Tractor won't cut off.

[louiedog]

I have a 1983 JD 302 industrial tractor with a 50 hp 3 cylinder diesel. The engine would not
run at a constant RPM and would fluctuate between 12 - 17 RPMs. I usually do not run the engine at a high RPM (over 20-25)so I was thinking it was getting clogged somewhere. I let the engine run for about 5 minutes at 20 RPMs and that seemed to smooth out the engine. The next day the engine seemed to be running normally until I went to shut the engine off. The engine kept running with the key in the off position. I turned the throttle level all the way down and after a few minutes the engine slowed to a stop. Does anyone know what is wrong? Thanks

Louiedog

 

[Recoveryhill]

I don't understand your RPM numbers so I'll assume you mean 1,200 to 1,700 and 2,000 RPM's.

On a diesel with a key switch, the key functions to stop fuel to the engine by operating a solenoid valve. Key on, solenoid open, fuel flows, starter motor turns it over, compression and ignition. Turn the key off, solenoid closes and engine stops. Diesels can scarf fuel such as crankcase oil under certain circumstances and do what's called "running away". RPM's build with unlimited source of combustable liquid until the engine blows but it's unlikely what you describe is anything related to that.

You say you turned the throttle all the way down and it kept running. Did the RPM's reduce to idle, when you throttled back or did it maintain higher RPM's? If you turned the key off and it was getting diesel fuel and not engine lube or hydraulic oil, the solenoid valve is not closing which could be electrical or mechanical. If you reduce throttle and RPM's don't follow, you have another problem possibly the throttle linkage. To have linkage issues and solenoid issues is possible, it's called bad luck!

I'd check the fuel line from tank to injector pump and change the filter if you haven't already done so. I'd energize the solenoid and see if it is opening and closing properly, you could use a jumper to provide power so you could observe. I'd trace the throttle linkage, lubricate and check for movement from throttle to pump.

Someone lese here may have another take but that's what I'd look for.

 

[Tx Jim]

Sounds as if the governor drive ring in the inj pump is bad. Inj pump needs to be renewed with some good parts before you find a piston connecting rod protruding from the engine block..

 

[louiedog]

Thanks! I will check the solenoid and linkage. I have experienced the RPMs not reducing when the throttle is reduced. This happens sporadically.

 

[louiedog]

Would the governor drive ring prevent the engine from shutting off or would a bad governor drive ring not allow a constant RPM?

 

[SPYDERLK]

Would the governor drive ring prevent the engine from shutting off or would a >> bad governor drive ring not allow a constant RPM? <<

This.

 

[Tx Jim]

Would the governor drive ring prevent the engine from shutting off or would a bad governor drive ring not allow a constant RPM?

YES bad governor ring can do as you stated

 

[Recoveryhill]

Sounds as if the governor drive ring in the inj pump is bad. Inj pump needs to be renewed with some good parts before you find a piston connecting rod protruding from the engine block..

Good Call.

From Oliver Diesel: "In addition to the housing pressure cold advance (HPCA) solenoid, there is a fuel shut-off solenoid (front terminal connected with a pink wire) located inside the pump housing cover that stops the engine by cutting off the fuel flow.

The fuel shut-off solenoid moves the governor linkage, which in turn rotates the metering valve.Shutoff solenoid in housing (top) engaging the shutoff rack on top the hydraulic head. To the left of the hydraulic head is the governor assembly

When the ignition is off, the solenoid is no longer energized and the return spring pulls the shut-off rack to the "OFF" position, which through the governor linkage rotates the metering valve to cut off fuel.

The minimum/maximum engine speed governor, located under the governor cover maintains idle speeds under varying engine loads and limits the maximum speed of the engine.

The governor assembly comprises weights, the governor arm, low idle spring, idle spring guide, main governor spring, main governor spring guide, and the guide stud.

Governor weightsThe governor weights are rotated by the drive shaft. Their centrifugal force controls the metering valve at minimum and maximum engine speeds.

At idle speed, the governor weights don稚 exert much force, so the spring on the governor keeps the metering valve nearly closed.

At high engine speeds, the centrifugal force of the governor weights moves a pivot arm, compressing the spring, and rotating the metering valve to an almost closed position.

At engine speeds other than idle or maximum, the driver directly controls the metering valve through the accelerator/throttle linkage. At those engine speeds the force of the governor weights and the governor spring tension are balanced, so that neither can influence the metering valve.

A pressure regulator protects the transfer pump from excessive output pressure caused by high engine speeds or because of a restricted fuel return line.

When the valve is closed during normal operation, the valve spring holds the piston forward, blocking the regulating slot in the valve thus rendering it inactive.

As output pressure increases, the valve opens. High-pressure fuel pushes the valve piston, which compresses the spring. If the pressure is high enough to overcome the spring痴 force, the piston will be pushed back, uncovering the regulating slot in the valve. This will allow fuel to flow back to the input side of the pump, thus relieving output pressure."

And....The Guy Who Changed Everything Diesel:

http://files.asme.org/asmeorg/Communities/History/Landmarks/10001.pdf

 

[Tx Jim]

Recoveryhill
Please explain this statement From Oliver Diesel: "In addition to the housing pressure cold advance (HPCA) solenoid"???

There's no cold advance solenoid on JD 302 that I'm aware of.

 

[Recoveryhill]

Tex,

That wasn't posted as JD specific information. It was posted to help explain Rotary Distributor Diesel Fuel Injection Pumps, which from Mr. Roosa's invention, all modern mechanical fuel pumps were derived, including JD's. I picked up the article where it began discussing the shut off solenoid and governor. Mr. Roosa's Stanadyne pump offered among other features, various timing options for engine manufacturers, cold advance being just one. I might add that recent advances in Fuel Injection have again changed the rules and the newest electronic systems are quite different.

Link to the full article: Oliver Diesel - Engines & Outdoors

Louiedog: It seems that the fuel shut off solenoid and the governor are holding hands. I now see more clearly how the two problems you have, failure to shut off, and un-commanded RPMs could easily be related. Sounds like rebuild or replace time, for your fuel pump.