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Open Roads Forum  >  Class A Motorhomes

 > Onan Marquis 5000 won't start

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nehuge

chandler, az

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Posted: 11/24/12 01:45pm Link  |  Print  |  Notify Moderator

Hi all, have a 1995 Thor Residency, 460 motor, and 1000 hours on an Onan Marquis 5000. Sorry I don't have the actual model off the sticker (KYxxx, etc).

It has been running fine then on our last trip it stalled. We were going somewhere so I figured I'd leave it and mess with it when I got back. I got it to restart once, then it ran 10 seconds and died. Now it won't even crank over. This one has s carburetor with an altitude knob hanging under it (5ooo ft. to 10000 ft). It has a lever on the airbox for the air filter that shows winter and summer settings. I pulled the fuel filter off since I don't know a maintenance history of the unit.

Question #1: When I crank the unit over with the fuel filter off, exactly how much fuel should be coming out of the fuel line onto the ground or into a container? Upon first hitting start, it sort of squirts out, and the longer I hold the start button down as it's cranking the starter, it slows down sort of a half of a trickle. Is that normal? Or should this be squirting out the whole time faster?

I'm replacing the fuel filter anyway but I don't know if what I said above shows signs of a fuel pump. I can't remember if there is a fuel pump 'hum' that it's supposed to make or not. If it were a fuel pump, where the heck is it on this unit?

mdprince

Santa Clarita, CA

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Posted: 11/24/12 02:48pm Link  |  Print  |  Notify Moderator

Well, I'm not the expert you wanna hear from (they will chime in) but -

1) make sure your fuel tank is at least 1/2 full

2) in my experiences with mechanical and electric fuel pumps, the flow (GPM) should remain steady

3) are you removing the fuel line for testing, before or after the fuel filter ?

4) get a timing light and hook it up, crank the generator and look to see if the light is flashing - if it is, you're getting spark and the fuel flow (be it pump, filter) become more suspect.

Air - Fuel - Spark

mp


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2004 Jeep Rubicon Toad/Brake Buddy or
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hershey

Albuquerque,(fulltime) NM, USA

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Posted: 11/24/12 03:51pm Link  |  Print  |  Notify Moderator

As mdprince stated......on RV generators you must have about a 1/4 to 1/2 tank of fuel for them to operate. Safety feature so you don't run out of gas on your RV out in the boonies.
You started with probably the best place to look, the fuel delivery....I'd spring for a new filter before going any further. Let us know what your find.


hershey - albuquerque, nm
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bsinmich

Holland, MI

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Posted: 11/24/12 03:52pm Link  |  Print  |  Notify Moderator

I had a similar problem on my '96 Pace Arrow. The cause of mine was the gas line had gotten brittle and cracked, letting air in. I had to run a new gas line and the problem cured. If you run the starter too long you will overheat it and burn it up. If you can blow back through the gas line it would indicate a leak comeplace on the line.


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LVJ58

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Posted: 11/24/12 07:16pm Link  |  Print  |  Notify Moderator

bsinmich wrote:

I had a similar problem on my '96 Pace Arrow. The cause of mine was the gas line had gotten brittle and cracked, letting air in. I had to run a new gas line and the problem cured. If you run the starter too long you will overheat it and burn it up. If you can blow back through the gas line it would indicate a leak comeplace on the line.


x2

Had the same problem with ours, cracked fuel line sucking air had it replaced last year generator runs just fine now.


Jim & Sherry Seward
Las Vegas, NV
2000 Residency 3790 V-10 w/tags & Banks System
2003 Suzuki XL/7 toad

mdprince

Santa Clarita, CA

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Posted: 11/24/12 07:27pm Link  |  Print  |  Notify Moderator

A little "off topic" but my sons '95 Dodge truck started leaking today from the top of the gas tank ! Probably - old cracked fuel line !!

TyroneandGladys

Chandler AZ

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Posted: 11/24/12 07:49pm Link  |  Print  |  Notify Moderator

Call for an appointment with
Mesa Precision Motor Service
31 E Vine ave
Mesa, 85210
480-969-5851
I use them for repairs and maintaince. Totaly fair and honest and they know what they are doing.


Tyrone & Gladys
26' 1986 Coachmen


nehuge

chandler, az

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Posted: 11/26/12 09:17am Link  |  Print  |  Notify Moderator

mdprince wrote:

Well, I'm not the expert you wanna hear from (they will chime in) but -

1) make sure your fuel tank is at least 1/2 full

2) in my experiences with mechanical and electric fuel pumps, the flow (GPM) should remain steady

3) are you removing the fuel line for testing, before or after the fuel filter ?

4) get a timing light and hook it up, crank the generator and look to see if the light is flashing - if it is, you're getting spark and the fuel flow (be it pump, filter) become more suspect.

Air - Fuel - Spark

mp


The fuel line looks newer and feels okay. I'm removing the line before the fuel filter. Either that or maybe the carb is gummed up? It ran so perfectly though before.

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