MEP-804A cranks but no start, suspect solenoid on side of injection pump

[robertsears1]

MEP-804A cranks but no start, turned out to be mag pickup

I bought this 804A with about 46 hours and it now has ~120. I am sure it is the correct hours since it was so clean when purchased. It has been reliable with the only exception being the fuel system. Two or three times, it has lost the prime. Using the manual priming pump (3) corrected things. Eventually, I replaced the priming pump with one purchased from eBay.

About six six months ago, it would not run. It had run fine about a week prior so I suspected it had lost the prime or had air in the fuel lines as before. After pumping the manual priming pump and getting fuel fine out of the bleed screws (1) on the injection pump (IP), I gave it a try--no start and it acts like it is not getting fuel since no smoke from the exhaust. On and off for the next several months, I would get in the books and reprime the fuel. One thing I noticed is that fuel did not seem to go beyond the IP because I could never get fuel out right next to an injector where I had cracked the fitting. So it seems like something all of a sudden in the IP quit letting fuel through.

I am suspecting that perhaps the problem is related to what looks like a solenoid on the left side of the IP (2). I tried to remove it today but it seemed to be connected to the rack (I think) and I was losing the feeling in my hands since it is so stinking cold. There are two wires that go into the solenoid labeled 150B16 (white) and 149B16 (white with blue stripe). Is my assumption correct that this is what shuts down the generator when power to the solenoid is cut and the strong spring on the rack shuts off the fuel? I could not see any kind of fuse behind the panel that might have blown. My voltmeter did not register any voltage with the main switch in run. If I am correct that this shuts off the fuel, wouldn't there need to be voltage present to energize the solenoid and pull the rack so fuel can pass? I ended up buying a 804B with a Yanmar engine with about 360 true hours and it runs fine but it has an electric fuel pump vs the mechanical pump on the Isuzu for the 804A

 

[155mm]

I would start here TM 9-6115-643-24, pg 2-304 magnetic pickup.




Follow directions exactly. Update please if that doesnt fix it

 

[155mm]

item 2 is the fuel cut off/throttle control. there is a bolt and a funny spring that holds that in the IP.

Also that has its own oil, so if you take off that plate, make sure to refill the oil.

If I remember that is in the instructions for IP replacement. If you dont have to dinker with that solenoid, dont. Its a PITA to get adjusted correctly. so if you dont have to, dont.

Guy will pipe up when he gets out of bed and probably have more ideas, but magnetic switch is the first thing to check everytime, unless you can see the fuel leaking.

You are correct, there should be voltage there, but it has to go thru the governor controller first, and to get the controller to release the angry pixies, the magnetic switch has to say the motor is turning. here is the flow chart. These 2 flow charts overlay each other at the engine/magnetic sw for the start/run sequence.

 

[Guyfang]

Morning all,

Robert,

155 Gave you some very good advise, he has been to this rodeo once before himself. Don't fool with the Electric Actuator, (what you call the solenoid on the side of the IP) unless you have to.

Here is how the whole thing works. The connection between the Electric Actuator and IP is tricky. Some people, (like me) had to try at least 3-4 times to get it right. That requires removing it each time. Most replaced actuators, are replaced because the MPU was bad, and people didn't check it.

When S1 is turned on to the start position, the MPU, (magnetic Pick Up) counts the teeth on the flywheel as they go by. The signal is sent to the electric Governor, and the governor tells the electric actuator to open up the IP and let fuel into the injectors. That the simple version. So, before you tear the IP and actuator apart, you need to do some testing.

Simple test is to go to the A5, Electric governor) and measure between terminals 16 and 17, for between 2-3 volts AC, while someone is cranking the engine over for you. It is possible to do this by yourself, but its a PITA. What you want to see is 3 volts AC. 2 volts, is too low, the closer to 3 the better. BUT NOT over 3 volts. If you have no voltage there, disconnect the wires from 16 and 17, and measure ohms. You should have 900-1200 ohms. If you have the correct ohms reading, pull the MPU and see if it has a great huge blob of oil and metal filings on the end of it. Clean and reinstall. The procedure is in the book. FOLLOW IT TO THE LETTER. If you don't, you will grind off the end of the MPU and need a new one. Most MPU failures are due to not following the procedure properly. After reinstalling, try starting the set. If you pull out the MPU and it has about 42 miles of hair thin wire following it out of its hole, get another MPU. If the voltage is too low, the governor will not work. Nor will the actuator.

Have you downloaded the manuals from the SS TM forum?

Attached is some help with the procedure, but read the TM also. This attachment is also in the downloadable TM section of SS TM forums.

Governor adjustment
View attachment Volt Reg-MEP-804A & MEP-804B.pdf

Resist the temptation of "adjusting" the A5. It is factory set, and is mostly set right. It is possible to "fix" a generator until it no longer works. A good place to start, is the A5. Try the above procedures, and let us know what is happening.

