Refusing to refuel.
THAT'S WHERE YOU CONNECT A FUEL CAN TO THE MBU's FUEL TANK BY MEANS OF A CAN ADAPTER AND A HOSE.
AN AIR COMPRESSOR DRAWS AIR OUT OF THE MBU'S TANK AND ALLOWS FUEL TO FLOW IN.
YEAH, THAT'S HOW IT'S SUPPOSED TO WORK.
BUT WHAT IF YOU SET UP THE EQUIPMENT AND FOLLOW THE STEPS--JUST LIKE IT SAYS IN THE TM--AND THE MBU STILL DOESN'T REFUEL OR REFUELS VERY SLOWLY?
FIRST OFF, CHECK INSIDE THE 5-GAL FUEL CAN. MAKE SURE IT'S NOT DRY.
IF THE CAN HAS PLENTY OF FUEL, THEN SOMETHING'S PREVENTING THE FUEL FLOW, AND YOU NEED TO HUNT DOWN THE CULPRIT.
HERE'S HOW TO GET HOT ON THE TRAIL ...
START BY WORKING YOUR WAY THROUGH THE TROUBLESHOOTING FLOWCHARTS IN WP 0008 00-4 AND WP 0019 00-3 IN TM 10-7310-281-13&P.
THEY COVER REFUELING PROBLEMS IN DETAIL.
IF THE FLOWCHARTS DON'T SOLVE THE PROBLEM, FOLLOW THESE STEPS ...
1. Look at the fuel tank cap on the side of the burner. Make sure its gasket is in good shape. If it isn't, replace it with NSN 7310-01-462-4867. (A missing or leaking gasket allows air instead of fuel to flow into the tank.) Tighten the cap on the tank.
2. Disconnect the 5-gal can fuel hose from the MBU's fuel fitting.
3. Power up the MBU. Then press the FUEL button. The air compressor will start to run and draw air out of the fuel tank.
4. After a few seconds, depress the middle of the fuel fitting. You should hear a hiss as air rushes into the tank. That rushing air tells you the MBU can draw fuel. It also means something outside the MBU is blocking fuel.
If you depress the middle of the fuel fitting and you don't hear rushing air, chances are the MBU has a stuck check valve. The stuck valve prevents the MBU from drawing fuel.
Fuel Block Outside the MBU
If you suspect a fuel block outside the MBU, you can narrow it down to two sources: the fuel can adapter or the 20-ft fuel hose.
* Look at the fuel can adapter. Make sure its dip tube is in place and it reaches the fuel.
* Inspect the quick disconnect couplings on the adapter and the fuel hose. Clean them if they're dirty.
* Run high-pressure air through the adapter and hose to unblock them. If that doesn't do the trick, get a new adapter with NSN 7310-01-455-3736. Get a new hose with NSN 7310-01-455-3735.
A Stuck Check Valve
OVER TIME, IMPURITIES IN THE FUEL OR SMALL DEBRIS CAN GET STUCK IN THE CHECK VALVE, CAUSING IT TO STICK.
ONCE THAN HAPPENS, THE MBU CAN'T DRAW FUEL INTO ITS TANK. YOU NEED TO FREE THE VALVE.
FOLLOW THESE STEPS ...
1. Remove the four 7/16-in nuts that hold down the MBU's top pan. Lift the top pan up and out of the way of the check valve.
2. Disconnect the air line from the check valve.
3. Test the air line by pressing the FUEL button. (DO NOT press the START button.) The MBU should draw air through the air line. Put your finger over the end of the line. You should feel suction. This means the air line is open and drawing air.
4. Remove the check valve from the solenoid. You'll need two 9/16-in wrenches or two adjustable wrenches. Hold the solenoid firm with one wrench while loosening the check valve with the other wrench. Take care not to turn the fitting on the solenoid valve.
5. Reconnect the air line to the check valve.
6. Test the check valve by putting your linger over the end of the valve. You should feel suction. This means the valve is working.
7. If you don't feel tiny suction, the check valve is stuck closed and you need to un-stick it. Look for the spring-loaded plunger inside the threaded end of the valve. Use a pin punch or a small screwdriver to gently push the plunger in. It should take only slight pressure to free it. Make sure the plunger moves in and out freely. Make sure you feel suction at the end of the check valve.
8. Disconnect the air line from the check valve.
9. Reconnect the check valve to the solenoid and the air line to the check valve.
10. Reinstall the MBU's top pan and tighten the four 7/16-in nuts.
The Hose and the Adapter
NOW YOU HAVE JUST ONE MORE CHECK TO PERFORM ...
1. Connect the fuel hose to the MBU's fuel fitting and to the fuel can adapter. Don't screw the adapter into the fuel can just yet.
2. Press the FUEL button and put the adapter's dip tube into the fuel. Within a few seconds, the MBU should pull fuel through the fuel hose.
3. If it does, screw the adapter onto the fuel can. Your MBU is back in service.
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|Title Annotation:||Modern Burner Unit ...|
|Publication:||PS, the Preventive Maintenance Monthly|
|Date:||Mar 1, 2007|
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