# Vanguard Twin runs rough on hills



## Country Boy (Mar 18, 2010)

I have a 23hp Vanguard (can't remember the model #, its from 2006 or so) in a Simplicity garden tractor at work that has been giving me fits. It ran perfectly fine last year, but this year has been giving the owner troubles. It runs perfectly fine on flat land and moderate hills, but when he mows his backyard (its a very steep hill the whole way up and down), it starts sputtering and running like crap. If I try driving it on the 45+ degree hill by the loading dock, it runs fine, even when I park it there for a time. Seems the deck has to be running for it to act up. I can't run the deck on that hill because its gravel and not very smooth so I can't easily test it. What I do notice in the shop is that if you have it idling and snap it up to full throttle, it will respond, then start mildly surging, then even out and run smooth as glass again. I have removed and flushed the tank (found a bunch of debris in there), changed the fuel filter, and removed and flushed the carburetor. The carb was clean as clean can be inside when I took it apart, with no apparent dirt or varnish in there. I blew carb cleaner and compressed air through all the ports in both directions, but it made no difference. One other thing I have noticed is if you let it sit for a few days in the shop, and try to start it, it has to crank a very long time before it will start. Almost like the carb and fuel lines are dry and it has to pull from the tank. Shouldn't be happening if you had it running before because the bowl should still have fuel in it. I'm about to toss this tractor off the loading dock if it doesn't work, and the owner is about ready to help me (he hates the tractor with a passion).

Any ideas on this? I'm not very familiar with the dual bore carb on these models, so if there is anything I am overlooking, please let me know! :dazed:


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## jhngardner367 (Apr 5, 2011)

Rich,check the breather & breather hose,to see if the breather is plugged/staying open,or the hose is leaking. That could cause the fuel starvation,under load,and also cause the dry start condition. You might also check the fuel pump.
There is also a weird,and kind of rare problem,if the carb has a fuel solenoid:it's been found that the fuel solenoids sometimes "flicker" under heavy loads,due to loose contacts at the connector.


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## Kohuth77x (Mar 16, 2012)

Replace all your hoses, fuel hoses that is with a new fuel pump and a new am pressure tube and diagram, mine did that identical thing, that fixed it


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## Country Boy (Mar 18, 2010)

jhngardner367 said:


> Rich,check the breather & breather hose,to see if the breather is plugged/staying open,or the hose is leaking. That could cause the fuel starvation,under load,and also cause the dry start condition. You might also check the fuel pump.
> There is also a weird,and kind of rare problem,if the carb has a fuel solenoid:it's been found that the fuel solenoids sometimes "flicker" under heavy loads,due to loose contacts at the connector.


By breather, I am assuming you mean the crankcase breather assy on the valve cover? I'll check that this morning. I did notice a bit of oil on the air cleaner base assy when I took it out to clean the carb. More than you normally see from oil vapor, but not so much to cause problems with the filter. The filter was dry and clean. I'll also check the solenoid connectors. I had thought to try a new pump to see if it changed anything. I have a few here in the parts bin.



Kohuth77x said:


> Replace all your hoses, fuel hoses that is with a new fuel pump and a new am pressure tube and diagram, mine did that identical thing, that fixed it


I can try new hoses, though these seem to be in excellent condition. What do you mean by "am pressure tube and diagram"? Did you mean "Diaphragm"?


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## Kohuth77x (Mar 16, 2012)

Yea sorry about that, iPod make some stupid corrections sometimes


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## Country Boy (Mar 18, 2010)

I was digging into this today, and the breather looks fine. Fuel lines are all in A-1 shape, fuel pump pumps like crazy. Tore the carb off again and ran a fine wire through every port available and then some. Blew everything out again. I tested the solenoid and discovered it sometimes sticks and won't engage unless you very gently touch the tip or tap it on something. Will try a new solenoid and see what happens. Still wanna toss this thing off the dock.... :argh: :dazed:


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## jhngardner367 (Apr 5, 2011)

Rich,is that the Nikki 2 bbl carb ?


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## Country Boy (Mar 18, 2010)

It is a 2 barrel carb, can't remember if it is a Nikki or Walbro. Bowl is held on with 4 screws, black plastic float, thin shaped o-ring to seal the bowl to the carb body. There is a brass tube coming from the bowl out at an angle an its capped off with a rubber cap. Not sure what that is for as it leads directly into the bottom of the bowl.


