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Last Updated on September 5, 2024 by Paul Clayton
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Onan Generator Starts But Won’t Stay Running – Troubleshooting
Facing issues with your Onan generator not staying running can be pretty frustrating, affecting the overall efficiency and performance. We provide step-by-step instructions for diagnosing and resolving the problem, aiming to enhance your understanding and ability to maintain your Onan Generator effectively.
- Fuel Issues: Check fuel level; add if low, replace old fuel.
- Faulty Spark Plug: Look for wear and carbon build-up.
- Dirty Carburetor: Clean using carburetor cleaner after removal.
- Damaged Ignition Coil: Test with a multimeter; replace if faulty.
- Faulty Fuel Pump: Listen for a humming noise. Replace if faulty.
Understanding the potential causes and implementing the right solutions can ensure the optimal function of your generator.
The Onan generating set is a hardy machine specifically developed to cater to the energy requirements of the average homeowner and RVers.
The power generator is so reliable that it has become one of the go-to generating sets for RVers looking to sustain their appliances.
Over the years, it has also proven its mettle as a great backup power source. However, the Onan power generator has been plagued by specific issues, as numerous owners have filed complaints concerning difficulties with the operation.
One of the most reported problems is that the generator can be turned on but shuts down as it does. It simply does not stay running.
This can be a frustrating issue, mainly if you rely on the generator to power the appliances in your RV.
Additionally, Trying to fix the problem without troubleshooting or having the necessary tools could cause you to damage the equipment.
Things to Bear in Mind Concerning the Onan Generator
Thankfully, troubleshooting the Onan generator is not as difficult as it seems. However, it is only tricky if you can understand the fundamentals.
There are various reasons why the Onan generator will start but won’t remain running. This article aims to help you troubleshoot through each problem.
Nevertheless, it is essential to remember that, as with many other electronics, it might be best to call a professional to handle the problem if you do not feel confident in troubleshooting the generator.
The Intricacies of a Working Onan Generator
Generally speaking, on the Onan generator, the role of the control board is to regulate primary functions. The principal function is ensuring the generator supplies enough LP gas or diesel.
This means that it is the role of the control board to shut down the generator immediately the moment it recognizes a shortage of fuel pressure and fuel.
If nothing is faulty with the control board, the regulator receives a field flash voltage, which preserves the stable application of the numerous appliance loads.
Depending on the scenario, the regulator could decrease or increase the load before transmitting it via the generator’s field circuits. When viewed from a technical standpoint, the regulator acts as inbuilt protection against the possibility of overload.
If your Onan generator for your RV does not come with a regulator like BGE and NHE models, the generator will come with a rectifier. Once the generator is started, the control board moves to deliver current via the positive terminal of the bridge rectifier.
A relay set in the control board closes and opens while the oil pressure fluctuates. This change determines the status of the bridge rectifier.
If there are no issues and everything is smooth, the machine’s rotors begin getting DC voltages once the bridge rectifier comes on. The Onan generator’s performance relies on many components working together smoothly when viewed as a whole.
Required Gear and Tools
When you do not have the correct tools, troubleshooting will likely bring out an indefinite result. For this reason, you must get the necessary gear and tools before assessing the Onan generator.
Generally, you will have to get a working multimeter to examine and inspect important generator components and their readings. Accessing these components will require you to disassemble the generator, so you must have some screwdrivers and wrenches.
Also, getting a hardy pair of rubberized gloves might be handy. This should be all the gear you require; however, if you feel it is better to be safe than sorry, you can also wear goggles and a facemask.
Troubleshooting the Onan Generator
Once you have all your required tools and gear, you are now ready to troubleshoot what the problem could be. When it comes to the case of the generator starting up but not running, there are a few potential issues and components to point the finger at. They are:
- Faulty control boards
- Sticky switches
- Bad regulator
- Ground or short in the rotor
- Damaged wiring
Faulty Control Board
It would be best if you tried to turn the Onan generator on and get it running. As soon as this happens, use your multimeter to check the voltages on the AC output. If there happens to be no voltage on the AC output, move to check the voltage on the field flash via the pin located on the control board.
If there happens to be no voltage on the field flash, then the board might be defective. If this is the case, the issue of your Onan generator starting up and shutting down can be fixed by changing its control board.
Sticky Switch
A sticky switch is one of the leading causes of an Onan generator starting and then shutting down after some time. This is an issue that seems to happen very frequently.
The cause is the generator’s oil pressure switch, which sticks open when the generating set has not been used for a prolonged period.
In numerous cases, the way to sort this issue out is by engaging in multiple start-stop cycles. You could also add a bit of tapping to help dislodge the switch.
Bad Regulator
If the field flash has a seemingly standard voltage, then the issue might be caused by the regulator. The way to determine if it is the regulator is to run 12 volts via a diode to the regulator’s pin 9.
If, after doing this, your Onan generator begins producing slightly low or standard AC voltages, then the regulator is flawed and should be swapped out.
Ground or Short In The Rotor
The last spot people look at when discovering the source of an Onan generator starting and stopping is the regulator’s mating plug.
It would be best if you used the multimeter to determine the resistance rating between pins 10 and 9 of the plug.
The average reading should be anything from 22 Ohms to 28 Ohms. Should the reading produce a rating lower than 22, there may be a shortage in your generator’s rotor.
Conversely, if the reading is way higher than 28 Ohms, the rotor may have a ground.
Damaged Wiring
if you have checked the regulator and discovered it is working as it should, the generator may have specific connectivity problems caused by faulty or damaged.
To find out if this is, in fact, the case, you should check if the wiring between the regulator pin and the field flash pin is connected and working correctly.
How Do You Read an Onan Generator Fault Code?
Reading an Onan generator fault code is essential for efficient troubleshooting and maintenance.
This process begins by locating the Start/Stop/Prime switch on the generator, which can be found behind the access panel.
After pressing ‘Start,’ observe for three flashes from the switch. This indicates a service code fault.
Press the ‘Stop/Prime’ on the control switch to identify the specific issue. This action triggers a two-digit service fault code to flash, revealing the precise nature of the problem.
By following these steps, you can effectively read and interpret an Onan generator fault code.
Final Words
The issue of an Onan generator that starts but won’t stay running can be attributed to various factors. Foremost among these are fuel issues.
Always check the fuel level and replace old fuel if necessary. Additionally, a faulty spark plug could be the culprit. This is usually characterized by wear and carbon build-up on the spark plug.
Moreover, a dirty carburetor can also cause an Onan Generator to start but fail to stay running. In such a scenario, cleaning the carburetor using a cleaner after removal is advisable.
Another potential cause of this problem is a damaged ignition coil. To ascertain this, you should test the ignition coil with a multimeter and replace it if it is faulty.
Finally, a faulty fuel pump could also be responsible for the Onan Generator’s inability to stay running. You can identify a defective fuel pump by listening to a humming noise from the generator.
If any such noise is detected, it indicates a need to replace the fuel pump. By addressing these potential issues adequately and promptly, you can resolve the problem of an Onan generator that starts but won’t stay running.
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