I've got an '85 Ford L9000 with a Detroit 6-71 engine. Engine was running fine and I decided to pressure wash it this past Sunday. Truck sat until yesterday because I was doing some brake work on it. Went to start it yesterday and the engine was full throttle and ran away. I had to put it in gear and let the clutch out to shut it off. Any idea of what could be wrong or is it just a coincidence and an injector is stuck open. Like I said, it ran fine before I pressure washed it. Could it be possible that the pressure washer knocked a wire off? I don't believe the injectors are electrical; am I right? Guess I just should have left the engine filthy dirty. I took the air intake elbow off and covered it with a piece of sheet metal and tried it again with the air throttle down, and it smokes like hell with black smoke. Any and all advice appreciated.
Remove the valve cover and check for a stuck injector control rod. It could be any one of 6. The best way is to pull the engine kill cable and see which control rod doesn't move.
There's no engine kill cable. It turns on and off with the key.
You can still do the same thing with the key.
Guess I'll give it a try. I wish there was something easier than taking the valve cover off. I'll probably do it tomorrow, weather permitting - it's outside. Thanks. As far as you know, there's nothing electrical on those valves, right? Funny thing is, I knocked the wire off the shut-off solenoid while pressure-washing and I had to solder a new terminal on that to repair it.
Yes! Do not even think about starting it until you remove the valve cover and confirmed all six injector rods move in and out nice and easy. Does this engine have the emergency shut down flapper in the inlet to the blower? If you don't know what I'm referring to let us know and one of use should be able post a picture. One more thought can you post a couple pictures of the engine, one from each side? Might see something else to ask about!
No emergency shut down flapper. Wish it did! I had to take off the big rubber air intake elbow and use a piece of sheet metal over the air intake to shut it down. It's pretty scary when that thing is running and you can't shut it down. Good idea - I'll take a couple of pictures and post them tomorrow.
Removing the v. cover will tell the tale.. Sorry for your troubles.. Good luck.
First runaway I ever had was a 6-71. Sound like a tornado siren when they wind down. Consider it a test of the bottom end Like they said above the only sure way is to pop the valve cover off and take a look at the injectors. Nothin electrical related to the injectors or rack under there. It’ll be obvious if there’s one stuck.
I doubt pressure washing did anything that requires removing the valve cover, I would like to see pics of the governor and the blower. Especially the shutdown solenoid and the throttle linkage. Did this engine overspeed? or just go to 2100 RPM and stay there? Lots of variables here. Is there an air controlled PTO throttle...? Heck, something may have been knocked over center in the linkage when it was washed. Seen it.
If your injector rods are ok check your air box drains. I have seen 2 run away from oil build up because someone plugged those drain hoses thinking they were stopping oil leaks.
As you can see above, I was able to get the cover off and take a couple of pictures. Don't really know exactly what I'm looking at. I see one injector that's noticeably lower than the other 5. You can't really tell from the picture. I'm thinking that could be the one? If it is, how do I get it unstuck. I have the two fuel lines off of that one but there/s really nothing to pry against. I don't want to pry against the rail as I don't want to bend or break anything.
You need to use the key or jumper the shutdown solenoid or whatever it takes to work the rack control rod from WOT to shutdown with the engine not running. All the injectors have a little rack that runs in and out of them. One may not be moving. The arms that stick out from the main rod/tube should all move in unison. Those breakaway springs are there to allow a stuck injector not to stick up the whole works.
Looks like an air shut down cylinder. Its pretty hard to get a full blown run away with that style rack if only one injector is stuck. Gently clamp a small pair of vice grips on the rack tube, it should rotate easily between full fuel and off. While operating the rack watch the individual control rods on each injector down close to the head, make sure they all move in unison.
With the key turned on or the air line to the stop cylinder disconnected.
I'm not familiar with that style governor, there's talk about an electric shut down solenoid, does it have air throttle instead? That cylinder certainly looks extended. Edit!! guess I should have read the first post!!
How much should they move? I tried it without the air shutoff disconnected and without the key and they don’t move very far. Got hungry and taking a dinner break so I’ll give it a try with the key on and the air shutoff disconnected tomorrow morning. Thanks for you help!
