Cat 312B Won't Turn Off

ArlingtonGuy · Feb 14, 2010

I bought this excavator a few months ago, and the seller told me that sometimes it didn't want to turn off properly. And that did happen every once in a while, but now it seems to be getting worse. Today I had a really hard time getting it to stop. Even completely blocking off the air filter didn't work. Putting the engine under load, by trying to run the tracks for example, doesn't help.

When you turn the key off, all electrical is off, but the motor just goes to an idle and keeps running. Turning off the main electrical disconnect has no effect.

I've tried adjusting the throttle stop at the intake to allow the throttle to close a little more, but that doesn't help. There's a solenoid near the throttle that I can pull on, and it makes the motor run rough, then it will usually die, but not always. I don't see a fuel shut-off solenoid anywhere, or even an emergency shut down lever.

Can one of you tell me what is supposed to turn off these engines? I have a parts book, but no service or operator's manual.

Thanks!

freedom digger · Feb 14, 2010

The engine has an electric solenoid that strokes the fuel shut off on the injector pump when you shut off the key.Then it returns to the run position after a few seconds.Disconnecting the power won't work as it takes power to run the solenoid circut through it's cycle.You should be able to manually shut down the pump by pushing the throttle control rod by hand.
What year is your machine? I have a repair manual for a 2000 if you need help I may be able to scan and send you what you need.

Arabhacks · Feb 14, 2010

Wrong tree.

Hello.

Sounds like you are barking up the wrong tree.
You said that "There's a solenoid near the throttle that I can pull on, and it makes the motor run rough, then it will usually die, but not always".
This sounds like the shutdown solenoid, and as was pointed out, it operates only for a second or 2.
Try feeling the solenoid and have someone turn the key to the on position but do NOT start it!
Wait a few seconds and turn the switch to the off position.
The solenoid should engage for about 2 seconds.
If this is in fact the case you may have a mechanical problem and not an electrical one.

cps · Feb 14, 2010

Perkins Engine stop solenoids do give in from time to time! They can be replace quit cheap from after market parts, i would try that!

John C. · Feb 14, 2010

I believe that machine has the Mitsubishi engine in it. I don't recall it having a solenoid. As I recall the throttle motor pulls the throttle lever back to the stop engine spot and then releases a couple of seconds after the alternator stops turning.

I'm thinking you need to recalibrate the throttle system. I don't know how that is done on this model but maybe someone here might know.

Good Luck!

ArlingtonGuy · Feb 14, 2010

Thanks!

I really appreciate your suggestions. I did as you said, and had somebody turn the key on and off. Sure enough, as the key was turned off, the solenoid pulled the rod for about two seconds, and then released. At last I know what should stop the engine, and that the solenoid itself is functioning.

It appears to pull the rod about 3/4". I adjusted the rod so that it pulls about another 1/4". It's getting dark, so I haven't tried it yet, I'll wait until tomorrow. Not a good idea to have an excavator running in the dark that you can't shut off.

I really appreciate the help from you guys.

Oh, the machine is a '95.

Brian

CRAFT · Feb 14, 2010

I had the same thing happen from time to time on mine .... and you are on the right track that solenoid pulls the shaft back and I had the problem of the ball joint falling off ... it is a dry lube ball and it simply wore out, thats probably where the excess slack came from on yours ...YOU DON'T want to have to replace the electronic throttle control motor ... VERY PRICEY ... here it was about 1200.00 and then it has to be calibrated which can be done thru the secret button ...if you feel the pad where the existing buttons are you can feel the spot where it looks like there should be a button and there isn't .... but it is , one is hidden behind it and there is a sequence of pushing it and another one which puts it into a self calibrate mode .... call your Cat product support guy he can fax you a copy of the method to do it .... you are very right it is a Mitsi engine ....good-luck

gasfield315c · Feb 14, 2010

had my 315 at work do that to me one time, just kept turning the key on and off and it eventually shut down, only did it that one time though

heavylift · Feb 14, 2010

I ran a 312 that wouldn't shut off... called the office .. they said it does that now and then.... first day I stalled it like they said.... second day... well it didn't work...
It set there idling backwards for about an hour and a half.... even with a pop cup over the exhaust.. until the mechanic(parts changer) showed up...

All that smoke coming out off the air cleaner made it look like the machine was on fire....

They don't have it anymore .... they sold it to some poor sap at a richie auction in texas....so if you bought a 312 with a new engine..... but no drive.... well barely fuctioning drive about 3 years ago

RobVG · Feb 15, 2010

This probably doesn't apply but we had a 311 that wouldn't shut off. It actually throttled up because one of the cables from the motor control had broken. You couldn't buy just a cable for it- they wanted $700 for a new control so I welded a new hyme joint onto the old cable.

Cpc- the Perkins fuel shut off solenoid require power to let the fuel flow. Unless somehow it’s shorted, a bad solenoid will cause a no- start. Never had one go bad - usually just a wire that’s fallen off.

Heavylift- Sometime parts changing is part of the game. I’ve sent jobs out to different dealers and they certainly threw parts at the problems until they found them. If you have such little respect for your mechanic I suggest you tell the company to hire a trained technician or some old guy that really does know everything and see what they say. The savings from the wage paid a “parts changer” vs. a “real mechanic” probably pays for any parts sitting on the shelf.