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## ftorleans1 (Jul 12, 2009)

If the engine has a low oil sensor, you may have an issue with the sensor. I have seen the sensors ground the ignition system due to a bad wire connection or if the sensor has crud on the sensor tip. Make sure the oil is topped of and try running with out the sensor connected and see what happens. I have a pressure washer which has a Honda engine with a low oil level sensor. It would act up on any incline and sometimes on flat ground. Replacing the sensor fixed the problem. With your situation, Revving the engine would cause an influx of oil splash and could possibly cause the sensor to kill or partially kill the ignition system. If you are absolutely sure the carb is clean, that your float is good and not sticking, the fuel solenoid checks out ok, look into a bad low oil sensor if so equipped...
Good luck!!!Keep us posted!!!


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## jhngardner367 (Apr 5, 2011)

Gotta agree with ftorleans1,Rich.hadn't thought about it having an oil sensor(old-timers disease,you know)!


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## Country Boy (Mar 18, 2010)

I don't think it has an oil level sensor, but it does have an oil pressure sensor on the oil filter housing. I snipped the tip off the solenoid this morning and reinstalled it (new part won't be in until late next week) and tried running it that way. It still surges a bit when revving it up, and sometimes when dropping from full throttle to 3/4 throttle (the control has 3 detents). I tried running it up a steep hill by the dock with the deck running, and it only surged once. I barely noticed it at that and it could have been the trans engaging again as I was parked on the hill and holding the trans partly in forward to keep my position. This thing has really got me baffled. It runs smooth as glass otherwise and I can't find even the smallest speck of dirt in the carb. Even the fuel filter was clean when I changed it. The engine only seems to surge a bit when revved up or down suddenly or when on a hill (though I haven't been able to duplicate the hill climbing problems the customer claims). He said the unit ran perfectly fine last year, but this year it started surging on the hill in his back yard. Nothing I have done so far has had even the slightest impact on how it is running. I think the solenoid was the cause of my dry start issue, but not the running issue.


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## jhngardner367 (Apr 5, 2011)

Rich,check the coil,and the governor setting. Also,how are the plugs looking? What happens if you put it in neutral,when it starts doing this?


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## Country Boy (Mar 18, 2010)

Plugs are brand new, customer replaced them when it started acting up. I haven't been able to replicate the problem yet, so I am not sure if the trans will affect the running. I can check the coil, but judging from the spark I got from the torn spark plug boot that I replaced, it is in good shape. The spark was arcing almost 3/4" to the block. When it first came in it was running rough all the time and replacing that boot seemed to take care of it. I tested it after doing that and it seemed to run fine on the hill. He used it and brought it back with the same problem. No matter how steep a hill I climb, and no matter how long I leave it sit on that hill running, it never seems to act up here. The hill I am testing it on is almost 45°, but I don't know how steep his back yard is.


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## jhngardner367 (Apr 5, 2011)

*23hp*

Rich,
I just had a thought.Is he mowing across the hill,or up/down the hill? Is it possible,that the hill is SO steep,it allows just a bit of oil to get in the air cleaner assy,causing it to stumble,and as it levels out it burns clean,and runs ok?Going UP the hill,it may starve for fuel,due to the severe angle.
If you can get the owner's manual,it may give a clue.Some models had a limit on running angles,and some had a switch that would kill the engine in a rollover/steep angle run,if the blades were engaged.


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## Country Boy (Mar 18, 2010)

From what I gathered from his description, he is mowing up and down the hill. He said it worked perfectly fine since he bought it (2006) and just started acting up this spring. I think the excess oil I have been seeing in the air box (though none on the filter) is from driving down the steep hill. He made it sound like the problem only happens on the uphill climb and otherwise it runs fine. I agree with the fuel starvation, and I adjusted the float to increase the fuel level in the bowl this time around. I will find out how it worked this weekend and see if that made any difference. He picked it up Saturday so he could cut his grass and he will bring it back today or tomorrow if it doesn't work right.


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## rptfromme (Apr 26, 2011)

I'd try a compression test, dry and wet, and check the intake gaskets. I've seen gaskets leak under load. Strange, but true. Also, check any safety switch connections.


