Slow Fuel Fill Problem Diagnosis
#1
03-14-2009, 09:17 PM
Slow Fuel Fill Problem Diagnosis
There are numerous complaints of Hyundai vehicles being hard/slow to fill with fuel. The general indication is that when refueling, the gas pump shuts off repetitively after only adding a minor volume of gas – usually ¼ gallon or less. The fuel seems to back up into the fill tube, causing the automatic shut off on the pump to activate. The fuel gradually subsides in the filler neck, and another ¼ gallon or so can be added before shutting off again.
There are two general possibilities which would cause the issue: (a) a restriction directly preventing fuel from entering the tank, or (b) a restriction preventing vapors from exiting the tank and thus not allow fuel to enter. All cars built from 1999 onward have had included an onboard fueling vapor recovery system. What this means in a nutshell is that fumes from the entire fuel system are no longer vented to the outdoors, but are instead re-cycled through the vehicle air intake system.
(a) Those things that can directly restrict fuel fill include damage to any part of the filler neck or gas tank:
1. Damaged filler neck
2. Pinched or twisted hose between filler neck and tank
3. One-way fill valve in tank (at the filler entrance to the tank) sticking shut
4. Tank damaged under fill entrance to tank.
(b) Things that can prevent proper venting include blockages anywhere in the onboard vapor recovery system:
1. Blocked leak detection pump outlet
2. Restricted charcoal canister filter
3. Restricted charcoal canister itself (usually by liquid fuel in canister)
4. Sticking vent valve (sometimes called rollover valve) in top of fuel tank
5. Any of the vapor hoses from the tank to the canister to the leak detection pump pinched or twisted.
One of the most common causes of blockage in the venting system is from fuel entering the vapor vent lines and directly into the charcoal canister. The liquid gasoline gets absorbed by the charcoal in the canister, causing it to swell and it blocks off the vapor vent lines. So how does a clogged canister filter prevent you from filling up with gas? The gas tank contains both fuel and air. As you fill it up, the gasoline displaces the air, and the air has to escape somehow. BUT the air that is displaced is full of gasoline vapor. Being harmful to the atmosphere, it can't just be vented directly into the air, so the vapor recovery system is set up to capture these vapors through a series of vent lines that lead to a square box full of charcoal, which absorbs the gas vapors. When the gas-soaked charcoal swells and blocks off the vent lines, it is preventing the air from escaping the tank. In order to put gas in, the air has to have some way of getting out, and the only way for it to get out is through the vent lines. The repair here involves replacing one of the components in the fuel vapor recovery system. (one-way valve in the tank, vent valve in the tank, liquid-vapor separator near the tank, carbon canister or canister close valve.) The most common first choice for repair is the canister, but the other components may well be plugged.
1. Canister close valve could be clogged with charcoal or not working
2. Canister filter may need replacement
3. Electrical connection to the close valve may be broken
4. Canister may be damaged
5. Purge valve from the canister may be clogged
6. Vent hoses may be clogged
The only real solution is a thorough step-by-step trouble shooting approach as described below.
General diagnostic procedures: hard-to-fill fuel tank
All 1999 and later Hyundai vehicles incorporate an emission control system known as On-Board Refueling Vapor Recovery (ORVR). A general schematic of the system is provided below. Some owners may experience difficulty filling their vehicle with gasoline and a premature shut off condition. Following are trouble shooting steps to be taken.
Step 1- Isolate which half of the system is blocked: Verify that the 1/2" vapor path from the fill vent valve on the gas tank to the air filter on the charcoal canister (see schematic below) is completely free and clear. Make sure the fuel tank is below 1/4 tank full. Disconnect the hose connected to the canister side of the liquid-vapor separator (see schematic below). Take the vehicle to a known "good" or major brand gas station. If the vehicle readily accepts fuel, the restriction is located between the liquid vapor separator and the air filter. If the vehicle does not easily accept fuel, the restriction is located between the liquid vapor separator and the fuel tank.
On-Board Refueling Vapor Recovery (ORVR) Schematic: The following components are contained in the ORVR system: Fuel Cut Valve, Fuel Fill Vent Valve, (anti-spit back), Liquid-Vapor Separator, Charcoal Canister, Canister Close Valve, Air Filter all connected by various hoses and pipes. 1999 Sonata and Accent have additional components as shown.
Step 2: After the restriction has been isolated to either half of the system, inspect each component to make sure it is free and clear of any restrictions Do this by verifying that no back pressure can be felt anywhere between the fill vent valve and the air filter at the canister.
