731 Stalls by itself

[731 Warrior]

I hope someone can help...Last snow season, I ran my machine to clear snow from my driveway (all 700 feet). Needless to say, the machine ran well for about 20 minutes, then stalled and shut down. Fuel level was full. Oil temp, I believe was normal, no high tempt lite. Hydraulics were also good, no pressure lite...I did not see leaks, and the hyd oil level was full. After 10 miunutes, I restarted the machine and let it warm up for about 10 minutes and discovered no problems, and then another 20 minutes later the same thing...it stalled and stopped without being placed in shutdown. Took it to the Bobcat shop last year for help and the mech's could NOT reporduce the symptoms. This snow year is going to be frustrating and impossible if I can't get this machine to run consistently. Any help is appreciated.

 

[Tazza]

Do you have fuel additive? i wonder if its geling or something causing it to stall. These machines ran a two cylinder deutz, the only way to shut it off is lack of fuel or to throttle it back. It would have to be a fuel issue, be it the lift pump or filter being plugged.
When running, i assume it runs well?

 

[731 Warrior]

Do you have fuel additive? i wonder if its geling or something causing it to stall. These machines ran a two cylinder deutz, the only way to shut it off is lack of fuel or to throttle it back. It would have to be a fuel issue, be it the lift pump or filter being plugged.
When running, i assume it runs well?

Tazza, I do use a fuel additive to preserve the diesel. It is the Deutz 2 cylinder machine runs loud but strong and smooth...last nite I thought of vapor lock ion the fuel tank too and will check to see if there is a vacuum in the tank after the next shut down...would getting the fuel system flushed help clean out the tank and the lift pump? Where is the lift pump?

 

[OldMachinist]

Tazza, I do use a fuel additive to preserve the diesel. It is the Deutz 2 cylinder machine runs loud but strong and smooth...last nite I thought of vapor lock ion the fuel tank too and will check to see if there is a vacuum in the tank after the next shut down...would getting the fuel system flushed help clean out the tank and the lift pump? Where is the lift pump?

If this only happens when you're plowing snow and you are sure there's no water in the fuel system that's freezing up likely the air cleaner is icing. When it shuts down and sits the engine temp warms the air cleaner back up and lets it run again. Below is from a Caterpillar document on air intake problems.
Air Cleaner Icing

Air cleaner icing can occur in saturated air environments when the dew point of the ambient air is near freezing. Small disturbances to the air such as velocity and pressure changes at the air cleaner inlet reduce the moisture-holding capacity of the air. This results in moisture condensation and ice crystal formation. The ice buildup reduces the airflow area and increases the pressure differential across the air cleaner. Several techniques may be used to overcome air cleaner icing. One solution is to heat the intake air slightly. It is not necessary to heat the air above freezing. The air requires only enough heat to be above the dew point. Heat can be supplied to the air cleaner housing by ducting engine room air. Heated air from the exhaust piping or muffler, or electrical heating tape may also be used.​

 

[Tazza]

If this only happens when you're plowing snow and you are sure there's no water in the fuel system that's freezing up likely the air cleaner is icing. When it shuts down and sits the engine temp warms the air cleaner back up and lets it run again. Below is from a Caterpillar document on air intake problems.
Air Cleaner Icing

Air cleaner icing can occur in saturated air environments when the dew point of the ambient air is near freezing. Small disturbances to the air such as velocity and pressure changes at the air cleaner inlet reduce the moisture-holding capacity of the air. This results in moisture condensation and ice crystal formation. The ice buildup reduces the airflow area and increases the pressure differential across the air cleaner. Several techniques may be used to overcome air cleaner icing. One solution is to heat the intake air slightly. It is not necessary to heat the air above freezing. The air requires only enough heat to be above the dew point. Heat can be supplied to the air cleaner housing by ducting engine room air. Heated air from the exhaust piping or muffler, or electrical heating tape may also be used.

Interesting, i'd never have thought that. One of those times i'm glad it never gets below freezing here.

 

[731 Warrior]

Interesting, i'd never have thought that. One of those times i'm glad it never gets below freezing here.

Well...good idea on the air cleaner icing...but when I ran in the winter, the machine was warmed up and I knew that there was warm air circulating into the intake, however it stalled this past SAT in beautiful earth moving weather...a good 75 degrees in the shade and I really needed to get some earth moved. Is there a possibiility that I am vacuuming out the fuel in the tank which is causing fuel starvation? or is there possibly enough water in the tank to just stall out the motor?

 

[Tazza]

Well...good idea on the air cleaner icing...but when I ran in the winter, the machine was warmed up and I knew that there was warm air circulating into the intake, however it stalled this past SAT in beautiful earth moving weather...a good 75 degrees in the shade and I really needed to get some earth moved. Is there a possibiility that I am vacuuming out the fuel in the tank which is causing fuel starvation? or is there possibly enough water in the tank to just stall out the motor?

Thats totally possible. You can try running it from a bottle of fresh fuel. Does the primer bulb go flat? does the machine slowly die? or suddenly just stop?

 

[731 Warrior]

Thats totally possible. You can try running it from a bottle of fresh fuel. Does the primer bulb go flat? does the machine slowly die? or suddenly just stop?

Tazza, The motor winds down in about 3-5 seconds...with no response from the throttle. I did catch the wind down in time sometimes with going to FULL throttle and winding up the RPM...it would sometimes NOT shutdown right away...I would run another 10-15 minutes then it shuts down again. I was planning on taking a fuel sample from the tank by disconnecting the fuel line from the tank going into the fuel filter and check for water mixed in with fuel. I also was looking to change the fuel filter and take a sample from it too. I am not sure there is a primer bulb - is it like the rubber bulb on my weed wacker? and where is it located in the fuel system?

 

[bobbie-g]

Tazza, The motor winds down in about 3-5 seconds...with no response from the throttle. I did catch the wind down in time sometimes with going to FULL throttle and winding up the RPM...it would sometimes NOT shutdown right away...I would run another 10-15 minutes then it shuts down again. I was planning on taking a fuel sample from the tank by disconnecting the fuel line from the tank going into the fuel filter and check for water mixed in with fuel. I also was looking to change the fuel filter and take a sample from it too. I am not sure there is a primer bulb - is it like the rubber bulb on my weed wacker? and where is it located in the fuel system?

Primer bulb: not like your weedwhacker. It's in the fuel line, between your tank and the filter. If there isn't one, there should be, and it should be simple to get one and insert it in-line. Fits easily in your fist, black rubber, oval shaped. ---RC