Switch fuel rack or compression release?

[mbryner]

Got it.  

I won't use the input fuel line or decompression lever for shutoff, and I will figure out a ball valve system on the air intake for emergency shutdown (in a future project).

My questions were about routine startup and shutdown.   Consensus is closing the fuel rack is the only way to go.   Thank you gentlemen.

BTW: Bruce, thanks for the video link.     How you did it would be very simple to implement, but I wanted something that would kill the engine if the 12 V power was lost.   Your explanation of how you would do it again is exactly what I had in mind.   Didn't recognize you as rocketboy w/ your new name on this forum.   

[sailawayrb]

...all taken off a scrap cruise missile

ROFL ..... yeah, ok .... I am not a rocket scientist and don't have any spare cruise missiles to scrounge parts from

Well, I am sure something appropriate could be had from American Hose or McMaster-Carr.

What can I say...I like to improvise...and I don't like to let things go to waste that are at hand...

Bob B.

[sailawayrb]

Leakage into the supply lines at fittings etc. should be possible to prevent but there is other leakage points (for negative pressures) in the high pressure injector pump itself that can lead to possible start up problems later as well as possible mechanical damage to the IP.
This was kicked around at great length in an earlier thread.

I don't understand this train of thought at all...  I have used an electrical valve for years on LP side of IP for "routine shutdown" without any issue. I don't recall, but I am not surprised that this was discussed previously...and that speculation and ignorance led some to believe this wouldn't work. I do recall similar discussions on the LE site...the classic example being that one had to use a ton of concrete and could NOT use a resilient mounting system to run Lister engines, but several of us proved that was pure BS. I sure wish more people would take the time to actually prove things for themselves in lieu of believing outright what others claim.

However, I do agree with every other sentence you wrote.

Bob B.

[Crofter]

Shutting off the fuel supply will eventually stop delivery so in that sense "it works". The pump will continue delivering until a vacuum is created and the pump starts to gulp vapor. There is no primary delivery section so it depends on gravity to keep it full. The plunger is not well sealed and air will leak in. Normally the pump is under slight positive pressure and the bit of fuel leakage seeps out externally. This leakage is more noticeable as the IP gets some time on it. Under a vacuum for a period of time air will leak into the pump. If you look closely you can see a few avenues of potential ingress. It does not take much air internally to result in missing and farting or even entirely refusing to restart without bleeding. Not specific to the mico pump, but some do not like to be run dry by having supply restricted. You may get away with it but the scenario is one that tends to create problems and it is not good design to shut down by that method.

I don't think it has anything to do with a ton of concrete, just a pump that is not designed in the method of sealing or valving to act as a lift pump. I think in Lister setup info they specify the minimum and maximum positive head the pump should have.

[Horsepoor]

Oh no, I'm not Rocketboy, thats Bob Gross my neighbor removed about 30 miles. When I signed up on the old LEF back in 2005, I couldnt think of a catchy handle / name, so I just registered by first name (Bruce), not very original uh. So I just signed up here using the same name.

Update: Figured it was about time to pick a decriptive name. As the husband of a horse owning wife, I am truely Horse Poor.

[mbryner]

Actually, Jens, I was trying to visualize how you did it.   I was at work until about 9 pm tonight so I couldn't look at the engine in person.  Tomorrow morning I'll go out to the 'roid and see what you were talking about.

Bruce, when you added the link to rocketboy's youtube vids I thought you were him w/ a new name.   My bad.

[mbryner]

OK, I got it.   You're saying to put the solenoid in series w/ the spring.   Duh.   That would work perfect.   When the solenoid is energized (pulled in), you adjust the spring tension for 650 rpm.    When there's no power to the solenoid, the spring falls limp and the engine stops.    Too easy.   Thank you.   

