or hunting problems that can be traced to the fuel system, the root cause is probably not a warrantable failure. Component failures due to Fuel Varnishing are not covered under warranty.

If the Generator is not operated often enough to run a number of gallons of gas through it every month, it will start to develop Fuel Varnish. Emptying the tank will not prevent varnishing, because a small amount of fuel always remains in the gen-set fuel system, ie the carburetor. A slight decrease in efficiency can have a huge impact on performance. The generator may start but sometimes will surge or hunt at various loads. It will surge or oscillate between acceleration or deceleration of the engine speed, and never settle on a certain operating speed. Speed affects the output voltage so any surging greatly hampers the gen-set from providing stable electricity.

See your operator's Manual under the section "Generator Set Exercise", it states the set should be run with at least a 50% load (AC ON) for two hours every four weeks.

Onan also recommends the use of a Fuel Stabilizer (see Fuel Stabilizer)

The Hour Meter is normally located with the Remote Start Switch inside the living quarters. The Hour Meter displays the number of hours the Generator has run. The Hour Meter can not be re-set. If you replace your Generator, you should replace the Hour Meter so it will register the correct number of hours the Generator has run. The Hour Meter is also used to determine when maintenance should be done, for example: when to change the oil.

http://www.cumminsonan.com/locator

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Fuel varnishing is a gummy residue that clogs the generator carburetor and fuel pump. It's caused by the deterioration of fuel that sits in the engine too long. Depending on fuel quality and storage conditions, gasoline can deteriorate in as little as 30 days. As long as you refuel frequently with fresh gasoline, and exercise the unit regularly, fuel varnishing is less likely to occur. But if you leave the same gasoline in the tank for several months, you're very likely to have problems.

The only way to prevent fuel varnishing is to treat the contents of the tank supplying fuel to the generator with a fuel preservative, and to exercise the set. Onan has developed a fuel preservative and stabilizer, OnaFresh (TM). Onan recommends adding this preservative to the fuel, especially on infrequently used Generators.

Once varnishing has occurred, adding a preservative will not correct the problem.

Onan offers a "Premium Fuel System Cleaner" for use with its generators.

see also, FAQ >> Generators >> READ THIS FIRST, VERY IMPORTANT

"Sea Foam" in my opinion, works excellent and can be purchased at you local parts store , - and I've also seen it at Walmart.

Well, you had to ask

87 Octane, Minimum.

Onan says your gas generator will use 1/2 gallon of gas per hour of operation. And that would mean more or less in a Load or No Load status.

It was said, that if you use 89 Octane you Generator would be 33% more efficient. Which means instead of using 1/2 gal per hour, it would use 1/3 gal per hour, which is less than 1/2 gallon.

This is one example of a secondary Fuel Pump location for a Roof Mounted Gas Generator. This Fuel Pump in located in the Rear Tack. Another popular location is under the trailer, behind the axles between the I-Beams or cross members. There's normally a plate you have to remove to access the pump.

Attachment: 

The Primary Location for the Fuel Pump
The primary fuel pump is located in the Generator Compartment. Just follow the fuel line and it should lead you to it. The fuel pump can be replaced without pulling the Generator out of it's compartment. The Solenoid and the Power Board have to be removed to get to the fuel pump. It's not very difficult.
_________________________________________________________________________

The Prime Button is the same Button you use to Start/Stop the Generator. Pushing down on "Stop" will start the Priming of the Generator. Sometimes it's noted on the Button as 'Stop/Prime. As seen in these photos, it does not say Stop/Prime, only Stop. But the function is still there.

** Photo A shows the status of the Switch when the Generator is not running.

** Photo B. When you push down on the Stop Side of the Switch, the small Light comes on showing you that Priming has begun. Hold it down for the count of 10 to 30 seconds.

** Photo C. Push the Start side of the Switch down for a count of about 10. If it does not start, prime it again. It may take 2 or 3 times if it hasn't been started that day or if it's cold outside.

Note: If the Generator does not start, see Generator > Troubleshooting > Onan Gas Generator Won't Start

** Photo D, Generator is running and the Light is on. If the Generator stops the light will go out.

Note: See also the Hour Meter. This tells you how many Hours the generator has run, - and it's also a good indication of when the next Oil Change is due. Change the oil after the first 25 hours and every 175 hrs thereafter.

Attachment: 

On a new Generator change the Oil after the first 20 hours. Reference the Hour Meter at the Start/Stop Switch.

Change the Oil and Air Filter every 150 hrs thereafter. The MicroQuite holds 1.6 qts of Oil. The Oil Drain is in the middle, on the bottom side. Above freezing, 30 weight oil is recommended. There is not an Oil Filter on the MicroQuite.

Spark arrester or muffler. Clean every 50 hours. Remove 2 plugs, start engine and run for 5 min. and any debris will be blown out. Replace the plugs once it's cooled down.

