4-53 diesel runaway 3

[johnnypixon]

I have 1966 4-53 diesel engine in a hydraulic excavator of the same year. Today when I started the engine it floored itself to full throttle and held itself there for about 20 to 30 seconds in spite of the fact that I had the throttle off. Then it dropped itself down to idle. I always push the throttle lever about 1/2 open and then back to almost closed BEFORE I press the start button (that's what is says to do in the series 53 manual). I'm thinking its either an injector that froze open and then with heat and vibration fixed itself, or the throttle mechanism on the engine itself stuck open because I never run the machine at full throttle and today I pushed the throttle lever farther foreward than usual before I started it. I don't think it is an injector because I've worked the machine hard for the two previous days and usually injectors stick after they sit for along time. On top of that the engine hums beautifully, you can hear it harmonizing with itself in perfect time. I checked the throttle cable that goes to the engine and did not see anything wrong externally. Does anyone have any ideas?

 

[ivymike]

drippy injectors leaving a puddle after shutdown? engine oil leak into intake via valve seals (or turbo seals, or other)?

 

[bcs5274]

detroits upon startup put the fuel rack to full fuel upon startup and then the governor pulls it back, if one or more scrolls in each injector or several injectors or the rack assembly sticks it will hold the injectors at full fuel, checks this before it doesn't come back and the engine explodes from over reving

 

[MikeHalloran]

This would be a good time to fit an air shutoff valve so you can deprive it of oxygen even if it starts using lube oil for fuel.



Mike Halloran
Pembroke Pines, FL, USA

 

[johnnypixon]

Thanks for all the great advise. Three of the four injectors are, I believe, original-- I replaced one. I'm going to replace the three old ones. This 1966 4-53 gm diesel has an emergency air shut-off accessible just below the blower. But I've read some horror stories on runaway detroits sucking in seals and various air shut-off mechanisms. I'm going to mount a CO2 fire extinguisher inside the cab with the hose of the extinguisher leading to the air intake of the engine. The plan is to blast co2 into the air intake and then flip the air shut off after the engine slows or shuts down.

Where the throttle cable attaches to the engine is a part of the engine I've never taken apart-- I don't even know what it is called. A diesel mechanic told me not to play with the govener. Can I take this thing apart and see if something is wrong in there, or will I be opening a can of worms?

 

[TheBlacksmith]

Good advice; it's a can of worms. If you have three original injectors in there from 1966, I'd replace them. They're leaking, sticking or both.

 

[johnnypixon]

Is the govener the assembly that the throttle cable attaches to?

 

[topcatproduction]

Is this a 2 stroke blown diesel? I think it is unlikely that at least 3 injectors have all packed up at the same time (they wont be electronic anyway will they?), these problems are usually simpler than they seem, I would think it much more likely that one component failed than a whole load at the same time for the first time, does it have a mechanical injection pump? If so I would suggest that the rail in the pump got stuck open temporarily, maybe even just the cable.
These engines are so simple compared to modern diesel and petrol engines (no common rail injection, throttle bodies, plugs, electronic pumps etc etc) they just squirt diesel into each cylinder and it runs, thats about it on an old diesel, too quick or smokey = too much fuel, no run = no fuel or timing (highly unlikely).

 

[MikeHalloran]

Yes, the part that the throttle cable attaches to is the governor. It has some complicated parts inside, and some very touchy and un-obvious adjustments that may require special tools to get right. Every _other_ part of that engine is relatively simple.




Mike Halloran
Pembroke Pines, FL, USA

 

[dgallup]

This is most likely a throttle linkage or governor problem. Did the engine rev beyond it's rated high idle speed? If it did then the problem is in the governor and/or rack. If it just went to high idle or less it could be the throttle linkage.

You need a qualified technician to work on the governor but you can check out the throttle linkage to the governor your self.

 

[johnnypixon]

I'd say that the engine went to the max rpm that the governor is set to(2200 rpm). It stayed there for about 20 seconds and then dropped down to the slow idle I normally expect with the throttle lever in the slowest position (which is where it was when I pressed the start button-- but note, I pushed the throttle lever all the way open then back to slow BEFORE I started the engine and I think something got stuck because I never, in the seven years I've owned this machine, opened the throttle up that far. What ever got stuck, got stuck when the engine was off, and then after I started it and it raced to full throttle it heated and vibrated itself unstuck). Today I started it and it was fine-- runs flawlessly. The throttle cable is a very thick wire and I cannot see anything between the throttle lever inside the cab and the cable's attachment to the governor that could account for the engine running at full when the lever in the cab is in the slowest position.

It could be drippy injectors if they only drip when the engine is warm. I only ran the engine for a minute yesterday so I don't know if a drippy injector problem would present itself today.

 

[MikeHalloran]

The 'throttle' control doesn't control the engine speed directly. It represents a mechanical command to the governor, which controls the fuel rack.

The fuel rack, which may or may not literally be a gear rack (in this case I think it is), is what adjusts the amount of fuel that the injectors deliver per stroke.

I suppose it's possible that the rack is a little sticky in the part of its travel where it's rarely been used, or maybe a piece of debris jammed it temporarily. This would be a good time to change the lube oil if you haven't done it recently.




Mike Halloran
Pembroke Pines, FL, USA

 

[bcs5274]

the rack or governor is sticking, these engines have fuel to a port in the heads and the amount of fuel injected to the cylinders is controled by rotation of scroll plungers in each injector, if any of this mechanism doesn't move freely the governor cannot back of fuel til the fly weight assembly gets strong enough to move it

 

[rmw]

You had something stick in the throttle linkage or the rack linkage. Is the top of the governor box where the throttle cable attaches and where the shaft(s) disappear into the governor clean? I suspect that there is accumulation built up in that area and when you pushed the throttle over farther than its normal travel (since 1966 - and no, no electronics on Detroits back then - still pretty much WWII stuff) it got jammed and stuck.

Check and see if there are any grease zerks on the linkage, and if so, have they been greased since 1966? How do you kill it? Does it have an electric or air kill or do you just move the throttle to a position of zero fuel? If the latter and you left it there after the last time you killed it, I doubt dribbling fuel or fuel puddles in the engine.

My Detroits always responded a little more smartly after a good greasing of the throttle linkage.

Did you notice anything unusual about the exhaust when this excursion occurred? If there were a lot of unburned fuel present, or lube oil being burned, your exhaust would indicate it. My last Detroit would lay down a smoke screen as it burned all the oil that puddled inside the engine (from the myriad of places that a Detriot can find to leak, internally and externally.)

The detroits I dealt with were air killed and until air built up enough pressure to activate the air solenoids (pistons) hitting the kill switch wouldn't kill it.

Now, a trip of the engine combustion air valve would, however and in a hurry.

And, NO, NO, NO, don't touch the inside of the governor housing, or any of the external settings. Guys that can do that are getting rarer and rarer, now that electronic engines are in vogue. Even when the old rack system was king, the guy who could do it and do it right was rare too.

rmw

 

[dicer]

It is supplied on all 2 stroke detroits, the emergency air shut off valve, it preceeds the blower. And is specifically for runaways. Since a blown seal can let enough oil in to cause it. Anyway don't you have the knob in the cab that says emergency shut off ??? Pull that and the air valve closes. And yeah the governor could be going bad, oil accumulation etc.

 

[johnnypixon]

Thanks for all the help! I really appreciate it.