Is there a gap between the low plunger and the rocker arm? if not it's just in the firing position for that cylinder. Do not pry against anything. Why did you pull the fuel lines?
Greg, it is extended. It’s in the shutdown position right now.
Okay, I got confused after I reread the first post. You mentioned air throttle, and electric shut down solenoid.
With the shut down cylinder extended you wont be able to move the rack tube. it will be a good time to check the racks, a stuck control rack will be in toward the injector body. the rest will be pulled out. The racks are the little rods connected to the levers on the tube that go into the injectors.
Not sure if this will help explain things but I'll give it a try! In the picture above the tube with the green arrow is pointing along with the levers with the two slotted screws in them is what people are suggesting you rotate. I know your's is a little different as yours has screws with jamb nuts and springs holding them in position against the screws. Your style should not tend to go to a run-away condition but I won't say it is not possible. What you need to check on the injectors is the movement of the yokes the red arrow is pointing towards. You should see them all move in and out the same amount on every injector. You may have to turn on the key to get the shut down system to allow the tube to rotate free. If one or more of the yokes(red arrow) does not move in and out that would be the problem injector. Anyone want to add or clarify what I'm saying here feel free as trying to put things in to words instead of being there and showing it in person can be tricky! Looking again at the pictures of this truck I'm thinking the air solinoid is powered to kill engine so might be easy to just remove the hose from it to let you move the rack tube by hand with a little help from a pair of pliers!
As a side note on this problem I have a question. Did Detroit do away with the emergency shut down flapper when they went to the spring loaded levers on the tube with the single screw adjusters for the rack? 99.9% of the Detroits I worked on over the years had the two screw adjusted rack levers and I just don't recall how the one or two I may have worked on with the spring loaded levers like this truck has.
Yes they did, I have had a stuck injector in a 12V71 with spring loaded rack levers and it was still tough to get it shut down. Of course the stuck injector was at full fuel and part of a complete "white box" set. This was 300 feet out the shop door after an inframe.
So I guess if one injector is able to keep a 12V-71 running against the spring loaded lever I can imagine that it could even be worse for a litte 6-71! Maybe not going to the ballistic state like the rigid levers but enough to cause one to not want to stay put and do what needs to be done. Seems like I recall hearing someone say the best way to stop a run-away was to point a CO2 fire extinguisher at the air filter. Not sure if that would be a good idea if running without any air intake filter.
Shut off the air supply and it will calm any runaway down real fast . Ask Robbie Lawler ? " Funky Ben Askren " shut off the air …..
Looks good Ken. Hopefully the OP understands what you described
It would probably work for a minute but what if you ran out of CO2 before the engine completely stopped? It would pop right back to 4000 RPM and you would be standing there with an empty extinguisher in your hand.
New twist to the story. It finally stopped raining and I was able to put vice grips on the tube and with the solenoid disabled everything works back and forth and super smooth. The new twist is, the fellow who comes and helps???? Me out once in a while changed the oil one day when I was working on the brakes. Evidently the truck has the wrong dipstick in it. Instead of adding 7 gallons of oil, which I believe is the capacity of this engine, he kept adding oil until it said full on the stick which was 10 gallons. So I figure 3 gallons overfilled. Then it sat for 2 weeks with the extra 3 gallons. Could it have sucked oil out of the crankcase immediately when I started it and went into runaway? I’ve since drained 3 gallons of oil out but could residual oil still be in there somewhere? Thanks again for all your help!
You shouldn't be able to overfill the engine to the capacity that it overfills in the airbox providing your drains on the side are clear. Yes it can get there but the drains are there to keep oil build up from happening. These engines can run away from engine oil, especially when the oil is saturated with diesel fuel. Most of the time I have seen it is from dirty engine oil and a turbo/blower seal failure or plugged up airbox drains. You would more than likely have a hydraulic lock on a cylinder if the air box was THAT full of oil. Stranger things have happened but I don't feel at this point you have found the issue 100%. When you operating the fuel control tube, did you actually watch each injector control rod move in and out of each injector? The control rod will still move with a stuck injector since they are spring loaded. An easier way to tell for sure is to remove the control rod pin from the rack itself (it is a small dowel pin with a cotter pin keeper). With the control rod disconnected, the injector rack should move from fuel to no fuel (in and out) with NO tension at all. If there is any drag then you will need to locate which injector is causing it. If your are good at that point, come back and post and we can give you other things to look for, but the faulty injector movement is the most common cause of a runaway engine.
