Isuzu 35 runaway engine

[Geoff12345]

Hi, I'm new to this forum malarkey,  hopefully I'm posting this correctly. 

My problem is this.. My engine has not been started for a long time. When I finally got it started, the revs built higher and higher. The stop button wouldn't work, nor would the lever on the pump. I cut off the air supply and it stopped. Very scary, I've never heard a diesel engine rev so high. Tried again and same deal. Ideas gratefully received. Many thanks. Geoff

 

 

[WotEver]

How’s the oil level?

[RAM]

Hi Geoff, I am nowhere near as knowledgable as most people on this forum but I believe that this can happen when diesel mixes with the engine oil, usually through a leak on the fuel injector pump. This has happened to my engine twice but the problem was spotted before the engine could 'run away' with itself. I think this is why WotEver has asked the question re oil level.

 

[WotEver]

1 minute ago, RAM said:

I think this is why WotEver has asked the question re oil level.

Yup. It can also happen if it’s over-filled. I’m no expert either though. 

[cereal tiller]

55 minutes ago, RAM said:

Hi Geoff, I am nowhere near as knowledgable as most people on this forum but I believe that this can happen when diesel mixes with the engine oil, usually through a leak on the fuel injector pump. This has happened to my engine twice but the problem was spotted before the engine could 'run away' with itself. I think this is why WotEver has asked the question re oil level.

 

The Lift pump Diaphragm Can also split or become Porous allowing Fuel to mix with the Engine Oil raising the level and causing Runaway.

[Geoff12345]

Thanks for the prompt reply's .I'll check the oil tomorrow and report back.

[Geoff12345]

Ok then. Oil level under the high level mark and no sign of contamination.

Any more ideas please ?

[Tony Brooks]

Gas leak into the engine room?

Otherwise all I can think of is a stuck control rod/rack,  especially if its an Izusu with separate injector pumps. However I would have expected a good pull on the manual stop lever to shift it unless the stop lever pulls an internal spring.

[Geoff12345]

Thanks Tony. No gas leaks . Would you know if the control rod/rack is connected to the govenor and if so how to proceed with freeing it off. 

[Tony Brooks]

I have no idea about Izusu specifics but the governor does move the control rod but it may not be mechanically fixed to it. Typically the governor consist of a pair of bob weights on bell cranks so as the engine speeds up the weights fly out making the bell cranks push back against the governor. As the weights and cranks are spinning its hard to get a mechanical connection between the two.

There is typically a fairly light spring that tries to push the rack to full speed so when the engine stops the rack is expected to rest in this position (full speed or even excess fuel).  When you open the throttle you pre-load a heavier spring that also pushed the rack towards maximum speed. However as the engine speeds up the bob weights and bell cranks exert enough force to push the rod back towards the idle position so when running the rack is balanced between the pair of springs with whatever pre-load you have put on them and the force of the bob weights.

When you operate the stop the rack is normally mechanically pulled back to beyond idle to the no fuel position. This is why its a bi hard to understand how /why you could not stop it with the stop lever on the engine. Even if the rack has rusted in its supports or is stuck with frozen water.

Typically the governor has a spinning domed pad the pushes on the rack.

Because I have no details about the Izusu system I can't really suggest how you check the rack is free. Hopefully someone else will be along who can. If the weather was very cold when you tried it its even possible it might free itself off with higher temperatures.  Can you get a  fan heater into the engine bay for a few hours? Its a long shot but may work.

 

 

[Phil Ambrose]

If your fuel filter is blocked an engine can scavenge fuel ie engine oil from the sump and run away on that, or so I've been told  

Phil 

[Tony Brooks]

Just now, Phil Ambrose said:

If your fuel filter is blocked an engine can scavenge fuel ie engine oil from the sump and run away on that, or so I've been told  

Phil 

Maybe the air filter but I can't see it doing it with a fuel filter on an Izusu. Now a hydraulically governed DPA pump aka BMC 1.5 possibly because they will rev up for a time when starved of fuel.

[Phil Ambrose]

2 minutes ago, Tony Brooks said:

Maybe the air filter but I can't see it doing it with a fuel filter on an Izusu. Now a hydraulically governed DPA pump aka BMC 1.5 possibly because they will rev up for a time when starved of fuel.

I'm not knowledgeable enough to say one way or an other but on my last boat I had a 2.2BMC Commander and when that displayed run away symptoms a change of fuel filter solved the problem

Phil   

[Geoff12345]

Thanks guys, I'm heading towards Tony's reply as the problem as I've examined the fuel filter and no issues. There was however water present, which has now been removed.

The stop lever has little to no movement on it. So will try a fan heater in the engine bay first and  try moving it further.

Thanks again for the advise Geoff 

[Tony Brooks]

Certainly worth a try for the cost of a filter or two.

Some 2.2s had a DPA pump but all the ones I saw were mechanically governed. However that does not mean some were fitted with hydraulic governors and that would do as you say.

[Eeyore]

Hi Geoff

I fear that the combination of “not been started for a long time”, and “water present” in the fuel could have lead to corrosion in the injection pumps. I have seen this on three different engines, but the principle is the same. You could try removing the electric shut down solenoid from the back of the engine; this may give sufficient access to push and pull directly on the rack. If the rack “frees off” it is likely to be a short term fix as the particles of corrosion are still in there. I really hope I’m wrong on this one, but it does sound familiar.

Steve (Eeyore)

[Tony Brooks]

46 minutes ago, Geoff12345 said:

Thanks guys, I'm heading towards Tony's reply as the problem as I've examined the fuel filter and no issues. There was however water present, which has now been removed.

The stop lever has little to no movement on it. So will try a fan heater in the engine bay first and  try moving it further.

Thanks again for the advise Geoff 

If water got into a pump element and it froze that would cause it.

[BEngo]

Assuming a Bosch type unit pump, surely frozen water inside the pump element would stop or limit  its up and down moving,  thus giving either expensive noises or a piston stuck in the up position?   I would also expect any pumpable ice to end up in the injector pipe and cause injection difficulties soonish?  I can see frozen water outside the pump element stopping the rack turning the outer helical part of the element , leaving the pump in the full chat position but that would also probably impede the flow of diesel to the elements.

My money is with Tony on a stuck rack though. whatever the cause.

 

[Tony Brooks]

55 minutes ago, BEngo said:

Assuming a Bosch type unit pump, surely frozen water inside the pump element would stop or limit  its up and down moving,  thus giving either expensive noises or a piston stuck in the up position?   I would also expect any pumpable ice to end up in the injector pipe and cause injection difficulties soonish?  I can see frozen water outside the pump element stopping the rack turning the outer helical part of the element , leaving the pump in the full chat position but that would also probably impede the flow of diesel to the elements.

My money is with Tony on a stuck rack though. whatever the cause.

 

My reasoning is that the cam can produce a far higher force than the bob weights so may well break ice for vertical movement but might not for rotary. However its all conjecture and I bet we never get to know the cause.

[Geoff12345]

Excellent answers , somebody else came back to me about corrosion in the pump but didn't have a fix for it. Removing the solenoid sounds like a way in. Will check tomorrow. 

Ice sounds feasible but the problem was a while back before the cold snaps. I turned my back on it for a while but spring's  coming and it' time to sort it out.

Thanks for all the replies .. appreciated.