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J.R.
J.R., Small Engine Technician
Category: Small Engine
Satisfied Customers: 7444
Experience:  Owner of outdoor power equipment business, repairing all makes and models.
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I have a 5hp ( 158cc) Briggs and Stratton ( Series 500) attached

Customer Question

I have a 5hp ( 158cc) Briggs and Stratton ( Series 500) attached to a power washer.
Last time it was used was in the SPring and it was working well.
Now it starts and runs long enough to use up the fuel that has been injected when the priming bulb is pressed, but wont keep running.

Fuel is mostly fresh
( did see some small black debris in tank)
also I retrieved a flat disc a bit bigger than a quarter with a hole in the centre from the tank!!!( strange).

what procedures should I use to check to see why fuel isnt flowing?
Submitted: 2 years ago.
Category: Small Engine
Expert:  J.R. replied 2 years ago.

Hello and welcome to Just Answer,

The flat disc in the fuel tank is likely off of the gas cap. It is not a big issue. Clamp the fuel line shut and then take the bolt out of the bottom of the carburetor that holds the bowl on. That is the main jet. It has holes in the sides and one down through the center. Use a small wire and clean out those holes and then try it. Let me know.

Customer: replied 2 years ago.
Dont quite follow. there is a large bolt that is horizontal and holds the gas tank on (as well as a few others) its not a main jet. carb is held onto top of gas tank with at least three screws
can you be more specific to this model? is the black plastic right angle piece of hose that runs from the metal line to the carb the fuel line? ( its about 1/4 inch diameter!

Is there some way I can get a picture to you?
Expert:  J.R. replied 2 years ago.

Sorry about that. I thought you has a larger engine. Sorry. You have the tank mounted carburetor. On thatt model the problem is likely the diapram that needs to be replaced.

http://outdoorpowerinfo.com/repairs/briggs_pulsa-prime_carb.asp

Customer: replied 2 years ago.
that series of pictures in the link sure makes some leaps!!!! so you are saying the carb has to come off and so all the little light wire/spring links ( throttle choke etc) have to come off? can you walk me through this?
Expert:  J.R. replied 2 years ago.
Customer: replied 2 years ago.
OK I got the carb off and disassembled and cleaned.
only thing I cant see is the main nozzle ( the last picture in the link you gave me. Where is it?
Expert:  J.R. replied 2 years ago.
You do not need to worry about the main nozzle on your style of carburetor. Just replace the gasket and diapram.
Customer: replied 2 years ago.
OK diaphragm seems to be intact I blew out all the channels and emptied the gas tank and will fill with fresh. Will let you know when Ive re assembled it!!!
Expert:  J.R. replied 2 years ago.
The diapram is likely stiffened. That is normally what happens. It may seem pliable, but trust me once you have a new one in your hand you will see how stiff the old one is. Replace the gasket and diapram.
J.R., Small Engine Technician
Category: Small Engine
Satisfied Customers: 7444
Experience: Owner of outdoor power equipment business, repairing all makes and models.
J.R. and 2 other Small Engine Specialists are ready to help you
Customer: replied 2 years ago.
OK I re assembled and got the same results engine runs after priming but stops. I will buy a new diaphragm and gasket.
Expert:  J.R. replied 2 years ago.
Thank you. Let me know.
Customer: replied 2 years ago.
JR Well I replaced the gasket and diaphragm, made sure the fuel filter at the bottom of the pick up tube was clean. COuldnt do much with that other strainer looking thing( different from the picture mine has a fine wire mesh over it) filled with clean filtered fuel Reassembled and...same results starts right away and runs until priming fuel is used up ( 1-2 seconds) then stops...... Ideas now?
Customer: replied 2 years ago.
I am awaiting some more ideas to fix this are you still with me?
Expert:  J.R. replied 2 years ago.

Ok,

If it is still doing the same thing then it sounds like something is plugged up internally in the carburetor. Make sure that you have the gasket and diapram positioned correctly.Make sure the diapram is against the tank. Make sure the fuel you are using is less than 30 days old. Those plastic carburetors do not like to be soaked, so if you still have problems then you may need to replace the entire carburetor.

Customer: replied 2 years ago.
something is plugged up" what could that be and what do you suggest? I blew through the fuel pick up tube and it was clear. The gasket and diaphragm are on the right way the fuel is new.

Customer: replied 2 years ago.
lets be logical Fuel is OK as it starts right away on being primed.
Problem is therefore with drawing the fuel into the carb - yes? how is that done? vaccuum? what mmakes the diaphragm pump the fuel? so if there is a leak at the Carb to head O ring or a crack in the carb it wont work? what did you mean when you said they dont work when soaked? did you mean they distort and lose a seal?

What is that other tube with the strainer on it and what does it do?

