sick 471 detroit

[robby]

has been running great for years... had been sitting a few weeks and while working it we opened up the throttle from 3/4 to full (engine 170-degrees, oil pressure 70lbs)... Engine was fine for a minute and then died down to an idle quickly while billowing a thick cloud of black smoke.... the emergency trip is functional and in its proper place... moving it made no difference in running other than at shut-off position (killed it).... setting throttle at idle position helps alleviate smoke but still abnormal amount... a higher throttle position actually causes lower rpm and increased smoke... non-turbo engine.... seems like blower trouble (not enough air) but never had this prob before, not sure what it is.... air filters are oil bath and are not restricted. :Banghead any constructive ideas are welcome

 

[Zed]

Check the blower drive shaft is not stripped and blower not rotating. but every one I've seen stripped the engine will not run. Easy enough to take off the blower inlet and check by hand if the rotors will turn by hand (not good).

 

[hector gemme]

Remove the blower trapp and in rear you have a screen should be plug and if the drive shaft was stripp or brook the motor stop running or to much oil in air filter base.

 

[pjflyer]

Try doing a search here. I can remember someone posting a similar problem, and it was a simple fix. One of the ol' pros had the answer.

 

[willie59]

Every time I've seen the blower drive strip, engine will only start momentarily, but it won't continue running. Have you checked your fuel filters and condition of fuel, may have sucked up some garbage and got it in the injector rail.

 

[robby]

...and you're saying clogged fuel filters or bad fuel would cause overly-excessive black smoke? As I posted, the problem here is not fuel, problem is the apparent and rather obvious lack of air in the mix....

I don't think the blower drive is broken or stripped, I can hear a slight whistle in the exhaust, but not like it used to sound... It will probably run all day if I let it until all the black smoke and soot clogs everything up... Gonna try to check the trap screen on the blower as hector advised

 

[willie59]

...and you're saying clogged fuel filters or bad fuel would cause overly-excessive black smoke? As I posted, the problem here is not fuel, problem is the apparent and rather obvious lack of air in the mix....

Not saying that's your problem, only saying to make sure you check everything, including fuel and filters so that you know for certain that's not the problem. True, thick/black smoke is typically indicative of incorrect air/fuel ratio, but on occasion, things do happen that fly in the face of conventional wisdom, that's why I say check everything.

BTW, anytime the subject of Detroit engine comes up, I'm always compelled to ask if the user is using multigrade (15W/40) diesel oil. If so, that's the wrong oil for that engine and it will cause all sorts of problems, including pre-mature engine failure. The correct oil is SAE40 with a sulfated ash content of less than 1.0%.

 

[shopguy]

Check the air box drain tube elbow at the block?

 

[51kw]

We had a 7500 ford and it would smoke black when the fuel filters were ready to be changed. Didnt go with normal thinking but thats the way it was.

 

[robby]

took off air box cover. Screen is clean and rollers roll only with engine cranking... There is a very light coat of greasy carbon along each roller valley and no sign of defects or damage to the metal anywhere, and no restrictions in the rest of the air intake system...

Have changed fuel filters again as per suggested here (they had already been done less than 40 engine-hours ago) and nothing changed, I'm still getting heavy black smoke/soot. At this point my next look will be at the injectors or something to do with the pump, perhaps something is stuck wide open allowing too much fuel into the cylinders...

I have been running 15W-40 in engine due to the cold climate and elevation on top of this mountain, yet people here are saying 40W is what engine calls for... They are correct but I question the use of straight 40W in such cold climates and the fact the 15W-40 gives the engine an oil pressure in excess of 130psi cold and 70psi at 170-180 degrees.. Won 't straight 40W cause the oil pressure to be more excessive than this? I had a tractor that called for straight 50W in winter and one cold morning the oil pressure blew the cartridge oil filter can up 25ft to hit the ceiling of the shed and everything got an oil bath. It busted out a chunk of the cast base all around the hold-down bolt. The mating threads remained intact and together. As I understand it from the lubrication specialists, 15W-40 means at room temperature it pours like 15W but has protection equivalent to 40W ...

 

[willie59]

Your thinking about the oil, cold pourability, yet good viscosity at operating temp, is spot on concerning the 15W/40 robby. But, that applies to modern engines, which a Detroit is not. Not only was that engine "designed" to use straight weight oil, but it's a fact that those engines do not like multi-grade oil, it will actually destroy them. It would be nice if they would run on multi-grade, but the friction modifiers and other additives that create the "desirable properties" of multi-grade are the very thing that Detroit cylinders, pistons, and rings do not like.

You may think I'm crazy, but I've seen this happen myself on Detroits using multi-grade. Drain that stuff out, refill with Delo 100 SAE40, and run the dog snot out of it. You may have to do 2 oil/filter changes to get the residue of multi-grade out of the engine, but there's a good possibility you'll see your smoke issue go away.

If you're dealing with extreme cold, install a silicone pad heater to the bottom of the oil pan and plug it in during cold nights. Not only will the oil be warm, the engine will start much happier.

 

[robby]

Thanks for that info, it's time for an oil change anyway... That old tractor I mentioned called for 70W in summer and 50W in winter, people probably think I'm making that up but it's right in the operators manual. It was from 1932 and started on gas and ran on kerosene, thus the engine ran at temps exceeding 200-degrees, thus the call for the very heavy motor oil. It sure did crank hard.