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## Country Boy (Mar 18, 2010)

Well, I finally got the solenoid in and the tractor is back to get it installed. When I was taking off the air cleaner housing to get at the carb, I noticed that there is even more oil in the air cleaner area. Enough to make me suspect something is up with the engine beyond fuel or electrical systems. I am going to do what rptfromme suggested and do a leakdown test on both cylinders and check for blown head gaskets or bad rings/valves. The breather is in excellent shape, but the oil is a bit down and it seems to be weeping quite a bit from the valve cover gaskets and the whole intake/head area. He has mowed several times since I last saw it and there is definitely more oil there now than before. I hope I am onto something here.


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## Country Boy (Mar 18, 2010)

Hmmm. That's interesting...

Pulled the sparkplugs on the engine today and found the #2 plug was covered in a white oily substance (oil and water mixed). There was a drop of water across the plug gap as well. The piston had a few drops of water on it as well. Pulled the #1 plug and it was normal.

Did a leak down test on the engine and found the intake valve on cylinder #2 is leaking (got a 55% leak on that cylinder). Did the other side and got 95% leak that seems to be coming mostly from the exhaust valve. Pulled the valve cover on the #1 cylinder, and it looked fine, brown oil, rockers in place and slightly loose (seem to be set correctly, not hanging up on the valves). Pulled the #2 valve cover and found both push rods bent and laying in the bottom of the galley. I guess that solves the rough running problem then. It was running on one cylinder the entire time, but ran like a top on flat ground like that. Now to find out why the push rods bent. Both valves open and close smoothly and don't hang up, though the intake still leaks. Have to pull the heads next week and find out why the valves are leaking.

Customer said it ran fine last year when he put it away. First cutting it was running like it is now. Could the valves have set up in storage and caused the bent push rods? The valves seem loose and smooth now.


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## jhngardner367 (Apr 5, 2011)

The tappets could have stuck,from rust. That could cause the bent pushrods.


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## Country Boy (Mar 18, 2010)

Both rods were bent in the middle, about a 10° bend. Didn't really see white residue in the galley or the valve cover, but the breather did have some in it this time (didn't see any the last time I checked the breather). I'll know more when the parts come in and I can pull it apart. The customer insisted that I bolt it back together and drop it off so he can cut his grass this weekend. I tried to tell him it wasn't recommended, but he insisted. At least the bent pushrods are out of there so they can't hang up on anything or get into the crankcase. It strikes me as odd that this engine ran so smoothly on one cylinder. The last Briggs (an Intek 26hp) that we had in the shop with bent/missing pushrods on one cylinder ran like crap. The customer knew right when it happened because he could hear the change in how the engine was running.


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## Country Boy (Mar 18, 2010)

Well, I got it done and out of the shop. When I pulled it apart, I discovered a thick deposit of burnt oil on the bottom side of the #2 head. The exhaust valve guide had loosened and moved, so it overheated on that side. The other head was fine. I found no debris around either cylinder, so I am at a loss to explain why one cylinder overheated and the other one didn't. This is the 4th Briggs engine with a blown head due to overheating that I have worked on in the last couple years. The distributor I get Briggs parts from said that they believe Briggs has a known issue with overheating, but Briggs won't admit to it. I just worked on a Kohler engine for a friend of mine that had blown both head gaskets, but it happened at about 2400 hours. That tractor gets the snot worked out of it plowing and tilling his father in law's 3 acre garden (Simplicity Legacy 25hp). This tractor with the Briggs only cuts lawn and it overheats and fries the engine. I personally think Briggs runs them too lean so they run hot to begin with. We had a Briggs 9hp Intek we sold to a guy (the same guy with the 3 acre garden) for a shredder to shred paper for bedding for his chickens. It had an old Briggs 8hp engine on there that was simply worn out after nearly 30 years on the shredder. The 9hp engine ran about 2 hours and the head overheated. Briggs had us install a new head. It ran about another 3 hours and it overheated again. They had us replace it again, and told me to have the guy run it at about 1/4-1/2 choke. Since he started doing that, it hasn't had any issues. The last head replacement was 5 years ago now.

All I can say is I won't be buying a Briggs engine anytime soon. We sell mostly Kohler, Kawasaki, and Tecumseh engines, and by far, we sell the most repair parts for Briggs engines. My recent experiences with their engines have really soured me to them. It seems like anything built after about 2005-2006 is junk, and that is also when they switched to Metric fasteners on all the engines. I wonder how much of their stuff is made in China now days... frown


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