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GregB

fuel delivery problems

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GregB

Been struggling with fuel delivery problems on what started as a 17GTH. Now has a 16hp briggs. I have replaced fuel tank, no filter inside, new see thru in line filter, new carb. When it acts fuel starved, no visible gas is in the filter.

What can cause no fuel to be in the filter ?

Its a gravity system, the fuel tank cap is loose, so no vaccuum. Tank is very full. I have blown back thru the fuel line, bubbled strongly in the tank.

At a complete loss here ............

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spi

I had a B19 that had a similar problem. I also tried everything I could think of at least twice. what cured it for me was to replace the shut off with one that pointed straight down instead of 90 deg.

you wouldn't think it would make a difference, but it did for me.

Good luck

Jim

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rokon2813

Greg, did you replace the fuel line?

I've seen a couple that deteriorated inside in such a way that fuel would flow inside the lining of the hose, blocking the flow in one direction. Blowing backwards through it opens it temporarily.

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Bill725

I have a B&S 10HP in my 725 which is taller than the original 7-1/4HP. Because the 10HP carb is taller, I can only use the top half of the gas in the tank because there is not enough head pressure to force the gas past the in line filter and needle into the fuel bowl. I also put a shut off between the fuel filter and the carb so I can fill the filter with gas before connecting the gas line hose to the carb. Otherwise it is very difficult for the gas to displace the air in the filter.

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GregB

Went down to the garage this morning. Turned on the fuel, the empty filter filled right up, without changing anything but the shut off ?

Is it possible to "vapor lock" a Briggs carb from Engine heat?

Funny thing I just remembered, when it shut off from no fuel yesterday there was condensation? on the outside of the intake manifold just above the carb.

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MrSteele

Hard to vapor lock a rubber line.

I had your problem a few years ago. My solution is not the best, but it works, just have to replace filter when tank is empty. I installed my fuel shut off just below the carburetor, about 2" before the carb fitting. The filter is under the tank, barely visible behind the sheet metal. I have had no problems since.

I usually like the shut off between tank and filter, so that you can shut the fuel off to change the filter.

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GregB

Well my problamatic 16hp Briggs is at it again.  Been running fine, good full filter when it is 60-70 degrees outside.

But when outside temp in the 80's it continues to run the filter and carb dry. ???????

I even put a pulse pump in the fuel line.  Does a pulse pump have to be bolted fast to work correctly?

 

This was to be my main mowing tractor.  But if I cannot get past this, I'm going to yank this engine out and put a twin back into the tractor.

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spi

Try a different tank. Lash it  some place above the engine and plug the same fuel line to it. It runs okay then it's either the tank or its location. If it doesn't work then the problem is down stream.

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jlasater

Replace all the fuel line. Possible there's a "flapper" inside the line that is blocking off flow.

Pull the fuel line from the carb, does fuel flow out? If not, pull line from pump. Does fuel flow out? If not, pull line from fuel filter, does fuel flow out? Just work your way backwards. Is there a sediment screen in the fuel tank that's plugged?

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GregB

Did all that.  Different tank, no filter.  All new line and filter.  Replaced the carb with a known good one. Even put a pulse pump into the mix to create a little input pressure, although probably not much.

 

It only does this when it is hot outside and when I am mowing, working the engine.  This tractor has always seemed to me to run hot.  IE: I feel heat coming towards me when I am using it. 

My thought remains heat is the instigator , as when it is cooler it all works like it should.

Does anyone know what the cylinder head temp of a "normal" 16hp is?

Or temperature of block near carb?

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GregB

Still giving me fits.

Yesterday I went over to Father in-laws to look at his pair of 7116's.  Noticed he had the curved tin over the driveshaft that mine did not.  Everything else is the same.  Also he bought the one new, so its as he bought not altered.

Came home and found that shield, trimmed it to allow for the Starter/generator belt.

Mowed and it got hot ran out of gas. The frame was so hot next to the engine, below the carb, I could not hold my hand on it !

I did notice that the muffler outlet is slightly off the hole in the frame to exit the exhaust.

So today I will try to shift the muffler around, maybe try to extend it out thru the frame, even if it is temporary.

Maybe also add a 12v muffin fan to pull hot air out thru the hood vents.

 

Could having a starter/generator motor change the airflow that much?

 

Edited by GregB

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GregB

I doubt it is heat soak in the fuel line.  I think the whole engine is running hot, ie: my comment about the frame near the carb being too hot to touch.  But this only happens at ambient temps above 80 degrees.  Runs fine, does not run out of gas, when it is cool out. 

Does anyone know what external temps a correctly running Briggs 16hp under load should be????

Head temps, block temps etc?

