Briggs Carb Problem / Question

[KE4AVB]

BGS, I think you are confusing the Briggs date code with the Husqvarna date code. Of course I am nearly through my first pot of coffee already.

Craftsman 917.288570, Serial: 091411A019030 was actually produce September 14, 2011. Where as the Briggs Code: 110907YG is 2011, September 07. One of the quickest installation of a new Briggs I have seen lately in a new Husqvarna mower.

I am fairly certain you will not any this year installed this quick.

Off the to stores as my cabinets are bare this morning but I am having to keep them this way so I stay on my diet; although, I think I ate one of my table legs this morning.

[bgsengine]

BGS, I think you are confusing the Briggs date code with the Husqvarna date code. .

Yup, I did.. forgot the Husqvarna/AYP date codes are bass-ackwards from Briggs..

[lefty]

I got the same result this morning. Wouldn't start. If I could wax for a moment, my guess is there's some sort of diaphragm in this that allows fuel to flow in one direction. Which should close and keep fuel from flowing in the wrong direction. Maybe it is failing and overnight as the fuel drains backwards allowing a sort of airlock to formulate? I just put a used, known-good pump on it to test it. But I have to wait until tomorrow. Once I start it for the day, I have no problems all day. It's only the next day that it won't start. When I first turn the key, it almost starts but doesn't. It gets about 1 or 2 pops off and then just cranks. Until I relieve the pressure by disconnecting the fuel line. Then it turns right over and starts right up. And continues to start periodically every couple of hours or so.

[bgsengine]

If I could wax for a moment, my guess is there's some sort of diaphragm in this that allows fuel to flow in one direction. Which should close and keep fuel from flowing in the wrong direction. Maybe it is failing and overnight as the fuel drains backwards allowing a sort of airlock to formulate? .

Umm you just described how a most any fuel pump works- even mechanical fuel pumps will have check valves as you describe - and typical results of a failed flapper (check valve) or flapper spring.. assuming the carburetor is the high point. HOWEVER, with a float carburetor, consider: How would it possibly be sucking fuel back out the carburetor, which should still have enough fuel in it to start and run for 30 seconds to a minute - long enough for fuel pump to pull fuel from tank and replenish (except in uncommon cases where the run between tank and carburetor is much longer, such as on some old Wheel Horse and John Deere models, where runs may be up to 4 or 5 feet of line)

[lefty]

I don't know.

If the check valve in the pump is not seating properly, could a larger column of gas in the line prior to the pump drain the bowl? The fuel line drops substantially from the pump as it heads back to the tank. The other line heading to the carb is very short and almost level. Since the pump appears higher than the tank, if allowed to, wouldn't the fuel have a tendency to want to move through that line toward the tank?

I don't know...I'm hurting my brain over here. I guess I could just check the bowl. I threw a different fuel pump on there yesterday so we'll see how it goes in a bit. Plus I'll be replacing the o-rings in the carb soon.

The good news is that it eventually starts...it just takes some patience and doing. So success is attainable I'm sure.

[KE4AVB]

What is strange is that it is developing a vacuum between the carburetor and the fuel pump. Try setting a gravity fed tank and let it sit over night. First with the fuel pump inline and then with the fuel not inline. I wondering if the fuel pump is going bad causing this problem or you have a fuel line problem before the pump. It is a long run from the back of the mower.

[lefty]

I'll try that. Thanks. In the meantime, I did a leak down which came out good on both. I have spark on both sides during the no-start condition.

[lefty]

I got the same results. Thank you for the hook up on the orings. They fit like a glove.

I think I may have overcomplicated this for everyone, including myself.

I think this is a simple carb issue. I put 100lbs into both cylinders and they held 93-94lbs each. I got good spark during my no-start condition. My flywheel key is intact. I can get it to start with some carb cleaner and then it runs fine. I thought I had a fuel flow issue but I've been working on that and I think I may have been chasing my tail on it.

Am I overcomplicating this? I cleaned the carb and it looks good but how many times have you heard that? I think I may have to bite the bullet on this one and try a new carb at this point. I'm going to take another run at this one in the cleaner. My apologies on this one.

[Arkie]

Does not appear to really fit your vacuum issue on this one but do keep in mind that some small engine gas tank vents are designed to seal a pressure and allow air to enter the tank preventing a vacuum lock.

Also that is good info about the itty bitty jets being different sizes in the bottom of the emulsion tube.on some of the Nikki carbs. was not aware of such.
But since the jets are side by side in parallel into the same tube I do not see how they would upset anything if they were swapped in place?

AND if those jet o-rings do not have a good friction fit the engine will usually surge and hunt.
I keep old emulsion tubes and carbs around for those parts so I can maybe dodge the high price for the little o rings..

[KE4AVB]

Sounds like you got a choking problem.


And yes Arkie 0.62 is high for the tiny o-rings but they are still a lot cheaper than the $12 jets.