How to prevent a MEP 002A / 003A from run away by means of maintenance and a Frequency Monitor

[peapvp]

Since this has happened in the past, I thought it might be a good idea to point our esteemed members in a better direction:

1. Check your fuel cutoff solenoid as per manual and that the plunger moves absolutely freely. Dust and Humidity can get the plunger stuck or to move hard, when unit is outdoors for prolonged period of times. The protective boot gets damaged or starts to dry-rot.

The -12 manual gives us these suggestions:



2. You may want to buy and install a AC Frequency Monitor with configurable alarm relay (dry contact) and wire the contact in series with one of the two leads of the Fuel cutoff solenoid.

If the Frequency of the Power goes over the set-point (selectable), say like 65 Hz or 70 Hz, then the alarm relay is active and the Normally Closed Dry Contact will open and turn off the 24 VDC to the Fuel Cutoff Solenoid, shutting the engine down within 1 to 3 seconds

Your Cutoff Solenoid has to be in pristine condition anyway and then you can sleep well. No matter if the Genset was started manually and you went back to sleep in your warm and cozy bed or through remote start.

These units cost about $ 350.00 to $ 400.00 and this company has them for sale:

PFB01CM24 FREQUENCY MONITORING RELAY

Product Manual is posted here as pdf

 

[Scoobyshep]

A great set of first steps however this only works assuming there isn't a failure in the solenoid or governor assembly (or an alternative fuel source). These are rare edge cases, but its important to know that the solenoid isnt a 100% catch all

 

[peapvp]

A great set of first steps however this only works assuming there isn't a failure in the solenoid or governor assembly (or an alternative fuel source). These are rare edge cases, but its important to know that the solenoid isnt a 100% catch all

@Scoobyshep correct, that’s why I pointed out the maintenance of the fuel cutoff solenoid, giving it some tlc and it greatly reduces the risk of a runaway damage if the Genset is left unattended while running.
If alternate fuel sources enter the picture, especially worn piston rings, then there is no saving the engine.
Hence, he who doesit the maintenance, shall be rewarded..,.

 

[Scoobyshep]

@Scoobyshep correct, that’s why I pointed out the maintenance of the fuel cutoff solenoid, giving it some tlc and it greatly reduces the risk of a runaway damage if the Genset is left unattended while running.
If alternate fuel sources enter the picture, especially worn piston rings, then there is no saving the engine.
Hence, he who doesit the maintenance, shall be rewarded..,.

Just wanted to close the loop, all falls back to the 6 Ps.

 

[AfghanVeteran2010]

I have seen some sets that cut off the air flow to the engine, might be an idea looking into.

 

[Chainbreaker]

Thank you! Very timely for my current MEP-003a issue (Runaway)! If it ever quits raining here (my shop & barn are presently full without any extra room) I'll be jumping back into troubleshooting my -003a's issue.

If can't find the culprit soon I just might have to look into developing my own "Rube Goldberg solution" to closing off the air intake on my -003a to cover all the bases. I can see installing a flapper valve or sorts appended to the top of intake stack that initiates (closes) on a frequency rise above X% that then triggers a fuseable link, or relay, that then drops a weight attached to flapper lever to shut off airflow as a failsafe!

 

[Scoobyshep]

Thank you! Very timely for my current MEP-003a issue (Runaway)! If it ever quits raining here (my shop & barn are presently full without any extra room) I'll be jumping back into troubleshooting my -003a's issue.

I just might have to look into developing my own "Rube Goldberg solution" to closing off the air intake on my -003a to cover all the bases. I can see installing a flapper valve or sorts appended to the top of intake stack that initiates (closes) on a frequency rise above X% that then triggers a fuseable link, or relay, that then drops a weight attached to flapper lever to shut off airflow as a failsafe!

Can do the same thing with an inert gas injected to the intake

 

[peapvp]

Thank you! Very timely for my current MEP-003a issue (Runaway)! If it ever quits raining here (my shop & barn are presently full without any extra room) I'll be jumping back into troubleshooting my -003a's issue.

