How do I purge excess air from tank manually on aRobinair 34788NI

• Park the Taurus on a level surface, set the parking brake and turn off the engine. Chock the wheels.
• Open the hood and disconnect the negative battery cable.
• Stand on the passenger's side and shine the flashlight along the firewall.
• Look for a plastic cylindrical object about 2 inches high, mounted on the firewall near the right fender. This is the purge valve. You should see a thick black hose entering it from the driver's side of the unit.
• The Ford Taurus canister purge control valve is a part of the evaporative emission control system, which keeps fuel vapors from escaping into the atmosphere. Pressure inside the gas tank fluctuate due to fuel level, environmental conditions and driving style. The extra vapor is vented into a storage canister under the rear of the car, outside the fuel tank, and is fed into the purge control valve through a rubber hose. The power-train control module monitors fuel tank pressure through a tank pressure sensor. It opens the canister purge valve as necessary to keep this pressure within design limits.

There are a lot of coolant lines around the Northstar engine, but not one called a "purge line" that I am aware of. The coolant system is designed to be a closed system, and is never purged.

However, there is a rubber drain line on the pressurized overflow tank that will release coolant on excessive pressure sensed by the rad cap on the tank, or if the rad cap is faulty. If the system has a leak anywhere, it will not hold required pressure and that will always cause overheating. If you are losing coolant, that is the first place to look (bad rad cap, or cracked tank or line from the tank to the rad).

There is no such thing , What code do you have if any ? There is a purge solenoid for the EVAP system ! evaporative emission system. An there is a vent solenoid , a fuel tank pressure (FTP) sensor.
The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent valve to atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the control module will command the EVAP purge valve ON, open, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent valve OFF, open, fresh air will be drawn through the valve and vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge valve into the intake manifold to be consumed during normal combustion. The control module uses several tests to determine if the EVAP system is leaking.

Well, I don't think so. The pressure sensor will throw its own code (0450, 0451, 0452, 0453, or 0454). And likewise, the fuel level sender or sensor could also throw its own codes (P0460-P0464).

I'm not sure the level sensor and the pressure sensor are linked together. They are separate on a 2005 buick century, the pressure sensor being at the top of the tank located on the fuel pump module, but Cadillac: anything is possible.

Since you replaced the purge solenoid, there may be a problem in the circuit. The purge should have battery voltage to it with the key on. The ECM will ground the circuit internally when the purge is wanted. One symptom of a purge valve that isn't working or stuck closed can be a whooshing sound when the fuel tank cap is opened, indicating excessive pressure in the tank.
A shop's scan tool could be used to command the purge valve on to check it.

Hi there:
DTC P0496 - EVAP (evaporative emission) Flow During A Non-Purge Condition


The P0496 DTC code is a generic code which applies to all vehicle makes. A quick search on the 'net shows that this code seems to be more common with GM (Chevy, Pontiac, etc.) vehicles. In Acura, Honda, Hyundai, Kia, and Mazda vehicles, this code is described "EVAP system high purge flow" which is the same thing.

This DTC checks for undesired intake vacuum flow to the EVAP system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve OFF and the EVAP canister vent solenoid valve ON. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system

If vacuum in the EVAP system is more than a predetermined value within a predetermined time, this code is set and the MIL (malfunction indicator lamp) is illuminated.

Symptoms of a P0496 DTC will include MIL illumination, and most likely no other noticeable symptoms. Some may experience a hard start / crank condition. In some cases the engine may run rich which may not detected, but can cause damage long-term (think: catalytic converter damage).

Potential causes of a P0496 EVAP code include:

• Faulty purge or vent solenod/valve
• Plugged EVAP canister
• Failed EVAP / fuel pressure sensor
• Poor electrical connection
• Short electrical circuit condition
(Hyundai, Isuzu)
• Faulty canister purge valve
• Blocked vapor canister
• Faulty vent solenoid
• Leaking EVAP system hose (Hyundai)
• Faulty purge flow sensor (Kia, Mazda)

Possible Solutions

The most common fix for this DTC is to replace the purge solenoid valve. However, be sure to do a proper diagnosis before replacing parts!

Ideally you would use an advanced scan tool, with the ignition on and engine off, you seal the EVAP system using the Seal/Purge function. Then, watch the fuel tank pressure sensor reading when you turn the purge off. If the pressure value is higher than the normal range set by the manufacturer, replace the EVAP canister purge solenoid valve. Refer to a model-specific repair guide for the proper specification.

If you don't have access to the scan tool, you could always disconnect the vacuum line at the purge valve going back to the charcoal canister. Unplug the electrical connector on the purge valve, start the engine, then put your finger on the valve where you disconnected the line. If you can feel vacuum there, the purge solenoid valve is faulty and needs to be replaced. Alternately, you could simply remove the purge solenoid valve and blow into it. It is normally closed, so if air goes through then you need to replace it.

If the purge valve checks out good, either the problem with the valve is intermittent or there is a problem with the fuel tank pressure sensor. To test the fuel tank pressure sensor you will need to have a high end scan tool to monitor the tank pressure with the gas cap removed. If the sensor shows vacuum with the gas cap removed, there is a problem with the fuel tank pressure sensor.

Here is a picture of one purge solenoid valve. Yours may look similar or different, consult a factory service guide or your local vehicle dealership for more details.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Are you sure is was high air pressure and not vacuum? Most modern automobiles have fuel tank purge systems which will place the fuel tank under low pressure (or vacuum). If you remove the fuel cap immediately after travelling a long distance or while the engine is still running, it could be normal to hear a "hissing" sound when removing the cap as the pressure in the tank will equalize when the cap is removed.

