BCS 850 fuel problems

[cmyoung2]

BCS850, 14 hp B&S Vanguard. Motor seems to run fine with light loads on level ground, put the 32" bush hog on a slope and it seems to run out of fuel. Let it sit, it will recrank and run for a short period. I thought dirty carb, cleaned, thought kink in fuel line, replaced all the lines. My repair shop was surprised that the motor was gravity feed, he thinks that engine was designed to be on a stationary unit, and he was also thinking vapor lock, so I added a electric fuel pump. Still dies especially on slopes after 10-15 mins. After last shutdown, I opened carb and it was low on fuel. Fuel pump is pumping fine, new fuel filter. Any ideas?? I am getting rather frustrated.

 

[Tbolt76]

I had an 850 that would act like this if you let it sit all winter with gas in it. Mine was gravity feed, as I thought all of these were, and many other machines were like this as well, shouldn't matter. Bad gas clogs these carbs up unless you put in Stabil or some other treatment, or maybe drain altogether. Find a reputable briggs dealer who can rebuild the carb. It doesn't take much to clog the little passages in the carb with varnish, etc. When my Vanguard engine blew (camshaft came out the back of the engine housing), I bought a Honda 13hp from Earthtools, best move I could've made.
Tom in Raleigh

 

[cmyoung2]

Tom, Had the carb off, soaked in Chemtrol for three days (at the B&S repair shop) cleaned it completely more than once. I only use non ethanol gas in all my small engines.
I can hear a gurgling noise and see air bubbles in the gas tank between start attempts, but can't figure out how air can get into the lines. All fittings are clamped with screw type clamps, all gas lines are new 1/4" lines made for gas. I like the Honda idea if I could afford it.

 

[Tbolt76]

Is it possible that the fuel shut off is cracked enough to let air in? I don't think that a second/auxillary fuel pump is necessary. I'd call Joel @ Earthtoolsbcs.com to get his help, he's the biggest BCS dealer in the country. I hope your shop is reputable, I've run into a few here in the Raleigh area that talk a good game, but that's about all they are good for. Maybe the pump is pumping to much fuel compared to demand and flowing back upstream? Sometimes pumps have a vent line of some sort on older cars. I'd think adding a pump could be part of the problem. Are the spark plugs fuel fouled (black)? That would indicate getting too much fuel in addition to rich exhaust. Keep us posted.
Tom

 

[cmyoung2]

No fuel shut off valve. Fuel pump has no vent. When it dies, carb bowl is almost empty, but when the pump is turned on, fuel flow is good. When the engine runs, it is good, right at 3200 rpm, no sign of running rich I still think a vapor lock issue, but thought the pump should push it through. Did the same thing without the pump.

 

[Tbolt76]

Are your cooling fins clogged? There are shields around them that can clog if you are doing a lot of mowing. Vapor lock (I assume you already know this) is usually a function of running hot. Mine had clogged with leaves from flail mowing long windrows of them to grind them up for mulch. If not, I still keep coming back to something wrong with the carb or maybe its sucking air---bad gasket from rebuild? Mine had two mounting gaskets with a plastic plate in between, maybe there is something going on there? If you didn't replace those gaskets (which I assume you did-they don't come off intact usually) then maybe they are heating up and leaking?
Tom

 

[cmyoung2]

Cooling fins are clean, took the cover off and blew everything out. They actually were pretty clean for what I think is a 95' machine.
When I bought it a couple of months ago everything was OEM I think. Gas lines were formed, had the cut off valve and filter. Ran fine for short light work, but when I started mowing it would die after 10-15 minutes, so I figured dirty carb. Took it apart, cleaned with carb cleaner, everything seemed to be open. Inside was tarnished, but not really gummed up like I have seem. No effect, same problem. After a couple of tries at that, took the carb off and had local shop tank clean it just to make sure. They could not find anything wrong. Still same problem. Got to thinking vapor lock because the gas lines do run fairly close to the heads, so I raised the gas tank 1" with spacers to help keep things cooler, and so I could see. Still no good. So I thought 20 year old gas lines might be an issue, replace all, bypassing the shut off valve so they wouldn't kink. Still no good. Took it to the shop, they thought it was a fuel feed issue but could not figure out why, seemed to work better with a full tank of fuel, seems to cut off more on slopes. Have taken the carb apart just after it cuts off, and the bowl is empty, so I still think it is a fuel feed problem. Added a electric fuel pump, 1 to 4 psi, it seems to pump fine, engine runs fine, but still dies when it gets hot. The gasket in the carb is a fiber gasket, does not stick to either side so it is still in good condition. It does seem to die faster on slopes, but that's what I have, very little flat land. And some of the slopes are steep.

