MEP-002A Engine Stop Solenoid

[Wildchild467]

I had my MEP-002A Engine Shut Down Solenoid go bad and shut down my generator. Something internally must have gone bad because it was rapidly going in and out and would not stay in to the "run" position. I ordered an aftermarket one and that one lasted about a total of 15 minutes run time but I am past the 3 month return policy. I bench tested it and it does not work.

What is the best option go to with getting a good quality fuel shutoff solenoid? My original one had a total of 160 hours on it when it failed. Is the OEM one prone to failure? They want a lot of money for an OEM one and was wondering if somebody made any adapters to use another OEM quality one that will perform better? Right now I don't have any faith in OEM Engine Stop Solenoids for these generators. Thank you for your help.

 

[Guyfang]

The OEM part was normally a very dependable part. Take the old OEM solenoid and bench test it. Hook 24 volts up to it. It still moves in and out?

 

[rickf]

Was your oil pressure staying steady and at a reasonable pressure or was it very low at the time? Will it start when cold but do this when warmed up? Sounds like an oil pressure issue to me. You have checked the oil level haven't you?

 

[Chainbreaker]

The original OEM brand was "Woodward" that were installed and as Guy mentions were very reliable. I've never had one fail in 12 years.
I take it you've already searched P/N's: ONAN 307-1101 WOODWARD SA-1637-24.

Also, if governor RPM linkage is not adjusted properly, they will hunt with RPM pulsing high to low but that normally shouldn't cause engine to shut down.

Can you lift up the solenoid fuel stop linkage to keep it running or does it still shut down? If so, it could be a faulty safety switch: Oil Pressure or Temperature.

 

[Ray70]

The OEM is definitely very reliable. I've never had a bad one. I do have a spare available if you need one send me a PM, but always test first, make sure yours is bad!

 

[Guyfang]

Test, test, test!

 

[Wildchild467]

I checked the oil level and yes, that is good. When I bench tested the original one, its pulsed back and forth really fast. I pulled the top part of it off and there is a set of contact points in there and soon as the plunger goes all the way up, it opens those points and goes all the way back down, then repeats this again. but like I said, its really quick like the solenoid was acting like a jack hammer on the fuel shut off lever on the injection pump. Also it did this when I was trying to start it which when its in the start position, this bypasses the low oil pressure signal that it gets to cut solenoid power. Im also getting a solid 24 volts to the solenoid as well.

Its weird because I would like to know why it failed and why its acting like a jack hammer when 24 volts is applied. The generator has always been kept inside since I have had it and it has been good. I bought the generator from uncle sam with only 2 hours on it. So it was rebuilt at some point.

If anybody has anymore ideas, I welcome them. Also thank you all for responding, I appreciate it.

 

[Wildchild467]

Was your oil pressure staying steady and at a reasonable pressure or was it very low at the time? Will it start when cold but do this when warmed up? Sounds like an oil pressure issue to me. You have checked the oil level haven't you?

I kind of responded to this in my last post but wanted to answer more of your questions. It did this when it was warm, when it failed. Oil level was full, where it always is (good idea). It also did this while cranking with the switch in the start position which bypasses the low oil pressure circuit, so that's not the issue from my troubleshooting. Thank you for the response and questions. Any other ideas?

 

[Ray70]

If I'm reading this correctly it sounds like you put 24V to the solenoid and rather than retracting and holding, if is bouncing back and forth.
If so there is something wrong with the solenoid. It should just pull and hold whenever it is powered on.
Can you send a picture of the internals of the solenoid? perhaps something is wrong in there causing it to "Jackhammer"!

 

[rickf]

I kind of responded to this in my last post but wanted to answer more of your questions. It did this when it was warm, when it failed. Oil level was full, where it always is (good idea). It also did this while cranking with the switch in the start position which bypasses the low oil pressure circuit, so that's not the issue from my troubleshooting. Thank you for the response and questions. Any other ideas?

But what is your oil pressure gauge reading? And like Ray said, did you try holding the arm up to see if it stays running and I would ad to that to closely monitor the oil pressure gauge while doing it. The other sensor that can shut it down is the overheat sensor. I think that one would be more inclined to just shut it off and not bounce. I have never had one of those apart but what you are describing with the points and the way it is working sounds almost like it is designed to operate that way? That would make no sense. Why are the points there? Is it actually supposed to go full travel?

I know, I am not much help by answering you questions with questions of my own. LOL.

 

[Wildchild467]

If I'm reading this correctly it sounds like you put 24V to the solenoid and rather than retracting and holding, if is bouncing back and forth.
If so there is something wrong with the solenoid. It should just pull and hold whenever it is powered on.
Can you send a picture of the internals of the solenoid? perhaps something is wrong in there causing it to "Jackhammer"!

You are reading it correctly. When 24 volts was applied on the bench, it should just retract and that it... but mine was doing the "jackhammering"... exactly. I did take it apart to try and figure something out but didnt find anything conclusive. There is a set of breaker points in there that opened up when it was in the up position so i dont know what the idea was of that. It could get confusing if I try to explain it more, so I will try to get a picture of it tonight and post it. Its not what I would think by just being one coil and two leads coming out of it for actuation. I think what happened is one (if there are more than one?) coil got an open circuit somehow and wouldn't actuate.

 

[Wildchild467]

But what is your oil pressure gauge reading? And like Ray said, did you try holding the arm up to see if it stays running and I would ad to that to closely monitor the oil pressure gauge while doing it. The other sensor that can shut it down is the overheat sensor. I think that one would be more inclined to just shut it off and not bounce. I have never had one of those apart but what you are describing with the points and the way it is working sounds almost like it is designed to operate that way? That would make no sense. Why are the points there? Is it actually supposed to go full travel?

