Question on very strange behavior

[COBRAJET]

I was using the truck to pull some sapplings out of the ground today...usually very easy work for her. I got 6-8 out when I got to a 4" one or so. I pulled it out easy and backed up so my son could undo the strap. The truck was running really funny. It was belching exhaust out of the intake. I looked down and the oil pressure had gone to "0" ...usually 30 at hot idle and 60+ on the road. I put the truck in second to park it around 30 feet away and 2nd was reverse as was any other gear I shifted into. I am not crazy....no matter what geat I selected the truck went backwards when I let the clutch out. The truck was in 6X6 LOW when this happened...it has air lockout. At this time I shut the truck off. I restarted it and it was like nothing happened. No more exhaust out the intake...oil pressure was normal and the gears did what they were suppose to. I put the truck back in high, disengaged the front axle and drove it around for a few minutes like nothing ever happened.
Can someone please explain this one to me??

 

[Stretch44875]

Call me crazy, but sounds like the engine was running in reverse? That would explain backwards, no oil pressure, and exhaust out intake manifold. How it happened I have no idea.
Dennis

 

[bomar76]

I didn't think it was possible on an LDT, but is sure sounds like it was running backwards.
The old 2 stroke Detroits were easy to get started backwards (stall engine on uphill grade, roll back, release clutch while in forward gear and away you go)
Seen that fiasco several times.


BTW Cobrajet...you need to add your LOCATION to your sig line!!!!!!!

 

[COBRAJET]

I added a location, but it has not put it up. Running backwards would make sense. The truck did not stall, but it may have hit the end of the tow strap and been pulled backwards. Hopefully nothing was hurt. It seems just fine. It did not run for longer than 15 seconds. Pretty strange indeed.

 

[Dieselsmoke]

Oh yeah, saw that happen one time at Ft. Carson. Guy had a heavy load on a deuce and dumped the clutch without giving it any fuel, truck was facing up a slight grade so as the truck lurched it basically stalled and started back up in the wrong direction.

 

[Jim145]

I did that once with a 3208 cat no real damage occured I did shut it off after 30sec or so when I figuered something was wrong. I think I was going up a slight hill and when I went to take off I rolled back a little bit then it must of started running in reverse.

 

[rdixiemiller]

A lot of the old 2 stroke golf carts used "engine reverse" to back up. he reverse switch reversed the starter/generator fields and cranked the buggy backwards. On a 4 stroke, it could be rough on the engine, sucking the oil out of the bearings instead of pressurizing them....
15 seconds shouldn't hurt anything.

 

[patch]

Yeah, this happened to me a cupola times in the service when I was a motor pool mechanic- 63 Bravo. One time we were pull-starting another 5ton and somehow got it running backwards...5 speeds reverse and 1 forward, very wierd. Next time it happened, was driving a deuce, forget the situation but I'm thinkin', Oh yeah, no biggie; shut 'er down probably within 20-30 seconds then start up and drive off with no ill effects either time that I recall. After that I tried to duplicate this behavior a number of times, but could never figure out just how i did it. Some strange convergence of momentum, gearing and throttle, i guess, with a bit of inexperienced driver thrown in to complicate things. This was 25 years ago and I probably haven't thought of it until I saw this thread. Funny, the memories ya can dredge up after so many years! Well, guess the moral of this long-winded tale is..drive it and have fun with it! Cobrajet, I don't think you did any permanent damage to your truck; just one of those things, shrug yer shoulders and drive on!

 

[JohnnyReb]

I would agree that the engine ran in reverse. I had it happen on an old Detroit. :freaked: I would suggest you change the oil because of the blowback of soot from the exhaust. After that it ran fine.....

How did you shut it down? We had to throw a coat over the exhaust to stop the "intake".

 

[COBRAJET]

The truck shut off when I pulled the shut down knob.

 

[JohnnyReb]

That is interesting. I need to look at the shut down plate on the deuce. Some old detroits had two shut down knobs; one was labeled "emergency" which was used when the engine reversed....the standard plate would not work because it would not overcome the force of the exhaust blowing back thru the intake.

The emergency shut down had a heavy spring and had to be reset by hand after use; basically re-cocked....

 

[rdixiemiller]

The emergency shut down on a Detroit was to kill the air supply to the mill. This was needed if the blower oil seals let go. The engine would run on motor oil until it ran out, at which point the engine was toast. The engine would run away at high RPM, burning hot oil. We had this happen on an 8V53 in one of the boats. We kept the engine in gear, the prop was enough to keep the engine from overrevving. We popped the emergency airbox shutoff, but it leaked enough air to keep the engine running at 900 rpm. We stuffed a towel into the intake housing to finally shut down the engine. The normal kill cable was a fuel shutdown in the injector system, like a deuce uses.

 

[JohnnyReb]

You learn something everyday. What type of Detroit did you have?

I am familiar with the oil seal problem but was also taught to use the emergency shutdown if it reversed as well.

I looked at the deuce and have learned that the shut down is a restriction of fuel.....but I am pretty sure our 8V71 had a primary air restrictor plate for shut down... I know where the truck is located and I will look at it to make sure...

 

[Westech]

I use to do that to my friends 88 chevy short box. He would leave it running somewhere and I would jump it it get going about 5mph and shut it off then hit the key and put it in R and pop the clutch. That all ended when he put it in 1st and backed in to a car, and I got a black eye.

 

[rdixiemiller]

We ran 8V53's and some 6V53's. The 6-71's didn't seem to be as much of a problem. We didn't have the running backwards problem on the boats, no way for that to happen. I could see that happening on a truck.