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18hp Briggs L108 fuel issue, Push rods swapped?
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Posted by
spudthegreater none (
My Page) on
Thu, Apr 14, 11 at 11:46
| Long story short, had an issue of a blown gasket causing oil to choke out the engine, didn't know it was a gasket until I had the entire engine apart on a table...Well I have since put it back together, new gasket and after a lot of trial and error, I am having an issue with fuel feed. I have adjusted the valves to where it starts up correctly now, but I may have swapped the push rods. Would this cause a fuel issue in the carb? If I put some fuel in the intake, i can get it to start and run for a few secs, but then it acts like it is not getting fuel. the fuel line has fuel pouring out when i disconnect the line from the carb, so I know it has fuel to the carb, but the carb does not seem to be processing the fuel correctly to the engine. Thoughts? |
Follow-Up Postings:
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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all the similar posts I've seen on this forum point towards a need to more thoroughly clean the carb - by taking it fully apart, soaking in appropriate cleaner, running a thin copper wire thru all orifices, blowing everything out with clean compressed air, reassembling with fresh gaskets from the correct carb kit.
also do a net google search to find illustrated parts list for your particular carb and/or a service procedure to keep you from making errors - or at least taking a lot of pix bfore/during/after to help... |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| "I have adjusted the valves to where it starts up correctly now, but I may have swapped the push rods. Would this cause a fuel issue in the carb?" Push rod in the wrong place will not cause the symptoms you mention. Depending on WHAT 18 hp Briggs you have, IF it is a model 31----, the aluminum push rod goes on the Intake valve. Note that there are probably a half dozen B&S 18 hp engines and they are not all the same so model number is always important. Does it have a fuel solenoid sticking out the bottom of the carb? Does it have 12V to it when starting/running? Is the plunger in the solenoid working? Does it click? Does the plunger work freely when solenoid is removed? Walt Conner |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| IT is a model 31777p if my memory recall is correct. the fuel solenoid works fine, it engages when the key is turned off, I cleaned out the carb and the float seems to be working fine, it is plastic, with a rubber tipped needle float seat. I hate to put down another 50 bucks and not have it be the carb, but I cannot think for the life of me what else it could be, but the carb. I see no evidence of any fuel pump in this system, and I do seem to get fuel from the line when I dis-connect from the carb fuel intake. You asked if it has 12v to it when it is starting and running, I guess my answer is yes, it starts from a 12v battery source, but I dont know about when it is running since I cant get it to run more than a few seconds after I put some fuel in the intake. |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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How old is the battery? Is the battery charged, and is it connected into the charging loop? Or, are you starting it from a battery sitting on the floor?
Where is the fuel tank? Under the seat/fender assembly? If it is there you will have a fuel pump. If the tank outlet is higher than the carburetor, it may not have a fuel pump.
Also, check the bolt that holds the bowl on the carburetor, for tiny holes that you may have missed! A lot of engines have them, and some don't. |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| ***"You asked if it has 12v to it when it is starting and running, I guess my answer is yes, it starts from a 12v battery source, but I dont know about when it is running since I cant get it to run more than a few seconds after I put some fuel in the intake."*** Actually, the question that was asked simply meant "Is there 12 volts present at the wire that feeds the fuel solenoid when the key is in the run or start position."
That question was not to imply that the engine had to actually be running to check for 12 volts.
If you have a 12 volt test light, turn the key to the run position and check the fuel solenoid wire for 12 volts (or "battery voltage").
Or if you do not have a test light, or a volt meter.....simply touch the fuel solenoid with a finger or two and turn the key switch on and off.
If you feel/hear the fuel solenoid clicking, there is a very good chance that 12 volts would be present at the fuel solenoid when the engine was running normally. |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| Well, I figured out the problem, or at least "A" problem. I had been having issues with the oil from the dipstick vent which pushes air into an inline fuel oil breather device and noticed that I had plugged it a couple years ago to prevent the oil bypass from starving out the fuel. So now I can get it to run but still have oil spooging into the fuel air line choking out the carb. I had set this piece of junk aside for two years due to disgust of having paid 1700 bucks in 2004 for it new. I wont make the same mistake again in buying an L series briggs and stratton John Deere ever again. what a hunk of crap. Thanks for the advice though. |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| Mownie, Do you understand any of this gobbly gook? Sounds to me like the crankcase breather is not working but really doesn't "compute" to me. Walt Conner |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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***"Mownie, Do you understand any of this gobbly gook?"***
I think that stg needs to look at the Briggs IPL for his engine to determine the correct nomenclature for some of the components that have been cited in his discourse. |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| The device is round, has a copper metal screen and has the fuel line from the tank connected to it, then a line from the engine oil dipstick connected to it and then the line from this breather to the carb. It appears that this is what provides fuel pressure since without it the fuel wont feed directly from the line that comes from the tank. THere is NO FUEL PUMP on this model so dont tell me to look to the fuel pump. for whatever reason oil seems to foam out of the copper screen and drip onto the deck, and eventually it kills the engine. (oil and fuel mixing i presume) I sold it last night...tired of fighting it. |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| Is there any chance the component pictured below is your mystery object? 
|
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| That be the unit. the round copper colored disk near the middle of it just off to the upper left of the center circle, is what had oil spooging out of it which would choke off the carb after a few min's of running. I thought it was a blown gasket and after taking it to a JD implement shop, the mech thought so to. So I replaced all the gaskets and reassembled. Still does it, so With two other JD lawn tractors in possession and working, one with a Kawasaki twin and the other a Kohler, I got rid of the Briggs two nights ago, (mind you this has been going on for two years)It took two years to build some initiative to reassemble the mess and get it running again. Tell me your thoughts, i might be able to relay them to the guy who bought it from me. he doesn't live far away... |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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At this point my only thoughts are:
(1) The component pictured above is the fuel pump (that's a fact, not just a thought).
(2) I pity the poor guy who bought the tractor (but you might not want to tell him that). |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| Not disagreeing with you, that certainly seems to be the function of it, but the mech at the JD Implement didnt call it a fuel pump. Anywho, why is there oil comming out of it? And i sold it to him for a steal of deal so I dont feel to bad about it, but I am glad I got rid of it. |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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It is a "pulse vacuum operated" fuel pump.
It works because there is a hose connecting a diaphragm chamber in the pump body to the crankcase area of the engine (this could be a valve cover, the engine case itself, or a portion of the oil dipstick tube).
The pressure inside the engine crankcase changes from a positive pressure to a negative pressure (vacuum) as the piston(s) move up & down.
This "pressure pulse/vacuum pulse" cause the pump diaphragm to move in & out in its chamber and fuel pumping action takes place on the opposite side of the diaphragm.
Oil is "spooging out" of the chamber atmospheric vent on the pump because the engine has (or had) a serious problem of excessive crankcase pressure which has likely damaged the diaphragm chamber and oil is now migrating up the pulse hose and out the fuel pump diaphragm chamber vent. ***"the mech at the JD Implement didnt call it a fuel pump"***
As a professional mechanic myself I would beg to ask "Who called that guy a mechanic?" |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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| So it could just be the fuel pump after all since the unit engine was dismantled, inspected and reassembled with new gaskets etc...? |
RE: 18hp Briggs L108 fuel issue, Push rods swapped?
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I will only go so far as to say the fuel pump has been damaged.
The engine might also have other problems such as a defective crankcase breather oil separator causing oil to get into the intake system and/or affecting the crankcase pressures.
In fact....I'm wondering if this is related to your having plugged "something" a couple years in an effort to "control oil". |
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