Troubleshooting LX279 runs well on flat, fuel issues on hills

   / Troubleshooting LX279 runs well on flat, fuel issues on hills #1  

BruceWard

Platinum Member
Joined
Sep 28, 2008
Messages
850
Location
Central, AR
I am making progress but would appreciate any advice.

I am aware of and using tips from these two threads

LX178 quits/won't run until cool - TractorByNet.com

and

http://www.tractorbynet.com/forums/.../170236-lx279-fuel-problem-17-horsepower.html

I have not checked for a broken wire under the battery but will do so. I charged the battery before my first attempt at mowing.

I bought a LX279 (17HP, water cooled, Kawasaki FD501V) last week. I mowed a large area at the sellers house and it ran great. My yard is mostly 10 degree plus slopes. I brought it home and tried to mow on the slope. It would die going up, down or across the slopes. Several mechanic friends who have looked at it believe the problem to be fuel delivery. When it dies it will run on choke or not at all once restarted. When it would not run at all we found that it would run if we removed the air filter and blocked off the intake. The fuel filter typically has very little gas in it. Fuel runs backward through the filter when the engine is turned off.

The seller told me that the carb was professionally cleaned this spring. My guess is that he left gas in it over the winter.

This is what I have done so far.

1. Replaced all fuel hoses and fuel filter. All three hoses from the tank to the filter, from the filter to the pump and from the pump to the carb.

After this it ran great with a strong idle at minimum throttle on level ground but died after about 100' of mowing on the slope. Gave up on driving it up the slope and towed it up the hill.

2. Verified that voltage was being sent to the carb fuel cut off solenoid. Then removed the solenoid to check its functionality. I found that it had been cut and was only functioning as a plug. I discusses this with the local small engine shop who said the solenoid only prevented back fires and they cut them off all the time.

3. Added 1.5 ounces of sea foam per gallon to the fuel and sprayed blaster lawn mower tune-up into the air intake while running (two 5 second bursts). Left the mower running at 50% throttle to work sea foam through engine. It died about 20 minutes later.

4. Gave it time to cool down and decided to test fuel pump output. I expected about an ounce a minute so I disconnected the output from the carb and placed the hose in a one fluid ounce syringe. It filled in a few seconds. After reconnecting the fuel hose it would not maintain seal with the original clamp so I replaced both clamps between the pump and carb.

I started and let it run at 50% again. It ran for about 30 minutes this time.

After letting it cool down I took it back to the slope. It died a few times but I was able to mow 400 feet or so before retreating up the hill to flat ground. The second or third time it died we were not able to start it without removing the air filter and blocking the intake. After it started I was able to mow a little more and then go back up the hill. I found that it ran better at about 50% to 66% throttle on the hill.

5. Gave it two more five second bursts of blaster lawn mower tune-up. Then removed the rear metal cover and changed the remaining clamps. I also pulled the fuel pickup and found it to be complete and clean. Careful if you do this, the fuel flow from the pump to the filter is gravity feed so it will flow out quickly.

At this point I took it to another slope area and mowed perhaps 500 feet before it died. I was able to restart with the choke on. I finished mowing and nursed it up the hill with the choke on. I had mowed at about 66% throttle.

6. Used a water hose to wash out the radiator. I tried to remove it but decided that was a larger project than I had time for today. The radiator appeared clean before I used the hose. It is mounted horizontally on top of the engine. A large fan under the radiator pulls air through it and out the front. The air flow through the radiator was significant before and after the cleaning. While running with the engine warm the air coming out is warmer than the ambient air.

I started it and it has been running at about 50% throttle for the last 75 minutes. The engine temperature warning has not come on. I am trying to let it burn through the sea foam in the tank.

