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gene, RV Mechanic
Category: RV
Satisfied Customers: 1100
Experience:  28 yrs exp in the industry
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My onan marquis won't run with the front spark plug hooked

Customer Question

My onan marquis won't run with the front spark plug hooked up. When I connect it, it only runs when the start button is held down. If I disconnect the front plug wire, it will run on the back plug.
JA: Will the headlights turn on? Is the battery fully charged?
Customer: This is an rv generator. No headlights. The battery is charged since it starts fine with just the back cylinder connected.
JA: What year is your Marquis?
Customer: It is a 1999 motor home, but I think the generator is a 98.
JA: Are you fixing your Marquis yourself? What have you tried so far?
Customer: I am trying to fix it myself. I have replaced the computer and disconnected the oil pressure switch too. Still the same problem.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I have also verified that there is a spark and fuel in both cylinders.
Submitted: 2 months ago.
Category: RV
Customer: replied 2 months ago.
I just tried disconnecting the voltage regulator to see if I could troubleshoot. I forgot to reconnect the plug when I started it and nothing changed. It would still run on the back cylinder only, but not with the front one connected also.
Expert:  Hank F. replied 2 months ago.

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

What is the full model number of the genset?

Customer: replied 2 months ago.
It is an Onan marquis 7000. Serial number is *****
Expert:  Hank F. replied 2 months ago.
The 7NHM is the model number.
Try switching the plug wires at the coil.
Does the same cylinder cause it to quit, or does the opposite one cause it to quit?
Customer: replied 2 months ago.
I just got charged an extra $24. I was told it was only $5. What is the other $24 for?
Expert:  Hank F. replied 2 months ago.

For billing questions, you need to contact Customer Service.

Customer: replied 2 months ago.
Thanks. I will swap the wires at the coil and let you know what I find.
Expert:  Hank F. replied 2 months ago.
Customer: replied 2 months ago.
Swapping the plug wires at the coil didn't change anything. It will run when the front plug is disconnected, but not when they are both connected.