Allotment Gardening Advice Help Chat
Chatting => Equipment Shed => Topic started by: Andrew Burrow on March 05, 2010, 18:30
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Hi
Does anyone have any expertise on Briggs and Stratton 3 HP model 80832 engines.
I cannot get mine to run for more than 30 seconds to a minute and then it cuts out. It needs to start on full throtle and with little or no choke despite low temperature.
I have tried adjusting needle valve and it will only start on 1/2 to 3/4 turn open. Petrol tank has fuel and the fuel valve is open.
It used to start first full every spring not having been used since the previous spring. In Spring 2008 a friend borrowed it and the pull cable broke and they took it in to a dealer and had it serviced. I have not tried it since then and the above symptoms are the result.
Has anyone any ideas?. Thanks for any thoughts
Andrew
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Good evening Andrew and welcome to the site. Is the petrol fresh and have you checked the plug? Is it a 2 stroke or 4 stroke engine?
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Hi David
It is a 4 stroke and the petrol is fresh. Poured into an empty tank.
Kind regards
Andrew
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Is the oil fresh too?
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Hi David
It is 4 stroke so the oil is not a problem - it just lubricates. The spark plug is new. Mind you your previous comment made me think about dirty fuel. The tank was empty but could be the previous petrol evaporated leaving grease residue in the tiny outlet from the tank. I checked the air inlet to the tank and that is clear but it could be a partially clogged outlet. I will check that.
Kind regards
Andrew
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There could also be condensation in the tank, have you cleaned the filter? I would flush the petrol out and refill.
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Thnaks for that idea. I am not sure there is a filter. Which makes me think again
Andrew
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Hi,
Very often when petrol has been left in the fuel tank (and sometimes when it has evaporated) a residue is left on the small Gauze on the end of the pick up pipe inside the fuel tank, also if there is a diaphragm type of pump fitted, this can become "baggy" with age and stops working correctly.
From what you describe, it seems that you will need to remove the fuel tank and carb assembly from the machine and strip it to clean it out thoroughly.
I would suggest you replace any diaphragms and gaskets with original parts.
This might help,
http://www.briggsandstratton.com/eu/en/pdf/illustrated_parts_list/100/MS4030.pdf
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Hi
Many thanks for this thought, it seemed like the likely problem. Spent all of Sunday pulling entire fuel system apart including the carb. There was a gauze filter but no pump. Gravity fed and fuel definitely gets to the carb. Amazing amount of junk in the system and all got cleaned out. The net result is ..........no difference. The engine will fire but not run. I think I am going to get the fork out!
Andrew
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well, if you're sure it's not a fuel problem, then it must be the points/ condensor.
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Hi Gwiz
I still think it is a fuel problem because it will fire but not run. I just do not know enough about carburetors (yet) to solve it. There is some info from other that says that engines that will start but not run often have a root cause of a faulty diaphram. Cant find one of these in my carb but will see what info I can find on the net. My symptoms are just those of a faulty diaphram.
Thanks for your help
Kind regards
Andrew
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Hi, could you clarify a few points?
In first post your say it "runs for 30 sec to a minute" and the last post ,"fires and does not run",which is now the case and has anything changed since you stripped the carb?
Is the carb screwed directly to the tank or fed by a tube from the tank?
If the latter,is the float chamber held on by a single bolt,did you remove and clean the jets/emulsion tube in the carb?
Can you post a picture of the carb?
g8r
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Is there a little square plate on the side of the carb held on by (normally) 2 or more screws?
diaphragm behind it.
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Is the exhaust clear I've had a similar problem with a mixer engine! Took the fuel line to peices plus umpteen other checks, turned out to be a blocked exhaust!
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Thank you for the thought. The exhaust is clear.
Kind regards
Andrew
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Hi Gwiz
I still think it is a fuel problem because it will fire but not run. I just do not know enough about carburetors (yet) to solve it. There is some info from other that says that engines that will start but not run often have a root cause of a faulty diaphram. Cant find one of these in my carb but will see what info I can find on the net. My symptoms are just those of a faulty diaphram.
Thanks for your help
Kind regards
Andrew
Small engine carburetters are simple, because theres almost no moving parts. Replace the rubber diaphragm and the gasket. If that doest work, then its either not the carb or the carb is furred up in the fine channels. You can try totally dismantling the carb and using steel wound guitar string as a fine cleaning reamer, and cleaning out the channels that way. The diaphragm usually incorporate two flap valves so the failure of the diaphragm generally kills the engine stone dead apart from a few seconds running. You will have to strip it down totally really, clean it all and reassemble, theres never any point in half doing it.
Another strategy is substitution, if you have another carb you''re reasonable sure works ok. New carbs are a silly price - like £100, which is uneconomic.
It does sound like fuel starvation. The only other possibility is the fuel feed - airlock, or vacuum in tank holding the fuel back.
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Dear Gwiz,
I took the carb apart the other day but perhaps not fully. I did not see a diaphram, so I need to do this again more fully. Thanks for your comprensive comments and the thought on substitution.
Kind regards
Andrew
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Hello Andrew
In your first posting you quoted the model as 80832. That makes it a 3hp vertical crankshaft engine with a flo-jet carburettor. If so it won’t have a diaphragm or fuel pump as the tank is above the carb. The flo-jet is a bit of a pig to service as the lowest point for fuel is the space between the jet tube and the adjustment needle. Any water gathers there and corrodes the threads in the casting so the needle won’t screw in, and the jet won’t screw out for servicing. You are supposed to remove the jet tube to split the carb if you want to get at the float chamber etc. but you can usually wiggle it apart especially if the jet is loosened a turn or two. Blow everything out with an air line and, if the jet will screw out, you can initially set the needle by screwing it right in, not too tight or you will mark the needle, then screwing out 1.5 turns. Final setting is by setting the throttle at half revs and screwing in until the revs drop, then out until the revs drop then back to halfway in between. The pilot jet is then set in the same way with the throttle on fast tickover.. If the jet didn’t come out, the needle won’t screw right in so initial setting is guesswork.
One other thing, the symptoms of a dying B & S coil is poor starting, followed by running for a minute or two then stopping.
Regards, Richard
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Dear Richard,
You certainly know your Briggs and Stratton. Your description of my engine and carb is spot on. I will try once again on the carb, but I have pretty much done everything you said. Remarkably, I had no problem getting the jet or needle valve to move. Your idea on the coil maybe a step forward. Would I get one from Briggs and Stratton? Their web site does not even recognise my model number.
Kind regards
Andrew
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Dear Andrew
I am more used to the horizontal crankshaft versions of the side valve B & S engines but the magneto coils are the same. Coils are fairly expensive so be sure the fault is definitely not the carb or plug before buying a new coil.
Some early 3hp engines had a three pole mag and I don’t think these are compatible with the two pole type but if you have a two pole mag, replace it with the contactless magnetron type, prices are much the same and you won’t have to worry about points needing cleaning after a lay up. Any local Briggs & Stratton agent can supply the right coil.
Regards, Richard
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Dear Richard, GWIZ and all,
I now have a fully functioning engine on my rotavator. I am sure that it was junk in the carb, fuel line etc. I cleaned the carb and tank replaced the fuel line that was perishing on the inside causing a black dust etc. But the thing that finally got it started was Richard's advice that the needle valve should be opened 1.5 turns to get an initial start up. The manual said 1/2 to 3/4 and it would fire once and stop. When openned to 1.5 times it almost ran. On 2 times it ran and i could tune it. It now runs better than it ever did.
Many thanks to all.
Kind regards
Andrew Burrow