If the tank filled easily when disconnecting the vapor hose to the canister (meaning the blockage is in the canister or close valve), inspect the canister and replace the filter if needed, and the canister if broken. Replace the canister close valve if clogged Check by blowing with lung pressure. The Charcoal Canister filter is located with the canister at the left rear corner of the vehicle. You'll need to remove one or two 12mm bolts/nuts to lower the canister assembly. You'll then need to separate the canister close valve from the filter and snap it off the canister.
If the tank does not fill easily when the canister is disconnected, the blockage is between the tank and the canister.
First check for obvious problems that would prevent fuel from entering the gas tank:
1. Damaged filler neck
2. Pinched or twisted hose between filler neck and tank
3. Tank damaged under fill entrance to tank.
Then check for kinked hoses in the vent lines, that can cause back pressure.
Then check for restrictions in the liquid vapor separator, by blowing through one end of the pipe using lung power. NO back pressure should be felt.
Then, verify that the Fill Vent Valve is open by carefully removing the valve and confirming that the white plastic shut-off plunger moves freely inside its cage. This valve is accessed from the top of the gas tank.
Then check the Fuel cut valve for restrictions. This is also accessed from the top of the fuel tank. If the fuel cut valve plunger is stuck closed, a hard-to-fill condition may result. Verify that the plunger moves up and down freely allowing fuel to enter the tank, but does not allow fuel to travel up the neck (under pressure). The plunger should be "up" (closed) in its free state.
IMPORTANT When working with the Fill Vent Valve and associated plumbing, be sure to replace the hoses into the proper hose clips to prevent fuel from getting trapped / puddled in the vapor hose. Return fuel from the liquid-vapor separator must have a clear path to drain back to the tank.
Special Notes:
(a) 1999 Sonatas have a Four Way Valve located between the liquid vapor separator and fuel tank.. The Four Way Valve provides an additional vapor path to the canister during refueling.
Proper operation of the valve is as follows: Air flows freely in either direction through the 1/2" ports. Air flows freely in either direction through the 1/4" ports. Air flows from 1/2" port to the 1/4" port when blowing into one of the 1/2" ports while plugging the other 1/2" port. Air does not flow from 1/4" port to the 1/2" port when blowing into one of the 1/4" ports while plugging the other 1/4" port
(b) Also NOTE that 1999 Accents have two (2) liquid vapor separators: one located on top of the fuel tank, the other located alongside the filler neck.
(c) Also note that one owner had a novel, no-cost solution. You can give it a try before investing in the long-term solution. Here is his feedback: “I have the same type of quirkiness on my 01' Elantra. My fix was to fill up when the gas needle is at the half way mark rather then when it's on empty. I was told by an attendant that fumes can build up in the tank and the pressure can cause the gas nozzle to pop out. I was guilty of driving around on near empty then only filling up but since I started filling up it up when the needle is at the half way mark the problem went away. You may have to do this a couple of times before the problem goes away.”
There are two general possibilities which would cause the issue: (a) a restriction directly preventing fuel from entering the tank, or (b) a restriction preventing vapors from exiting the tank and thus not allow fuel to enter. All cars built from 1999 onward have had included an onboard fueling vapor recovery system. What this means in a nutshell is that fumes from the entire fuel system are no longer vented to the outdoors, but are instead re-cycled through the vehicle air intake system.
(a) Those things that can directly restrict fuel fill include damage to any part of the filler neck or gas tank:
1. Damaged filler neck
2. Pinched or twisted hose between filler neck and tank
3. One-way fill valve in tank (at the filler entrance to the tank) sticking shut
4. Tank damaged under fill entrance to tank.
(b) Things that can prevent proper venting include blockages anywhere in the onboard vapor recovery system:
1. Blocked leak detection pump outlet
2. Restricted charcoal canister filter
3. Restricted charcoal canister itself (usually by liquid fuel in canister)
4. Sticking vent valve (sometimes called rollover valve) in top of fuel tank
5. Any of the vapor hoses from the tank to the canister to the leak detection pump pinched or twisted.
One of the most common causes of blockage in the venting system is from fuel entering the vapor vent lines and directly into the charcoal canister. The liquid gasoline gets absorbed by the charcoal in the canister, causing it to swell and it blocks off the vapor vent lines. So how does a clogged canister filter prevent you from filling up with gas? The gas tank contains both fuel and air. As you fill it up, the gasoline displaces the air, and the air has to escape somehow. BUT the air that is displaced is full of gasoline vapor. Being harmful to the atmosphere, it can't just be vented directly into the air, so the vapor recovery system is set up to capture these vapors through a series of vent lines that lead to a square box full of charcoal, which absorbs the gas vapors. When the gas-soaked charcoal swells and blocks off the vent lines, it is preventing the air from escaping the tank. In order to put gas in, the air has to have some way of getting out, and the only way for it to get out is through the vent lines. The repair here involves replacing one of the components in the fuel vapor recovery system. (one-way valve in the tank, vent valve in the tank, liquid-vapor separator near the tank, carbon canister or canister close valve.) The most common first choice for repair is the canister, but the other components may well be plugged.
