Trouble Shoot Briggs Fuel Pump

[R4665]

Briggs V-Twin
Model 44M777 0418 B1. SN 081212YG
On a John Deere Lawn Tractor

Symptom: Fuel is not reaching the carb.

I removed the fuel line from the Carb. When the engine is cranked, no fuel comes out of the fuel line. I checked the vacuum hose that connects the pump to the OHV cover. It had a small tear where it attaches to the pump. I taped up the hose as a temporary fix. I do not believe there is an air leak now.

I removed the fuel line that connects the gas tank to the pump. I blew air back through the line and could hear bubbles in the gas tank, so it appears there are no blockages in the fuel line. I did notice that the fuel line connects to the top of the John Deere gas tank. There is a tube that goes to the bottom of the tank. So there is no gravity feed and fuel pump must pump the fuel from the bottom of tank up the tube and to the carb.

The owner says he used the mower in 2013. Over the winter he cranked it two or three times. But when spring 2014 came, the engine would not start.

Questions:
1. What would cause a fuel pump to go bad? Gas sitting in the fuel pump?
2. Any way to clean or service the pump (Briggs Part Number 808656)?
3. Any further tests to run before I replace it and the vacuum hose?
4. Any other reasons fuel would not be getting to the Carb?

Thanks for your help.

[bgsengine]

Before condemning the fuel pump, make sure the dip tube is not broken or cracked - With fuel line coming off top of tank, there is a "Dip Tube" that goes from the fuel fitting to the bottom of the tank - any cracks , breakage, or other such problems (or air leaks where fuel line connects to the dip tube fitting) and the fuel pump will be just sucking air, and thus, just pumping air, no fuel.

[R4665]

Correction: briggs engine code is 0148.

Before condemning the fuel pump, make sure the dip tube is not broken or cracked ... the fuel pump will be just sucking air, and thus, just pumping air, no fuel.

Your suggestion gave me an idea. On the pump, I disconnected the fuel line coming from the gask tank. I then connected a spare fuel line to the pump and put the other end in a gas can. With the fuel line disconnected from the carb, I turned the engine over and gas flowed throughout the pump into a container. So the pump works.

The Deere gas tank had about 2" of fuel in the bottom. I thought it was enough fuel to at least get gas to the carb. I put in a gallon of gas which filled the tank half way. When I tested the fuel pump, it worked. Gas flowed through the pump. So either there is a crack in the lower 1/3 of the pickup tube in the gas tank or the Deere just requires a half tank of gas to get started.

However, the engine will not start. Fuel is getting to the carb but is not getting to the engine. The solenoid is working. I have tested it and you can hear the solenoid click open when the key is turned

The briggs v-twin engine has a Nikki carb. There is a plate on top of the carb you can remove. Underneath the plate are two brass tubes. Fuel is supposed to come up the tubes and then to the engine. That is not happening. When I removed the carb earlier, there were two brass main jets. Both fell out of the carb. I just noticed on the parts list that there two part numbers -one is for the Left Jet and the other for the Right Jet. So, apparently the jets are different. I have no idea if they are installed correctly. Do you know if the jets have markings that indicate which is left and which is right?

Also, the linkage that operates the two choke plates is confusing. When looking At the control bracket from the front of the engine, the right linkage has a spring attached and, when the throttle is in the run position, has tension when moved up and down. However, the left linkage has no tension and no spring is attached. When the throttle is put into "choke" position, the the right linkage appears to push the choke plate closed (I cannot see what is going on inside the carb). The left linkage appears to do the same, but I'm not 100% certain..

So, does any of this make sense? Three issues:
1. Fuel is not flowing from the carb bowl to the engine.
2. Main jets may be reversed.
3. Confusion over how the linkages are to be connected and how they work.

[bgsengine]

So, does any of this make sense? Three issues:
1. Fuel is not flowing from the carb bowl to the engine.
2. Main jets may be reversed.
3. Confusion over how the linkages are to be connected and how they work.

Last item first - From your description it is working correctly - there's not 2 choke plates - there's the choke (before venturi) and throttle (after venturi)

However, if you put the carb on bass ackwards, (it is possible on some designs) it won't work right.

#2 - No idea - with those carbs, generally they just get a new carburetor if they are badly fudged up. The jets are indeed a L & R (because the distance between carburetor venturi and intake valve is different between the 2 cylinders) and those jets must be in the right place for proper operation. It'd make more sense if they called them #1 and #2 rather than Left and Right as direction may be subjective depending on who's working on it... but as I've only bothered to have one of them apart and just put jets back in the same place they came from, I never paid attention to that detail.

and finally for #1 - as above - it won't get fuel if the carb ain't set up right. - Not only do the jets need to be in the right holes, they also need to be in the right orientation, among other possible issues. Judging by your confusion with the setup and operation of both the linkages and the jet positions, I'd probably suggest bite the bullet and spring for a new carb, if all you want is to get 'er running - If you are looking for a technical training seminar on those Nikki Carbs, it won't be me doing the presentation

[R4665]

there's not 2 choke plates - there's the choke (before venturi) and throttle (after venturi)

I removed the carb (again) and paid closer attention and you are right (of course). The choke (linkage on the right of the carb) opens and closes correctly. The governor is attached to a spring that is attached to the choke linkage. So when the governor moves back and forth, the choke plate opens and closes. The throttle (after Venturi) is held open when the choke cable is engaged. When the throttle cable is in the run position, the throttle is free to open and close. There is not a spring attached to the throttle linkage. This appears to be correct. I took several pictures before I started work and there was not a spring attached to the throttle linkage. This setup is the opposite of what I am used to in single cylinder engines. The throttle plate is connected to the governor with linkage and a spring and the choke plate remains open in the run position.

I found a great series of pictures of the inside of the Nikki carb.
Part One. http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb.asp
Part Two. http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb2.asp

Engine still does not start. Fuel is not being pulled from the carb to the engine in the choke position. Next step is to remove the nozzle body and clean all of the passages. (Part Two pictures 9 & 10). I hope this solves the problem.

[bgsengine]

The choke (linkage on the right of the carb) opens and closes correctly. The governor is attached to a spring that is attached to the choke linkage. So when the governor moves back and forth, the choke plate opens and closes.

Are you sure you have throttle and choke determined correctly? Is this a 4-bolt rectangular carburetor?

When installed on the engine, and you are facing the carb side of the engine, looking at carb, the choke linkages (and choke) are on your LEFT, and furthest away from you (closest to the air filter) While the THROTTLE is on your right, and linkage goes down from that DIRECTLY to the governor arm - and the governor arm has a spring attached that goes to the control head (which your throttle cable on the machine connects to)

and The throttle (after Venturi) is held open when the choke cable is engaged. When the throttle cable is in the run position, the throttle is free to open and close. There is not a spring attached to the throttle linkage. This appears to be correct. I took several pictures before I started work and there was not a spring attached to the throttle linkage. This setup is the opposite of what I am used to in single cylinder engines. The throttle plate is connected to the governor with linkage and a spring and the choke plate remains open in the run position.

I found a great series of pictures of the inside of the Nikki carb.
Part One. http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb.asp
Part Two. http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb2.asp

Engine still does not start. Fuel is not being pulled from the carb to the engine in the choke position. Next step is to remove the nozzle body and clean all of the passages. (Part Two pictures 9 & 10). I hope this solves the problem.

Also use those pictures to positively identify which is choke and which is throttle because the THROTTLE lever needs to connect direct to the governor arm, (which then has a spring that connects to control head which the throttle cable of the tractor is hooked to) - The choke linkage is a simple link (In the photos on that website, and all the ones I have seen) which is hooked separately to the choke cable. From your description, sounds like you have a single control head that also does choke function when activated , which in your initial post , is described pretty correctly - choke is spring loaded to remain open until the control lever is moved to choke position at which point a portion of the control head contacts the choke link pushing the choke closed.

Notice the Nozzle body which is behind the CHOKE SHAFT which will tell you which end is choke side of the carb, and that end should be closest to the air cleaner intake.

[R4665]

Notice the Nozzle body which is behind the CHOKE SHAFT which will tell you which end is choke side of the carb, and that end should be closest to the air cleaner intake.

Boy, do I feel like an idiot. I've only worked on single carbs where you can see the choke with the air cleaner off ... In other words the choke faced out. But on this carb, the choke faces the engine which is where the air intake is. So, I've been looking at everything backwards. All of the linkages are correct ... choke linkage on the left and the throttle on the right. Duh.

Still have to figure out why fuel is not being drawn into the engine. I need to verify that the choke plate is closing correctly. Will tackle again tomorrow.

Thanks for the patience and advice.

[R4665]

Problem solved.

1. Original problem: engine would not start. After removing the carb, I found that gas not getting to carb. The only thing wrong was the gas tank did not have enough gas. Although it had about two inches of gas in the bottom of the tank, it was not enough. The pickup tube inside the gas tank may have a crack, but the tube and tank are not accessible without taking off the body of the John Deere. Even then you cannot get into the tank to fix it. So, keep plenty of gas in the tank.

2. In reassembling the carb, I connected the choke link to the wrong hole in the carb. Once I connected it correctly, the choke engaged and the engine fired up and ran great.

3. I lucked out in putting the main jets in the correct order. I had a 50-50 chance.

Thanks for the info and suggestions. I learned a lot about v-twin carbs, fuel pumps, gas tanks and troubleshooting.

[bgsengine]

Problem solved.

1. Original problem: engine would not start. After removing the carb, I found that gas not getting to carb. The only thing wrong was the gas tank did not have enough gas. Although it had about two inches of gas in the bottom of the tank, it was not enough. The pickup tube inside the gas tank may have a crack, but the tube and tank are not accessible without taking off the body of the John Deere. Even then you cannot get into the tank to fix it. So, keep plenty of gas in the tank.

One final point - They are inserted to the tank with a rubber grommet, OR they are screwed to the tank with 4 screws and retainer plate - But for the most part they are serviceable without pulling fenders off, (Might need to UNBOLT fenders to shift it around to access the shut-off/Elbow/Dip Tube) - note I said "for the most part"

2. In reassembling the carb, I connected the choke link to the wrong hole in the carb. Once I connected it correctly, the choke engaged and the engine fired up and ran great.

3. I lucked out in putting the main jets in the correct order. I had a 50-50 chance.

Thanks for the info and suggestions. I learned a lot about v-twin carbs, fuel pumps, gas tanks and troubleshooting.

Good, glad you got it fixed, but if the dip tube is cracked, that crack is gonna spread eventually to where you'd have to keep tank topped off all the time.. So, may want to look closer at that area and see just what it would take to gain access to pull out dip tube and replace... best time to do that is before it fails, so you'll have some idea what you're up against

[R4665]

Great suggestions. Thanks for all of the help. Very helpful forum.