 

[robertsears1]

Thank you 155mm and Guyfang, I will check things out and report. I have spent all morning retrieving my latest treasure from Ft Bragg. It is some kind of aviation fuel distribution apparatus with a 60 kw generator and a 20 hp electric motor on a trailer. The plan is to use this to power my Curtis C89 air compressor so I can finally use the surplus blast cabinet I bought about 5 years ago. The 20 hp motor should give me 65 cfm. I think the first thing I blast will only cost $6000, I better do a volume business to work that down some. I got within 1/8 of a mile from the house when one of my maypop tires had enough, so now I have to fix that. Then the fun of getting it off the trailer without damage to it or me begins, they claimed it weighs 5k. I think I am starting to have a generator problem. 2 MEP 804s, a 003a, 1.5 002a, and now this thing.

Robert Sears

 

[Guyfang]

Take some pictures of the inside of the gen set. Its a Zoomy gen set, so not military standard. I wont have TM's for it. If you don't have them, you might need to start looking. Looks interesting.

 

[robertsears1]

Got the tire fixed and have it on my land now with a lock on the hitch so it doesn't decide to walk off. I didn't steal this at $3600 all in. I believe three other folks were bidding on it. I called Stateline about 1630 but the lady said everyone had already booked, will try tomorrow. I jumped the battery from my truck for a while and the panel starts coming alive, need to do some studying to see what does what. Got to love the MEP generators with the nice placards telling how to make it work. This thing has almost nothing. I looks to have a 4 cylinder turbocharged diesel Perkins engine. We have those on our Massey Ferguson tractors although this one was made in the UK. The picture just before the black fuses is a block heater. It looks to have quality, water and explosion proof switches. There is some kind of transformer inside to get single phase to run some things. Here are some pictures. I love that I can now use my ipad for pictures, thanks to someone for that great increase in capacity!

Robert Sears

 

[robertsears1]

It's alive!! Just like 155mm and Guyfang said, the magnetic pickup (MPU) was the problem. Why didn't I ask 5 months ago? I did try to use the troubleshooting guide but it does not seem to address the MPU, it goes into playing with the injector pump (IP) which I really did not want to do, after making sure no air is in the lines. I was looking in the -24P instead of the -24 but the guide is the same. I could understand the symptoms but not the cause since the IP was not letting fuel through. I guess experience was the key here. After cranking with lots of black smoke until it cleaned up, I was going to put a load on it with a FDECU-5 using the heat strips. It kept showing a short when I would try to run the heat strips in the maintenance mode even after running a ground from the house. The 804B does not do that on the same unit. This 804A has always seemed sensitive to a high demand of current and I have seen a procedure to check that in the future.

When I reinstalled the MPU after cleaning the funk off, 1 turn out would only give me 0.7 vac. I had to turn it in 1/2 turn plus a RCH to get 2 vac and called it good enough since I don't want to grind off the end. It really smoked while cranking and didn't want to catch for a while. I have changed the title of this thread to possibly help someone in the future.

Again, thank you 155mm and Guyfang!

 

[Guyfang]

Good to hear.

Yes, the troubleshooting for this gen set sucks. Only a threat of world war gets CECOM to change a manual. Cost too much money.

If it continues to be a hard starter, you need to get closer to 3 volts AC from the MPU. If you hold the S1 up and the starter grinds, you need to get closer to 3 volts. It kind of looks like there was some starter grinding going on there.

Anyway, good job. The pictures are very good "teaching aids", I might like to get on or two for future referance.

 

[robertsears1]

Thanks for your help Guyfang. I will probably try to raise the voltage some if it needs alot of starter in the future . I believe the original crank was the first in at least six months and there was probably air in the lines from the IP to the injectors since it cranked right up after that. Did you notice how they made the connections to the MPU "Robert-proof".

On the 60kw civilian generator, I have been gathering knowledge. It looks like it was made in 2007 and has about 125 hours total. There is no fuel tank so I am going to start with Jerry cans and the adapter that came on a MEP generator or there is another one that came with my M17MCHF lightweight decontaminating apparatus. I am going to turn into Mr Picture since it's so easy with the iPad now. I did bump the starter and it sounded OK so I am going to hook up the block heater today and see what happens after we get cleaned up from our little bit of snow that is going up the right coast now.

Does anyone know how to edit the title of this thread. I was able to add the part about the magnetic pickup inside the thread but did not see how to change the overall thread title.

Robert Sears

 

[sdsuguz]

All thanks for providing this thread...Having the same symptoms Robert(thread originator) experienced. I have an 804a with a Bosch style priming pump losing prime and my first thought was that I was not reseating the hand prime pump correctly and hence kept losing prime with a lot of black smoke. I'm convinced that this newer style Bosch hand pump is not meant to be reseated and is always extended. Will try the MPU tomorrow and report back on the fix.

 

[Mrekieta]

Do the same troubleshooting steps apply to the 804B?

 

[Guyfang]

Do the same troubleshooting steps apply to the 804B?

Yes. ANY TQG set that cranks, but will not start, should be first checked at the MPU. The mag pickup is a wonderful way to make an engine work at its best, but when its ground off, out of adjustment, Bad or wires broken, the set is dead. So check this first.