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Mower Man

Backfiring Engine when under increased load

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That in my mind would prove its a carb problem. Running lean problem.  You might try something. With on hand on the throttle and the other on the choke increase the RPM and at the same time shut the choke fast and give it more throttle and let up on the choke when it starts to flood out. Do this several times and make sure you give the engine time to recover. This should clean out a partially blocked passage way inside the carb.

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On 5/14/2017 at 8:13 AM, Mower Man said:

I ran another tank of gas thru it and it only backfired and quit once.   If it does it more then rebuilding the carburetor is the next step.  I will have to find the model number and order the rebuild kit.

 

Now it will run for 20 min and then it backfires and quits and I can restart it in a couple of minutes to run long enough to park it (10 min).  Maybe it is the carburetor?

 

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Did you try what I posted in post #51?   Also, is it equipped with the fuel shut off solenoid? Did you bypass the safety controls and try it?  We need to rule out something here instead of just saying rebuild the carb or purchase a new one. First, try the choke thing that I mentioned in post #51 and see if that pulls any blockage thru the carb. If that doesn't work then I suggest that armed with a can to catch fuel you take the fuel line off the egress side of the solenoid  if so equipped. Gas will either flow easily with the key on or it will dribble. If it doesn't flow good the problem is there. If it does flow move on or consider the fact the solenoid might have a problem that develops after say 20 minutes and check it again for flow.

 

I would try another can of either lacquer thinner or the seafoam stuff. Put it in the tank start it up let it get warm shut it off and let it sit overnight and see if it starts and runs the next day and if its any better.

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This could be the classic "debris in the fuel tank" restricting fuel flow at the screen on the shut-off valve. What can happen is debris/junk gets redistributed in the tank when fuel is added. As the fuel is drawn from the tank this junk ends up back at the screen. When there is no more demand for fuel the junk will drift away from the screen but it does not go far. The next startup will result in a shorter period of time before flow is restricted.

 

Start out with a least 1/2 a tank of fuel.

Remove the fuel hose from the fuel pump or near the front of the tractor and let gravity completely drain the tank back into a fuel can. Watch the flow rate. It should not change from start to finish. If it does change it is time to remove the tank and give it the hot water soap cleanup with a good flush. Save the spoils to see just what was in it. You may be amazed. A few hours in the hot sun will evaporate any water left from the process.

 

Have seen the screens get what appears to be a calcium buildup but is likely oxidation from ethanol fuel. While working in the area it may be worth replacing the valve so you are good for another 20 years. The rubber bushing the valve pushes into is easily obtained as most makes use the same one.

You can also cut the screen off the valve and add an inline filter to the fuel hose closer to the engine so it is easier to replace next time but still get a new rubber bushing.

 

Garry

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That's a good thought. I'd remove the tank and clean with lacquer thinner and not worry about cleaning it with water. The lacquer that is left in the tank is of no consequence. So, where is that fuel solenoid valve? They have been used in several different ways over the years in different applications. I've seen them screwed into a "T" connector that is threaded into the carb. The valve allows flow into the carb bowl. I've seen them in line between the fuel tank and the carb.

 

I think I remember someone saying this model has a fuel solenoid valve. Like I said if so equipped it would make sense the way it is starving that it just might be the problem. Anyway if so equipped need to check its operation.

 

So far the poster seems to be making progress with his run cycle getting better so we are close.

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Re-read the poster #15 post. What sticks out ? I'll answer that.....its the 20 minutes of run time before it has a lean backfire and experiences problems. Check the fuel shut off valve! Its a solenoid and as a coil it can develop an open and the valve will shut resulting in a fuel blockage. It sits 10 minutes and makes internal connection and  now he is able to start it again. Before it would not start. May be a blockage AND a solenoid coil problem.

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Well.  I did not rebuild the carburetor.  Just using fresh Regular Auto Gas and it has been running fine the once a week for 30 min that it takes me to mow our lawn.

I am surprised that it is running so well now in the heat of summer.  Oh well.  Enjoy the heat.