ArlingtonGuy · Feb 15, 2010

Making Progress

Thanks to the various useful suggestions this group has made, I'm making progress.

I discovered that the ball-joint where the pull rod from the solenoid attaches to the shut-off lever on the injector system was loose, and the threads screwed up on it so it couldn't be tightened. I found an exact match at the auto parts store and installed that. I found that if I tightened it, the lever would bind and not work correctly. Evidently, someone had installed the wrong joint in the past, and left it loose so it didn't bind. Then, it got looser and looser so that it wouldn't pull far enough. I thought it was odd that it had 1/4-28 thread instead of most stuff on this engine which is metric. It's a Cat 3064T motor.

So, I ordered the correct joint and rod from the local dealer, and hopefully it will operate smoothly and with no slop after that. I'm not sure exactly how to adjust it, but I guess I'll just keep adjusting the rod shorter until it just shuts off.

These parts from the dealer are expensive. Can anyone recommend any on-line sources for Cat parts that might be cheaper?

Thanks again for the help you guys have provided.

willie59 · Feb 15, 2010

ArlingtonGuy, the one thing you need to pay heed to when adjusting your shut down solenoid linkage is the solenoid has to hit bottom. The fuel shut off lever on the injection pump has a limit of travel. If you have the linkage adjusted to where the fuel lever hits its stop, but it keeps the solenoid spool from hitting bottom inside the solenoid, it will burn it up in short order. When the solenoid powers up, the spool inside of it has to hit bottom.

ArlingtonGuy · Feb 16, 2010

Adjusting Shut-off

Thanks for the tip about adjusting it so that the shut-off stop doesn't occur before stroke-end of the solenoid. That's valuable information.

How do you go about adjusting this way? Can you pull on the solenoid and adjust it so that when it's pulled all the way out, the lever isn't fully stroked? I'm not sure what's in the boot at the end of the solenoid, so don't know how much travel difference there is between pushing and pulling.

Thanks for any help in how to do this.

cps · Feb 16, 2010

John C. said:
I believe that machine has the Mitsubishi engine in it. I don't recall it having a solenoid.

Hi John, I might be wrong but im 95% sure that the 312B's here in Ireland had a Perkins Engine, It may even have been badged Cat!

I also had one machine that would not stop with a perkins engine changed the solenoid and it never looked behind it, but i dont think thats the problem here!

JBSSU · Feb 17, 2010

The Cat 312B has a perkins engine, although it is branded Cat. Sounds like you have the problem under control it was in fact the lik between the shutdown solenoid was worn not allowing the lever on the pump to go to the complete fuel off position. Now you just need to get the linkage adjusted properly.

CRAFT · Feb 18, 2010

The 312 engine is definately a Mitsibishi engine and not a perkins .... go ask a Cat dealer product support rep ..... finding some of the stuff on the machine to be standard thread and not metric is not uncommon, as I mentioned before when I replaced the ball joint on mine because it kept falling off due to excessive wear, I ran the quarter inch fine thread chaser over the rod .... Just go and buy the one from Cat, sure its a bit more money but look how long the original one lasted and at least it'll take the constant vibration ... after market ones are what they are CHEAP... and when you take off the old one just remember where the lock nut was positioned so when you screw the original brand new one on it'll be the same rod length ....it worked for me.....

ArlingtonGuy · Feb 18, 2010

It shuts off!

Thanks to your helpful suggestions, my machine turns off again.

The correct parts (new rod and end-joint) allow it run run free when all tightened up, and it seems to work well. For adjustment, I pulled the solenoid manually as far as I could, and made sure that the lever it was pulling would travel a little further than that.

I'm not sure of the origin of the machine. It's a CAT 3064T motor. But I read a press release on the net (circa 1990) that Perkins announced that they would be providing 3000-series motors to CAT, branded as CAT, so that may be it. So it sounds like CAT is American, Perkins motor (England), but the replacement parts were made in Japan. Is the machine made by somebody like Kumatsu in Japan? It seems to be all metric from what I've worked on so far. No matter where it's made, it seems to be good quality and I enjoy running it.

Anyway, thank you all for your help and support, it's greatly appreciated.

Brian

JBSSU · Feb 18, 2010

Awesome job!!!..... Yes the 3064 is a Perkins engine(Cat has a large stake in Perkins)The same engine was used in all 311,312,& 315 A & B series machines. Some of these machines were built in Belgium & some were built in Japan By Shin Mitsubishi.

nickg · Jan 24, 2022

freedom digger said:
The engine has an electric solenoid that strokes the fuel shut off on the injector pump when you shut off the key.Then it returns to the run position after a few seconds.Disconnecting the power won't work as it takes power to run the solenoid circut through it's cycle.You should be able to manually shut down the pump by pushing the throttle control rod by hand.
What year is your machine? I have a repair manual for a 2000 if you need help I may be able to scan and send you what you need.

would you be able to send parts manual. my solenoid burnst out and im trying to replace the throttle cable!

Mark13 · Jan 24, 2022

nickg said:
would you be able to send parts manual. my solenoid burnst out and im trying to replace the throttle cable!

I'm guessing he won't see your question. The thread is 12 years old and it looks like he hasn't been on here since Christmas Eve 2014.

Cat 312B Won't Turn Off

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