File 34 of 80
Prev | Next

fuel-tank-bronco.jpg | Hits: 25371 | Posted on: 1/20/06 | View original size (448.47 KB)

Fuel Tank mounting & rollover valves
IF THE IMAGE IS TOO SMALL, click it.
Despite the details shown here, MOST of the straps I've found are installed the other way, with the nuts at the FRONT.

E1TZ-9047-K Tank-to-Neck Filler Hose
F2TZ-9002-M Tank, 32gal '92-96 (large hole)
FOTZ-9002-D Tank, 32gal '90-91 (large hole)
EOTZ-9002-G Tank, 32gal '80-89 (small hole)
D8TZ-9A147-A Skid Plate, 32gal '80-96
D8TZ-9A147-B Skid Plate, 25gal
D8TZ-9092-A Tank Strap

34976 Nut (13mm crimped w/integral washer)
N851380 Bolt (13mm head w/integral washer MC9.8 )
382873 Washer (flat thick)
N620482 Nut (15mm crimped w/integral washer)

All fuel tank vapor valves make use of a small orifice that tends to allow only vapor and not fuel to pass into the line running forward to the vapor storage canister. This assembly mounts directly to the fuel tank using a rubber seal.

Fuel vapors trapped in the sealed fuel tank are vented through the orificed vapor valve assembly in the top of the tank. The vapors leave the valve assembly through a single vapor line and continue to the carbon canister for storage, until they are purged to the engine.

The vapor valve assembly mounted on the top of the fuel tank is used to control the flow of fuel vapor entering the fuel tank vapor delivery line which conducts vapor forward to the canister in normal circumstances. If due to extreme conditions, excessive pressure is generated inside the tank, the purge port opens up, allowing fuel vapor to escape to the atmosphere, and stabilizes pressure inside the tank. The valve assembly has a head valve which prevents the fuel tank from overfilling during refueling operation. The valve assembly also has a spring supported float assembly, which prevents liquid fuel from entering the vapor delivery line during severe handling, steep grades or in the event of vehicle rollover.

The fuel fill cap (F4TZ-9030-C '87-96; E1AZ-9030-A '78-86 w/o lock; D6AZ-9030-B '78-86 locking) is sealed and includes a built-in pressure-vacuum relief valve. Fuel system vacuum relief is provided after 3.5 kPa (0.50 psi) and pressure relief after 11.0 kPa (1.6 psi). Under normal operating conditions, the fill cap operates as a check valve, allowing air to enter the tank as fuel is used, while preventing vapors from escaping the tank through the cap.

The Fuel Tank Vapor System -

Gasoline is extremely volatile in almost all environments, and even diesel is aromatic. Since these vapors can be flammable or noxious, they must be contained & routed to the engine to be burned. But they are produced even when the vehicle is unused for long periods, so a simple tube from the fuel tank to the engine would still allow them to vent out the air filter. Also, during hot weather or violent maneuvers, the quantity of vapor generated can exceed the engine's capacity at low RPM, so the vapors must be stored & their flow regulated.

The system begins in the fuel tank where one or more valves (4.9L/5.0L Valve E7DZ-9B593-A & Grommet F6TZ-9B076-AA; 5.8L/7.5L Valve E8UZ-9B593-A & Grommet E8UZ-9B076-A) are used to vent vapor pressure, but also to exclude liquid from the vapor system due to overfilling, slosh, or rollover. There may also be a pressure sensor to monitor the system's operation & effectiveness, and/or a vent valve (CANV solenoid, or built into the cap) to allow fresh air [b]into[/b] the fuel tank or vapor system. As vapor exits the tank, it flows thru a tube to a canister containing carbon (activated charcoal), which absorbs the fuel vapor, but allows air to pass. Depending on the size of the fuel tank, there may be several canisters, or a larger canister. Older canisters are vented, but they're known to collect water, so most modern canisters are sealed. Another tube leads from the canister toward the engine's intake, but it may contain a regulator valve (CANP solenoid, or VMV). The vapor system may also combine with the PCV system at this point.

Since the fuel tank is ultimately connected to manifold vacuum, the filler cap must be vented to prevent the tank from collapsing in the event of a failure that applies continuous vacuum to it.

Being virtually a zero-maintenance system, most faults are simple valve failures, hose leaks, or mechanical damage (collision, road debris, etc.). A collapse of the fill hose or blockage of the filler neck's vent port can cause slow filling & "burping" - neither of those symptoms indicates any problem with the vapor system.

. .

Faults in the evaporative systems are usually detected by the use of a special machine which pumps a non-toxic non-flammable high-visibility smoke into the vapor lines to make leaks evident. But a common source of evaporative codes on '97-04 vehicles is the operator not securing the fuel filler cap. Earlier vehicles didn't detect this, and later vehicles are designed to exclude this from turning on the CEL. They typically have a separate warning for the fuel cap.

See also:
. . .