This engine has only a few hours on it the power washer is rarely used and it was new three years ago. WHat could go wrong if it sits doing nothing?
Expert:  J.R. replied 2 years ago.
The tube with the screen is the pickup. When you soak the plastic carburetors in the acid it can and will distort them. Check the small rubber elbow and make sure it is not cracked.Let me know
Customer: replied 2 years ago.
small rubber elbow cant be relevant can it? Its a breather

what else could be blocked in the carb?
What do you use to clean carbs of gunk?
the long tube with the screen on the end is the fuel pick up tube is the other one with the fine mesh allover it ( but not in the pictures you sent on the link) a fuel return?

should I use gasket goo to help counteract any possible distortion in the carb at the gasket or the O ring into the cylinder head?
Expert:  J.R. replied 2 years ago.
Do not use any gasket goo. The rubber elbow is the pulse tube that works the diapram. Use a spray carburetor cleaner to clean it.
Customer: replied 2 years ago.
aHA! You are referring to the small rubber elbow about 1/4 inch bore that runs from the carb to a metal tube that runs over top of the tank and under the engine block?
OK that sounds promising as it looks a little ratty! ( Local shop said it was the crankcase breather!!!!)

will get back to you
Customer: replied 2 years ago.
ok the rubber thingy is |OK..so before I go oput and buy a new carb can you answer these for me please.

the shorter bu fatter tube under the carb you said was the return gas line. I have the screen off and there is a little blue cap with a hole in it. I can neither suck nor blow through it so I can assume it is blocked. how do I remove that little cap?

Between the carb air intake and the entrance to the cylinder block there is a little protrusion on the carb with a hole in it that goes right through to the tank gasket. should this have a cap on it? Otherwise it is open to the air and leaning the mixture seems like a funny thing.
willtry to send pictures to illustrate what I am describing
Customer: replied 2 years ago.
ok the rubber thingy is |OK..so before I go oput and buy a new carb can you answer these for me please.

the shorter bu fatter tube under the carb you said was the return gas line. I have the screen off and there is a little blue cap with a hole in it. I can neither suck nor blow through it so I can assume it is blocked. how do I remove that little cap?

Between the carb air intake and the entrance to the cylinder block there is a little protrusion on the carb with a hole in it that goes right through to the tank gasket. should this have a cap on it? Otherwise it is open to the air and leaning the mixture seems like a funny thing.
willtry to send pictures to illustrate what I am describing

how do I send you a file?
Customer: replied 2 years ago.
re last note forget last items the hole is where the throttle shaft goes of course - I was getting tired. so the shorter tube that sticks down and has a mesh over it - Ive removed the mesh and there is a plastic insert with a hole. Should I be able to blow through this or is it a one way valve and I should be able to suck through it? at present I can do neither and when I insert a thin wire into the hole in the centre it stops hard after a few millimeters. Is this a clue?

This is the last round after this - its a new carb!!!

Ian
Expert:  J.R. replied 2 years ago.
The center hole has a check valve in it. You should be able to blow air through it.
Customer: replied 2 years ago.
OK what is the technique for removing the little plastic cap with the hole init as this may be the problem.
( If its the fuel return line why would the check valve allow you to blow from the tank side? wouldnt it be checked that way and open the other?

Expert:  J.R. replied 2 years ago.

See attached link. This is the entire service manual for that engine. Click on download and wait for the timer to expire and then click on download again.

http://www.4shared.com/document/_BVdyGa_/briggs_l_head.html

Customer: replied 2 years ago.
thanks for this JR. I managed to get the carb stripped down even got the main jet out and all cleaned. But still the same response so I am probably going to take this to the dealer. But give me one more shot.

HOw does the gas tank vent to prevent a vacuum being pulled? If the tank isnt venting the fuel wont flow..and isnt it a strange coincidence that that little quarter sized plate with the hole was in the tank? oould it be a tank venting thing?

Expert:  J.R. replied 2 years ago.
Can you post a picture of the quarter sized plate?
Customer: replied 2 years ago.
yes how do I post pictures?
Expert:  J.R. replied 2 years ago.
Click on the paperclip in the toolbar. Make sure it is a jpeg format.
Customer: replied 2 years ago.
hmm I use Google chrome as my browser and I dont see a paper clip in fact I dont see a tool bar! Ill try my other computer.
I have the photos on my blackberry is there an e mail address I can send to?
Customer: replied 2 years ago.
JR
Lets try one more angle and assume the gas is getting through but air isnt.
When I "start" the engine with the primer and it runs for a few seconds, as soon as it starts to run there is a lever that is joined to the throttle that causes the throttle to move hard over perhaps shut. I assumed this was some automatic choke arrangement - but this lever comes from under the main body of the engine and I cant see where it comes from. Its on the left of the carb looking from the tank side of the engine.
Expert:  J.R. replied 2 years ago.
That engine uses an air vane governor. That is what the linkage connects to.
Customer: replied 2 years ago.
could this be responsible for the problem? cutting off air> what if the linkage was connected to the wrong hole in the throttle plate bracket?
Expert:  J.R. replied 2 years ago.
It could. It should be in the hole closest to the air filter mount.

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