 

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Posted (edited)

August 25, 2017  

Well,  After running it once a week for about 30 min all summer long without any backfires it started doing it again.  The fuel tank was 1/8 full so I filled it up and cleaned the air cleaner and the backfiring persisted.  It backfires to the air cleaner and makes a nice light show.  The Fuel filter was full but the Regular Auto gas was from July.  Could that be too old?

Any ideas appreciated.  I feel like I am back to square 1.

 

Edited by Mower Man

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49 minutes ago, Mower Man said:

Regular Auto gas was from July.  Could that be too old?

Image result for yes

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Its not an oil/gas mix so I will say no. My mowers are currently running on early July gas without a problem. Its got to most likely be a fuel pressure or carb problem in my humble opinion.

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Just for everyone'd info:

 

Seafoam engine treatment in a can and Seafoam in the spray is the SAME STUFF. It will clean out passages in spray form if it gets to it. It will decarbon pistons and fog motors. I sold it for 10 yrs. I have personally stopped a ticking lifter in my old truck by adding to the oil. I have seen it stop a knock in my B-I-L's car. I have stopped my wife's Dodge Caravan from pinging by spraying it down a throttle body and fogging the engine. I add a little to the gas on my 520 and the surging problem at idle is almost completely gone.  It works. 

 

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If your cheap like me you put kerosene in the oil to free up the lifter and use water down the carb to clean carbon deposits off pistons.

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I'm not cheap. 

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3 hours ago, Mower Man said:

Regular Auto gas

 

1 hour ago, 6bg6ga said:

currently running on early July gas without a problem.

If he was running ethanol free gas I wouldn't think it was the problem, but he isn't!

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Good catch there 953.. I made the mistaken assumption that everyone here knew NOT to run gas with ethanol in ANY small engine.  Definitely part of the problem. I will gladly pay the .50 a gal extra to not purchase gas with ethanol in it.

1 hour ago, squonk said:

I'm not cheap. 

 

 

I am. I belong to the gun of the month club. I have wheel weight lead to buy and reloading components to purchase. I have to cut corners somehow.:think: to feed my shooting obsession.

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Posted (edited)

did you recheck the seat switch connection to make sure you are not experiencing the same problem. I'm late to the party and just read the whole thread. I have a 99 314-8 and when I started reading this thread the first thing I thought of was a safety switch killing the motor, Mine will kill the motor if I push the brake to hard,try and mow in reverse without turning the switch under the seat, put it in gear with the park brake set, and can't remember all of the other possibilities. I haven't worked mine for several years. It has lead the life of a trailered show queen.

 

I've done the pull the chock up till the motor almost chokes out and I've also put my hand over the carb with out the air cleaner and choked it all but out also, be very careful with this method on what motor you are doing it to I;ve been told you can suck the flesh off your hand, at least that was what I was told years ago.

 

One more thing in regards to gas, I use pump fuel, but only hi-test 92 octane. I usually buy my fuel every 2 months with rewards card from Giant Grocery stores. So my gas can be several months old before I ever put into my tractors,and then the gas can sit for in the tractor for up to a year or so, becuase the tractors only get run a couple of hours at best in a year. Now I do add sta-bill to my gas when I buy it.

years ago after buying my 88 Dodge Dakota I was having problems with it and took it back to the dealership. they thought they would replace my throttle body fuel injectors. When the mechanic pulled the air cleaner off and looked down the throttle body throat he was amazed at how clean it was, he turned to me and asked if I run hi-test gas and I said yea I do. He said that hi-test has additives that keeps your injectors clean that regular does not. right then ans there I decide I would only run hi test fuel. I have gone back to running mid grade fuel with the hi cost of fuel these days tho. mid grade is a mix of hi-test and regular. been running it in my cars for years without problems. But I always run hi-test in my L & G equipment

.

Don't know if any of this will help you for sure, but I hope it does something for somebody. good luck and hang in there we'll help you figure it out

 

 

 

 

 

eric j   

Edited by ericj

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