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I have an Onan Marquis 5000 in my 1994 Thor Residency

Customer Question
I have an Onan...

I have an Onan Marquis 5000 in my 1994 Thor Residency motorhome. We were using the generator while we were on vacation. We shit it off at the end of the day

Mechanic's Assistant: What's the make and model of the generator? And can you guesstimate how old it is?

We shut it off at the end of the day and it would not restart the next day. If you hold the start button on and give it a little throttle manually it will start and run until you let off of the start button but the generator never controls the throttle as it should. You have to hold that on as well. I did your test and on J4-7 it has 9.28 volts, J4-9 goes to 9.63 when you first push the start button but drops to 1.63 immediately after while cranking. J4-10 has 4.83. I have already changed the control board and it made no difference.

Mechanic's Assistant: Do you plan on doing the work yourself?

Yes

Mechanic's Assistant: Anything else we should know to help you best?

Nothing more than I have just sent

Submitted: 1 month ago.Category: Small Engine
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Answered in 5 minutes by:
1/5/2018
Technician: Hank F., Technician replied 1 month ago
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15,519
Experience: Certified on Onan and Generac generators
Verified

Hello, my name is ***** ***** I am going to assist you with this.

What is the full model number of the genset?

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Customer reply replied 1 month ago
5bgmfa261050
Technician: Hank F., Technician replied 1 month ago

The last digit of the model number will be a letter, not a number.

I am going to assume it is the letter "D". Please verify and let me know if it is not.

The single most common cause of this issue is that the set is no longer producing electricity.

The first thing you need to do, though, is to check your oil level and make sure it is full.
Low oil pressure will also shut the set down.

If the oil is good, remove the control panel from the front of the genset.
Set your meter to ACV.
Connect the black lead to a good ground.
Connect the red lead to the back of the circuit breaker (either one), on the terminal farthest away from you.
Press and hold the start button for 6 - 8 seconds, and note the voltage.
How much voltage is there?
.

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Customer reply replied 1 month ago
D is correct
Technician: Hank F., Technician replied 1 month ago

Ok.

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Customer reply replied 1 month ago
I am not with the unit at the moment I will check and get back with you.
Technician: Hank F., Technician replied 1 month ago

Not a problem at all.

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Customer reply replied 1 month ago
When connecting the red probe to the back of the circuit breaker and the black probe to the ground and cranking it it got up to about 36 volts
Technician: Hank F., Technician replied 1 month ago

This unit has in issue with the throttle linkage becoming disconnected from the governor actuator.

Remove the black cover from the top of the genset, and see if that is what happened on yours.

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Customer reply replied 1 month ago
Even if I do the throttle manually it will only stay running if I hold the start button in
Technician: Hank F., Technician replied 1 month ago

That is because of the low voltage. But you have to get the engine to where it will start without manipulating the throttle first.

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Customer reply replied 1 month ago
Why does it shut off even when I am holding the throttle as soon as I release the start button
Technician: Hank F., Technician replied 1 month ago

Please read my last post.

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Customer reply replied 1 month ago
Please listen to what I am saying what does the linkage coming off of the governor have to do with it losing power when I let off the start button it does not feel like it is off of the governor either
Technician: Hank F., Technician replied 1 month ago

You said you got 36 volts while it was cranking. Voltage must be read while it is actually running. The voltage is too low.

If voltage is too low, the engine will not stay running when you let off the start switch.,

This unit also has speed protection. If it is running too fast or too slow, the governor controller will shut the unit down.

It is virtually impossible to hold the throttle in the narrow range required to keep the unit running. That is why that must be corrected first.

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Customer reply replied 1 month ago
Linkage all looks intact
Technician: Hank F., Technician replied 1 month ago

You have the black cover off?

When you press the start button, does the governor actuator move?

If so, which way?

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Customer reply replied 1 month ago
It's not moving
Technician: Hank F., Technician replied 1 month ago

If the governor actuator is not moving while the engine is cranking, you have an issue with either the governor actuator, the governor controller, or the main control board.

This is going to be a very time consuming affair, and I do not have time to finish it. It is 11PM here, and I have to get up at 5 to go to work, so I will opt out and let someone else take over.

Sorry.

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Customer reply replied 1 month ago
Thank you for your help and have a good night if there is a problem with the low oil sensor could that cause the problem
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Hank F.
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15,519
15,519 Satisfied Customers
Experience: Certified on Onan and Generac generators

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