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Fuel Troubles On Sears Gt18

carburetor onan fuel fuel delivery

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#1 Utah Smitty OFFLINE  

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Posted May 17, 2013 - 09:54 AM

Well, once again I'm stumped by fuel problems on mom's GT18.  I cleaned the carb and put new gaskets and needle in it when we first bought the tractor.  I also rebuilt the fuel pump that's on the side of the carb and replaced the fuel filter.

 

It ran fine for a couple weeks, but then started cutting out, etc.  I replaced plugs, and points, and checked the fuel line for leaks--everything was fine.

 

I installed a low pressure electric fuel pump--again helped for a few weeks and then same problem again-- rough running, stalling out, sometimes black smoke coming form exhaust.

 

I removed the electric pump, and replaced the line from the crankcase to the pump. Also cleaned the gas cap and made sure it was venting. Also made sure the dip stick was sealing.

 

... it worked for about 3 months then the same problem started again.

 

Mom thinks that it might be a pinched fuel line-- which I will check out. 

 

The only other thing I know that it might be is that it has somewhat low (85-90 psi) compression, but both cylinders are withing 10% of each other. Could low compression make it so the fuel pump doesn't have enough suction?  I have 4 machines with Onan twins, and, with the exception of my GT 18, they all seem to be fussy this way.

 

I need to get this repaired today so I can get it back to mom this weekend.  Any advice would be appreciated.

 

Regards,

 

Utah Smitty


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#2 MH81 OFFLINE  

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Posted May 17, 2013 - 11:14 AM

Could you swap coils with your GT?  


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#3 HDWildBill ONLINE  

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Posted May 17, 2013 - 11:24 AM

How about trash in the tank?  It seems like when you work on it, the problem clears up and then comes back which to me would indicate something that gets cleared and then stops back up.


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#4 olcowhand ONLINE  

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Posted May 17, 2013 - 11:27 AM

The coil could be the issue, but I'm like Bill & wonder if trash is blocking the fuel tank outlet.  I had similar issues with a 145HP Massey diesel and finally pulled & flushed the tank & she runs like new again.  Had lots of crap in the tank.


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#5 Marty'70 ONLINE  

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Posted May 17, 2013 - 12:08 PM

The coil could be the issue, but I'm like Bill & wonder if trash is blocking the fuel tank outlet.  I had similar issues with a 145HP Massey diesel and finally pulled & flushed the tank & she runs like new again.  Had lots of crap in the tank.

 Yup I had the same problem with my farmall 450 diesel. chased it for quite a few weeks till i found trash getting sucked to the outlet line.... pi$$ed me off when i found all it was after changing filters blowing out lines, checking injection.... you name it.


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#6 Utah Smitty OFFLINE  

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Posted May 17, 2013 - 12:20 PM

How about trash in the tank?  It seems like when you work on it, the problem clears up and then comes back which to me would indicate something that gets cleared and then stops back up.

I'll swap out the coils and also check for trash in the tank... I hadn't thought of these things..

 

Smitty


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#7 olcowhand ONLINE  

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Posted May 17, 2013 - 01:54 PM

 Yup I had the same problem with my farmall 450 diesel. chased it for quite a few weeks till i found trash getting sucked to the outlet line.... pi$$ed me off when i found all it was after changing filters blowing out lines, checking injection.... you name it.

 

 

Yep, been there, done all that! 



#8 Cvans ONLINE  

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Posted May 17, 2013 - 11:07 PM

I have one of those GT18's setting here that is almost brand new. If we lived closer I would make you a deal you couldn't refuse as I'm getting tired of looking at it. Hope you get yours running again. 


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#9 Utah Smitty OFFLINE  

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Posted May 17, 2013 - 11:08 PM

Well, I finally got the tank out.  Swirled it around and dumped it out... a few flakes of paint, a little bit of sand, and a bit of fluff, like cottonwood that may have been the problem...

 

I ran a new fuel line as well.  The old one was clamped to the chassis in a pretty hard to reach spot.  I cut the head off a 2" long 1/4" bolt and ran it into the old hose then slid the new hose on the other end.  Wiped down both hoses with brake cleaner. then wrapped electrical tape to hold them together.  I started pulling from the tank side, and sprayed a little WD-40 on it, and eased it out.  The "joint" held up for a moment then came through. It was late, so I'll finish up tomorrow.

 

Hopefully this will solve the problem.

 

Smitty 


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#10 Cvans ONLINE  

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Posted May 18, 2013 - 09:39 AM

Sounds like your getting close.



#11 Utah Smitty OFFLINE  

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Posted May 22, 2013 - 01:59 PM

Well, I got everything back together--clean tank, new fuel line, new filter... started and it ran fine... and then started to surge like it was fuel starved.  Eventually got so bad it would only run with the choke on all the way, and then only at idle...

 

I'm stumped.  I took it back to mom because I need to clean the yard--she'll keep using mine until I get some time to work on it again...

 

Smitty



#12 MH81 OFFLINE  

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Posted May 22, 2013 - 02:09 PM

How long was it running before it started that US?



#13 SearsYellow OFFLINE  

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Posted May 22, 2013 - 02:50 PM

I have a GT 19.9 that has the Flo Jet Carb. I worked on it for 4 hours oneday and finally got to the point I said the heck with it. It was two days later before I got back to it and I turned the key and it fired right up. It has ran great since. I do not know what happened between time A and time B but I am thankful it happened.

 

 

The one thing that is a constant PITA with these carbs is the spring on the float. My next door neighbors wasn't running great but he took the spring out and it ran great after that. I don't know if it comes off and blocks fuel from getting past the needle or what.


Edited by SearsYellow, May 22, 2013 - 02:50 PM.

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#14 HDWildBill ONLINE  

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Posted May 22, 2013 - 06:13 PM

Smitty does the carburetor have a Fuel solenoid on it?  I've got one in the shop that has a bad one on it, it won't run with out the choke and even then it wants to surge.  But it does it all the time not just after a while.


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#15 olcowhand ONLINE  

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Posted May 22, 2013 - 07:26 PM

The fact it starts running fine, then gradually requires more choke & even less rpm's definitely sounds like the fuel level is dropping in the bowl, but for what reason exactly I do not know.  







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