Replace the Spark Plug, Fuel Filter every 450 hrs. In an emergency, use a dime to check the spark plug gap.

Adjust Valve Lash and Clean or Replace Cylinder Head every 450 hrs, by an Onan service center.

The Onan 4000 MicroQuite has no Oil Filter. It uses an 1/8 of an ounce of oil per hour as part of the cooling process, so check the oil at least every 8 hours.

There is an altitude adjustment on the Carburetor. Power from the Generator decreases as altitude increases. It maybe necessary to run fewer appliances (at the same time) at higher altitudes.

There is NOT a Low Oil Shut off or a High Temp. Shut Off, unless you know for a fact these features are on your unit.

If you notice oil in the air cleaner (breather) housing, this might be caused from Blow By from the OHV that feeds back to the Air Cleaner through a hose. You can pull the OHV cover that has about 7 screws in it and replace the breather valve and gasket. Onan Reed Valve # 123-1920 - Gasket # 110-3860

Popular Onan MicroQuite 4000 watt or 4K Generator

Attachment: 

Onan 4,000 watt or 4K, Microquite Spec K, ID Tag

Attachment: 

Always, the Generator should be first on and last off.

You can find the starting procedure in the Onan Operator's Manual, or if you don't have it do the following.

1. The Generator will start easier if Large Electrical Drawing appliances are off like the Air Conditioner, Microwave, Electric Skillets, Electric Hot Water Heaters, Curling Irons and Hair Blowers.

2. If you're starting the Generator for the first time of a day, at the Start Button, push the Prime Button down for the count of about 10, and then push START for about the count of 10.

3. If it doesn't start, hold the Prime down for about 30 seconds, then the Start for the count of 10.

4. You may have to prime again, but the Generator will usually start after two or three priming cycles. The indicator light will blink while trying to start and once running the indicator light will glow constant. ( see, Generators / Priming )

5. If you hold the Start button down for a long period of time, the starter will get hot, quit cranking and the Status Indicator Light will blink a Fault Code 4. You then have to wait for the starter to cool down before trying to start it again. Onan says the Generator will shut down after 15 or 20 seconds of cranking if it doesn't start. I think it is best not to get the starter hot to the point where it quits trying to start. ( see also, Generators / Fault Codes )

6. Once the Generator is running, wait till you're sure 110 volt is present before turning on any heavy load appliances like the Air Conditioner or the Microwave. A good indication 110 volts is present, - the Microwave Light will come on.

Note:
You may notice that once the generator is running you don't have 120 Volt AC electricity immediately. Depending on what kind of ATS switch there is, it may take 60 seconds or so for the switch to connect.
(see also, FAQ > Electrical > ATS Switch Defined )

7. Make sure your Carbon Monoxide Detector is working properly inside the Living Quarters. A Carbon Monoxide Detector does have an Expiration Date, so periodically you will need to install a new one. The Date is usually printed on the Detector.

8. Turn off all heavy load appliances ( A/C and Microwave ) and let the Generator run for a couple of minutes to cool down before shutting down the Generator. This reduces back firing and run-on which increase the life of the Generator.

9. If the Generator is running and you have no 110 volt AC present, check the Breaker at the Generator.

Note: In a lot of cases, the 4,000 watt gas or 3600 watt propane Onan will not run the Air Conditioner and Microwave at the same time. Since the Microwave is only needed for a few minutes, turn the AC off while you're using the Microwave, then turn it back on.

Photo A shown with the Door off. You don't want to run the generator for very long with the compartment door removed. It causes improper air flow which effects cooling.

Photo B is where you check the Oil. This unit uses approx. an 1/8 of an ounce of Oil per hour as part of the cooling process. Check Oil regularly.

Photo C is the connection for the Remote Switch located in the Living Quarters if so equipped. This connection services the Start/Stop functions as well as the Hour Meter.

Photo D is the Spark Plug.

Photo E is the Power Board or Control Board. This is the Computer / Brains of the Generator. If this part fails, the Generator will not run.

Attachment: 

Unless noted, these parts are for the Popular Onan MicroQuite KY, Spec J & after

Operators Manual - for the 4K Onan Gas, 3600 Watt LP - Spec KY - part # 981-0147

Ignition Coil - 4K Onan MircoQuite - Onan # part # 0166-0866

Spark Plug - 4K Onan MicroQuite - Champion RN14YC, Onan # 167-0275
Spark Plug - 2.8 K Onan Microlite - Champion RS17YX

Carburetor, Gas - MicroQuite - from Camping World - SKU # 25009
Carburetor, Gas - MicroQuite - Onan # 0146-0785

Air Filter - MicroQuite - Onan # 140-3280

Fuel Filter, Secondary - NAPA # 3031 > CarQuest # 86031
(this is just a regular fuel filter between the fuel tank & the generator)

Breaker Switch at Generator, MicroQuite - Onan # 0320-1323

Fuel Filter on Engine at Pump, MicroQuite - Onan # 149-2457

Fuel Pump at Engine, MicroQuite (also used for the Secondary Lift Pump) - Onan # A029F889 or AO29F887
( this is the newest Onan Pump and replaces all older pumps, Example Onan # 0149-2311-01 or 02)

Main Power Computor Board - Onan # 327-1413 ( replaces 300-5046 )
( see photo - FAQ > Generators > Photos, Onan Troubleshooting > 4000 KY Gas............ )

On a New Guardian Generator, change the Engine Oil and Oil Filter after the first 25 hrs.

