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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14821
Experience:  Certified on Onan and Generac generators
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I have a Generac 15000 watt generator. It has a 1 liter engine.

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I have a Generac 15000 watt generator. It has a 1 liter engine. When I tried to start it it would not start. I gave it a shot of ether to see if it is a fuel problem. The engine did not try to start. Pulled a spark plug and grounded it to engine block to check spark there was none. I opened engine control panel to check start switch, Switch was good according to ohmmeter. opened front cover to check coils to spark plugs. The coils were good according to ohmmeter. there is a diode in series with feed to ignition coil. diode was good. open one way reversed leads and a reading was present on meter. Do not rember reading. opened control panel checked all rectifiers and diodes seem good. The unit has a Generac OD5304 govener control board. If the board is bad will this eliminate spark? By the way I checked oil safety switch. Had continunity. Jumped wires together no luck. Checked the shutdown relay. Put 12 volts to coil relay changed state. Checked contacts with ohmmeter contacts opened and closed when power to relay was energized add DeEnergized. Checked starting relay same result good.
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My name is XXXXX XXXXX I am going to assist you with this.

What are the model and serial numbers of the genset?
Customer: replied 4 years ago.

The serial # XXXXX(NNN) NNN-NNNN There is no model number listed. I brought up schematic diagrams up for a Centurion and it seems to be close.

According to your serial number, this model number is(NNN) NNN-NNNN
I did not realize you had a portable set - you should have specified that.

Does your set say "Ultra Source", or have any other markings on it? XP? GP?
Customer: replied 4 years ago.

It says Generac Guardian 15000 on one sticker, and on the other sticker which is located on the panel with the recpticles it says Industrial/commercial 15000 watt.

This is an Ultra Source genset.

For a no spark condition, the first thing you need to do is to remove the wire #18 from the ground stud located right above the oil cooler.
Insulate it so it can not touch ground, and check for spark again.
Do you have spark now?
Customer: replied 4 years ago.

I thought it was a spark problem. I went through the print and everything checks out. I now have spark. The engine starts and stalls immediately. I had gas in it about a year. I drained the fuel, Replaced with new fuel, replaced thefuel lines. It has a plastic fuel pump on the valve cover. It seems to be pumping fuel in sperts.I think it is ok but not shure if it is putting enough pressure. I pulled the carb off and blew air through ports they seem clear, the govener seems like it is working it opens and closes the throttle.

If the fuel is coming in spurts, the fuel pump is working.
The problem is in the carburetor.

As gas gets old, it turns to varnish and clogs up the passageways inside the carburetor, not allowing enough gas to get to the engine.

This condition is cumulative. Every time gas sits, the varnish builds up just a little more, like coats of paint, until eventually gas can not flow. It will not happen overnight, but the symptoms can show up all of a sudden, even while simply stopping to refill with gas.

The use of fuel additives, such as Sta-Bil or Sea Foam will not stop this process from happening. They will greatly slow it down, but the gas will still go bad.

When this happens, either the engine simply will not start, or it will not run without the choke on (this reduces the amount of air getting pulled into the engine, changing the fuel/air mixture), or it will run but surges.

Another issue that varnish in the carb can cause is that the varnish may not allow the float needle to seal properly against the seat, causing the flow of gas to not shut off when the bowl is full. The result will be gas overflowing the carb and running into the cylinder, and possibly out the air intake. If the gas gets into the cylinder, it will seep past the rings and down into the crankcase. This will be evidenced by your oil level being over-full and/or the oil smelling like gas.

If this is the case, you will need to change the oil and filter, if it has a filter.

The only 2 solutions are to either replace the carburetor or give it a good, thorough cleaning.

When removing the carb, make sure to take a good picture, or make a good drawing of where all springs and linkages are attached. This will make reassembly much easier.

Most people believe that cleaning a carb involves removing the bowl and wiping it out, then spraying some carb cleaner through it.

This is simply insufficient. It takes months or years for this accumulation to build up – it just can not be removed in minutes.

To properly clean the carb, you must remove it, disassemble it (making sure to remove all non-metal parts), and soak it in a commercial solvent for several hours. Soaking it overnight is even better.