1. Canister close valve could be clogged with charcoal or not working
2. Canister filter may need replacement
3. Electrical connection to the close valve may be broken
4. Canister may be damaged
5. Purge valve from the canister may be clogged
6. Vent hoses may be clogged
The only real solution is a thorough step-by-step trouble shooting approach as described below.
General diagnostic procedures: hard-to-fill fuel tank
All 1999 and later Hyundai vehicles incorporate an emission control system known as On-Board Refueling Vapor Recovery (ORVR). A general schematic of the system is provided below. Some owners may experience difficulty filling their vehicle with gasoline and a premature shut off condition. Following are trouble shooting steps to be taken.
Step 1- Isolate which half of the system is blocked: Verify that the 1/2" vapor path from the fill vent valve on the gas tank to the air filter on the charcoal canister (see schematic below) is completely free and clear. Make sure the fuel tank is below 1/4 tank full. Disconnect the hose connected to the canister side of the liquid-vapor separator (see schematic below). Take the vehicle to a known "good" or major brand gas station. If the vehicle readily accepts fuel, the restriction is located between the liquid vapor separator and the air filter. If the vehicle does not easily accept fuel, the restriction is located between the liquid vapor separator and the fuel tank.
On-Board Refueling Vapor Recovery (ORVR) Schematic: The following components are contained in the ORVR system: Fuel Cut Valve, Fuel Fill Vent Valve, (anti-spit back), Liquid-Vapor Separator, Charcoal Canister, Canister Close Valve, Air Filter all connected by various hoses and pipes. 1999 Sonata and Accent have additional components as shown.
Step 2: After the restriction has been isolated to either half of the system, inspect each component to make sure it is free and clear of any restrictions Do this by verifying that no back pressure can be felt anywhere between the fill vent valve and the air filter at the canister.
If the tank filled easily when disconnecting the vapor hose to the canister (meaning the blockage is in the canister or close valve), inspect the canister and replace the filter if needed, and the canister if broken. Replace the canister close valve if clogged Check by blowing with lung pressure. The Charcoal Canister filter is located with the canister at the left rear corner of the vehicle. You'll need to remove one or two 12mm bolts/nuts to lower the canister assembly. You'll then need to separate the canister close valve from the filter and snap it off the canister.
If the tank does not fill easily when the canister is disconnected, the blockage is between the tank and the canister.
First check for obvious problems that would prevent fuel from entering the gas tank:
1. Damaged filler neck
2. Pinched or twisted hose between filler neck and tank
3. Tank damaged under fill entrance to tank.
Then check for kinked hoses in the vent lines, that can cause back pressure.
Then check for restrictions in the liquid vapor separator, by blowing through one end of the pipe using lung power. NO back pressure should be felt.
Then, verify that the Fill Vent Valve is open by carefully removing the valve and confirming that the white plastic shut-off plunger moves freely inside its cage. This valve is accessed from the top of the gas tank.
Then check the Fuel cut valve for restrictions. This is also accessed from the top of the fuel tank. If the fuel cut valve plunger is stuck closed, a hard-to-fill condition may result. Verify that the plunger moves up and down freely allowing fuel to enter the tank, but does not allow fuel to travel up the neck (under pressure). The plunger should be "up" (closed) in its free state.
IMPORTANT When working with the Fill Vent Valve and associated plumbing, be sure to replace the hoses into the proper hose clips to prevent fuel from getting trapped / puddled in the vapor hose. Return fuel from the liquid-vapor separator must have a clear path to drain back to the tank.
Special Notes:
(a) 1999 Sonatas have a Four Way Valve located between the liquid vapor separator and fuel tank.. The Four Way Valve provides an additional vapor path to the canister during refueling.
Proper operation of the valve is as follows: Air flows freely in either direction through the 1/2" ports. Air flows freely in either direction through the 1/4" ports. Air flows from 1/2" port to the 1/4" port when blowing into one of the 1/2" ports while plugging the other 1/2" port. Air does not flow from 1/4" port to the 1/2" port when blowing into one of the 1/4" ports while plugging the other 1/4" port
(b) Also NOTE that 1999 Accents have two (2) liquid vapor separators: one located on top of the fuel tank, the other located alongside the filler neck.
(c) Also note that one owner had a novel, no-cost solution. You can give it a try before investing in the long-term solution. Here is his feedback: “I have the same type of quirkiness on my 01' Elantra. My fix was to fill up when the gas needle is at the half way mark rather then when it's on empty. I was told by an attendant that fumes can build up in the tank and the pressure can cause the gas nozzle to pop out. I was guilty of driving around on near empty then only filling up but since I started filling up it up when the needle is at the half way mark the problem went away. You may have to do this a couple of times before the problem goes away.”
#6
07-21-2009, 03:46 PM
99-30-002 GENERAL DIAGNOSTIC PROCEDURES (HARD-TO-FILL FUEL TANK)
DESCRIPTION
All 1999 and later Hyundai vehicles incorporate a new emission control system known as On-Board Refueling Vapor Recovery (ORVR). A general schematic of the system is provided below.
Some owners may experience difficulty filling their vehicle with gasoline and a premature shut off condition as a result of the gas pump nozzles installed at their gas stations. The nozzles at these stations are in the process of being retrofitted or replaced by the nozzle manufacturers. In the meantime, owners should follow instructions posted near the gas pump, and/or try filling the vehicle at a different gas station.
If the refueling difficulty continues, verify that the 1/2" vapor path from the fill vent valve on the gas tank to the air filter on the charcoal canister (see schematic below) is completely
free and clear. To perform the procedure below, make sure the fuel tank is below 1/4 tank full.
To quickly determine the general location of a possible vapor path restriction:
On-Board Refueling Vapor Recovery (ORVR) Schematic
The following components are contained in the ORVR system:
After the restriction has been isolated to either half of the system, inspect each component to make sure it is free and clear of any restrictions. Verify that no
back pressure can be felt anywhere between the fill vent valve and the air filter at the canister.
NOTE
1999 Accents have two (2) liquid vapor separators: one located on top of the fuel tank, the other located alongside the filler neck.
When checking the liquid vapor separator, blow through one end of the pipe using lung power. NO
back pressure should be felt.
Verify that the Fill Vent Valve is open by carefully removing the valve and confirming that the white plastic shut-off plunger moves freely inside its cage.
If the fuel cut valve plunger is stuck closed, a hard-to-fill condition may result. Verify that the plunger moves up and down freely allowing fuel to enter the tank, but does not allow fuel to travel up the neck (under pressure). The plunger should be "up" (closed) in its free state.
IMPORTANT
When working with the Fill Vent Valve and associated plumbing, be sure to replace the hoses into the proper hose clips to prevent fuel from getting trapped / puddled in the vapor hose. Return fuel from the liquid-vapor separator must have a clear path to drain back to the tank.
Four Way Valve
Purpose:
The Four Way Valve provides an additional vapor path to the canister during refueling.
NOTE
1999 Sonatas have a Four Way Valve located between the liquid vapor separator and fuel tank.
Proper operation of the valve is as follows:
warranty information:
Normal warranty operation codes and times apply.
DESCRIPTION
All 1999 and later Hyundai vehicles incorporate a new emission control system known as On-Board Refueling Vapor Recovery (ORVR). A general schematic of the system is provided below.
Some owners may experience difficulty filling their vehicle with gasoline and a premature shut off condition as a result of the gas pump nozzles installed at their gas stations. The nozzles at these stations are in the process of being retrofitted or replaced by the nozzle manufacturers. In the meantime, owners should follow instructions posted near the gas pump, and/or try filling the vehicle at a different gas station.
If the refueling difficulty continues, verify that the 1/2" vapor path from the fill vent valve on the gas tank to the air filter on the charcoal canister (see schematic below) is completely
free and clear. To perform the procedure below, make sure the fuel tank is below 1/4 tank full.
To quickly determine the general location of a possible vapor path restriction:
- Disconnect the hose connected to the canister side of the liquid-vapor separator (see schematic below).
- Take the vehicle to a known "good" or major brand gas station.
- If the vehicle readily accepts fuel, the restriction is located between the liquid vapor separator and the air filter.
- If the vehicle does not easily accept fuel, the restriction is located between the liquid vapor separator and the fuel tank.
