Diagnostic Test

During a re-fueling event, as fuel enters the Fuel Tank, the fuel vapors in the tank must be vented to prevent early fuel shut off. On a properly functioning system the vapors escape the tank through the MFCV or Liquid/Vapor Separator and Drain Valve (LVS), into the Canister Tube and flow to the Charcoal Canister. The fuel vapors are trapped by the charcoal in the canister. The clean air vents through the ESIM, to the Fresh Air Filter, and out to the atmosphere. When the fuel level in the tank rises and the liquid fuel reaches the MFCV or LVS, the float closes the vapor venting orifice inside the valve. The pressure inside the tank will increase causing the ICV to close and fuel to back up inside the filler tube. When the fuel reaches the sensing port aspirator in the fuel fill nozzle, the fuel flow shuts off. This prevents fuel from spilling out of the fuel filler tube.

If there is a restriction or blockage in the venting path, an early fuel shut off condition will be present. A vehicle can experience a hard to fill condition related to the following three reasons:

1. Fuel nozzle sensitivity.
2. There is a blockage in the tank venting.
3. There is a blockage in the venting on the fresh air side of the system.

For the MFCV (shown below) to vent properly, the top diaphragm portion of the valve must be able to adjust to atmosphere through the Recirculation tubing when the Gas Cap is removed, or the Capless Filler door is opened.

Courtesy of CHRYSLER GROUP, LLC

The following diagnostic procedure should help to determine which issue is causing the hard to fill condition.

Courtesy of CHRYSLER GROUP, LLC

DIAGNOSTIC PROCEDURE: 

1. Ask the customer the following questions: If the early shut off condition is only present at certain stations, happens consistently after the first few seconds of fueling, or stops after repositioning the nozzle, the issue is most likely due to a nozzle sensitivity issue. The only other possible issue could be if the Inlet Check Valve is stuck or sticking and not allowing fuel to flow freely into the tank. If the condition happens regular at multiple stations, or after a few gallons are filled, it is most likely a venting issue. Continue diagnosing in step 2.
   1. Is the condition present at only one station or multiple gas stations?
   2. Does the nozzle turn off immediately after a few seconds or after a few gallons?
   3. If you pull the nozzle out slightly or turn the nozzle to different positions does the early shut off condition stop?
2. Some of the conditions that can cause a hard to refuel condition will also set other evaporative system faults. Use the scan tool to check for any evaporative system DTCs. If DTCs are present perform the DTC diagnostic procedure first before continuing. If no DTCs are present, continue diagnosing in step 3.
3. If equipped with a capless fuel filler,  use the emergency funnel to inspect both doors, and the filler tube for any foreign objects or debris. Verify the doors can open and close properly. A bore scope may be used to inspect inside the filler tube. If the capless doors are damaged or any obstructions are found the entire fill tube assembly should be replaced. If there are no obstructions/damage or the vehicle does not have a capless fuel filler, continue diagnosing in step 4.
4. Raise the vehicle and visually inspect for a kinked or pinched Filler Tube, Canister Tube, Recirc Tube, or ESIM Vent Hose/Filter. Repair or replace any obvious issues. If the tubes appear okay, continue diagnosing in step 5.
   NOTE:

   JL and JT do not have a MFCV or a LVS. There is a pass through in the Fuel Delivery Module (FDM). If there is fuel in the Recirc tube or the charcoal canister, it is possible the line has come off inside the fuel tank. This condition may also set DTC P0441. Replace the Charcoal Canister and check for a disconnected or broken line to the Fuel Delivery Flange inside the Fuel Tank. Reconnect the line and confirm proper retention or replace if necessary. Perform the "ESIM/Purge Flow Forced Monitor" test to confirm system is repaired. Verify hard to fill condition is no longer present.

   NOTE:

   TECH TIP: The fresh air side may be able to be evaluated before continuing to step 5 and disconnecting tubes and attempting to refuel at a filling station. Start the engine, allow purge to activate and observe the Fuel Tank Pressure reading in the scan tool data. Typically, the system pressure will drop below the ESIM regulation point and stabilize between approximately -600 and -800 Pa. After turning the engine off the vacuum relief weight inside the ESIM will vent the pressure near the regulation point (approximately -500 Pa). If the vacuum created is far greater than normal and doesn't vent to the regulation point when the engine is turned off, there is likely a blockage on the fresh air side of the system. Try removing the hose between the ESIM and Fresh Air Filter and testing again. If the system functions normally with the hose disconnected, the Fresh Air Filter or hose is blocked.

5. This step is designed to split the system between the tank side and fresh air side.  The fuel level should be low enough to allow enough fuel to be put into the vehicle to make a proper determination (example: less than 1/2 tank). Also, do not refill from a storage tank. Use a gas station filling pump to refill. Disconnect the Canister Tube either at the Fuel Tank or Charcoal Canister. The Canister Tube will be the larger of the tubes connected at either the tank or canister. Attempt to refill the vehicle.
   NOTE:

   Read through the entire test before going to the fuel station and attempting to refuel. Some of the other checks may be able to be done while at the pump refueling.

   1. If fuel flows freely without early shut off, the issue is with the fresh air side of the system (Canister or ESIM vent/filter). Continue diagnosing in step 6.
   2. If the early fuel shut off condition is still occurring, the issue is with the tank side of the system (MFCV LVS, or Recirc Tubing). Continue diagnosing in step 7.
6. Reconnect the Canister Tube. Remove the vent hose at the ESIM or Fresh Air Filter and attempt to refill.
   1. If fuel flows freely without early shut off, replace the Fresh Air Filter or repair the restriction in the vent hose.
   2. If the early fuel shut off condition is still occurring, replace the Charcoal Canister. If the Canister Tube was disconnected at the Fuel Tank, check the tube for a restriction before replacing the Charcoal Canister.
7. Disconnect the Recirc line at the Fuel Tank or Fuel Filler Tube and attempt to refill.
   1. If fuel flows freely without early shut off, replace or clear the Recirc Tube or check for an obstruction in the Recirc Tube portion of the fill tube.
   2. If early fuel shut off is still occurring, drain the fuel from the tank, remove the fuel filler hose and check for an obstructed or hard to open Inlet Check Valve. If the Inlet Check Valve is not obstructed and opens freely, the MFCV or LVS is restricted and will require replacement. Replace the Fuel Tank or Fuel Pump assembly depending on the MFCV or LVS location in the system.
   NOTE:

   On some vehicles the MFCV or LVS is welded into the Fuel Tank. On other vehicles the MFCV or LVS is part of the Fuel Pump Assembly. If the MFCV or LVS is not visible on the tank or pump, it is mounted inside the Fuel Tank. If the MFCV or LVS is mounted on the Fuel Pump Module, it should be replaced before replacing the Fuel Tank.