Every 100 hrs thereafter, change the Engine Oil, Oil Filter, Air Filter, Fuel Filter and clean or replace the spark plug.

Oil Capacity is .84 US Quarts. Summer months use SAE 30 or SAE 10W-30. Winter months use SAE 5W-30.
DO NOT USE SAE 10W-40

Run the Generator 30 minutes under load (with AC on) twice a month.

http://www.generac.com/Service/DealerLocator/

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1. Large Electrical Loads like the Roof Air, Microwave, Air Dryers and such should be OFF before starting the generator. You're not going to tear anything up, it's just easier on the system and could prevent a breaker from tripping.

2. If the Generator is cold you'll need to Prime if first. The Prime button is on the Remote Start Switch inside the LQ and/or it's on the Generator. Hold Prime down for 10 to 15 seconds then Press Start. If it doesn't start after 10 to 15 seconds, Prime again.

3. Once the Generator Starts, let it run for a couple of minutes to let it warm up before you turn on a heavy load like the Roof Air.

Note:
You may notice that once the generator is running you don't have 120 Volt AC electricity immediately. Depending on what kind of ATS switch there is, it may take 60 seconds or so for the switch to connect.
( see also, FAQ > Electrical > ATS Switch Defined )

4. Before you turn off the Generator, turn off any heavy load appliances like the Roof Air and let the Generator run for a couple of minutes to cool down.

I'll see if I can find the answer

In the back of the Guardian Owner's Manual there is a troubleshooting guide.

1. The Guardian has a Low Oil Shut Off. Check the Oil. It will not start until the safe oil level is obtained.

2. There is also a High Temperature Shut Off. You might try giving it more fresh air or park in the shade. Maybe the Sun needs to be on one side of the trailer which puts the Generator on the shady side. Do not remove the generator cover and let it run for a long period of time, this will cause improper cooling.

If it's mounted in a Manger, open the Manger Door to give it more fresh air. Check to make sure nothing is blocking the way the generator gets air. For Example, the Manger door is vented but someone has put something over the door blocking the Vents.

You might try to start it first thing of a morning (coolest part of the day) to see if heat is the problem.

3. If it won't start, won't even turn over; Check the Battery and/or the Battery connection. Just because the cable is on the battery post does not mean it's making a good connection. Check for a blown fuse. At the Starting Panel on the Generator there is a 7.5 amp fuse.

4. If it cranks but won't start:
* Clogged up Fuel Filter
* Faulty Fuel Pump

5. Starts hard and runs ruff. Check the Air Cleaner and/or Spark Plug

6. Engine starts but shuts off when the start button is released.
* Low engine oil
* Defective Oil Pressure Switch
* Defective High Temp Switch
* Defective engine control board
* Overheated Engine

7. If the generator is running and you have no electricity in the LQ, check the breaker at the Generator.

go here to locate an Owners Manual http://www.generac.com/Service/ManualSearch/

** Quitepact 40G, Model 4700 Gas & 4701 LP
* 0D9723 - Air Filter
* 0D4511 - Pre Cleaner
* 070185B - Oil Filter (Fram Autolite 65)
* 087769 - Fuel Filter - Gas Only
* 0E7585 - Spark Plug (Champion RC14YC) (AC R45S) (Gap .030 inch)
* 086729 - Starter Solenoid/Relay
* 081675 - Ignition Coil
* 075281 - High Temp. Switch
* 087798 - Start/Stop Switch
* 092113 - Prime Switch
* 0D7513 - Fuel Pump - Gas Only
* 0D8332 - Carburetor - Gas
* 0F5759 - Carburetor - LP

** Primepack 50, Model 2010 Gas & 4164 LP
* 07311 - Air Filter
* 081646 - Pre Cleaner
* 070185B - Oil Filter
* 087769 - Gas Only
* 0E7585 - Spark Plug
* 0D1227 - Starter Solenoid/Relay
* 092572 - Ignition Coil
* 075281 - High Temp. Switch
* 087798 - Start/Stop Switch
* 092113 - Prime Switch
* 090475 - Fuel Pump
* 0A6562 - Carburetor - Gas
* 0A7336A - Carburetor - LP