Tuesday, September 8, 2015

Generator - Replacing Onan 4000 Microquiet Fuel Pump and Fuel Filter

Thanks to John DaCrema for this excellent summary of this task.

Be safe when doing this. Think about what could go wrong and plan accordingly. When working on the wiring be sure all electronic power is OFF and DISCONNECTED. When working with the fuel lines be sure to have a fire extinguisher handy. When reconnecting power on the other side of the RV have a spotter in front of the generator looking for smoke. The job is easy but there are a lot of steps. Not paying attention will bite you and could bite hard.

Required Tools:

Camera (cell phone will work just fine)
Small ratchet (3/8th)   
Short extension (a second short “wobbler extension” will make the job easier)
Socket set open (a deep well 1/2” socked would be nice but not required)
Open end wrench set
T30 Torx driver (and adaptor if needed for the ratchet drive)
Vice grip, plug or other clamp to stop fuel flow in fuel line   
Plastic fuel tank (or what you own as long as it fits under the RV)

The second and third characters of Model No, KY in the picture and the last character in the model number, K in the picture, are used to determine what Onan pump, filters and spark plug are needed. Make a note in your manual what number you have.
Parts to order and/or buy:

Onan Fuel Filter,
Onan Fuel pump,
18 inches of fuel line 1/4 inch inside diameter (ID)
Teflon plumbers tape
Onan Air Filter
Fuel hose clamps,
1/4 inch barbed connector(s)

Fuel Pump, or Fuel Line?

Some Lazy Daze RVs have had a fuel line issue. These seem to be from the late 1990s and the issue lasted until the early 2000s. With this in mind it is a good idea to conduct a simple test. For the sake of discussion the gas tank is up stream and the generator is downstream in the fuel flow.

1. Go to the generator compartment and remove the cover for the generator. To determine which side the fuel line is most likely located look for the starter solenoid and air filter. In the picture the air filter is labeled and the starter solenoid is the rusty item below and to the left of the air filter. The fuel line will be on the underside of the RV. It will run up against the exterior of the Onan generator housing outside of the area where these two items are located.

2. Where the fuel line meets the generator you will see the clamp holding the fuel line to a barbed connector. 
Clamp the factory fuel line a few to several inches upstream of this point to stem the fuel flow. Note, unless the fuel filter has been replaced at some point, the hose clamp will not be the same as pictured. It will be a compression clamp common. That type of clamp cannot be reused. The shiny object the fuel line is connected to is the new Onan fuel filter. (Off topic: The fuel filter alone can be replaced or just tightened by removing the hose from this location.)

3. On this step MAKE SURE YOUR EYES are NOT UNDER the connection to the fuel filter. Some fuel is going to leak out and you do not want it on your face. Once the fuel line is securely clapped disconnect the fuel line fuel line. I had to cut the line off the old fuel filter. There was enough line to reconnect. But only just enough. Plug the fuel line and make sure the gas is not leaking from the line.

4. Attach the 1/4 inch fuel line you purchased to the fuel filter. Place the other end of the fuel line in the Gas can.

5. Prime and start the generator. Make sure there are no gas leaks at the new fuel line connection.

·    If the generator runs fine for a longer period of time than it does when on the main fuel tank, the RVs fuel line between the generator and fuel tank must be inspected.
·    If the generator stalls as before while running on the external fuel source there is an issue with the generator system (fuel pump, fuel filter, carburetor, etc.).

7. Secure the external fuel tank for testing.  If the RV is going to be moved secure the fuel line. Remove anything (clamps) that might fall off.

Removing the Fuel Filter

It will be assumed: The test for the fuel pump failed. The fuel line between the generator and RVs fuel tank remains securely capped. The external fuel tank has been put away for now.

1. Remove the negative cables from the 12 volt batteries. It is a good idea to take a picture before removing the cables to help with replacing them. The smaller cables were good at hiding behind the batteries.
2. Next go to the generator compartment, open the hatch and remove the Onan cover.

3. Go to the area that holds the starter solenoid and air filter. The wiring harness, starter solenoid, and air filter will have to be removed.
4. Pull the harness gently to bring the weather proof connector out. 
Gently lift on three tabs to pull the connector apart. If you have not encountered this type of connector there is one on each shoulder and one across the middle. Gently pull these away from the keeper then pull the male section from the female section.
5. Remove the starter solenoid. Be sure to take pictures of which wires are on what post. Once
the wires are off, replace the washers and nuts so they don't get lost.

