Possible Overheating?

   / Possible Overheating? #1  

funpilot

Silver Member
Joined
Aug 21, 2005
Messages
112
Location
Chesapeake, VA
Tractor
PT 425
After about 3 hours of moving mulch, my PT425 slowly shut off, like something electronic told it to. I had been driving it at less than half throttle thinking that since I had almost no weight in the bucket, no need to use full throtle. Also idled often as I raked in the mulch. What is the proper way of driving this machine so that it does not overheat? It would start right up and if I played with the throttle, it would be ok. If I had it at full throtle, I had to drive it fast to keep it from shutting off. Less than 1/3 throttle, seemed happier but lugged....
 
   / Possible Overheating? #2  
Might be trash in the fuel tank outlet, fuel line or the fuel filter. I have had this happen twice. Does it run better if you choke it a little while running at high speed. This is a sure indication of fuel starvation. You can disconnect the fuel line from the fuel pump and blow air into the line back into the tank. Don't use your mouth. You could drain the tank and then disconnect the fuel line at the tank. The trash is most likely at the tank outlet. It is smaller than the hose. Call me if you have any questions. Or PM.

If when you let it sit for a few minutes it starts and runs for a while this is another indication of trash in the fuel system.
 
   / Possible Overheating? #3  
funpilot said:
What is the proper way of driving this machine so that it does not overheat?



These engines need to run at full throttle for proper engine cooling regardless of load! When you are off the seat, shut the engine off!
 
   / Possible Overheating? #4  
It's possible that your problem is the ignition switch. I have the same issue, and have not yet checked it out, but I was advised by PT that the ignition switch may need to be replaced.

Turning the ignition switch "off" should ground the ignition system. If it does NOT, then the fuel solenoid shuts off, and it takes a second or two at half throttle to shut off, and maybe 5 or 6 seconds to stop if at 1/3 or less throttle.

Because the engine stops by running out of fuel, it takes some cranking to get it started, and it stumbles and hesitates until the fuel line and carburetor bowl are filled again.

The reason I have not replaced the switch (about $22 from PT) is that some time ago they instituted a $50 minimum order, and I have enough hydraulic filters to last me for the rest of my life since I added them to my previous small orders to make the $50!!

When I return home in about three weeks, I'll be looking into whether the switch is actually bad or the grounding wire is broken or disconnected at either end.

Hope this helps.

Makr H.
 
   / Possible Overheating? #5  
funpilot said:
After about 3 hours of moving mulch, my PT425 slowly shut off, like something electronic told it to. I had been driving it at less than half throttle thinking that since I had almost no weight in the bucket, no need to use full throtle. Also idled often as I raked in the mulch. What is the proper way of driving this machine so that it does not overheat? It would start right up and if I played with the throttle, it would be ok. If I had it at full throtle, I had to drive it fast to keep it from shutting off. Less than 1/3 throttle, seemed happier but lugged....
I would have to agree with Fourteen, always run at full throttle. >>> Also idled often as I raked in the mulch. <<< I guess that's what you are saying ..... you got out and raked in the mulch.

If you get off of the machine I would turn it off. It could be dangerous to leave the Pt running while you are out of the saddle. You can hit the treadle by mistake when getting back in and run over your leg or someone else. If you do have to leave it running, I would just make sure your brake is on.

I run mine at idle just at startup with a little choke. Just until it starts to idle smooth, then I go full throttle the rest of the time until I turn it off. When I do turn if off, I back the throttle down about half way to eliminate the famous backfire.

I would also agree with Bob, if you haven’t done it yet, check out your fuel system for debris. I found a lot of it in my PT from the factory. I took off the tank, changed out the fuel lines, and flushed the rest of the system. I also changed the gas filter. It made a big difference.

As for the ignition, I am waiting for it to go bad. When the time comes, I will look into a better ignition switch, other than the one PT offers. I think the one from PT looks kind of cheap.
 
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   / Possible Overheating? #6  
I'd vote that your shut-off may be fuel related, not electronic. When it happens again, take the cap off of the gas tank and look in. If you see bubbles coming up from the tank outlet, you have a vaporlock problem. Shuttinig down after a few hours is EXACTLY what I was dealing with until 1) I removed the debris at the fuel tank outlet and 2) replaced the clear fuel line with better and 3) installed an electric fuel pump and 4) rerouted the fuel line to the right (cooler) side of the engine, which can't be done using the stock mechanical fuel pump mounted on the left side.

Mine doesn't shut down now but I know that gas is still vaporizing in the lines before the carb, just not enough NOW to shut it off. It IS enough to cause the engine to run hotter because of the lean fuel condition. I can tell also because I can hear the difference (when restarting after a short break) in the electric pump, whether it's pumping liquid or vapor.

I'm giving serious consideration to installing an electric radiator cooling fan on the right side of the engine cover that'll blow across the exhaust end of the motor and out the muffler side. I haven't decided whether to wire it to be "always on" or have it come on when the hydraulic fan does.

Phil
 
   / Possible Overheating? #7  
The switch i bought was an Oregon 33-399. Replacement for Scag #48798 and Briggs #493625. I think it was $15 at the tractor store.

422 w/robin engine.
 
   / Possible Overheating? #8  
cqaigy2 said:
The switch i bought was an Oregon 33-399. Replacement for Scag #48798 and Briggs #493625. I think it was $15 at the tractor store.

422 w/robin engine.
Thanks for that info, I will look into it for my PT. How do you like it ? better defined key? better quailty I'm sure.:confused:
 
   / Possible Overheating? #9  
Barryh said:
Thanks for that info, I will look into it for my PT. How do you like it ? better defined key? better quailty I'm sure.:confused:

I think it's a direct replacement. Probably just as cheap but it's cheaper.:p
 
   / Possible Overheating?
  • Thread Starter
#10  
OK, I definitely have bubbles coming out of the fuel drain from the fuel tank. I see NO debris in the outlet. I never had this problem until I took it in for maintenance. What could they have done to aggrevate the situation to cause it? I presume to do any of the work you suggested, I will have to siphon the gas out of the tank .... I am sure for more talented men like you this is a non issue. I'll bet it has been my one and only problem since I got it back from maintenance. Otherwise, best machine I have ever owned. But, I keep looking at the diesel model .... hmmm
 
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