I know, I am not much help by answering you questions with questions of my own. LOL.

Ya know, that's one think I don't remember doing is looking what the oil pressure was. I did check the oil level though and it was right to the full mark.

I did hold the arm up and it ran fine, no issue. I even removed the solenoid all together and it runs perfectly fine. So just to say it again, with the solenoid removed from the generator, it starts and runs fine, I just have to use my finger and push the throttle down to shut the generator off. So the issue seems to be isolated to the solenoid because when I bench test the solenoid, it does the jackhammering like I described.

I don't know why there are points in there. Just like a set of ignition breaker points. So when the plunger fully retracts (run position) there is a rod that comes up that is hooked to the same shaft the plunger is on and that opens the set of points. as soon as they open its like it shuts power off to the solenoid. so then the plunger drops because its spring loaded which caused the breaker points to become closed and then that powers the solenoid coil again and the plunger shoots back up.... which opens the breaker points again and causes the plunger to go back down... thus making the jack hammering like I was experiencing. Sorry for the long winded but you know how it is describing a situation over text. haha.

Those points are in there for a reason, but I'm not sure why. My theory is maybe two coils are in there working together and they use two to give it extra power to pull up and then soon as its all the way up, one coil shuts off to save some power/heat build up in the coil. then maybe one of the coils went back and caused my issue. That is just a guess though.

 

[Wildchild467]

If the solenoid was "jackhammering" while installed in the generator but did fine on the bench test, then I would know that the issue is somewhere within the generator... but that isnt the case. It jackhammers in the generator as well as outside the generator on the bench. Like you said Ray, they should be very reliable. To your point, when the power went out and my wife rolled over to me in bed and said, "Tom the power is out", I responded, "No its not" haha. Thats how much trust I had in the generator. We had a power outage for 5 days during an ice storm and I had to keep the family warm and stuff. Thankfully I had a Honda generator I was able to plug in and got us back up and going for the last day it was out. Knowing what I know now, I would have removed the solenoid and kept it running again.

 

[Ray70]

I've never opened a FSS but I think you are probably right as far as 2 coils. I bet both pull up the plunger and once it's up, the points open and only use 1 coil to hold the solenoid open, this will decrease power consumption and decrease heat buildup in the solenoid.
Sounds like your primary coil is dead and only the secondary is operating, so every time it opens, the points open up and then the plunger falls due to the primary coil being inoperative. The points then close again starting your jack hammer effect!

 

[Guyfang]

That sounds about right to me Ray. One coil to close it, one coil to hold it closed. the holding coil is defective. I never took one apart, as I think I have only seen 1-2 go bad, ever.

 

[Wildchild467]

I've never opened a FSS but I think you are probably right as far as 2 coils. I bet both pull up the plunger and once it's up, the points open and only use 1 coil to hold the solenoid open, this will decrease power consumption and decrease heat buildup in the solenoid.
Sounds like your primary coil is dead and only the secondary is operating, so every time it opens, the points open up and then the plunger falls due to the primary coil being inoperative. The points then close again starting your jack hammer effect!

Exactly! Figures if they rarely go bad, i would get one that went bad. haha!

I emailed Woodward and asked them to quote a new solenoid. They said that the SA-1637-24 is an obsolete solenoid and the replacement part number is SA-2779-A. EDIT: I ORDERED AN SA-2779-A AND IT WILL NOT WORK BECAUSE IT DOES NOT HAVE A RETURN SPRING FORCING THE PLUNGER DOWN TO THE STOP POSITION WHEN POWER IS REMOVED FROM THE SOLENOID.

I still haven't decided what I want to do yet. I want to replace it but the generator does work for now if I really needed it.

 

[Wildchild467]

Here is a picture of the inside of the fuel stop solenoid. I took some of it apart so it's not 100%. But as you can see there are two breaker points in there.

 

[rickf]

Ok, So that is actually one set of points that connects the one side to the other when they come together. Without seeing the rest of the assembly it is hard to tell what is connecting to what but it looks to me like that setup is connecting the circuit on the left to the circuit on the right. Now, with that said it could be that the point arm is energized and the power is transferred to both right and left when they close. Would need to see the whole assembly together.

 

[surpdlr]

Exactly! Figures if they rarely go bad, i would get one that went bad. haha!

I emailed Woodward and asked them to quote a new solenoid. They said that the SA-1637-24 is an obsolete solenoid and the replacement part number is SA-2779-A. Hope this helps somebody in the future if they want to source another one.

I still haven't decided what I want to do yet. I want to replace it but the generator does work for now if I really needed it.

I don't know if this helps or not...
SA-1637-24 is NSN 5945-01-048-9774
Also Cummins Power 307-1101

The New Woodward PN is NOT in the MCRL yet....

The ugly part in the surplus world will be that Brown Helicopter manged to sell 5ea or maybe 9ea? back in 2012 to the Government for $1,179.00ea.
So that will now set the Surplus aftermarket pricing more than likely...

Over the years it has become painfully obvious that some of the BIG Surplus buyers of the 1990's are running parts museums, hoping against hope that Uncle Sugar will pay BIG bucks for parts that they will struggle to sell even to us collectors.... Such is life I guess.

 

[Wildchild467]

I ordered a new solenoid from Drake Controls SA-2779-A and it does not have a return spring to force the plunger down to the stop position when the generator is in the off position. I am contacting them now about a return.