MEP-004 starting questions

[jagrdawger]

I have a generator based on the MEP-004 that is giving me some fits starting. This is a PU-794/g, the precise 20KW version of the MEP-004 from what I have gleaned from manuals. My issue is this:

When starting the generator I frequently get click that appears to be from the fuel system. If I continually cycle the start switch it usually will result in engaging the starter, cranking the engine and starting the generator sooner or later. It seems to take fewer attempts in warmer weather (60+) than cooler weather and it will rarely do anything but click below 45 degrees. 30-40 tries before cranking is not common. This is not a case of the starter spinning, but failing to engage the fly wheel, it just does not crank at all. I suspect a sticky relay or issue with the starter solenoid, but I am far from an electronics guru.

Suggestions?

Below is a picture of the unit. I would be interested in any information regarding what types of systems these were designed to power as well. They seem to be very uncommon.

 

[Guyfang]

This version of the good old MEP-004A was very seldom seen. And you have a gem! First off, the ASK, and then the load Bank on front. Very seldom! Does the load bank work? This PU set was used for certain radar, and electronic vans.

The click you hear should be the fuel solenoid, on the day tank. It can and will sound loud, when you hit the S-1, to start the set. Normally, you cant hear it over the sound of the gen set starting.

OK, places to start. I doubt its S-1. That switch is VERY reliable. But to test it, simply jump the switch. It could be your speed switch, S-9. Exercise the reset switch in S-9. Might help, but the only way to know, it to test. If you have problems with starting, disconnect the canon plug on S-9 and insert a paperclip into pins A and B of the plug. Hit S-1, and see if it turns over. If so, the S-9 is the culprit. You can also check continuity on pins A&B on the S-9. If it is open, then it wont start. When you hold it in your hand, there should be continuity on pins A&B.

You can also change out K-1 relay. Its just a little bitty fart, and there are several others in the set to change it out with. Of course, something else won't work, but then at least you know what it was. Then there is the K-3 Crank relay. Sometimes it can give the fault you wrote about. Easy to test, just use the TM to learn how. And then it could be the starter solenoid. You can jump it at the starter, to test. Sometimes, they go bad, but seldom. If it works by jumping it, then the problem is elsewhere. There is a very good troubleshooting diagram in the -12 and -34 books, have you downloaded the books yet? Beter yet, what book do you have?

 

[jagrdawger]

Guyfang, thank you for your response. I spent I fair amount of time in military manuals over 22 years in the army, but most of it was related to a howitzer, hummer or 5-ton and never with the electronics. I do not think these had a load bank on them or at least this one does not. There is a battery box on the drivers side fender and cable reel. I would be thrilled if it did. The space where most MEP-004s have the batteries contained a box for TM's that is difficult to get to due to the ASK right over head.

I bought this set from Camp Dodge, Iowa a couple of years ago. Once winter was over I cleaned the fuel tank which had plenty of sand in it. All of the filters and fluids were brand new. Bled the fuel system and once it decided to crank it started up with nary a sputter.

I have downloaded TM 9-6115-464-12, TM 9-6115-464-34, TM 5-6115-634-14&P & TM-9-6115-464-24P. Tonight I decided to give it a crank since it was about 60 degrees out. Planned to test a couple of your ideas. Well, it was like taking the car to the mechanic, three flips of the switch, it cranked over and started right up. Since I had the water barrel load bank hooked up and wanted to try it under load, which I have not done yet, I ran it for 30 minutes single phase with two 4500 water heater elements going. Registered about 40% load and maintained 240 volts and 59.5 hertz for the whole time.

Looking through the manuals I did not see references to the K-1 relay. I saw the crank relay exploded view in one manual, but did not find the trouble shooting procedures. I believe the speed switch on this model is the voltage adjust. You reference the S-9 as the speed switch and reset switch so I am a little lost. I will test the S-9 pins A & B tomorrow afternoon if I have a chance. I am out of town on work everyday the rest of the week and some days may run late.

Thanks

Doug

 

[Guyfang]

Doug,

That big box in front isn't a load bank? Thats where its suposed to hang, so the air output from the radiator would blow through it and keep it cool. Oh well.

I never liked the ASK. It made maintenace even harder, and when soldiers have to do something extra, well, sometimes it doesn't get done. And batteries were a real sore spot!.

The S-9 speed switch is on the left side, between the two filter canisters. Anything that has to do with engine speed (or better said hertz) monitoring, is controlled by S-9. The A&B contacts are for starting. They have to be in their normal position, (engine stopped, no RPM) for them to be closed. At a certain RPM, (its in the book, but not important to us) the S-9-1 contacts open. That kicks the starter out. Then the contacts between S-9 pins A&D close, allowing the excitor to get a jolt, to light off, (turn on) the main gen. If the excitor doesn't light off, you can always push the S-1 start switch up into the start position, to try again, and the starter will not reengage, because the S-9-1 is open. The S-9-3 contacts only come into play when you have an overspeed.