6. I could not get a good picture of the inside post while at step 5. So the picture of the other post was taken after the solenoid was removed. The solenoid is held in place with one T30 Torx bolt (not shown) and a locating tab. Note that in the picture the solenoid is upside down so what was the far side post in step 5 is now facing the camera. I should have cleared the loose wire out of the picture. There is only one wire connected to this post. Not two.

7. Generator with harness and solenoid removed:
8. The fuel pump is below the “brain” box. The box is held in place by two T30 Torx bolts. These bolts are accessed from outside the generator housing, but inside the Lazy Daze hatch. This is where the wobble head extension is very useful. Also the bolts on this RV were slightly rusted. I needed a ratchet to brake the bolt loose. Once the two T30s are removed the brain box is free. To remove it from the compartment I had to remove the air filter, then shimmy it out. There is a wiring harness on the bottom side of the brain box that does not need to be removed to proceed. I did remove and reconnect just to “reseat" the electrical connection. The harness/box connector is similar to that described in step 4.

9. With the box removed take a minute to take a picture of the ground wires and chassis connection. The author did not and that was the source of much needless, easily prevented worry. The ground is held in place with a bolt going through the housing. Inside the housing is a braided grounding strap. A green wire to the generator, a black wire to the fuel pump and two other white wires that go into the generators wiring hardness.

Outside the housing attached to the bolt is a lock washer and nut, then a ground wire back into the chassis and another lock washer and nut. Note that the ground wire is not double nutted in place. Each nut has a job. The first to secure ground inside the housing, the second to secure the ground wire to the chassis ground. DO NOT CHANGE this.

Now to replace the fuel pump and filter:
Check again for leaks. Then restart and run for twice as long as what the time was for the RV to shut down when it had a problem. For the first 10 minutes stay near the pump and connections looking for any sign of a gasoline leak.
·    Remove the one Torx bolt holding the filter in place. The other side slides out from a slot in the Onan housing. Disconnect the hot wire from its connection to the wiring harness.
·    Make the pump and filter into one assembly. Using plumbers tape wrap the threads to the fuel filter. No need for a lot. Two layers (turn the screw part 720 degrees as you wrap the tape) is more than enough. Be sure not to cover the tip that fuel flows through with the plumbers tape. Hand tighten to snug and then use a wrench for a few more flats until it is good and tight. Slide the assembly into the slot that held the old filter in place. Replace the T30 Tors bolt. Connect the hot wire to its connection.
1. Reassemble the ground.
2. Reinstall the brain box. Use a nail or drift once one hole is somewhat lined up to keep it in place then line up the second hole and loosely put in the first T30 then the second. Once both are threaded in place tighten.
3. Replace solenoid (pay attention to wires).
4. Replace air filter.
5. Plug harness back together.
6. Hook up fuel line.
7. Hook up battery.
8. Disconnect spark plug wire from plug
9. Prime fuel pump.
10. Look for fuel leaks at fuel line and fuel pump. It will be hard to see the pump/filter but you should be sniff for the odor of gas.
11. If no fuel leaks reconnect spark plug and start generator the local (outside) switch.
12. Run just a few minutes checking for leaks. Stop generator and let sit for 15 minutes.

13. Check again for leaks. Then restart and run for twice as long as what the time was for the generator to shut down when it had a problem. For the first ten minutes stay near the pump and connections while looking for any sign of a gasoline leak.
Go inside the RV. Stop the generator then restart to make sure the remote (internal) starter button   works. While the generator is running place the generator under load by running the AC for a while. While everything is running go outside and, you guessed it, CHECK FOR Gas leaks.
25. Shut down. Check once more for gas leaks after everything has cooled. You should be good to go.
26. The author might have been a little paranoid about gas leaks so check the next few times you run the generator.

Other Stuff:

Fuel line and barbed connector
This extension allows the socket to wobble on the nut, allowing the ratchet to be a few degrees off perpendicular.

Contributor: John DaCrema
Updated: 8 Sep 2015

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