MEP-003A

Johncar48

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I've been told most of my many years tinkering with small aircraft and diesel engines of all sorts and sizes that when you start them cold you should run them at idle, let the pressures build and the engine warm up. But I read somewhere that a good, continuous run generator should never idle or run below it's designed operating RPMs. Letting an engine warm up, kinda like me in the morning, sure makes a lot of sense. Can anyone out there'll me why it would be not so good to warm up an MEP-003A or MEP-803A before setting it to run at 1800 RPMs?
 

Ray70

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Simple.... on an 002 / 003, idling will overload the transistors on the voltage regulator and damage the regulator. Seen it plenty of times. on the 802/803 I'm not sure if they are as prone to VR damage from idling, but not looking to take a chance to find out!
Just start it up at 1800 to avoid damaging anything.
 

Ray70

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Update: John pulled out his IP and sent it up to me. I took it apart today and found exactly what I expected and MORE!
Not only was the plunger guide split in half, but the end of the throttle lever ( Control unit ) was snapped off inside the pump housing.
Also, the plunger sleeve was fairly well stuck to the plunger itself.
I assume that because the sleeve was stuck to the plunger, the first time the cam lobe pressed on the plunger, the sleeve couldn't slide along the plunger, so it moved up, snapping the end off the control unit. at the same time the gear is attempting to spin the frozen plunger but can't so the plunger guide split in half.
Luckily it is a model 50 so everything can be fixed.
I'm sure fixing the pump will get yet another 003 back into service!
 

justacitizen

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justacitizen

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Johncar48

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Well gentlemen, it's been a while so here goes.
After Ray rebuilt IP and injectors my 003A ran like it was new, so all was good. Started it about every 30 day to keep everything in good order...all still good.
Got busy and let it sit for about 6 months, batteries went dead and would not take a charge.
Replaced batteries and turns over very well...however I now have a Gremlin somewhere in the unit.
Gov. solenoid won't activate so removed it and tested with 24V. Worked well. Cleaned and replaced grounding strap. Replaced A1 & T1 relays. Still nothing. Manually held IP valve open but nothing.
Heater relays working OK...so here's th Gremlin: Every positive terminal I touch with a multimeter and then ground to frame, I get a tone. Gov. solenoid gives me a tone from both terminals along with heat and start relays. What in the world is going on? HELP PLEASE!!!
 

Guyfang

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When you touch the Pos and Neg terminal, you are supposed to get a volt reading, not a tone. Or with my Multimeter. So are you in ohms position? What voltage are you getting on the meter?
 

Johncar48

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what started all this was I was trying to find out which terminal on the gov solenoid was negative. So with batteries disconnected I touch multimeter (set to tone continuity) to one terminal and got a tone then I touched to the other terminal and laaaso got a tone. Don't think this is right but I'm a novice.
 

Ray70

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Hey John,
I assume you are finding that your solenoid doesn't pull in when you crank it?
It will not pull up until you begin cranking, then it will hold there as long as the machine fires up, otherwise it will close down after several seconds.
Also, if you have a break in the circuit for the over temp sensor, it may not pull in ever.

If you just turn the switch to prime/run it will not pull in the solenoid, you have to turn to crank position first.

As for your meter reading, are you doing the tests with the solenoid connected? If so, I bet that is what is "Confusing" you meter. It'd probably back feeding through the solenoid's coil. Disconnect the wires and try again and see what you get.
 

Johncar48

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SO with batteries disconnected and testing continuity between the 2 terminals on the IP solenoid I get a tone with the wires to the solenoid disconnected. Testing the continuity between the two wires feeding the solenoid I get nothing.
 

Ray70

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Ok, so when you test the 2 connections on the solenoid itself you are getting continuity, meaning the coil in the solenoid is good, which you also confirmed by testing the solenoid with 24V.
Testing the wires I would expect you should get a tone ( continuity ) when testing from battery negative to one of those wires.
If not it sounds like you may have a ground connection issue somewhere.
There is a connection on the side of the starter where your negative battery cable attaches to the stud. There are also 2 or 3 smaller wires on that stud.
One of those ( larger ) goes to your slave plug, the smaller goes inside the control cube to the terminal strip.
Check to make sure those connections are all tight.
Check that the connectors on the back of the Control box are all secure ( may want to unscrew and reseat them to ensure good connections )
You can use the wiring diagram to see which position on the terminal block are the grounds. and where the negative from the fuel solenoid is attached to the terminal block.
Have you checked the 2 solenoid wires to see if you get 24V + when cranking? That will tell you is you have a ground issue, a power issue or both.
 

Guyfang

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Ok, so when you test the 2 connections on the solenoid itself you are getting continuity, meaning the coil in the solenoid is good, which you also confirmed by testing the solenoid with 24V.
Testing the wires I would expect you should get a tone ( continuity ) when testing from battery negative to one of those wires. (K5-2, Wire # P55T16, if the wire # is readable)
If not it sounds like you may have a ground connection issue somewhere.
There is a connection on the side of the starter where your negative battery cable attaches to the stud. There are also 2 or 3 smaller wires on that stud.
One of those ( larger ) goes to your slave plug, the smaller goes inside the control cube to the terminal strip.
Check to make sure those connections are all tight.
Check that the connectors on the back of the Control box are all secure ( may want to unscrew and reseat them to ensure good connections )
You can use the wiring diagram to see which position on the terminal block are the grounds. (Should be TB4- 12,13, 14) and where the negative from the fuel solenoid is attached to the terminal block.
Have you checked the 2 solenoid wires to see if you get 24V + when cranking? (This is the key to the problem) That will tell you is you have a ground issue, a power issue or both.
Open to see comments. Glad you jumped in here Ray. It was 00:00 and had to work in the morning.

1645555959301.png
 

Johncar48

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Reconnected solenoid and checked voltage on start. It was 19.7 volts.
Solenoid still is not pulling up. Is it ok to hold the IP valve in the open position manually and try to start?
 

Johncar48

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Kerrville, tx
Well that didn't work at all. Wired IP valve open, engaged heaters, primed, start...starter engaged but engine did not fire at all. Hummmm! Checked all negative wires at starter and traced them inside control box. All good! This gremlin is a tough booger!
 
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