Then clean all solvent off with a spray type carb cleaner, making sure to get lots of cleaner into every hole and passage there is. Pay special attention to the tiny holes in the bore of the carb, under the throttle plate for the carbs that have these holes. Use lots of cleaner. And make sure to wear safety goggles to avoid getting the over spray into your eyes. There will be over spray.

Dry the carb with low pressure compressed air.

This is an EPA compliant carburetor, and as such, is not supposed to be taken apart or adjusted.

When you have an issue with it, you are supposed to replace the entire carb.

But, sometimes it is possible to clean them. Just remember, that as an EPA compliant carb, there are no parts available for it, so if you lose or break anything, you will definitely need to get a new one.

Occasionally, even a good cleaning is not going to be sufficient, and you may end up having to replace the carb anyhow. Be prepared for this.

If for some odd reason this does not help, please let me know so I can assist you further.

Please rate me 3 or higher, or reply to me if you need further help.
Hank F. and 2 other Small Engine Specialists are ready to help you
Customer: replied 4 years ago.

I lost spark. I pulled wire off oil safety switch unit does not have spark. I checked oil switch with ohmmeter it is supposed to be normally closed, it is. when I crank engine it opens when it sences oil pressure which leads me to believe it is ok. I pulled off wire comming from coils measured voltage about 1.5 volts dc. Carberator was opened seems clear sprayed with carb cleaner and blew compressed air through ports seem clear. where does spark get generated from? does govener control spark?
generator always ran good, Just one day did not start. I removed gas put in my car and had no problem with it. carberator had no varnish in it that i could see. Thanks for the help.

The governor has nothing to do with spark.
The spark comes directly from the coils.

Remove the #18 wire as I described above, and see if you have spark now.
Do you?
Customer: replied 4 years ago.

No spark. Plugs are wet pulled plugs blew them out with compressed air. They are new. Grounded plug cranked engine no spark.

Then what you need to do next is to remove the engine cover to expose the flywheel and magnetos (coils).
Remove the wiring harness from the tabs on the magnetos, and check for spark again.
If there is spark, the diodes in the wiring harness are bad, and the wiring harness must be replaced.

If there is still no spark, check the flywheel magnets for excessive rust. If they are rusty, use sandpaper to clean them up.
Check the air gap between the magnets and magnetos. It should be .010". If not, adjust the magnetos to the proper gap.
Check for spark again.
If there is still no spark, the magnetos are bad and will need to be replaced.

Let me know how it goes.
Customer: replied 4 years ago.

I removed the magnetos checked them with a ohmmeter and they read 18000 ohms. I cleaned a minute amount of rust and dirt off the flywheel removed the diode harness, Reinstalled the magnetos and the engine now fires up. I reconnected the diode harness and the engine does not start. disconnected the harness and the engine fires. It seems to run full out no control. I am getting popping from carberator I am figuring without diodes no govener control and i guess the popping is timing is off. I checked diodes with incorrect polarity shows open circuit which is what you would expect. with correct polarity it shows 2.2 meg ohms on one and a little higher on the other. with good diodes installed will the govener control return and the popping stop or do you think i have to look elsewhere?

The diode harness has nothing to do with timing or speed control. It simply allows the engine to run or not.

The popping could be valves, carburetor, weak coil, or bad spark plug.
I'm not sure what you mean by 'running full out'. If the engine is simply running at rated speed, but does not slow down with idle control, this could be one of several things.

But if it is running too fast (racing), it could be an air leak at the intake, a bad carburetor, or a bad governor control.
Customer: replied 4 years ago.

It is racing actually running at 78 Hertz instead of 60 .

I have uploaded the procedure for checking the stepper motor.
Please do it and let me know what you find.

Click here to download it.
Customer: replied 4 years ago.

I have corrected the spark issue thanks to you, However i also have a carberator problem. I tried to clean it as you have stated earlier but it still does not work. I am trying to find a carberator but my old Generac Part # is 0C8526 and cannot find a repalcement # everytime I punch in the # the part does not come up.

Let me see what I can find for you.
There is a carb rebuild kit for this carb. It is part number 0C85260SRV.
If you wish to simply order a new carb, the new part number is 0E25480ESV,.

Both can be ordered through any Generac dealer.

Please rate me 3 or higher, or reply to me if you need further help.