LAS Motorhomes - Onan Generators

Onan Generator Servicing

1200 hour service of a LPG generator

Onan Generator

The Cummins Onan QG3300LP which is often referred to as a 3.3KYFR-4858 or even by its part number AO55EE855 is an LPG generator capable of producing 14.3 amps maximum power. This compact quiet generator (68 dB) only weighs 83 kg has proven to be a very reliable workhorse. One of the key factors to keeping your Cummins Onan generator reliable is regular servicing and keeping to the schedule.

When engines run on LPG the engine oil does not become contaminated anywhere near the same as an engine that runs on petrol. This key factor will allow increased running time as well as fewer oil changes.

LPG is a gas, unlike petrol which is a liquid, using LPG as a fuel allows spark plug intervals to be increased. If you read the periodic maintenance schedule in the operations manual you will see that the schedule for petrol and LPG are the same, in reality, you can increase the intervals as follows.

Periodic Maintenance Table

The first oil change should be kept at 20 hours, after that the engine oil frequency can be increased to every 300 hours. Also, the 500 hours can be increased to 600 hours, then I would advise the brushes to be changed at 1200 hours if the generator is being worked at 75% load and above.

Periodic maintenance Schedule

The 1200 hour service

This service requires the following:

The parts to carry out the service are as follows:

Replace the brushes

Once the brushes are fitted then you reverse the procedure by re-fitting the flywheel and the casings. That part of the service is now complete.

Replace the spark plug

Replace the spark plug

With that sequence of operations completed we need to generator to get it warm ready to change the engine oil.

Check and adjust the valve clearances

Replace the air filter

Change the engine oil

The lubrication system is only splash fed, this means the engine has no oil filter

Final checks

The final part of the service is to run the generator up and check the output voltage. This should be measured with no load (maximum 249 volts) and on full load with a maximum of 215 volts.

The HZ the generator produces is directly proportional to the RPM. 1 x HZ increase in output requires the engines RPM to be raised by 60.

Final Checks - Stage 1

Now check the RPM of the engine and without a load. You need to read no more than 51.5 HZ on load (3090 RPM) and no more than 52.5 HZ with no load 3150 RPM.

Final Checks - Stage 2

The above image shows the use of the rev counter. This reading was taken with no load which would be producing 50.97 HZ. Now you need to check the engine RPM when on load. Once you are satisfied you have set the engine within spec the service is then complete. A word of warning, if you do not get the RPM within spec the generator will automatically stop on code 14 – over frequency or 15 – under frequency.

All that's left to do is to put the generator back into the vehicle so it can produce prime power for another 1200 hours.

If you need more information on Cummins Onan Generators or would like to purchase one of them, please contact John on 01604 861999

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