If can't find the culprit soon I just might have to look into developing my own "Rube Goldberg solution" to closing off the air intake on my -003a to cover all the bases. I can see installing a flapper valve or sorts appended to the top of intake stack that initiates (closes) on a frequency rise above X% that then triggers a fuseable link, or relay, that then drops a weight attached to flapper lever to shut off airflow as a failsafe!

the professionals use this here on the air intake



Comes in different diameters, not cheap but still better then replacing an entire engine

Air Valve Shut Off

 

[Chainbreaker]

Since this has happened in the past, I thought it might be a good idea to point our esteemed members in a better direction:

1. Check your fuel cutoff solenoid as per manual and that the plunger moves absolutely freely. Dust and Humidity can get the plunger stuck or to move hard, when unit is outdoors for prolonged period of times. The protective boot gets damaged or starts to dry-rot.

The -12 manual gives us these suggestions:

View attachment 934693

Your mention above of "Dust and Humidity" & "The protective boot gets damaged or starts to dry-rot" caught my attention.

During my inspection of the solenoid, I used my finger to push the plunger upwards & it moved freely both directions, however I noticed a possible telltale sign... Where the upper two halves come together, I noticed something odd. Apparently, there is a gasket where the two halves of the solenoid housing mate together. Whenever I push up on the plunger, I notice some almost imperceptible "tiny bubbles" coming out from the seam (gasket material) where the two halves mate. That might indicate there are some internal water droplets (condensation) up top that could affect its internal electro/mechanical operation with inconsistent operation. I just might take it off & see if I can separate the halves & take a close look at the internals. If it shows any signs internally of deterioration, I just might rob another solenoid off another genset to see if that might be a solution to eliminating any future runaways.

 

[peapvp]

Your mention above of "Dust and Humidity" & "The protective boot gets damaged or starts to dry-rot" caught my attention.

During my inspection of the solenoid, I used my finger to push the plunger upwards & it moved freely both directions, however I noticed a possible telltale sign... Where the upper two halves come together, I noticed something odd. Apparently, there is a gasket where the two halves of the solenoid housing mate together. Whenever I push up on the plunger, I notice some almost imperceptible "tiny bubbles" coming out from the seam (gasket material) where the two halves mate. That might indicate there are some internal water droplets (condensation) up top that could affect its internal electro/mechanical operation with inconsistent operation. I just might take it off & see if I can separate the halves & take a close look at the internals. If it shows any signs internally of deterioration, I just might rob another solenoid off another genset to see if that might be a solution to eliminating any future runaways.

It probably will eliminate future runaways, except for the issue of runaway caused by alternate fuel sources which are more often then not badly worn piston rings. Then air cutoff is your only and final protection of any form of runaway
The fuel cutoff stops the inflow of fuel into injection pump regardless if the pump is working correctly or not

 

[Chainbreaker]

Actually, I'm probably guilty of over "overreacting to the runaway engine" expecting a much faster shutdown in my panicked state. Its shutting down when panel control switch is turned off or panic stop button pulled out just not quite as fast as expected under the circumstances. 10 ~ 15 seconds or so seems like eternity when an engine is rapidly accelerating & blowing black smoke!

The frequency monitoring relay you listed above appears to be an "excellent safety device" to install to prevent any unattended diesel engine runaways or electrical anomalies as detectable by Hz, with your noted exceptions above. Without having such a device, I doubt one could react fast enough if inside house watching TV, or whatever one might be doing, to prevent engine damage or damage to one's electrical appliances.

I'm going to return to my original thread so as not to clog up this informational thread with my particular incidents here.

 

[Ray70]

If you really want to get fancy, take a small throttle body off a 4cyl. fuel injected car, incorporate it into you air intake / filter tube and set it up with a 24V actuator powered off the fuel solenoid circuit.
When power to the FSS is cut, so is power to the throttle body, allowing it to snap shut and kill airflow.
Just make sure the idle air circuit in the throttle body is blocked off as well.

 

[Guyfang]

I have seen some sets that cut off the air flow to the engine, might be an idea looking into.


The only large gen set I ever saw in the Army with an Air Cut off System was the Stewart & Stevens 52-300, 45 KW gen set. It had a huge solenoid, that when energized, the solenoid snapped opened the passageway from the Air filter to the Air Intake Manifold. As soon as the Start switch was pushed up, you heard a very loud "POP", the solenoid snapped the passage way open, and the engine would start. On shut down, same deal. Push the start switch down, a loud "POP" and the engine spooled down. It was so loud, that at night, when a gen set shut down for a fault, the pop was heard easy 40-50 meters away. The 52-300 was world famous for running away. It had a Detroit Diesel 3 cylinder engine that was a hummer! But that was the only one I ever saw.