The K-1 is located directly behind the control panel. Open the control panel and on the wall behind it, is a circuit card, (look at the card for burn marks!). On it should be two relays. Little metal match box sized things. Un screw them, and swap them. One is K-1, and the other is K-6, I think. Do this before trying to start the set. Before, you said, the set started after 3 tries. That's why I would say swap the relAYS BEFORE YOU TRY AND START. ALSO; HAVE SOMEONE ELSE USE THE S-1 START SWITCH; AND YOU HOLD YOUR HAND ON THE STARTER. tHAT WAY YOU CAN FEEL IF IT'S ENGAGING; BUT NOT TURNING: Darn, hit the cap lock again! If the starter engages, but not turns, its the starter that is a problem.

There are a couple ways to test the K-3. One is to take it out, and apply 24 volts to the two small terminals. There should be a "klunk", and you get continuity between the two large terminals. Or, take the bottom part off of the Special Relay Box, (SP/R). Hook the SP/R box back up. Use alligator clips on your multimeter. Attach them to the two small terminals, on K-3. Set the meter to DC, and watch it when someone else starts the set. If you do not get voltage on the meter, then the problem is before the K-3 relay. If the K-3 gets voltage, and doesn't work, chances are that the K-3 is bad.

You can do the same with the starter. Put a meter on the start solenoid + wire, and to ground. Then have someone start the set. If you get voltage on the solenoid, and it dosnt work. Chances are the starter is bad. I am sure you have seen the same type of K-3 relay on trucks, and the starter is in principle, the same also. You just don't have a K-1 or speed switch, (centrifugal switch) on a truck. And a LONG time ago, back in the early 60's & 70's, some trucks did have speed switches.

Read this and see if it makes sense to you. When you get around to it, you get to it.

Later, Guy

 

[Chainbreaker]

You mention that above 60+ it takes fewer attempts to start and that it will rarely do anything but click below 45 degrees...

Just to cover the obvious...what are the condition of your batteries?

 

[jagrdawger]

The batteries were brand new 850 CCA's this summer. They are both testing around 800 on a midtronics tester on Sunday.

The original batteries were toast so I took the batteries out of my Ford Excursion several times over the year or so I putted around before I got serious about getting it going. With the original batteries it acted this way. Once I put new ones in and started flipping the switch to see if something would possibly unstick I was shacked when it did. It was also about 80 that day. It has started once or twice when it was cold, but the sun had been out all day so there may have been heat in it. It cranks very strong and starts quickly once what ever is the problem allows it to start cranking.

I plan to work through the trouble shooting this weekend, Work this week has messed with evenings in a big way.

It is a valid question...sometimes the obvious is easily overlooked.

 

[Chainbreaker]

Another thought...perhaps there is an intermittent grounding issue "somewhere" causing intermittent starting when grounding is lost due to some sort of temperature induced (expansion/contraction) open ground condition.

 

[jagrdawger]

Fighting a large grass fire on Saturday (part of my job) and some honey do's limited my generator testing time this weekend. I have not found the issue, but did test the following:

Swapped K-1 and K-6 with no change. What is the rubber cement like sealant they apply over these relays? They did not come out easily.

Wife worked S-1 while I held a hand on the starter, no sensation of any action inside.

Had digital multimeter on solenoid and grounded to bare frame as S-1 was worked and held in start. Occasionally jumped to 14 or so volts, but only for a second or less a couple of times. Mainly just sat at zero or showed minor stray readings of up to 2 volts.

I should have some more time later this week to work on testing more issues such as K-3 and grounding.




On the positive side I finally ran the 803a I got around Nov. for about 30 minutes under a load of 2 x 4500 watt hot water heaters. Held voltage and hertz very consistent and registered about 65% power. It was the first time I got it warmed up. It has the reset tag on it so I need to get the regular oil out and get some break-in oil in it. It is now at 12 hours, got it at almost 11.

 

[jagrdawger]

Guy, I may have misunderstood your comment about the box on the front. The box in front of the radiator and the one on the back are large sound baffles. The box on the front fender running board by the fire extinguisher is the battery box.

 

[Guyfang]

The sealant on the circuit card and relays is GOOD! Keeps moisture, (and you) out of the picture. Take the 4 nuts off the back side of the control panel, and look at the back side of the card for overheating. Sometimes it gets so bad, it shows on the front.

But to me, it sounds more and more like K-3. You are getting there.