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MARK (LI)

I had a similar problem with a 12.5 Kohler on a small John Deere...I had put a nice glass filter on it and had your problem...changed the filter back down to a cheap plastic red one and it has been fine since that..the glass filter looked cool...but for some reason would not stay full of fuel, no matter what I tried on it

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kwt

Unless the fuel lines are totally full IE: no air, you WILL get reduced flow. How much reduction? Some. In order to make your fuel lines conducive to being totally full of fuel with no air, there should be no sags. From the carb to the fuel tank, the line should be on a constant rise. That way there is no chance for air to take up space better used for fuel flow. Simplejim understands this. I've taken a fuel line off the carb and held it down to bleed air from it, letting the fuel flow as it will in to a container, and QUICKLY slapped it back on the carb so as not to let air get in the line.

 

I've gotten away with sagging fuel lines, and they are handy while servicing, but if I'm having the problems that GregB is having, I'm going to make sure that the fuel lines are FULL of FUEL, and not somewhat full of fuel and somewhat full of atmosphere.

 

Regarding simplejim's observation about having the filter vertical:, When it's vertical, it is full of fuel. When horizontal, it may become full of fuel over time by having the fuel slowly dissolve the air over time, but you and I know that when first run, you are only getting fuel transmission through 1/2 to 2/3 of the filter.

Sediment bulbs are old school, but they don't have this problem. The fine screen at the top outlet is always open to full fuel flow. I love sediment bulbs, but I'm not recommending one in this instance. I'm just pointing out how gravity systems used to be designed. If I had a filter in the tank, like say a B110, I would forgo an inline filter. These systems are run at less than 1 psi. 1 psi = 2.3 feet of head. ANY restriction will have negative effects.

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MikeES

Fuel filters and shut off valves all have a fuel flow direction arrows on them.  

Your engine may be running too lean causing overheating.

Operating conditions:  I have used my Briggs with no issues at over 100F outside.

Curved tin over the drive shaft??  I’m not aware of a large frame tractor with any shielding around the drive shaft.

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PhanDad
10 hours ago, MikeES said:

Curved tin over the drive shaft??  I’m not aware of a large frame tractor with any shielding around the drive shaft.

I believe the "curved" tin was a safety guard as opposed to anything to do with air flow.  Without the curved piece installed, there's a pretty good gap between the engine and battery/gas tank.  Easy for someone, especially a child, to get there had in there and touch the drive shaft.   Only installed with the 16HP single cylinder Briggs - it's not as deep as the twins.  

You can see it in this pic:

7116_0005.jpg.88f3d6ff7dd2fc41ec6dcf5e154d5013.jpg

 

 

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GregB

I might agree more, but the 2001 revision date Large Frame Repair manual I have says to adjust that tin to a 1/16" gap.  If if was safety even an 1/8th or 3/16 would be enough to keep inquiring fingers from the rotating parts.

I think back in 2001 the safety/liability police had not yet been effecting recommendations like today.

I figured an engineer had a reason for that dimension, not a lawyer.

 

Actually had to open up the slots a little bit to get to 1/16th. maybe a bit extreme, but I measure things for a living, Quality engineer by job title  sm03

 

Bill,

I will send you a response to the PM.

 

What I have done also is to make sure the fuel line is level to slightly "uphill" to the tank.

There also seems to be good airflow from the top shroud.

Had my IR temp gage on the carb and manifold when it was running at full throttle, and deck engaged.  Manifold was 85 degrees, carb not much more.

 

Next hot day mowing session will determine next steps.

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MrSteele

I had a Kohler in a Cub Cadet burning my left foot up while running. Scratched my head on that one. One could have cooked steak on the air coming out onto my foot! Turned out to be mouse homes in the fins. Have you looked under your sheet metal to see how many mice lived there over the winter?

On the subject of filters. And it is a subject. Be sure your filter is for a gravity system. A filter for late model engines with pressure systems will not allow enough fuel to flow to a gravity fed carburetor. Not sure what heat would change, but colder fluid is more dense and enough might flow through the filter to the engine to run it, while hot weather may heat it enough to prevent flow.

I cut regularly with an older model 10 HP at temps well into the upper 90s and low 100s with no problems.

On 6/3/2019 at 5:39 PM, GregB said:

There also seems to be good airflow from the top shroud.

That is what I thought on the Kohler, until I removed it and found bits of foam padding, lots of straw, some cotton material, etc...

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GregB


Did it to me again this weekend.  Tonite going to put the red and black briggs filter back on instead of the small dia clear one.  Going to hard wire a 12v muffin fan to the inside of the hood to come on when it is running.

IF that does not work, going back to the pulse pump, with it fastened to the blower housing.

All else fails the NOS 18hp Magnum is getting transplanted.

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