Murray 36" Lawn Tractor Drops RPM's Then Stops

[Veggie PAK]

The Model Number is 4-36508 and the date of manufacture is March 1983. This one cylinder, air cooled, electric start 11 h.p. lawn tractor was purchased from a Roses Department Store in 1984. I have the Owner's Handbook, but that is useless for this problem. The lawn tractor was well maintained, and then sat unused in a garage for probably 15 or so years. I'm trying to help my son get it fixed so he doesn't have to use a push mower. I've read some things about possible solutions to this problem. It has a new spark plug. It has a new battery. Let me share that there is no safety switch under the seat on this one that could go bad. No switches or wires of any sort for something like that located there. Below the seat but not connected to it on the frame of the tractor is the solenoid and a fusable link. I don't know how to check those to see if they're good. I've checked the air filter, gas filter, wires to see if insulation is worn off and shorting out. Everything seems to be ok. While it is running, after 3 or 4 minutes, you can hear the rpm's start to drop. Then it takes a few seconds for it to shut down this way. The odd thing is that it is a smooth drop. Like someone turned off the key. Oil is clean.

If anyone has some info on how to fix this, I would sure appreciate it if you would share it with me so I can help my son out.

 

[Rhodie Ranch]

Old gas? Nowadays gas doesn't last long, so we have to add an compound to make it last thru the winter months.

 

[vfem]

First, Murphy is right... gas isn't good anymore but for so long. Have you emptied and refilled all the fluids? Second, is the fan running? We had found a bad fan on ours was causing it to get too hot and engine would just die.

Also, worn looking or not... there may be a short in the wire running to the battery and while its running the connection starts to give or weaken.

Those sound most likely the causes to me.

Good luck!

 

[Veggie PAK]

It has new gas and oil in it (even though the old oil wasn't really dirty looking) and the "fan" that is inside the housing at the top of the engine is spinning with the rpm's. It's like a giant push lawn mower engine. You know, you can see it spinning under the protective shield with little round holes on the very top of the engine.

As far as the wires to the battery, it has an alternator (somewhere, so the book says) so it wouldn't get the power from the battery to run. Isn't that correct? I'm not a mechanic, in case you haven't determined that by now. I know just enough to get into trouble.

 

[seedcorn]

What does the inside of the gas tank look or feel like? After all these years sitting, you could have rust flaking off blocking gas flow. After the vacuum stops (engine dies), the flaking will fall off allowing gas flow again.

I had the sponge inside tank (stops splashing) go bad last year, blocking up the carb jet.

 

[Veggie PAK]

First of all, I want to thank everyone for their time in helping me try to figure this out.

Second, I said I wasn't a mechanic, but knew enough to get in trouble.

Third, I think I got it figured out. There is no rust in the gas tank because it is a heavy rubbery plastic. Apparently that is a specific design feature. After running the engine twice for as long as I could until it shut off, I had walked away to do something else. When I was going to walk past it to get by, I happened to notice the gas cap tilted hard to one side. It wasn't like that before, or at least I hadn't noticed it. I opened the hood and saw that the top of the rubbery plastic gas tank was sucked in, thereby drawing the spout to one side. I removed the cap and the tank sprung back into shape. The filler cap has a knurled thumbscrew of sorts on it, and you can turn it in or out, but you can't remove it from the gas cap. It must be a safety feature where gas doesn't evaporate into your garage when you store it after use. You can screw it up for open and down for closed. It had been in the closed position, so when you ran the engine, it ran until it used the gas up enough to draw a vacuum in the tank, and the engine wasn't strong enough to pull against it for very long. It was strong enough to suck the top down before it cut off due to gas starvation. I opened the valve on the cap and started it up. I drove it around for 23 minutes without it cutting off, so I declare it "fixed"!

I have NEVER seen a gas cap with a valve on it like that.

Again, let me say thanks for the time you spent thinking about this for me. I really am thankful for this site and the related ones where we can feel free to ask each other's help on different issues. Thank You All, and the owners of this wonderful site.

Edit Note: Funny, but the owner's manual didn't say a word about that. Not even in the troubleshooting section.

 

[Rhodie Ranch]

Well, we all learned from that! My DH's push mower won't stay running either. So I'll mention this to him. As he sweatedly pushed the ****** thing up hill back into the garden shed the other day, muttering bad words...

 

[vfem]

Well I am so glad yours was an easy fix! (Or you were lucky enough to have that moment to notice something wasn't right!)

Our mower just got sold to someone else to fix. Big issue.... I drove our mower into the pond last year and ever since we've had to fix one thing or another on it. So I declare... its time for a new one!

 

[Nyboy]

Lol I did the same with a brand new mover. I thought it would steer like a car. Wanted to mow weeds along pond bank. Ended up in middle of pond. Had to have it towed out. Everyone on my street laughted at city boy ending up in pond

 

[vfem]

Lol I did the same with a brand new mover. I thought it would steer like a car. Wanted to mow weeds along pond bank. Ended up in middle of pond. Had to have it towed out. Everyone on my street laughted at city boy ending up in pond

ROTFLMAO!

Yeah, this city girl don't mow no more... I leave it up to hubby. Oh well!