I'll second everything Vetech63 said! I'd have to do some digging but seems there is a chart that will give oil pan capacities for various oil pans, or maybe I'm thinking about an 855 Cummins manual???? I do like the idea of pulling the pin on the fuel tube and seeing how it works with the governor out of the picture. To make it clear see picture below. The yellow arrow is pointing to the pin Vetech63 is taking about. One thing if pulling that pin I would suggest putting some paper towel under that area as the oil drain back hole is right near there! One more suggestion is when removing the cotter pin take out the one that is to the right in the picture and reinstall it from the left side as you look at the pin in picture. Really doesn't matter BUT! if you get interrupted and forget to put the new cotter pin in there is a good chance the pin will stay in place as the valve cover will tend to prevent it from falling out. You really don't want to have that pin come out while engine is running. You could end up with all six injectors going to full fuel and the shut down solenoid will have no way to stop it! One more suggestion. If at anytime the engine does try to run away again and you decide there is nothing you can do and you want to make a run for it, run in a line parallel with the crankshaft. If parts are going to fly out they will most likely come out the side of the engine!
Before I started it again I would have a emergency system in place to shut the air off to the engine. A piece of board or plywood to stick over the intake with the filter removed. A heard of a sleeping bag sacrificed by wrapping over a air cleaner intake in the past. He was a bold fellow. Whatever you can easily use to stop the air from entering the engine will only help you in a runaway.
My brother rebuilt an 8v71, and when he started it, it ran away. He had put a piece of 1/4 plate by the front tire, but somebody took it without him noticing. He ran around the shop hunting something, and grabbed a piece of 1/4" plywood. He put that over the intake and she sucked a perfect round hole in it and kept on screaming til she grenaded!
I heard a story about a guy that threw the service manual over the blower on an 8V-71 and it ate the book a page at a time and blew confetti out the stacks.
Headed there this morning to look at this ill post back what we find.
Oh boy!!!
Easy fix i tried to convey over the phone but i think OP was a little apprehensive about tackling it anymore. After i reinstalled the throttle return spring the problem was solved. It wasn't running away just immediately going to governed rpm. Fun fact these detroits dont have an internal throttle return so if you remove it from the governor lever it will not return to idle by itself any more. Also attempted to adjust his clutch for him and did get it a little better but i think it needs a clutch. OP would like to have me back at some point to give her a full tune up and I'm happy to oblige. OP is a real good old school guy great to work with. Happy to report a happy ending here, but i told em if he keeps this thing painted junk cummins tan it's going to keep trying to kill itself. Lol
Looks like the wiring could do some with a few zip-ties! And about the hose going to whatever it is under that cookie can?
LMAO!!!!!!!!!!!! THESE POST KEEP ON HELPING NO MATTER HOW OLD THEY GET MY FRIEND , I NEEDED THAT LOL IN A SURE NUF 'STRETCHED WIRE HARNESS WEDNESDAY' KINDA WAY..MANY THANKS!
I WASNT THERE BECAUSE I WAS TOO YOUNG AT THE TIME BUT THERE WERE WITNESSES TO A COUSIN OF MINE DOING THE SAME THING TO A MACK R MODEL (NOT SURE WHAT ENGINE) BLOWER AND ALMOST SHUT IT DOWN BUT OL' MACK(?) ENGINE SLOWLY HEAVING BLACK SMOKE AND SHOP MANUAL DEBRIS STARTED BACK GAINING..NOTICING THIS HE QUICKLY JUMPED UP ON THE STEER TIRE AND SAT ON INTAKE WITH LEFT CHEEK AND NOT THE ONE MOM KISSED YOU ON AND SHUT OL' MACK DOWN HOSS! HIS ONLY SACRIFICE WAS A INTAKE SIZE HICKY THAT FAINTLY BLED THRU HIS JEANS ON 1 AZ CHEEK THAT DAY BUT WAS NOTICEABLE IN MIRROR HE SAYS FOR COUPLE WEEKS TILL GONE LOL! IF ITS A LIE THEY TOLD IT!!