There is no electricity at the location the 471 is working, thus a heater is not an option.... I suppose I could rig up a quick-coupler coolant hose jumper system on it and my truck. Seems a major pain but is better than replacing an engine. As for extreme oil pressure I'm concerned about blowing gauges and lines and filter canisters. I thought these motors had a pressure relief bypass valve but I don't see one.

I'm sure baffled why this thing doesn't seem to be pushing enough air through it... The blower is turning and howls just fine and there are no restrictions to be found anywhere leading up to the rollers... Although the engine runs on all cylinders (and makes so much smoke), the exhaust doesn't create enough pressure to hardly open the rain cap on the muffler. The affliction came on very abruptly while it was working fine. After changing fuel filters and fuel and ensuring no air restrictions, engine still starts and runs and responds to throttle, but just like before the smoke loads up and engine bogs down as the throttle is increased. The smoke smells like excess fuel, not crankcase oil. Strangest thing I've ever come across in over 40 years. Had tons of old cats and cummins and deeres etc, but nothing that acted like this little 471.

 

[robby]

I felt all around the bottom of the air box and there's no drain tube anywhere

 

[John C.]

It sounds like you have a stuck injector rack. Pull the valve cover and remove the pin that connects the rack to the governor. Make sure the rack moves freely in both directions. The older 71s has a two screw adjuster for the rack and it was a solid connection to the injector. Newer units have a single screw adjuster which is spring loaded. When an injector froze on the solid rack, the engine would be stuck at what ever the throttle setting was and you couldn't shut down the engine. The newer spring loaded unit at least let you slow down the motor in the hope of killing it under load.

I used to see this in boats all the time. It only takes a bubble of water hitting the injector to bust and freeze the inside of the injector. I've seen tips that blew off from the sudden steam and imbedded themselves in the piston crown.

 

[robby]

yeah the injection system was the next place I was headed to look... never had a 471 apart before so had no idea what I was to find under the valve cover until you replied. thanks.. this is a 1972-73 machine.... maybe get a chance tomorrow to check it out, unfortunately there's a 800+ pound house covering the engine and hydraulic area, I don't know if I can get at the upper end without removing it. Not much room up in there.

 

[Zed]

Have you checked the fuel pressure yet? From memory it should be around 45 - 75 Psi at high idle. As John said, if it has the old style 2 screw rack and one of your injectors has the rack stuck, it should be stuck at that position and not responding to throttle inputs. Whereas the new style rack, if there is an injector with stuck rack for example in 1/4 open, it will be revving higher at idle, but still responding to throttle inputs.
What about air box pressure? There really should be an air box drain on the block. It can be at the front or rear of block, usually on the opposite site to blower, but it could also be on that side too... I don't know what the airbox pressure should be, but you should be able to feel air flow when the engine is running.
Just thinking outside the box, when you said it came on abruptly, could there be some external influence that is putting load on the engine?
Does it sound like the engine is loaded up, different than before?

 

[Zed]

Another question you can answer for us, does it sound like it is running on all cylinders? Not missing or running rough?
You can do a cylinder cut out test on it with a large screw driver. (you will need to get that 800lb engine house off first!)
With the rocker cover off, fire it up. With said big screwdriver, wedge it down hard between the top of injector and the fuel line nut. This will hold the injector plunger down, and effectively stop it working. If that injector is good, you will hear a different note in engine as it will only be running on 3 cylinders. Also check if there is any difference in exhaust color. If you have a bad injector, and cut it out, there will be no change in exhaust note, and the exhaust color might clear up.

 

[capnkel]

I,ve run Detroits for years,id put my money on either a striped blower drive shaft,or blower drive coupling.They can be striped,but still turn just enough to keep the engine going,but blow black smoke like crazy.Blower shaft and drive are both easy fixes,and a very common wear item on those engines.


A stuck injector wouldnt likely make it smoke very much,and i believe it being a 70s vintage engine would have the older 2 screw rack that would be binding with a stuck injector.


Sae 40 weight is the normal oil for these,sae 30 in extreme cold.The 6v71ta we ran for years ran on sae 40 for about 5 years with lots of valve issues.After talking to an engineer at detroit deisel we were told that engine should have been running a Delvac 12w40 oil,yes,12w40,never heard of it till talking to the guy.We changed to that and never had an issue since.

I noticed you mentioned it barely opening the rain cap,thats a clear indication there is very little air going through that motor.Those 2 strokes are pretty simple,i'd be yanking that blower drive and checking the shaft splines and the drive coupling springs and spline.Pretty sure thats where the trouble will be.

 

[willie59]

I can't say it doesn't exist, but I never seen nor heard of Mobile Delvac 12W-40 multi-grade oil. Are you certain you're not talking about Mobile Delvac 1240? Delvac 1200 series oils are mono-grade with sulfated ash content of 0.8%, an ideal oil for a Detroit. Delvac 1240 is the 1200 series oil, SAE 40 weight.

http://www.mobil.com/Norway-English/Lubes/PDS/GLXXENCVLMOMobil_Delvac_1240.aspx

 

[grandkobelco]

Ive never run a detriot but ive been repairing them since..........before my kids were born and I have a grandkid now, and I agree with capkel, youv got broken springs in the drive coupler or splines worn on the qwill shaft. As for oil willie 59 is right, Delvac is great oil for that engine wes.