MEP-802a & 803a

[Guyfang]

Will these gen sets only start with optima yellow tops? I replaced all 4 batteries. I gen runs fine the second won't start at the switch. It will prime the pump but when turned to start it makes no sound. Totally dead I had a diagnostics run on it and the gen shop tells me it's only getting 18 volts. Starter and relays all good. Don't know if it's a combo bad switch and electrical issue.View attachment 679550

The short answer is no. Any kind of battery that will fit in the set, and has enough CCA will do. Having said that, some batteries will not allow you to use the Army battery hold downs, or you have to modify them to work. Or make something that will work. OR find a battery that not only fits, but will let you use the army hold downs. If your AN/MJQ-35 Power Plant is going to become a fixed power source, holdowns are not a real big issue for some folks. I would have them, but when you are not driving down a rutted road, well you can get by without them, at your risk. If you intend to drive your trailer around, I would say you need them. What kind of batteries? Well, there are several threads where this subject has been discussed till the cows come home. General consensus is that everyone has there own favorite battery. Read and get smart.

In addition to the full set of MEP-802A gen set manuals, you need:

TM 9-2320-213-14&P for the trailer portion.
TM 9-6115-659-13&P for the Power Plant.
These manuals are posted in the TM Forum.

Please take a picture in the control panel, so we can see if you have a MK1, MK2 or MK3 S-1 start switch.

 

[DieselAddict]

+1 for what Guy said.

For testing purposes I use a couple of lawnmower batteries. They are in the 250 CCA range. They spin the generators over fine. I'm not suggesting to use these small batteries for a perm install. Any good quality full sized starting battery will work fine in the generator.

 

[Bmxenbrett]

I have 230ish cca lawn mower batterys in my 802a, they work fine. Even started a 803a one 6* morning just fine after pre heating for about 30sec.

 

[Lawman21]

Here is a picture of the switch. It will make noise in the prime/run aux position and in the prime/run position but will not start in the start position (No noise no clicks no turning over)

 

[Bmxenbrett]

Are you getting 24v at the small wire all by its self on the starter when the switch is held in start? If not are you getting 24v out of the switch when in start? Have you tested the voltage at the large lugs on the starter?

 

[Lawman21]

For the leak, look at the well nut thread, by DAYBREAK. There is maybe someone in the forum who will sell you one, or you can find one yourself. BUT read the thread. There are well nuts, and there are well nuts.

When you say you cant start the set. What do you mean? Will the starter turn over? Do you just hear clicking when S-1 is engaged? Have you tried S-10, to see if that will crank it? Do you have the manuals for the set? Have you read them? If so, did you try the troubleshooting? I hope you didnt pay anything to the "generator shop".

What kind of trailer are you talking about? A picture is always good. Most Power Units or Power plants do not allow you to combine the outputs. You can synchronize the outputs, but its only to allow you to take one off line and replace it with another set, without interrupting operation.

 

[Lawman21]

Are you getting 24v at the small wire all by its self on the starter when the switch is held in start? If not are you getting 24v out of the switch when in start? Have you tested the voltage at the large lugs on the starter?

I am on duty right and work night shift. I'm in California and off at 0700. I will try after I get home.

 

[Guyfang]

On the left side of the set, look at the S-10 Dead Crank switch. If it's not in the right position, the gen set wont start.

It's a three position switch. One position is NORMAL. It's to let you start and run the set. The second position is CRANK. Place the switch in the crank position, and the engine is supposed to turn over, but NOT start. The Third position is OFF. The set will not start, or turn over in this position.

If the switch is in the OFF position, change it to NORMAL and try starting the set with the S1 start switch. If it will not start, or turn over, place the S10 in the CRANK position. Does it turn over?

 

[Guyfang]

Here is a picture of the switch. It will make noise in the prime/run aux position and in the prime/run position but will not start in the start position (No noise no clicks no turning over)View attachment 679615

You have a MK1 switch. It's a very unreliable switch. That's why the army bought the MK2, (also not a real good switch) and at last went to the MK3 switch. It has a lifespan measured in eons. This is not to say your switch is bad. It may be perfect. That's why we follow the troubleshooting diagram in the books. Its best to not jump from one thing to another. Follow a system. Follow the instructions in Post # 108 first.

 

[dav5]

Guyfang you have amazing knowledge. Sorry to hijack the thread but would you mind telling me which switch I have and how to differentiate them? Thanks.
Ted

 

[Guyfang]

Guyfang you have amazing knowledge. Sorry to hijack the thread but would you mind telling me which switch I have and how to differentiate them? Thanks.
TedView attachment 679662

From the looks of it, a MK3. Better view would be from inside, but the MK3 knob is what I see. The mk1 and mk2 have almost the same knob, but the mk3 has a Bakelight knob, like yours.

A quick referance is this.
MK1 has a round switch, all plastic.
MK2 has a square switch, all plastic.
MK2 is round, has a bakelight knob and is made of porcelain and metal.

 

[Lawman21]

Guess my well nut is bad. Where can I purchase one or two of these?

 

[Bmxenbrett]

You can find that info in the faq here. I think it might have the heading of mep 802 803 filters and parts list.

 

[Lawman21]

Thank you.

 

[Lawman21]

Well Nut.

For the leak, look at the well nut thread, by DAYBREAK. There is maybe someone in the forum who will sell you one, or you can find one yourself. BUT read the thread. There are well nuts, and there are well nuts.

When you say you cant start the set. What do you mean? Will the starter turn over? Do you just hear clicking when S-1 is engaged? Have you tried S-10, to see if that will crank it? Do you have the manuals for the set? Have you read them? If so, did you try the troubleshooting? I hope you didnt pay anything to the "generator shop".

What kind of trailer are you talking about? A picture is always good. Most Power Units or Power plants do not allow you to combine the outputs. You can synchronize the outputs, but its only to allow you to take one off line and replace it with another set, without interrupting operation.

Does the back of the well nut screw into anything inside the tank.? Or does it just provide a seal. I didn't see anything on the schematics.

 

[Lawman21]

Does the well nut screw into anything inside the tank or does it just provide a seal. I didn't see anything on the schematics.

Thanks Eric

 

[Daybreak]

Does the well nut screw into anything inside the tank or does it just provide a seal. I didn't see anything on the schematics.

Thanks Eric

Howdy,

first, go ahead and start your own thread.

MEP-802/803 Filters and Parts the second post has a bunch of quick link info post for your reading. 3rd post has what manuals you need.

The infamous Well Nut info shows what it is, and how it works. and where to grab some.

MEP-80x startup routine a quicky video showing s simple startup routine and stop.

 

[Guyfang]

Right on the spot Mike! Lawman, there is much power in those links. And starting your own thread, allows you to get help, and people do not have to read 42 thousand pages of an old thread, and separate your problem from 16 other peoples problems.

 

[jamawieb]

Chrispyny may still have some left.

 

[CapePrep]

Hello All, I am about to pick up an MEP 803A. It has a tag on it that says "Engine Preserved". Does anyone know if there is anything special I have to do to the generator/motor to re-commision it? I know sometimes people will release tension on valve springs for example or certain fuel additives to get a motor ready for a long sleep. I don't want to try and start this thing and have any problems. Please let me know your thoughts. This is my first post and I think this is a great site!