The hood was broken so I am running without any hood at all. I plan to find one once I have the mechanical issues worked out. The ignition switch was not working well. I cleaned and tightened it and it seems fine now. The starter often spins but does not engage. Cleaning the starter is on my to do list.
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills
  • Thread Starter
#2  
It died again after about an hour and fourty minutes of running at 50% throttle. I was able to restart but it only ran under choke.
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills
  • Thread Starter
#3  
I let it cool down for about an hour. Then was unable to restart in any throttle or choke position. It did start after removing air filter and blocking the intake. After the blocked intake start it continued to start easily.

I was going to continue running through the tank of sea foamed fuel but discovered a fine spray of fluid building up underneath the fuel pump. The spray has a slight gas smell. It must be gas. Not certain if it is coming from the fuel pump or one of the hoses. Will figure this out on a cooler day.
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills #4  
Check the fuel pump. If the internal diaphram is ruptured it will expell gas out the bottom vent on the pump. Keep you fingers cross and hope it is only a loose clamp. You could have an intermitient electric connection near the starter or under the battery. there is a possibility a mouse chewed a wire after you brought it home without the hood. This could cause the slope problem. When the deck shifts it could cause the electrical problem to loose contact in a chewed wire. Doesn't cost anything but time to check this out.
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills #5  
Also check the gas cap for a clogged vent hole. Do this by loosing the cap enough to allow air flow around threads and see if it runs that way better.
Always mow at full throttle 100% of the time when deck is engaged. If you can ever get it to keep running. I had 2 problems with my LX279 the first was the gas cap plugged and caused the fuel pump to go bad and have to be replaced. The second problem was the chewed wire which I spliced and fixed. The chewed wire caused run problems just like you have described..
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills
  • Thread Starter
#6  
I will check the wires under the battery. Do you know if that wire was for the drivers seat safety switch? That is the only wire I am aware of going to the rear.

I forgot to add to my original post that I checked the vent on the gas cap. I can blow through it and the engine runs the same with or without the gas cap.

I am curious about the recommendation to mow at full throttle. It mows just fine at half throttle cutting a couple of inches off of thick bermuda.

A dying gas pump that has issues when hot would be a relatively cheap, easy fix. I have avoided ordering it since I had tested and found it pumping fuel. But I may try that next, especially since I saw the fire risk today.
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills #7  
Wires from the dash are routed under the battery to the starter area and there are 6 to 8 of them. I can't tell you what all of them are for without checking a wireing diaghram. You wouldn't think an eletrical problem would affect the running or fuel but I think some of them go to the electronic ignition system. Hopefully some others on the forum can give you more details and thoughts about your problem. :confused2:
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills #8  
I am wondering what was cut off and how this is working only as a plug from your original post. Do you mean the plunger was cut off the part was working only to plug the threaded hole it screws into?

2. Verified that voltage was being sent to the carb fuel cut off solenoid. Then removed the solenoid to check its functionality. I found that it had been cut and was only functioning as a plug. I discusses this with the local small engine shop who said the solenoid only prevented back fires and they cut them off all the time.
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills
  • Thread Starter
#9  
Yes, the plunger (rod) portion of the solenoid was cut off flush with base of the solenoid. I believe the normal operation of the solenoid to be to extend the plunger blocking fuel flow when no voltage is present and retract the plunger when voltage is present.

I believe your chewed wire problem was either a lack of voltage to this solenoid cutting fuel at the starter or a short in the seat safety switch circuit. From you description of the problem I believe your chewed wire was the solenoid wire chewed in two places. I believe the seat safety switch cuts spark and would kill the engine faster than the fuel starvation caused by the solenoid.
 
   / Troubleshooting LX279 runs well on flat, fuel issues on hills #10  
I think it had more to do with the spark or ignition as My soldnoid was functional and working. The starter would crank also but the mower would not run. My wire was making intermittant connection and it seemed to run OK after starting until I shut it off and the problem returned. Later it would only run with the choke half on and whenl I released the choke it would die. After I had spliced 2 wires it resumed normal opperation. One of the wires went to the bottom of the starter and the other went into a 3 or 4 way connecter then to the engine harness.
 
 
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