Hydrostatic lock discussion

[cranetruck]

Apparently this problem has been with the multifuels since day one. This note is from a 1964 PS magazine (image below).
I assume that they are talking about the flame heater nozzle valves. If that is so and since it is located below the level of the intake manifold, can someone please explain the scenario. How will the fuel end up in the combustion chamber?
The nozzle can leak, I have had one that was leaking, so that's not an issue.

It may be a good idea to check yours or if you don't have a need for it, just disconnect the lines to be safe.


Thanks,

 

[Rattlehead]

I always thought it was some common failure related to coolant in the cylinders. I am relieved to see this.

If you parked the truck and left the in-tank pump on via the main switch, I suppose it would slowly put a nice big slug of fuel into the turbo housing, where it would sit awaiting the next time the engine was started, then oops! Worse, if the engine actually fired off from normal injection before that slug of fuel entered the cylinder. Now you are running at nearly idle speed vs cranking speed, and fuel is the horsepower making the engine turn, not the starter motor. I doubt there would be any warning in this case, just click, vroom, kaboom.

 

[rdixiemiller]

Sounds like the fuel would be getting through the injection pump, injector, and down into the cylinder. You would have to have an issue with the pump, and a bad injector for that to happen.

 

[devilman96]

I think Rattle nailed it...

If the nozzle was leaking bad enough and you left the pump on long enough it would easily fill the turbo, intake, and eventually run into a cylinder or two filling them partially with fuel. When you crank the motor and it were to fire before a full 4 cycles it would be like a garden hose in your intake, fluid in your cylinders and *bing*... a bent rod(s)!! Wouldn't take much ether a cup of fluid in a cylinder would be enough.

I have had this happen with air intake systems on equipment left exposed outside in the rain... The system holds water, someone cranks it and... hello vacuum... good bye engine... Rain, fuel, whatever... liquids don't compress.

 

[Recovry4x4]

Man, that might take a while. Lets see, it would have to fill up the j pipe, and turbo before it would rise enough to fill up the intake. Maybe that's a good argument to retain a bad J pipe with the hole in the bottom. I disconnected the flame heater om the wrecker engine.

 

[Rattlehead]

It wouldn't have to completely fill the turbo, exhaust, and intake, it would only need to collect a bit in the turbo or wherever. Then when you start the engine, it sucks that slug of fuel into a cylinder and its all over.

Reminds me of something I hear about now and then with someone using ether to start a diesel with a charge air cooler. Something is wrong with the engine that won't let it start correctly, so they start giving it shots of ether. It doesn't start, so they keep doing it. What they don't realize is the ether has to get through the charge air cooler and all of the pipes before it gets to the engine. When the first bit of ether hits the engine and it starts, the engine rev's up and feeds on the now ether filled charge air cooler. Overspeeds and destroys itself.

 

[forklift]

So all you have to do to prevent lock is run the starter with the engine stop pulled?? That would be nice to know.Does anyone have the manual that cranetrcuks post refers to?(tm 9-2320-235-10) It' s not in the manuals section. I really don't want to mess my engine up. I have turned the accessory switch the wrong way before, which left everything one. Thankfully, the air pressure buzzer was so loud I heard it from my house.

 

[cranetruck]

This is according to TM 9-2320-209-10 (1965):

 

[rice]

The idea in just bumping the starter with the stop pulled is so if you have fuel in the cylinder, it will lock the engine before you start it so it doesn't destroy everything. If it starts before the fuel stops one cylinder, you'll need an engine.

 

[rmgill]

This is an argument for having accessories not on the main accessory switch or a separate switch for the fuel pump. How long could this be an issue? After all, one of the First Parade items..Oops (Dang britspeak), PM Checks before driving is to run the fuel pump and bleed the fuel filters. How long could this sort of leak take to deliver a deadly slug of fuel?

Hmm, makes me want to add a manual valve to the cold start system too.

 

[rice]

I would say, you'd have to leave the pump on for awhile to get that much fuel in unless you have a bad leak. This could also happen if you had a head gasket seeping water into the cylinder. I replaced the intake heater on mine because I saw it seeping fuel on the outside, I figured it might be leaking both ways.

 

[Blacksmoke]

So if you did determine that your engine was hydrostatically locked, how WOULD you remove the fuel in a cylinder? Remove the injectors & crank the engine?

 

[rice]

That would be the best way to do it..

 

[cranetruck]

As is so often the case, it's covered in the TM's:

 

[cranetruck]

Further "research" shows that the intake manifold adapter on the non turbo models (LD-465-1) is oriented in such a way that a leaky flame heater nozzle could actually cause fuel to drain into the intake manifold.
The nozzle is supposed to have check valves to prevent this. Early(?) LDS-465-1 engines (5-ton) had shut-off solenoids in the lines as shown in second image below. Wonder if those nozzles had check valves too...

 

[cranetruck]

Here is a flame heater nozzle leakage test procedure: