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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15186
Experience:  Certified on Onan and Generac generators
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Have a Briggs and Stratton home generator. Engine starts, runs

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Have a Briggs and Stratton home generator. Engine starts, runs for 10 15 seconds, shuts down, starts again...runs 10-15 seconds shuts down....does this about 4 or 5 times and then throws F4 fault code: Engine failing to start.
It's odd because the engine starts and actually runs for a while.
I switched Propane tanks to eliminate that as the issue...same thing.

Thank you for choosing Just Answer for the solution to your problem.
My name is XXXXX XXXXX I am going to assist you with this.


What is the model number of your genset?


Customer: replied 6 years ago.
Model #: 040298A-0
Briggs and Stratton 7000 watt Automatic generator

The most likely cause of this happening is that the set is not producing any electricity.


First, I do have to warn you that if this set is still under warranty, you really need to have it checked out by an authorized B&S dealer, or you may void your warranty.


If you are out of warrant, open up the control area to access the control board.

Right in the middle of the board are 2 wires marked E1 and E2.

These are the voltage sense wires.

Set your meter to ACV and connect one lead to each of these wires.

Start the set and note the voltage. It should read 240 volts.

How much voltage is there?


Customer: replied 6 years ago.
Hank, I'll check that and get back to you thanks.
Customer: replied 6 years ago.
Connected the leads, ran the generator, 2 volts.

Just as I suspected.

The set is not producing power, so the controller is shutting itself down.

Then it tries to restart to get power.

A vicious cycle.


Here is what you need to do next.

Remove the left side panel.

Inside, find the voltage regulator.

It's the smaller board with 6 wires attached to it, the wires are numbered 1, 2, 4, 6, 11, and 22.

Disconnect the number 1 and 4 wires.

Set your meter to ohms, and connect one lead to each wire.

What reading do you get?

Next, disconnect the wires 2 and 6, and ohm across them.

What reading do you get?


Customer: replied 6 years ago.
On 2 and 6 .002 I can't locate 1& 2 so I did
11& 22 : .034
Would a picture of this v regulated help?

No, it's a standard regulator.

But you are not looking for 1 and 2, you are looking for 1 and 4.


There are only 6 wires there - 1, 2, 4, 6, 11 and 22.

So if you know 4 of them, the other 2 are 1 and 4.


But the readings you got on those windings are good - the problem is not a bad stator.


Customer: replied 6 years ago.
Got cha 1& 4 to engine side.062 to panel side .402

I'm not sure what you mean by 'to engine side' and 'to panel side'.

These wires go from the voltage regulator to the brushes - they are what provides exciter voltage.


But either way, it is reading too low.

You need to follow these leads to the brush block, which is mounted in the bottom end of the generator.

You will need to remove the end cover to access them.


Remove the brush block.


Examine the brushes. They should not have any chips or cracks and should be worn in a smooth arc pattern. They should slide freely in the slots in the brush block.

If they stick or bind at all, clean the brush block with electrical contact cleaner.

They should extend out of the brush block a minimum of 1/2".


Now examine the slip rings. They are the 2 bands that the brushes ride on. They are made of copper and should be as shiny as a new penny. A light brown patina is normal, and should not be construed as damage. However, they should not be a dull black color. They should be smooth and not have any scratches or pits. If they are dirty, clean them by attaching a piece of scotch brite pad to the end of a small stick and holding it to the brushes. Remove the spark plug wires, ground them out to prevent damage to the coil and condenser, and press start to crank the set and make the slip rings turn. WATCH YOUR FINGERS!


Once the slip rings are clean, use an ohmmeter to ohm across the rings.

What reading do you get here?


Customer: replied 6 years ago.
Ok this is going to take a bit of time.
The wires go under the generator.
It would appear at first glance I will need to remove the entire unit (motor and generator) to access the brag block.
Not to big a deal as its supported by a frame, held with 4 bolts, but certainly a two man lift. As well as it'll take more time than I have available today.
Pick it ip again tomorrow.

Not a problem.


Customer: replied 6 years ago.
Thank you... :-)

You're welcome.


Customer: replied 6 years ago.
Hank I'm back. I pulled the generator out and removed the brush block. They are shiney, move freely, relatively smooth (small scratches) one has a chip in it, not huge but obvious.
The slip rings are a light brown, no scratches, look pretty good. I've not has the opporunty to clean them. uncleaned I get a .007 reading with the ohmmeter.


Great picture!


The brushes are definitely not too bad.


Here is what you need to do next.



We are going to manually excite the field to check the integrity of the generator.


Disconnect the brush wires. Pay attention to which wire goes to which brush.

Make up 2 jumper wires that will attach to the brushes.

Connect one jumper to the positive (outer) brush and to the positive terminal of a 12V battery.

Connect the other jumper to the negative (inner) brush, but do not connect it to the battery at this time.

Gain access to the AVR.

Gain access to the exciter wires, 2 and 6.

Start the set, and connect the negative jumper to the negative terminal of the battery.

Set your meter to VAC and measure the AC output at the receptacle of the set. It should be a minimum of 60 volts.

Test the voltage across the 2 exciter wires.

How much voltage is there?

Set your meter to VDC and test the voltage at the brush wires that come from the AVR, 1 and 4. Make sure you connect the positive lead to the positive wire.

How much voltage is there?


Disconnect the jumpers from the battery and shut the set down.


Customer: replied 6 years ago.
I ordered another set of brushes, $15.00, no big deal should be in in a few days.
I had to pull the generator out to get to the bush assembly so will have to reinstall it to complete the next test.
A few questions, for clarification:

1. AVR:?
2. Receptacle: Unit is hardwired to a transfer switch. Other options?
3. Generator has its own battery to start it. Can I connect jumpers to same battery?

It'll be a few days again before I can complete this test so I'll be back.

So sorry - I was using the test for a portable generator, and forgot to modify it.


1. AVR is the automatic voltage regulator - the one that has the 6 wires attached to it.

2. Test at the back of the circuit breaker itself.

3. It would be best to use the battery in the set - it keeps you from having to obtain another battery, or carrying one of those heavy son-of-a-guns around.


Customer: replied 6 years ago.
Can you give me a sense for what the options are after this set of test's.
I guess what I am wondering is are we still holding out hope we can replace some faulty "components" or am I getting closer to having to replace/rebuild a major element of this unit? If that's the case should i just mover foward in that direction anyway.

My guess is that the AVR is bad - this is the most common.


When you jump 12V to the brushes, and if it puts out voltage that way, it will tell us that the rotor and stator are intact, and that the AVR is bad.


If it does not produce any electricity, we are going to have to do a thorough diagnostic of the rotor and stator.


Customer: replied 6 years ago.
Tested at breaker: 200+ volts
Wires 2 and 6: 200+ volts
Brushes: 12.6 volts DC

Replce AVR?

Yes, sir.

By jumping the 12 volts directly to the brushes, you were taking the place of the AVR.

With the set putting out, it shows the rotor and stator are good, and that the AVR is not sending voltage to the brushes.


Isn't this much better than paying someone $75-$100 an hour to fix for you?

Plus, you learn a bit about how the set operates - which can help you in the future.


Customer: replied 6 years ago.
Oh absolutely.
And got a couple of zaps a long the way just to make it interesting.
Thank You for all you help.

Not a problem at all, my friend.


Please don't forget to click the accept button so I get credit for my time, and please consider leaving appropriate feedback for me, as this is how we are rated.


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