Briggs 3.5 won't stay running without choke on

[White94RX]

I'm hoping you guys can help me before I throw this thing in the scrap metal bin. I've got a McLane edger, with a B&S 3.5 on it. I think it is a 091202 or similar. Backstory is that like always, it sat unused for anywhere between 5-8 years. So I took the carb off, cleaned it out, and reassembled. It ran, but wouldn't stay running without some choke. I could play with the choke back and forth, and it would stay running. But if you turned it all the way off, it would die within a few seconds. Obviously I think it's fuel related, and the gasket between the gas tank and carb was barely existent, and I figured it was sucking air. In my search for a gasket set, of course I found a totally new carb, with gaskets for $20 on Amazon. Done. So I installed it, and it went well enough. Started right up and ran flawlessly for about 10 minutes or so. Throttle worked, choke worked, etc. Good to go, or so I thought.

I brought it home, and a few days or a week later, I went to run it again. It took about 15-20 pulls before it finally fired up, but when it did, it ran totally normally. Another week or so goes by and now I'm thinking about using it (itching to do some yard work, this cold weather is killing me). Now it starts right away, but does the same thing it originally did. Won't stay running without playing with the choke. So I'm thinking this chinese carb is junk, so I put the original back on, with the new gaskets from the new carb. Same issue. Won't stay running without working the choke. I really don't know anything about how these governors and springs work, but playing with it doesn't seem to change much aside from revving the engine super high. I tried bending the linkage up or down (effectively shortening or straightening it) with no change.

I'm thinking it has to be fuel/air related, right? I get my can of brake clean, and spray around with it running, and it's definitely seems to be affecting it. Aside from the gasket where the carb mounts on the tank, and carb to the engine, what else is there? And both new and original carbs behave the same way. Hoping someone can shed some light on this for me and get this thing running. I'm considering swapping it for a predator engine, but don't really want to put any money into it. It came free from my mother, and I've only spent $20 on it so far. Thanks!

 

[ILENGINE]

Depending on which fuel tank you have there may be a small shallow well built into the tank under the carb. If your carb has two fuel tubes, the long tube is used to pump fuel up into the shallow well where it is draw into the carb to be burnt in the engine. Sometimes that shallow well will rust through and have a hole in it preventing the well from holding fuel. So you may of had to crank several times to refill the well.

 

[StarTech]

The actual model and type would be nice so someone can look-up the engine.

 

[cpurvis]

The fuel pickup tube on this style of integrated tank/carburetor has a check ball in it. If it leaks, it takes numerous pulls to refill that tube before it gets to the venturi of the carburetor. It is replaceable.

There is no float chamber, float or needle and seat. The fuel tank itself takes their place.

The gasket between the carb and fuel tank is irrelevant to the fuel mixture. All it does is keep fuel from leaking out onto the top of the tank.

The easiest way I've found to start one of these that has set for any length of time is to remove the air cleaner and use your favorite starting fluid to get it running. I use a few drops of gasoline and it usually fires up on the first pull.

 

[White94RX]

Depending on which fuel tank you have there may be a small shallow well built into the tank under the carb. If your carb has two fuel tubes, the long tube is used to pump fuel up into the shallow well where it is draw into the carb to be burnt in the engine. Sometimes that shallow well will rust through and have a hole in it preventing the well from holding fuel. So you may of had to crank several times to refill the well.

The tank was a little rusty, but I don't think there's a hole in the well. When I've taken the carb off, it still has fuel in it. This doesn't explain why it won't run unless choked partially...

 

[White94RX]

The actual model and type would be nice so someone can look-up the engine.

Its a B&S 3.5 hp, on a McLane edger from the late 90's or early 2000's if I'm not mistaken. I posted in the original post the number on it is 091202. I may be a digit or two off, since the edger is at home and I'm posting from work, but I'll double check it.

 

[White94RX]

The fuel pickup tube on this style of integrated tank/carburetor has a check ball in it. If it leaks, it takes numerous pulls to refill that tube before it gets to the venturi of the carburetor. It is replaceable.

There is no float chamber, float or needle and seat. The fuel tank itself takes their place.

The gasket between the carb and fuel tank is irrelevant to the fuel mixture. All it does is keep fuel from leaking out onto the top of the tank.

The easiest way I've found to start one of these that has set for any length of time is to remove the air cleaner and use your favorite starting fluid to get it running. I use a few drops of gasoline and it usually fires up on the first pull.

Thank you for your input, but the carb has been removed, cleaned, and even replaced. The engine ran normally on two occasions, and then does not run normally now. It only runs when partially choked. My theory is that its sucking air from a leak somewhere, but aside from the two gaskets themselves, I'm not sure where else it could come from. Unless there's something beyond the carb before the actual combustion chamber...

 

[cpurvis]

Take a GOOD look at that pickup tube. It has a screen on the bottom or it might be cracked. These things are sensitive to fuel level in the tank as well. High manifold pressure will also reduce the ability of the tube to draw fuel from the tank.

My musings about how the carb works is more for the benefit of others. I know you know what the inside of your carb looks like but others may not.

Replacing carburetors with online cheapie carburetors, as you found out, doesn't always fix things.

 

[White94RX]

I appreciate the input. On the original carb, I broke the bottom half of the pickup off. I used a piece of vacuum line to act as a replacement. The new carb I didn't break obviously.

It's just funny how the first time I put the new carb on, it ran like a champ, just like it always had. And then the next time I ran it, it took a few extra pulls, but once it started it was fine. Then the third time it starts acting up. And now it does the same with both carbs. I'm a little perplexed. About ready to dump it for a predator engine from harbor freight. Hopefully they go on sale soon and I can score one for $99.

 

[cpurvis]

It should only cost a few bucks to put a new tube on your old carburetor.

I'll bet that fixes it.

This isn't the one for your engine but just a representative of the price, etc. There are you tube videos on how to replace it.

Briggs and Stratton 391813 Pick Up Tube - Jacks Small Engines