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MEP805B Engine Control Prime & Run position

Raptor01

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Does anyone know what happens when the generator control switch is placed in "Prime & Run" position prior to starting the generator? Should I hear something start to run like a fuel priming pump? Couldn't find a description of this switch position function in any of the Tech Manuals.
 

Raptor01

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Yes, you should hear the electric fuel pump come on. It should slow down/stop when it has primed the system.
Thanks for replying. I don't hear anything come on. Where is the electric fuel pump? Can you point me to a figure in the tech manual? I need to make sure it is getting voltage.
 

peapvp

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Does anyone know what happens when the generator control switch is placed in "Prime & Run" position prior to starting the generator? Should I hear something start to run like a fuel priming pump? Couldn't find a description of this switch position function in any of the Tech Manuals.
Is your Master Switch S3 in On or Off Position when you place the Engine Control Switch S1 in "Run &Prime" ?
 

Guyfang

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Wait!!!!!!!!!!!!! No you should NOT hear anything. Sorry, I was helping someone with an MEP-005A, and just kept thinking about a different gen set. Sorry, one hundred times. All you have is a hand operated primer hand pump. There is an AUX electric fuel pump. But no other electric fuel pump.

Tell us what problems you are having.
 

Raptor01

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Madera CA
Is your Master Switch S3 in On or Off Position when you place the Engine Control Switch S1 in "Run &Prime" ?
Hello.
Is your Master Switch S3 in On or Off Position when you place the Engine Control Switch S1 in "Run &Prime" ?
Hello, Master Switch is in the On position. BTW, the generator starts and runs fine. Just wondering what happens when the switch is in the Prime & Run position. The TMs just say to place the switch in this position. It does not tell you what to check for.
 

Raptor01

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11
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Location
Madera CA
Wait!!!!!!!!!!!!! No you should NOT hear anything. Sorry, I was helping someone with an MEP-005A, and just kept thinking about a different gen set. Sorry, one hundred times. All you have is a hand operated primer hand pump. There is an AUX electric fuel pump. But no other electric fuel pump.

Tell us what problems you are having.
Thank you. The generator runs fine after a fuel pump rebuild ($1500 in California). Just wondering what happens when the switch is in the Prime & Run position. The TMs just say to place the switch in this position. It does not tell you what to check for.
 

Guyfang

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The prime and run position.
With the engine off, all the run circuits are energized. It doesn't prime anything, as there is no electric fuel pump.
With the engine ON and running, All run circuits are energized, and the set operates.

This position is where the S1 will spring back to, after you start the set, it comes up, makes power, and you let go of the S1. This is the normal position for S1 to be in. The only other time the S1 is in another position during operation is the AUX/Run position. That's used for running off a separate fuel supply.
 

Raptor01

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The prime and run position.
With the engine off, all the run circuits are energized. It doesn't prime anything, as there is no electric fuel pump.
With the engine ON and running, All run circuits are energized, and the set operates.

This position is where the S1 will spring back to, after you start the set, it comes up, makes power, and you let go of the S1. This is the normal position for S1 to be in. The only other time the S1 is in another position during operation is the AUX/Run position. That's used for running off a separate fuel supply.
That clears it up for me. I assumed it was priming something because it is labeled "Prime & Run". Like they say, assuming makes an ass out of you and me:)
 

peapvp

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This is interesting,
as per -14 Manual we have three fuel related pumps:

1. Transfer Pump
2. Injection Pump
3. Auxiliary Fuel Pump

I am sure this must be utterly confusing to the innocent bystander and new owner of a 805/806 Bravo Unit

I am sure @Guyfang can explain in detail on how each of these pumps are operated and functioning

805B Fuel Diagram 2.jpg

805B Fuel Diagram.jpg
 

Guyfang

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The transfer pump, is a Lever/Arm driven pump.

Injector pump needs no explanation.

The AUX pump is only used to transfer fuel from a secondary source, to the generator fuel tank. When the fuel tank is full, a fuel level switch cuts the power off, and the AUX system is disabled, until the set fuel tank once again is mostly empty.
 
Last edited:

Raptor01

New member
10
11
3
Location
Madera CA
The transfer pump, is a Lever/Arm driven pump.

Injector pump needs no explanation.

The AUX pump is only used to transfer fuel from a secondary source, to the generator fuel tank. When the fuel tank is full, a fuel level switch cuts the power off, and the AUX system is disabled, until the set fuel tank once again is mostly empty.
Did not know that the Aux pump works will the fuel level switch. My Fuel Level gauge is inop. Troubleshot it down to a bad sender, Does anyone know of an aftermarket suitable substitute for the fuel sender (TM 9-6115-671-24P, Figure 11, Item 30)?
 

Raptor01

New member
10
11
3
Location
Madera CA
This is interesting,
as per -14 Manual we have three fuel related pumps:

1. Transfer Pump
2. Injection Pump
3. Auxiliary Fuel Pump

I am sure this must be utterly confusing to the innocent bystander and new owner of a 805/806 Bravo Unit

I am sure @Guyfang can explain in detail on how each of these pumps are operated and functioning

View attachment 936120

View attachment 936121
Notice that 1.16.5.5 describes the PRIME & RUN AUX FUEL position but there is no description of the PRIME & RUN switch position.
 

peapvp

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“whenever the ENGINE CONTROL switch is in the START position or in either of the two RUN positions.”

The Prime & Run position is the same as the Prime & Run with the addition of the Aux Fuel position in terms of functionality.

30 years ago, when this generator was designed, people understood and reasoned and applied logic differently then today.
The understanding that common sense should prevail was implied.
The internet was in its infancy, people used 14.4K modems for dial up AOL chat, no one knew what a iPhone, iPad, Android, WiFi, YouTube, facebook, instagram, TikTok, eBay, Amazon etc etc was.

In those days, at least in Germany, technicians knew they had to read the entire section of the manual to understand its functionality to properly troubleshoot the apparatus.
 

peapvp

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I hear you but a Technical Manual should be explicit and not leave anything up for "interpretation". Assuming is the mother of all f***ups.
This is not an assumption, but common sense and experience in reading and understanding TM’s, which are a different universe in its own right to begin with.
 

peapvp

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The audience of this manual is an 18 year old soldier or airman. Not a lot of common sense or experience there.
I applaud your bravery young man!
99.999% of all males in your age group in the United States do not even know what a 805B generator is or that they even exist.
There are no dumb questions, only dumb answers.

When I was your age, I once asked a very wise man of what “common sense” actually is.
He replied,
Common sense starts when you put a matching pair of socks on in the morning when you get dressed….,.
 
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