 

[farmerboybill]

If I remember right, you replaced the fuel cap? Try running it with the cap loose. Maybe the the fuel tank isn't venting properly. I have a John deere 60 that I've long intended to replace the cap because it'll die after 15 minutes work. Turn the cap, hear a whoosh, and get another 15 minutes run time. If I used it more, I'd change the cap..

 

[cmyoung2]

Bill, you are correct. I did replace the cap--cheap and easy first

 

[farmerboybill]

I guess I got sick of playing with the finicky Briggs V-twin engine and put a diesel on my machine. It was great when it ran well, but a royal pain when it didn't

Joel likes that engine, he might have some pointers if you give him a call.

 

[cmyoung2]

Talked to Joel yesterday. He said he really didn't work on many Briggs, had him baffled too. Today I took the fuel pump off, it started blowing gas out the vent tube, maybe a little too much pressure or not enough of a float valve seal? Anyway, hooked up to the Bio 100 and chipped for over an hour, no problems, and some of it was fairly large limbs as well as a lot of brush, so it had to work. Then hooked back up to the bush hog, 10 minutes and it started dying again. Is it just the steep slope? and it's really not that steep, I can stand and walk on it. Barely And it is a fuel problem, fires fine with a little ether, so it is fuel not electrical. I would consider re-engine with either a Honda or a diesel, but need to get it paid for first, which is difficult if it is not dependable.

 

[wstr75]

Is there a fuel pick-up tube inside the gas tank? If so, maybe the tube is sealing itself off in a corner when the tractor is mowing on a hill.

 

[cmyoung2]

The tank seems to be a good design with a sump low in the center. There has been enough fuel to cover the pickup hole, and all the lines are new. Good thought though.

 

[Bentleg]

Does it matter which way it is leaning, which way you are crossing a slope? Sounds like a float hanging...

 

[cmyoung2]

At first it seemed to be worse with the left side down, but now it doesn't seem to matter. It could be the float, I might have a chance to take it apart again tomorrow. Not real sure how to fix that.

 

[super55]

Where I used to work we had a walk behind mower that had a B/S Vanguard on it that would die out. Same type of symptoms your describing which led us to believe it was fuel related. We never really ended up fixing it but found out our culprit was a low oil shut off sensor in the bottom of the crankcase. When we got it on a pitch all the oil would run to one side and the sensor would ground out the ignition. Get it back on level ground it would crank right back up. Finally we just disconnected the wire. We knew when we had it on too much of a slope when it would start spewing out blue smoke. I don't know if yours has a low oil sensor but if it does it might be worth unhooking and see if the motor still does what it's doing.

 

[cmyoung2]

Mine does not have the low oil sensor, I don't think. And it will still fire, with ether, just after it dies, just will not continue, so I still think it is a fuel issue. What worries me is I may be on too steep of a slope. I measured and it appears to be about 25-30 degrees, not%. It shouldn't be a problem, I can walk it, the mower is stable, and some of the literature says you can bale hay at 45 degrees.

 

[wstr75]

CMYoung, the thread below may be helpful. Please scroll down to the arthurgreen Sept 16, 2007 comment. His fuel starvation problem troubleshooting found a crushed connector to be the problem:
Briggs & Stratton 18HP engine problem - Tractors Forum - GardenWeb

My guess is when running the chipper, the use is intermittent and thus the fuel consumption is less overall than when running the mower under constant heavy load.
Bill in NC

 

[wstr75]

On another topic, I saw where you had your 725 listed on Craigslist here in North Carolina a couple months ago and you recently mentioned it sold. I am planning to sell my 737 on Craigslist here in NC and would love to hear if you got your listing price for your 725. I felt your asking price was appropriate and reasonable.
Thanks,
Bill in NC

 

[cmyoung2]

Bill,
I got just about my asking price, unit went to Knoxville TN. The price was just tractor and tiller.

On another topic, I saw where you had your 725 listed on Craigslist here in North Carolina a couple months ago and you recently mentioned it sold. I am planning to sell my 737 on Craigslist here in NC and would love to hear if you got your listing price for your 725. I felt your asking price was appropriate and reasonable.
Thanks,
Bill in NC