Hi, the computer has sensed through the fuel tank pressure sensor that the vapor cannister is not evacuating properly. I have pasted details on the EVAP system below. Check the purge valve on top of the engine as shown below (#1 in picture). Make sure the electrical connector is on the valve, that the wires are not damaged, and check the hose for kinks. If all looks good, I recommend you replace the valve. A new valve is $23 at autozone. Please let me know if you have more questions and thanks for using FixYa.


Description & Operation
EVAP Canister
The canister is filled with carbon pellets used to absorb and store fuel vapors. Fuel vapor is stored in the canister until the control module determines that the vapor can be consumed in the normal combustion process.
EVAP Control System
The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent solenoid to atmosphere.
The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the control module will command the EVAP purge solenoid ON, open, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent solenoid OFF, open, fresh air will be drawn through the solenoid and vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon.
The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge solenoid into the intake manifold to be consumed during normal combustion. The control module uses several tests to determine if the EVAP system is leaking.
The EVAP system consists of the following components:
EVAP Purge Solenoid
The EVAP purge solenoid controls the flow of vapors from the EVAP system to the intake manifold. This normally closed solenoid is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapor to the engine. The solenoid will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.
EVAP Service Port
The EVAP service port is located in the EVAP purge pipe between the EVAP purge solenoid and the EVAP canister. The service port is identified by a green colored cap.
EVAP Vent Solenoid
The EVAP vent solenoid controls fresh airflow into the EVAP canister. The solenoid is normally open. The control module will command the solenoid closed during some EVAP tests, allowing the system to be tested for leaks.
Fuel Tank Pressure Sensor
The FTP sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1-4.9 volts. As FTP increases, FTP sensor voltage decreases, high pressure = low voltage. As FTP decreases, FTP voltage increases, low pressure or vacuum = high voltage.

SOUND LIKE YOUR EVAPORATIVE EMISSION CONTROL NOT WORKING.SCAN VECHICLE FOR FOR FAULTY FUEL TANK PRESSURE SENSOR MALFUNCTION.AND THE CANISTER PURGE SOLENOID VALVE OR CANISTER VENT SOLENOID NOT WORKING.CAUSING EXCESSIVE FUEL PRESSURE AND FUMES BUILD UP IN FUEL TANK.CHECK CANISTER IT COULD BE GAS SOAKED NEED REPLACING OR VACUUM LINES GOING TO CANISTER PURGE SOLENOID OR VENT SOLENOID COULD BE BROKEN.PURGE VALVE LOCATED ON THE LEFT SIDE OF THE ENGINE ON A BRACKET AND VENT SOLENOID LOCATED ON A BRACKET NEXT TO FUEL TANK.CHECK BOTH MAKE SURE VACUUM LINES NOT BROKE OR DISCONNECTED.MAKE THE ELECTRICAL CONNECTOR INTACT ALSO.FUEL PRESSURE SENSOR ON TOP OF TANK ON THE FUEL PUMP MODULES.ALL YOU CAN DO IS REMOVE CANISTER SEE IF FULL OF GAS REPLACE IT.AND CHECK FOR BROKE AND DISCONNECTED VACUUM LINES.THE DEALERSHIP HAS TO HOOK UP DIAGNOSTIC EQUIPMENT CHECK IT OUT.BE CHEAPER BECAUSE ALL THEM EVAP PARTS NOT CHEAP THAT WHY LET DEALERSHIP SCAN IT SAVE MONEY IT WILL CUT THE COST.WARNING DONT KEEP DRIVING VECHICLE.GAS VAPORS PRESSURE BUILD UP ON HOT DAY FUELTANK WILL BLOW UP LIKE BALLON.PRESSURE KEEP BUILDING UP.

P0452 Evap.Emission System-Pressure Sensor Low Input

The evaporative emission control system prevents hydrocarbon vapors from escaping from the fuel tank into the atmosphere where they could form photochemical smog. Gasoline vapors are collected in the charcoal canister. The Fuel Tank Pressure Sensor (FTPS) is an integral part of the evaporative monitoring system. The PCM monitors the FTPS signal to detect vacuum decay and excess vacuum. The FTPS measures the difference between the air pressure inside the fuel tank and outside air pressure to check the purge control solenoid valve operation and for leak detection in the evaporative emission control system by monitoring pressure and vacuum levels in the fuel tank during the purge control solenoid valve operating cycles.

The ORVR (On-Board Refueling Vapor Recovery) system consists of a unique fuel tank, flow management valve, fluid control valve, one-way check valve and vapor canister.

The ORVR (On-Board Refueling Vapor Recovery) system is used to remove excess fuel tank vapors. This is done while the vehicle is being refueled..

Fuel flowing into the fuel filler tube (approx. 1 inches I.D.) creates an aspiration effect drawing air into the fuel fill tube. During refueling, the fuel tank is vented to the EVAP canister to capture escaping vapors. With air flowing into the filler tube, there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the EVAP canister, the vehicle's computer controlled purge system draws vapor out of the canister for the engine to burn. The vapor flow is metered by the purge solenoid so that there is no, or minimal impact on driveability or tailpipe emissions.

As fuel starts to flow through the fuel fill tube, it opens the normally closed check valve and enters the fuel tank. Vapor or air is expelled from the tank through the control valve and on to the vapor canister. Vapor is absorbed in the EVAP canister until vapor flow in the lines stops. This stoppage occurs following fuel shut-off, or by having the fuel level in the tank rise high enough to close the control valve. This control valve contains a float that rises to seal the large diameter vent path to the EVAP canister. At this point in the refueling process, fuel tank pressure increases, the check valve closes (preventing liquid fuel from spiting back at the operator), and fuel then rises up the fuel filler tube to shut off the dispensing nozzle.