Runaway on startup 3,750 rpm

[moparguy]

1995 3500, 300,000 miles. P7100

Changed the fuel filter today, started the truck a couple times, no problems (or leaks). Hooked up the trailer and loaded the backhoe, ate lunch. Go back out, crank up and instantly 3,750 rpm. Pull manual fuel shutoff cable, no help. Quick frantic look under hood, nothing. No help in actuating fuel control rod to the P7100. No help in actuating the fuel shutoff on the pump. Jump back in truck and waste a bit of South Bend clutch choking the engine down in 4th gear. Back under the hood, wife actuates the fuel shut off cable, all appears fine. Throttle linkage is good.

So with the above complete I pull the intake hose off the turbo and find a short 2x6 that's placed near the turbo. Hoping it'd act right, crank, nope, wide open again. The good news is the 2x6 does it's job and shuts the runaway down.

A few more details; 3k GSK since about 2000 with about 250,000 miles on the kit. Home ground #10 fuel plate for the past 3 or 4 years (replaced the #5 installed with the 3k GSK). Never ran without a plate. Light spring in the AFC. Oil consumption has been consistent, a qt. every 3k miles or so, been about the same since new. I haven't pulled the outlet hose on the turbo yet to check for oil in getting to the engine via the turbo. No excessive smoke while it's at full high idle.

I'm guessing something amiss with the governor in the P7100. Sincerely hoping I don't have to pull the pump.

Guesses, advice, direction to internet info welcome.

RonR

 

[dieselshadow]

Pull the intake tube off the intake horn and check for oil. A lot of runaways happen when the turbo leaks oil into the intake. The engine will run quite happily consuming its own oil.

 

[moparguy]

Agree. That's on the list for tomorrow. Got to get it to the shop which is a bit of a project. Wife just had carpel tunnel surgery so her one hand driving of a non running truck is not what it needs to be. She really doesn't like pulling or pushing with the tractor or hoe, but that's what I see as about the only option.

I did check for freeplay on the turbo compressor wheel and felt basically none. Which makes me think that's not be the issue. We'll see though.

Thanks!

RonR

 

[moparguy]

It's going to be a few days before I tackle this little project but I've spent the past 3 hours or so doing my DD on the web. Unless I see something totally out of whack when I pull the AFC housing and look down at the governor springs I'm going to guess a stuck rack. If that's the case then the work starts.

A reoccurring tidbit I've ran across is the rack (rod) can rust and this is more likely with trucks that sit a lot. Well in the past year I've likely only put a couple thousand miles on the old truck. It's sat for over a month a few times without being started and with todays fuel I can see rust being possible.

If rust is the culprit, how likely (I wonder) are the barrels and plungers to rust? I'd think they were always wet with fuel even if the truck wasn't run for weeks. I mean, how would oxygen get into a sealed system to make rust possible?

If indeed the rack is stuck, any advice on dealing with it is truly appreciated. I'll be 70 in a few months and these arthritic hands sure don't look forward to pulling a 65 lb. pump and reinstalling it.

One additional bit of info, the rpm run up is a almost instant kind of thing, not a slow build. It's just like you had your foot on the floor while engaging the starter. Only 30 minutes prior to the full fuel event I'd started the truck 3 times and it didn't see anything like high rpm operation as I moved it a 100 yards or so with a 6,000 lb trailer hooked up.

RonR

 

[Tuesdak]

X2 Check the turbo compressor side for oil. If it's dry send the P7100 pump out to be tested and repaired as needed. Then do a compression test to see if any valves got bent from the overspeed. There is no shame in hiring a good local diesel shop to do the work and giving your hands a break.

I suggest getting an air shutoff valve installed.

How much did you slip the clutch to stall it out? It may have hot spots in the pressure plate and flywheel now causing you trouble in the future. It may need the flywheel and clutch replaced.

 

[moparguy]

Pulled the intake hose today, no oil, dry as a bone. Almost wish it was wet since that'd be a pretty easy repair.

Tuesdak said; "How much did you slip the clutch to stall it out? It may have hot spots in the pressure plate and flywheel now causing you trouble in the future. It may need the flywheel and clutch replaced."

Good point. I did ease into the clutch and wasn't sure it was going to hold. Quite a bit of smoke and stink for sure.

On the knife air shut-off. When I used to this truck in the patch many years ago, I never installed a air shut-off but did have a halon fire extinguisher installed by the turbo just in case. I sure wished it was still there yesterday.

Subject truck (yes the red/white one). It'll be a few days before it makes it into the shop, it sees few days in the weather but that's what it gets for laying down on the job

 

[Joe Mc]

So you mentioned "how does oxygen get into a sealed system to create rust?" Moisture from condensation in fuel tank. Not being a smart ass by any means here, but H2O (moisture in fuel tank) is Hydrogen 2 (parts) Oxygen. The fuel will carry water and go all the way thru the system, combust and out the exhaust. Once you shut down wherever it (moisture) stops it'll do its deed. Hope you find simple solution. At "only" 62 myself I know how much harder it is for me to work on mine than it was when i got it 20 years ago...

 

[Joe Mc]

I'm no 12v guru but it could be possible to install a spin-on water/fuel filter on frame (would need mount) and keep your other stock (guessing here) filter where it is? Check out type filter I'm thinking about FleetGuard # FS1001. I know Glacier Diesel Products has the kit (has components needed) to do the install. The filter has a twist drain on bottom to purge water. Oil is lighter than water, of course, so it would be on bottom of filter, after sitting a while before starting give a twist till you see fuel... Seems like a good alternative versus having to rebuild pump every how often. Think the kit runs $125 or so, been a while? You can call tell them what you're thinking and they can recommend what to do and give price for what you'd need = kit & hose. Hope this helps

 

[Bromiley99]

Pulled the intake hose today, no oil, dry as a bone. Almost wish it was wet since that'd be a pretty easy repair.

Did you pull the intake tube and only inspect the compressor wheel? That’s the way it sounds to me. You really need to look inside the hose that heads to the intercooler.

 

[AEdelheit]

The fact it stopped at high idles indicates a pump issue, not turbo. If it was a bad turbo and running off engine oil there would be nothing governing the RPMs and the hole in the side of the block from the broken connecting rod likely would have stopped it before the 2x4 did.

 

[moparguy]

AEdelheit, agree with your thoughts. If engine oil fueled, likely no way I'd have raised the hood or have been able to choke it down in 4th, unless the 20k of trailer and backhoe that was hooked up would've helped hold the truck. Then likely the South Bend Rally clutch would've totally gone up in smoke and then a big BANG!

Bromiley99, poor wording on my part. I'd already checked at the turbo and the shaft had almost no freeplay so felt pretty sure that wasn't the issue. That said, the final check was pulling the hose at the intake and it was dry.

Thanks for the input!

RonR

 

[BigPapa]

Just to clarify, we’re referring to removing the boot that clamps on here and looking for oil.

 

[moparguy]

Had a bit of shop time today and pulled the AFC, the rack is not froze. Moves fine. I suctioned the oil out of the back of pump and the governor springs along with everything else I could see looked good.

Was the rack stuck the 3 times I started it and the governor held rpm to 3750 and now it's freed up? Don't know. I'm going to put it back together and crank it one more time (actually the wife will and I'll be in position at the turbo with the positive air shut off 2x6 in hand). Regardless of what happens will most likely pull the pump and have it checked out.

Got the name of a local shop that can do a clean/inspect/repair and balance job which will likely be the next step. Wonder what the optimum cc fuel target for 300 hp from a 175 pump would be. Currently running a home ground 10 plate, have a TST 5 and 8 plate that have each seen many 10's of thousands of miles service. Be interesting to have the pump set to work at it's best and see how it compares to the standard plate changes.

My search efforts did find one thread https://www.turbodieselregister.com/threads/wont-shut-off-engine.219601/ where the poster had exactly the same situation with his '95. Rev to max high idle and the fuel shut-off wouldn't shut it down (manually operating the shut off rod did no good, same as mine). Unfortunately, the poster didn't follow up with the solution. If anyone has contact info for; love-horsepower, I'd love to contact him.

RonR

 

[moparguy]

Todays page of the story. Not finding any issues with the pumps fuel rail or governor I installed the old #8 TST plate (just want to see how it used to work, pulled it 15 years or so) bolted the AFC housing back on. Spent time reworking the manual fuel shut off works. Tightened up a linkage pivot point and rerouted the cable a bit to insure a positive shut-off.

With my bride (of 47 years ) in the cockpit and me at the turbo with the pine 2x6 air shutoff in place she cranked the engine over a few times with the fuel shutoff cable pulled out in the off position. No crank. Then push the cable in, crank, instant start and on the way to full fuel when I shut it down at the turbo.

Crank again with a 1/16" inch or so gap between one side of the 2x6 and turbo inlet and it runs at about 1500 rpm but with full fuel it smokes like a tire's on fire. Shut it down.

Bride finds a sweet spot on the manual fuel shut off that makes it run at a nice idle and no smoke. But alas it's still full high idle otherwise.

My hope was that if it could run for a bit without going crazy high rpm, then whatever is causing the problem might self-heal.

The primary reason for the hope expressed above is from little Bro. He related how his 70ish. HP Ford tractor (that might set for weeks at a time without being cranked) started not shutting down without choking it down in high gear. He started running off-road red diesel (no bio diesel) and it cleared up and hasn't happened since the change from B20 to straight diesel.

His theory is that old B20 can gum up the works, causing problems. The Cummins biodiesel info page supports the theory to a degree. Scroll down to the "what materials are incompatible with biodiesel" section https://www.cummins.com/engines/biodiesel-faqs.

I've been running WalMart fuel bought back in June or so. Filled both tanks with about 80 gals. of fuel and the pumps say "May" contain 20% biodiesel. The bed tank is empty now and the factory tank is at about 1/2. So if anything bad was going to happen due to old B20 looks like my truck is the poster child truck.

One bit of good news, the fuel shut-off works! Never let the rpm climb to full fuel 3,750 rpm though. That would have been the ultimate test.

Thanks for reading and any insights.

RonR

 

[AEdelheit]

I run B20 alot and worked on alot of equipment that ran bio , have seen issue with rubber fuel lines and lots of issues with home brew bio but the commercial out of the pump B20 I have not seen cause any issues internally. Would be very surprised if that was the problem.

 

[seafish]

I run B20 alot and worked on alot of equipment that ran bio , have seen issue with rubber fuel lines and lots of issues with home brew bio but the commercial out of the pump B20 I have not seen cause any issues internally. Would be very surprised if that was the problem.

I thought Cummins only OK'd 3rd gen trucks to run on B5...did I get that wrong ??

 

[GAmes]

If it is the bio fuel, which I doubt, one of the magic fuel additives could clean out the "gum" deposits.

It is my understanding the bio cleans the entire system and fuel filters need to be changed early when it is first introduced to an engine. I didn't have that issue but I read it somewhere.

 

[moparguy]

If it is the bio fuel, which I doubt, one of the magic fuel additives could clean out the "gum" deposits.

Realizing the low percentage probability of success, I'm going to pull the filter and fill it with Dee-Zol Plus from Bell Performance. Found a paper touting it's biodiesel performance. Seems the crystals that form in bio-diesel are different enough from dino-diesel that it requires a different additive package.

Once the filter is full and the now half full tank is topped off with dino-diesel that I'll also give healthy dose of the additive, I'll fire the truck up letting it run for just a few seconds at a air throttled low rpm. Shut it off and wait a day or two, giving the additive time to do whatever it's capable of.

I do expect I'll wind up pulling the pump but the truck isn't needed anytime soon and I really don't see a down side to the experiment. Saving $1500 to $2500 along with the pain/agervation of r/ring the pump for Just a couple more hours of my cheap labor makes the low chance gamble worth it.

We'll see.

RonR

 

[GAmes]

I really don't see a down side to the experiment. Saving $1500 to $2500 along with the pain/agervation of r/ring the pump for Just a couple more hours of my cheap labor makes the low chance gamble worth it.
RonR

I agree. Lifting a 44 pound pump out of the engine bay, then having to reinstall it, isn't my definition of fun

 

[Tuesdak]

My hope was that if it could run for a bit without going crazy high rpm, then whatever is causing the problem might self-heal.

You need to fix something and know the cause of the runaway before you start the engine again. Emergency shutdown and HOPE isn't going to fix it. The risk of engine damage is extreme. I watched my 6.2 with a 3600 RPM redline reach 4200 RPM once because the IP governor wouldn't limit fuel during a snap emissions test. The only reason it didn't blow up is because it bent valves in 7 of the 8 cylinders and lost compression. All 8 pistons were cracked, most main webs were cracked... It failed emissions that day due to sudden white smoke and wouldn't hardly accelerate anymore. I am very lucky it didn't let go and kill someone with all the people around in an emissions test station.

https://www.turbodieselregister.com/threads/finding-the-limits-of-the-gm-6-2-6-5-diesel.265481/

As politely as I could I suggested you get a new clutch. What I want to express is how lucky you got that it didn't grenade trying to stop the engine while slipping to the point of smoking leaving shrapnel in the dash after chopping your feet clean off. Slipping clutches or abused clutches are known to do this. Try not to recreate the emergency...

His theory is that old B20 can gum up the works, causing problems.

Biodiesel LOVES water. The leftover meth in it does a number on hoses and any "yellow" metal. The best way to "deal with Biodiesel" is get the best water separator you can. The rig that had a CAT water separator on it: I replaced the fuel tank and lift pump. The rig that didn't I replaced the entire fuel system like a CP4 went off: Tank to injector tips. The IP was rusted to the point of no core value.

B20 and rust may or may not be the cause of your IP sticking. IMO pull the pump before you hurt the engine beyond repair. I assume you have checked the intake for oil, but, after the pump is checked out you will know what steps to take next if any.

In depth info on when Bio goes bad and more info than is common knowledge.

https://www.turbodieselregister.com/threads/ulsd-and-biodiesel-exposed.248698/