On-Board Refueling Vapor Recovery (ORVR) Schematic
The following components are contained in the ORVR system:
- Vapor hoses
- Liquid-Vapor Separator(s)
- Fuel Fill Vent Valve
- Fuel Cut Valve (anti-spitback)
- Canister Close Valve
- Air Filter
- Charcoal Canister
After the restriction has been isolated to either half of the system, inspect each component to make sure it is free and clear of any restrictions. Verify that no
back pressure can be felt anywhere between the fill vent valve and the air filter at the canister.
NOTE
1999 Accents have two (2) liquid vapor separators: one located on top of the fuel tank, the other located alongside the filler neck.
When checking the liquid vapor separator, blow through one end of the pipe using lung power. NO
back pressure should be felt.
Verify that the Fill Vent Valve is open by carefully removing the valve and confirming that the white plastic shut-off plunger moves freely inside its cage.
If the fuel cut valve plunger is stuck closed, a hard-to-fill condition may result. Verify that the plunger moves up and down freely allowing fuel to enter the tank, but does not allow fuel to travel up the neck (under pressure). The plunger should be "up" (closed) in its free state.
IMPORTANT
When working with the Fill Vent Valve and associated plumbing, be sure to replace the hoses into the proper hose clips to prevent fuel from getting trapped / puddled in the vapor hose. Return fuel from the liquid-vapor separator must have a clear path to drain back to the tank.
Four Way Valve
Purpose:
The Four Way Valve provides an additional vapor path to the canister during refueling.
NOTE
1999 Sonatas have a Four Way Valve located between the liquid vapor separator and fuel tank.
Proper operation of the valve is as follows:
- Air flows freely in either direction through the 1/2" ports.
Air flows freely in either direction through the 1/4" ports.- Air flows from 1/2" port to the 1/4" port when blowing into one of the 1/2" ports while plugging the other 1/2" port.
- Air does not flow from 1/4" port to the 1/2" port when blowing into one of the 1/4" ports while plugging the other 1/4" port.
warranty information:
Normal warranty operation codes and times apply.
Last edited by NovaResource; 07-20-2012 at 11:35 AM. Reason: Fixed picture(s)
#8
03-12-2010, 09:14 PM
Thanks for great thread on fuel vent problems.
I've just had the EVAP code come up on my wifes 2000 Elantra. Did the simple cap check but its elsewhere in there but was not sure where. This write up and pictures are excellent and should get it to stop throwing that code.
Thanks very much for the grerat write up and show and tell pictures. Great web site.
I've been signed for quite a while but never had any problems here with any of my Hyundai until this one. Also have a 2005 Sonata and 2008 Sonata Limited. The Sonata 2005 was to replace the Elantra, but can't seem to kill it. When it dies she will take the Sonata 2005.
Thanks again.....
Swampy
Thanks very much for the grerat write up and show and tell pictures. Great web site.
I've been signed for quite a while but never had any problems here with any of my Hyundai until this one. Also have a 2005 Sonata and 2008 Sonata Limited. The Sonata 2005 was to replace the Elantra, but can't seem to kill it. When it dies she will take the Sonata 2005.
Thanks again.....
Swampy
#9
03-19-2010, 10:37 AM
Don't overfill the tank!
I'm not sure if this was mentioned in all the info above about slow-filling gas tanks, but my mechanic told me one sure was to ruin the charcoal cannister, with the result of a plugged breather pipe, is to overfill the tank.
I am certainly guilty of this. The gas pump nozzle shuts off, I keep filling slowly until gas is almost running out.
It makes sense to me that the breather pipe to the cannister is also full or likely to be.
Whaddya' think of that?
I am certainly guilty of this. The gas pump nozzle shuts off, I keep filling slowly until gas is almost running out.
It makes sense to me that the breather pipe to the cannister is also full or likely to be.
Whaddya' think of that?
#10
03-23-2010, 01:08 PM
New i30 fuel filling problem
I filled my new i30 1400 with petrol for the first time at Sainsbury's. It was a very slow & frustrating process & as the Hyundai dealer was close by I called in to inquire about it. All the models seem to have an identical filler system & the dealer said they are all slow to fill. The pipe from the filler cap is only 50mm deep & at the bottom there is a 20mm hole with a spring loaded flap valve behind it. There are also 2 small holes at the side of the pipe at the bottom. Filling is very slow as the pump shuts off unless the trigger is squeezed very gently. The Hyundai garage didn't seem to know why this was & advised withdrawing the nozzle slightly while filling. With only 50mm to play with this is a good way of getting splashed with petrol. It seems to me that the filler system is not designed for UK pump nozzles.
