The following general guidelines identify common fuel dispensing problems with Vacuum Assist Vapor Recovery nozzles, as well as trouble shooting analysis.
Common Maintenance Concerns for Vacuum Assist Vapor Recovery Nozzles
Each time a nozzle, hose, or breakaway is installed, the hose o-rings must be inspected for wear or damage. If an o-ring is excessively worn or torn, it should be replaced otherwise other problems will arise.
Other maintenance concerns are:
When changing scuff guards, it is not necessary to remove the spout. The vapor splash guard (VSG) can be squeezed together so it and the spout will fit through the spout hole in the guard.
If you do need to remove the spout, do not allow the spout and VSG to rotate with the spout nut. Should the spout and VSG rotate with the spout nut, the vent tube will be twisted off the tip end. It will then be necessary to install a new spout.
Addressing Fuel in the Vapor Return Line
Vapor assist nozzles can get fuel in the vapor line by several sources. The most common source is condensation from the return vapors. This amount would be relatively small. Another possibility is from defective equipment that makes up the vapor return line like a leaking hose, bad o-ring, etc. Another situation is the possibility of fuel recirculation during shutoff and topping off. The amount of fuel that the California DMS allows for recirculation is .75 ml/gal over a 150 car fleet average. This condition is more probable with a coax spout nozzle because the vapor collection point is inside the car filler neck. In comparison, a solid spout vapor assist nozzle has its vapor collection point outside the car filler neck.
Some dispensers are designed such that the vapor return lines are plumbed together at the top. If fuel is present in a vapor line and that nozzle is used, some of this fuel will be shuttled to adjacent hoses while the rest will be returned to the underground tank. This is how fuel can get into all the hoses on a dispenser side.
If enough fuel gets built up in the vapor line, it may be drained. The easiest method for draining the vapor line is by authorizing the dispenser, turning on the pump, point the nozzle down and lift the lever slightly but do not flow fuel. This method will allow the fuel to drain out. If the fuel in the vapor line is drained out of a coax spout nozzle, the fuel would run out near the end of the spout through the vapor collection holes. By draining the vapor line on a solid spout nozzle, the fuel would drain out between the vapor VSG and spout, which is its vapor collection point.
Meter creep occurs when after dispensing fuel, the nozzle is shut off, and the gallons meter slowly climbs up even though no fuel is being dispensed. The gallons meter should be observed for at least one minute to about five minutes. There are many root causes of meter creep.
In the logical order of the system design ( nozzle, hose, break away, hose, and dispenser) the nozzle is the first in line to be checked. If the diaphragm that allows use of the prepay feature fails, fuel will pass from the fuel side of the system to the vapor side. This fuel will drain out between the VSG and spout on a solid spout nozzle. A coax spout nozzle will have fuel that drains from the vapor collection holes near the end of the spout. Make sure there is a constant flow of fuel coming out. With a constant fuel flow verified, watch the gallons meter for a minimum of one minute to about five minutes and if the meter creeps install a working nozzle and repeat the procedure. If the meter creep stops and no fuel comes out of the installed nozzle, the old nozzle may be defective and may need replacement.
If meter creep exists at a fueling point and no fuel is draining from that nozzle, a system component other than the nozzle is leaking fuel from the fuel to the vapor path. A single elimination procedure must be used to determine the cause. Start this procedure by installing new inner hose o-rings. If the meter stops, the inner hose o-rings were bad. If the meter still creeps, install a new long coax hose. Now, everything is original except the long coax hose, and if the meter stops, the original inner long hose was bad. Otherwise, reinstall the original long coax hose and replace the breakaway valve. Make sure to install the breakaway in the correct direction! If meter creep stops with the new breakaway valve, the old breakaway was defective. But, if meter creep continues, replace the original breakaway and install a new whip hose. If meter creep stops the system had a bad whip hose, but if the meter does not stop creeping there is a problem inside the dispenser.
Fuel Leaking While the Nozzle is in the Holster
Several of the various methods by which fuel can be leaking from the nozzle while setting in the holster are:
1 If fuel is in the vapor line by means of a leaking vapor hose, defective breakaway valve, coax nozzle on an adjacent hose, etc. and the vapor valve is defective, fuel will drain out the vapor collection path. A defective vapor valve can be tested by dispensing fuel from an adjacent nozzle and placing a bag over the end of the suspected defective nozzle to close off the vapor path. If the bag collapses, then the nozzle may be defective. The nozzle should be replaced.
2 If the diaphragm that allows the prepay feature in the nozzle failed, thus allowing some fuel in the fuel hose to drain out the vapor collection path. This condition should be verified by testing the nozzle for meter creep, and if it meets that criteria the nozzle should be replaced.
Nozzle not Pumping Fuel
The reason that a nozzle will not pump fuel can be determined by several methods, which are:
Nozzle Continuous Shut-Off Condition
The most common cause of continuous clicking off is due to the pressure activated prepay feature. Therefore, the pump must be turned on and authorized before hose pressure is applied. This hose pressure allows the nozzle to open, otherwise the nozzle will continue to click off until the system is pressurized.
Premature shutoff occurs when the fuel tank is not full and the nozzle keeps clicking off. This is usually due to the automobile fill pipe configuration and/or high flow rates that causes fuel to splash on the sensing shutoff port in the spout. The nozzle should be moved around to find an optimum dispensing orientation and/or the flow rate should be decreased by setting the nozzle in a lower notch. Note, some automobiles are difficult to fill no matter how the nozzle is orientated or at what flow rate.
If the above problem persists, dispense fuel into a bucket and if the problem continues, most likely foreign debris has clogged the automatic shut off air path and the nozzle may need to be replaced.
Nozzle No-Shut Off Condition
This condition has several causes. If a piece of debris gets lodged under the poppet, the nozzle will continue to flow and not shut off automatically. This can be verified if the nozzle flows fuel when the lever is released. The dispenser should be turned off to stop the fuel flow. To check for debris, remove the nozzle from the hose, straighten the hose and drain into a bucket. If no foreign object is seen, drain the nozzle in the bucket and check for debris. If debris is found in the bucket, it is the cause of the no-shut off condition. Sometimes, however, the debris may not come out of the nozzle because it might be permanently stuck to the poppet or in the check valve.
Besides debris, if the spout was replaced, the spout should be checked for proper installation of the vent tube and spout seal. The attached sheet explains the procedure for proper spout assembly installation.
In either case the nozzle should be checked by latching the nozzle and submersing the spout in fuel to check for shut off. If the nozzle continues to flow fuel, something is preventing the nozzle from shutting off automatically. Therefore, the nozzle may need to be replaced.
This fuel dispensing trouble-shooting analysis sheet was designed to help identify various problems associated with refueling. The seven main topics covered here are problems and conditions that result from equipment failures to normal system maintenance concerns. This guide should be used as a reference only to the conditions covered above.