Skip to main content ↑ ↓
Topic: Onan Marquis 6.5k parts etc (Read 454 times) previous topic - next topic

Onan Marquis 6.5k parts etc

Greetings, I have been away for a while while my coach was getting some of the issues found on my trip to Austin, TX last June-July (never doing that again LOL). Got the coach into Oregon Motorcoach in Eugene. They seem to have fixed the Overheat issues and thought they had the Generator issues sorted, but it still seems to run rough after it has been running for a while. I noticed that as soon as I put a load on it it would start running rough then shut off. I rebuilt the regulator early in the rear and it seemed ok for a while. I changed it over the the HP vapor side. no change. I did not change the Fuel, or air filters when I did the regulator (stupid I know).
Any Ideas other than those filters that could be causing it? The Genny has only about 400hrs
Thanks for any help:)
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Onan Marquis 6.5k parts etc

Reply #1 –
Was there any grease/oil in the regulator when you rebuilt it?

Wouldn't hurt to start with a basic tune-up:  spark plugs, air filter.  Fuel filter only if the regulator showed contaminants. Make sure throttle linkage moves freely.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Onan Marquis 6.5k parts etc

Reply #2 –
Brett,
Yes it was Gunked up pretty bad.
Rebuilt, cleaned and replaced the gaskets. linkage seemed fine. Seemed to work OK for a while.
Changed and gapped the spark plugs but did not change the air or fuel filter. Stupid, I know.
getting those changed. MAy look at the control board and see if it might have a cracked solder joint. Don't know how common this would be, but if the PCB is not conformal coated, it could happen!

1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Onan Marquis 6.5k parts etc

Reply #3 –
Also make sure that the block heater is not turned on. Guess how I know b
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Onan Marquis 6.5k parts etc

Reply #4 –
Quote from: red tractor –
Also make sure that the block heater is not turned on. Guess how I know b
I'm not certain that mine has a block heater. There is a preheat on the dash that i release as soon as it starts.
I just checked the service manual and it says the preheater is only for gasoline models.
If anyone has different info, let me know. I can see where that might cause an issue under load!
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Onan Marquis 6.5k parts etc

Reply #5 –
Look for the block heater switch at the base of the bed.  It turns on the outlet in the engine bay on the front wall.  The block heater will be plugged into it.

At least on the 1993 U240, the block heater switch is red and has a light in it to alert you that the block heater is on.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Onan Marquis 6.5k parts etc

Reply #6 –
Quote from: wolfe10 –
Look for the block heater switch at the base of the bed.  It turns on the outlet in the engine bay on the front wall.  The block heater will be plugged into it.

At least on the 1993 U240, the block heater switch is red and has a light in it to alert you that the block heater is on.

Our '95 U240 had the same switch along with one for the water heater.

As far as the Preheat switch on the dash, it is my understanding that it is only used to operate the glow plugs on an optional diesel generator.  The Marquis 6.5 in ours didn't have any sort of preheating and always started fine even when well below freezing.
Dave and Kelli
1997 U295 40' Build #5188 CSGI
1995 U240 36' Build #4621 SBID-SOLD
2006 Jeep Wrangler Rubicon

Re: Onan Marquis 6.5k parts etc

Reply #7 –
Quote from: wolfe10 –
Look for the block heater switch at the base of the bed.  It turns on the outlet in the engine bay on the front wall.  The block heater will be plugged into it.

At least on the 1993 U240, the block heater switch is red and has a light in it to alert you that the block heater is on.
OK, now I know what your talking about.
Yes I have the Block heater switch for the CAT 3116. I could not see a block heater on the Genny.
I can see where that would run the chassis battery down if left on.
The issue is with the genny running fine until a load is applied or added!
Hoping that the filter changes will fix it.


1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Onan Marquis 6.5k parts etc

Reply #8 –
The block heater for the diesel is 120 volts so if it is on and you have other 120 items on like the air conditioners it will overload the generator on one leg and cause it to shut down the generator b
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Onan Marquis 6.5k parts etc

Reply #9 –
Quote from: red tractor –
The block heater for the diesel is 120 volts so if it is on and you have other 120 items on like the air conditioners it will overload the generator on one leg and cause it to shut down the generator b
Ahhhh, That clarifies things. So if the block heater is on, it can eat up the current and cause the generator to overload and shut down it down. So Running rough can be symptom of the genny being overloaded!
Good info!
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Onan Marquis 6.5k parts etc

Reply #10 –
 ??? Have you looked at the throttle governor assembly, mine would roll like an old Detroit industrial and really surge under initial load. I tightened up the slop in the assembly and end of problems, with close to 500 hrs and counting.
88 Grand Villa 36' ORED 3208 (throwaway)Cat.
 Build # 3150
Happiness is the maximum agreement of reality and desire.

Re: Onan Marquis 6.5k parts etc

Reply #11 –
Quote from: Olde English –
??? Have you looked at the throttle governor assembly, mine would roll like an old Detroit industrial and really surge under initial load. I tightened up the slop in the assembly and end of problems, with close to 500 hrs and counting.
Seemed good when I had it out, but I'm no real judge.
Will check it again:) Thanks
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt
 

Re: Onan Marquis 6.5k parts etc

Reply #12 –
I think that you said that you haven't changed the fuel filter. That can certainly cause a problem under a heavy load.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins