(sort of) runaway diesel

[sgtPluck]

This is not a true runaway-engine situation I'm having (thankfully) because
there is no smoke, oil level is not over-filled, and cutting the fuel does actually stop the engine.

What I am experiencing is the engine running at max RPM, and neither the kill switch nor manually adjusting the throttle lever on the engine stops it.

When it happened, The first thing I tried was pulling the fuel line out from the filter and it slowed down and stopped.

Here's what I'm suspicious of (but I don't understand why this would cause the issue)... My alternator regulator broke. I have a proper external 3-stage regulator on the way, so to get by for a day or two we bypassed the alternator regulator and installed a simple cutoff switch, so I could manually engage and disengage the alternator.

I *may* have inadvertently had this in the on position when I started the engine. I honestly can't remember due to the ensuing panic and confusion

I'm wondering if I did, could this have caused an issue and how? Or if it's unrelated, what might be the cause?

It is a Universal 25XPB with an electric lift pump (which is working fine.)

At this point I'm scared to turn it on again. My air intake doesn't have a manual shutoff and is a bit of an awkward shape for blocking air flow, although maybe I could work something up that'd do it. Yanking the fuel line doesn't work quickly enough for my nerves to take.

Any pointers are appreciated.

[Suijin]

I can't see how your alternator could have anything to do with it. How old is your engine? There are other ways to get a runaway situation other than overfilling the the oil, usually the result of a crankcase vent or worn seal. Do you have oil residue in your air intake? That would, depending on how bad it is, indicate an internal wear issue that would likely be responsible.

[rw58ph]

Sounds like the fuel silinoid still has power to it as it stays open. The best is to have a main battery on off switch to cut all electrical power to the engine

As to why the engine is wide open I would look at the throttle cable linkage. If that is not the case then call a mechanic. Every year I have a mechanic to check my work and the engine. Cheap insurance in the long run.

[sgtPluck]

Thanks,

The engine is a 2008 with around 700 hours on it.

How the alternator could be related is a mystery to me too, but it's the only thing that changed and everything was fine and dandy beforehand. I wondered if I had it directly wired in to the bank while the starter was cranking could that have done something to the lift pump... and could that be related? But the lift pump still appears to work, as in it ticks away when powered. I thought if I'd blown it and got an air leak or something it wouldn't work.

Will check if the solenoid is powered - which would explain the kill switch not working I guess. The cable linkage is fine, and I was manually manipulating the throttle lever on the engine to no effect. The idle has not been messed with.

Thanks for the advice.

[sailorchic34]

Well it does sound like a run a way, but with 700 hours that would be very unusual. I assume that the oil level is fine and not overfull. The Alternator has nothing at all to do with it.

If oil level is fine, then the injector pump has an issue. Either the fuel rack lever has fallen out of position, or the governor failed somehow. As it has a manual engine stop, I'm voting that the injector rack adjustment level has fallen out of the level. IE something broke at the injector pump/ governor linkage.

The engine stop level pushes the lever that the rack pin sits in and shuts the fuel off. if the rack pin broke off or the lever failed, no stopping the engine. So if the cable stop is fine then most likely the injector rack pin broke or slipped out of the lever (can't really slip out, but that would match your description. )

But only if the oil level is fine.

Unless your real handy with tools, hire a mechanic to pull the injector pump and check it out.

If your feeling like an explorer, you could pull the plate that the throttle and stop cable poke out of, (4 bolts, easy) and see if the rack lever, linkage to governor is ok. The rack should have zero resistance in it. You will want the engine shop manual too before you pull the plate.

[Cheechako]

It cant be the solenoid if you manually move the throttle lever and nothing changes. If the crankcase is not overfull and if there is no crankcase vent tube going to the intake that might be picking up oil somehow...then I go with Sailorchic... what else could it be?

[neptunesjester]

Had the same thing happen on a Ford Lehman. As soon as it cranked it went to WOT. It was the injector pump. Had the pump & injectors serviced and no more problem.

Later,
NJ

[neptunesjester]

I forgot to mention, the shutoff did nothing in that case. Had to close the fuel valve to stop the motor.

[sgtPluck]

Thanks for the very detailed information.

If there was oil getting into my fuel I should be seeing smoke, right? There was no smoke, just WOT. The oil level could be a hair high, but I've been running about 40 hours since last oil change and haven't had any problems.

I guess I'll ask the mechanic to look at it. The pump is a $1,700 part apparently. I hope I don't have to replace it!

Universal 200698 Sailboat Supplies, Engine Parts and Boat Parts

[neptunesjester]

That price is for a new injector pump. A shop should be able to fix/rebuild your existing one cheaper.

[zeehag]

omy. lookie what i started way last june.
rebuild the pump.
have fun.