Im working on a 1984 f250 with the 6.9 idi. Long story short im getting a run away engine problem.

Long story, i was driving around after figuring out i had a relay problem that was melting my starter wires(or something similar this was last year). I fix the relays with heavy duty one's (i didnt know the difference at the time, the first one split in two). It runs again for awhile no problem. I take it over to my buddys place and ive been getting a crank no start, i fired it up with either, this was the last time it fired up and drove. The next time i fire it up the run away engine problem starts. I got it to shut down by muffling the air intake. Ive done compression test via the glow plugs and everything was fine there. I believed it was the DB2 fuel pump, but I also own an 86 with the 6.9 as well, so I swapped the pump since it's a known working pump and installed it on my 84. The problem remains that it is unable to fire up naturally on its own without either. I tried it today to see and it ran away on me again. I have pulled the top cover off of the pump but I believe it's set right from the seems of things, but I do know that could also be a problem. ASSUMING, I'm smart enough to put that top cover back on correctly.

What else could be causing this possibly? A vacuum line not sealing? A wire possibly put on the wrong spot? I'm decently new to diesel, so forgive me for still learning some terminology. I know it's not a good picture to look at wires or anything but, just asking for ideas.

 

If the truck only starts with ether your glow plugs probably aren't working properly. Does your block heater work? You might try plugging it in a few hours before starting it to see if that helps. Make sure you don't mix ether and glow plugs, that could do damage.

The engine running away is probably an injection pump setting. I know if it's assembled improperly under the top cover it can cause a run away but I'm not sure of the specifics.

 

I completely removed the glow plug controller that was acting up and replaced it with a push button, count to 10 and it fires up, you might try that.

 

if you remove the top cover of the injector pump and then put it back on by just setting it down, you will get the runaway engine.
to properly install the top cover, you need to set it down about 1 inch forward, and then slide it back toward the firewall as it sits on the pump. this will ensure the shutdown rod goes UNDER the fuel lever.
if you just drop it down on the pump, the shutdown rod will sit OVER the shutdown lever causing a runaway.
also, with top off, make sure the governor and shutdown are working smoothly and not bound up.

 

If I'm reading that right, he got a runway on two different injection pumps, guys. The first runaway, was on IP #1. The second runaway, IP #2, which was taken from his other truck with no runaway issue. The 3rd runaway, was on IP #2 after putting the cover back on.

He's showing an N/A engine, so there's no turbo seal to blame. What's she running on? Oil? But from where?

No point in worrying about it not starting on it's own, since she's racing and wants to blow apart when it does haha.

 

What about a ruptured diaphragm in the lift pump, filling the base right up high with fuel?

 

if the crankcase was full of fuel, it would either act like hydrolocked from pistons not being able to go down, or the fuel/oil mixture would me pushed out the oil fill or someplace else.

 

I suppose the final IP test here would be to take IP #2 and put it back on the other truck and see if another runaway happens. Found a useful post here from genscripter where he suggested running a dedicated wire from the battery to the IP to rule out electrical gremlins causing the FSS to stay energized, which seems possible since the symptoms repeated with two different IPs.

 

Wait a minute. If we are talking runaway, nobody mentioned FSS.
Very clean 6.9 btw. Not related, but is this a factory setup for fuel return?

 

I just had a fuel shut off solenoid fail on me, in that I went to turn the key off and the engine didn't shut down. I pulled the wire off but it kept running. She wasn't running away. It just stayed happily idling, sucking up diesel. I pitched off the fuel supply hose (I replaced mine with rubber hose) until it stalled out. Replaced the FSS and problem gone.

He's claiming IP #2 just came out of his other issue free, running truck. He's got a known good IP in there, right now. Unless he pulled both IP's, went to grab a coffee, came back out and got them mixed up and put the same IP back in?..........Oh man, what if? I wonder if they've got distinguishable differences so he can tell them apart?

If it's running away, the FSS getting power isn't going to matter. She'll keep burning the oil that's feeding it. That's why the only way to stop a runaway is to block it's air, because you can't take away it's (external - oil) fuel source. Thankfully Atenchion knew what to do and saved his engine. I'm happy to say, I've never experienced it.........I've seen the videos and sure hope I never do either haha. Poor Atenchion had to throw out three pair of underwear so far!

 

This is interesting:
[This quote has been modified for better understanding.]

(The rest of the thread that came from was 99.9% worthless. Save your time. For the record, I agree with Tom at the end. The OP's issue was not properly diagnosed by his local shop. Low voltage to an FSS, will not cause a runaway haha. Trust me, just save your time.)

 

Thanks for the input everyone. Ill be getting back to looking at it here soon, no shop had actually looked at the truck. I'm doing this on what knowledge I've gained over the years of working on my jeep, and translating it over to the diesel as best as I can with a guy that knows much more about it than I do. I wish I could test the DB2 in the 1986, however I took it to a guy and the transmission I believe is shot due to my own negligence, so i turned the 86 into a parts truck for now to fix this 84 up. Both engines have ran, at some point, the 86 being the for sure good one for the time being. Ive tested glow plugs and they seeming to be fine.

Both DB2 fuel pumps are noticeable different as well thankfully, one has a 90 degree elbow on the back side to the return that has an S shaped return line, and the other is the one in the picture with a bassiclly straight line, with no 90 degree elbow on it.

From the seems of things I'm assuming both DB2 pumps are alright since the same problem is still presenting itself at this point. Im guessing either the top cover is on wrong or it's something else that I'll need to send it in for to actually get fixed with the proper tools, instead of me doing just guess work.

 

No, no. You can test the stuck open injector theory very easy and safely. Just, unhook the return line going to the tank and stick it in a gallon jug, 1/2 full of diesel. (keep the supply hooked right up to the lift pump as normal) You don't need to be told this haha but have your block off board/rag ready.

Start the truck, and block the intake some to keep it from revving to the moon. Now while taming it down by cutting off most of her air supply, watch your diesel jug. Is the fuel returning to the jug like it should be, or is it in fact, sucking it right up causing the runaway? As soon as you know the answer, shut her down. Block off the air. What makes this much more safe is, she can only suck up and run on the 1/4 gal of juice, even if you can't snuff her out. You want some in there, just to help verify it's being sucked right up.

If she's sucking up from the return line, then you've got an injector stuck wide open and now you know how to fix it. Pull them all and just replace them if age/ miles are unknown or have a shop pop test them and find your dud and just replace it.

I don't know if this is possible but the theory seems sound. Besides, I don't think there's any other explanation on an N/A engine.

You got this!

 

Oh, and if your not 100% sure if you put the top cover on right, just get another gallon jug, 1/4 full with fuel too hooked to the lift pump, instead of the tank haha. Might want to do this anyway. She can only run so far, if you keep her on short lease.

The top cover is fairly easy though. When it set it way forward (towards the trucks grill) and slide it back, you'll feel the spring action. If you feel this as you push back and down, your good.

 

Good thinking FordF250, that's definitely an option i can try doing without the special tools ive been dreading i may need one day haha. And ive got some nice remaned injectors sitting in the 1986 parts truck so I'll definitely be able to find out and swap em out easily. I'll report back once I figure it out in the next couple days. The holidays have already started for me so. Not much time till at least Wednesday