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Onan Marque 7000. some advice

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Old 10-10-2017, 08:11:00 AM
alber alber is offline
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Default Onan Marque 7000. some advice

Weeks ago I posted a thread asking $ 30 starters on Amazon from China verses the $ 125.00 Onan starters , ( no response too that question )

Was the mark up worth it ? Better Quality ?

Reviews were OK on the cheaper starter, I ordered one.
After 1/2 dz pressing the start button , ( hard starting ) never started the front assembly from starter broke apart into generator .
WOW , Found all parts.
Company that sold their product thru Amazon had great reviews, with phone # . Before returning I called them . NO hassle, they sent me another . Told me too keep for parts
A little detail so you understand my hesitation .
This Onan Marque 7000 year apx 1999 . Hardly any hours.
Enclosed in a seldom used food trailer
When trailer is used gets power from electric & protane gas
Every time I fired up generator always an issue, hard starting stalling not clean burning
Bugged me this expensive piece of equipment not working properly .
Recent weeks had some time too check it out.
Clearance in trailer limited generator held in place with two bolts, some wiring I Pulled generator from trailer, sits in my garage . Nice & easy too work on
Changed oil , filter, plugs, cleaned carb,
Original fuel pump was NG, Purchased a New fuel pump ( 5 psi ) Auto Zone .

Received replacement starter , so far works fine .

Fires up , runs about 10 minutes, ruff , but runs then gets bogs down stalls. Try too fire up back fires very loud that scares the hell out of you with a carbon stain on floor under muffler .
Trying too start it wont.
I let it sit a hour, fires up runs 10 minutes and same happens
Calls for low pressure fuel pump , lowest Auto zone had was 5 psi. I was anxious too get pump that day and not wait days if I ordered.
A person with same generator indicated he used the same fuel pump from auto zone worked fine
Should I put a smaller tip restricting fuel flow from pump avoid back fire ?

I wanted too take into a shop but I know it will be expensive and don't want too spend a lot for something I don't use.

Some thoughts
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Old 10-10-2017, 08:51:44 AM
Kevin K Kevin K is offline
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Default Re: Onan Marque 7000. some advice

It sounds like the "backfiring" is unburned fuel in the muffler being ignited.

Check the valve clearance. It may be too tight allowing loss of compression when the engine warms up, pushing unburned fuel into the muffler which is then ignited.

Make sure you have a fuel filter prior to the fuel pump. Replace any rubber fuel lines between the fuel pump and the carburetor. Flush out any metal fuel lines. Disassemble the carburetor and clean the float valve and inlet passages to remove anything holding the float valve open.

The fuel pump pressure may be too high. After you check the valve clearance and clean the carburetor, you can test this be using a temporary gasoline tank held a few feet above the generator and directly feeding the carburetor, letting it gravity feed the fuel. If it runs OK with this setup but not on the fuel pump, the pressure is too high and you will need to replace the pump with the correct model.
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Old 10-10-2017, 09:20:07 AM
Chas183 Chas183 is offline
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Default Re: Onan Marque 7000. some advice

Another thing to check is the choke.
Is the choke heater working as it should?
Check to see the choke is fully open when trying to start it again.
Like previously stated the carb my be dirty. Float stuck open?

You can use the fuel pump to fill the bowl, then unhook it.
This will let the engine run until the fuel bowl is dry to prove out if the pump is too much pressure.

When gravity feeding you will need to get a siphon started before hooking to carb and do not leave it this way.
If the float is leaking you could come back to fuel all over.

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Old 10-10-2017, 09:29:19 AM
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Billy J Shafer Billy J Shafer is online now
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Default Re: Onan Marque 7000. some advice

Normal pump pressure is around 1-4 pounds. 5 is the max limit but should work fine. I would go over the unit with the normal checks. Clean carb,valves set,exhaust clear.
I don't talk to myself. This early in the morning. Why the hell should I talk to you.
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Old 10-10-2017, 12:47:24 PM
len k len k is online now
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Default Re: Onan Marque 7000. some advice

Think Onan says 3 or 3.5 psi fuel pump, there are aftermarket pumps that do that for ~ $40.

Higher than that and float may not be able to shut off gas flow when carb bowl is full. Resulting in uncontrolled leaking of gasoline into intake ( running rich) and possible leaking gas out of carb onto ground, fire hazard.

Gravity feed.....If gas level ( gas can) is 10 ft above carb then pressure at carb is 3 psi. Assumes no pressure in gas can ( cap is loose or vented)

With exhaust carbon stain on ground . Sounds like it's running rich, try adjusting main mix jet ( bottom of bowl). Believe manual says initial setting is ~ 1.5 turns off the seat. A stretch but, muffler might be restricted from carbon. This gen has a carbon blow out plug on muffler, have to run gen to get it hot to unscrew the tight plug.

Check choke adjustment , on mine the choke heater is burned out. If yours is too someone may have leaned out the main jet somewhat to compensate and that's a compromise between being able to start and running rich when hot. But this might not be your problem, since you have a carbon stain on ground I suspect your not running lean when hot.

Engine will run ~ 15 seconds at no-load just on gas remaining in carb bowl.
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Old 10-17-2017, 06:51:33 AM
alber alber is offline
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Default Re: Onan Marque 7000. some advice

Follow up
Thanks for some of your responses. What I did find was choke was closed.
Held open with a screw driver and it ran 45 minutes . Spring was missing on bottom and arm not attached .
Slowly making headway . As my original post stated I seldom used generator and recently on a mission too have this generator working as it should
I can across a ONAN box on a shelf in garage. , Opening box, HOLY COW contained a carb. Looked used ,
Previous owner included box of parts when I purchased trailer 16 years ago. Totally forgot about Choke assembly was in tact and installed this carb figuring give it a shot might work
. Could not get if fired up. Did some basic cleaning . Had enough issues with starter and did not want too burn out this new starter .
Re installed working carb
Can assembly come apart and transfer too working carb. ? Middle spring assembly looks a little tricky ?
Found some oil in filter box . some oil blew on too the motor ? not a lot but hoping its not blow by ?

Thanks again
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Old 10-17-2017, 12:03:04 PM
len k len k is online now
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Default Re: Onan Marque 7000. some advice

Need numbers. Please post full model and serial number of gen. Onan made several versions.
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Old 10-17-2017, 05:59:41 PM
Kell1961 Kell1961 is offline
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Default Re: Onan Marque 7000. some advice

You should never run more than a 3.5 max pump on any flat head onan engine. The float in the carb is not designed to stop more than that. Check both plugs for fouling. Usually the front plug pulls nor fuel under low load due to an unblanced in take manifold. Unit may well need the valves adjusted as well but that will not do you any good until you decarb the conbustion chamber. You can do this with spary in products but best way is to pull the heads and do it the old fashioned way.
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