[sailawayrb]

Shutting off the fuel supply will eventually stop delivery so in that sense "it works". The pump will continue delivering until a vacuum is created and the pump starts to gulp vapor. There is no primary delivery section so it depends on gravity to keep it full. The plunger is not well sealed and air will leak in. Normally the pump is under slight positive pressure and the bit of fuel leakage seeps out externally. This leakage is more noticeable as the IP gets some time on it. Under a vacuum for a period of time air will leak into the pump. If you look closely you can see a few avenues of potential ingress. It does not take much air internally to result in missing and farting or even entirely refusing to restart without bleeding. Not specific to the mico pump, but some do not like to be run dry by having supply restricted. You may get away with it but the scenario is one that tends to create problems and it is not good design to shut down by that method.

I don't think it has anything to do with a ton of concrete, just a pump that is not designed in the method of sealing or valving to act as a lift pump. I think in Lister setup info they specify the minimum and maximum positive head the pump should have.

Thanks Crofter, your explanation helps me better visualize what you are saying.  I wish I could look at my IP to get final closure, however, I'm 8 hours from home and also using a 56K modem (that gets maybe 20K) for Internet access right now.  The good news is that I passed my OR GC exam yesterday. 

How exactly does the normal fuel rack cut fuel off without having this same issue?  My engine originally came with a mechanical valve between the fuel tank and the IP.  I have long since turned the fuel tank into a Lister "drip can" since I use both diesel and SVO.  I think this original mechanical valve was only intended to be closed when not using engine for long time.  However, I can imagine folks forgetting to open it before starting the engine and then having this same issue too?

Bob B.

[Crofter]

The stop cock (a bit are cake) is needed to be able to service the filter or what not, and also to prevent seepage through the IP. Remember its internals are fitted with very tight metal to metal clearances but still subject to some leak past.  The fuel rack rotates a helix that causes a change  in internal displacement. In other words a variable displacement pump. The shut down position results in zero volume displacement even though the pump still has access to fuel. It does not result in being choked into submission,

The fuel volume between the IP and any external fuel shut off, the elasticity of any connecting lines, drop in temperature, etc. all influence the amount of air that could be sucked back in if engine is killed by this means. The range of pump clearance would affect the odds of experiencing a problem of difficulties in restarting. It does not take much volume to air lock a pump that effectively has only a discharge check valve and no intake check valve. lntuitively we don't expect leakage into a pump designed to pump thousands of pounds pressure. Some injector pumps would be far less susceptible but the Mico is not very sophisticated and not designed to work under any negative pressure.

Obviously you had no problems with it but Jens did. His engine being a double gave much more opportunity. Using that method as a routine shutdown just exposes you to the possibilities of faltering or failing start up after a period of shutdown. No fun if you happen to be handcranking.

[sailawayrb]

Thanks Crofter, your description of the Mico IP essentially using variable displacement approach makes perfect sense.  I reckon I have been very fortunate not to have encountered a problem yet.  I am also glad that I stock piled several Mico IPs for spares.  Thanks  

Bob B.

[mbryner]

Bob B., congratulations on passing the GC exam.   I sent you a message off forum.   

[Horsepoor]

A little more money that a solenoid but perhaps a cleaner and simpler way to slam the rack shut or pull the ball valve level on the air intake shut with force.

http://www.fwmurphy.com/rp75/

Expensive at: http://www.murcal.com/Catalog/Rack-Pullers

[sailawayrb]

Bob B., congratulations on passing the GC exam.   I sent you a message off forum.   

Thanks Marcus.  I received and responded from Corvallis.  Hopefully our schedules will work out in May or July. 

Bob B.

[mbryner]

Sorry to revive an old thread, but I have a question and an update.

Question:   If the Mico injection pumps have a minimum input fuel pressure requirement, is there a maximum?   I have a 15 gallon cylindrical white poly tank that I would like to use for the cleaned/centrifuged WMO, and I want to mount it vertically to get a better view of how much fuel is left in it.   If I orient it vertically so that the tank bottom is above the fuel filter (before the IP of course), then the top of the tank is almost 3 feet higher than that.   I seem remember reading somewhere that too much fuel pressure into the IP is bad, but how much?   We're only talking about 2 psi here.

Thanks.

Hey, also I noticed some posts by Jens in this thread are missing when I re-read it today.   ??

So here's what I came up with for routine startup/shutdown: