BMW uses several types of fuel fittings. These include:
The quick release fuel hose couplings are one of two types:
These fittings lock onto a shouldered metal line and are typically found flexible hoses that attach to a metal line, such as the fuel feed or return lines of the fuel rail. The difference between the two types of unlocking devices is that the version with the integrated locking device does not require a special tool to remove. The version without the integrated unlocking device requires a release tool such as BMW Tool No. 16 1 050 or its equivalent.
The version with the integrated locking device will have a small shoulder protruding from the fitting which is pressed toward the fitting to release or install the fuel line.
The version without the integrated locking device requires the use of a release tool to press the clip recessed in the fitting to release or install the fuel line.
Conventional Screw Clamp
The conventional screw type clamped fuel fitting is such that a fuel line slides over rigid fitting and is held in place by a clamp which is loosened or tightened via a screw using a screwdriver or related tool.
These clamps are also available as tamper-proof clamps. A tamper-proof clamp has a screw type fastener that is used to tighten the clamp. However once tighten, the head of the screw is stamped such that the tool used to install the clamp will no longer seat well enough for the clamp to be tightened or loosened. Because tamper-proof clamps are designed to be used only once, they are removed by either cutting them with a sturdy pair of side cutters, or by clamping a locking type of pliers onto the screw head and turning the lock screw counterclockwise to loosen.
Once a screw type clamp is loosened, slide it off the portion of hose that is attached to the fitting, and the hose can be removed. Tamper-proof clamps should not be reused and replaced with a conventional screw type fuel line clamp. An example of this type of tamper-proof clamp can be found on the M44 fuel rail return hose.
Crimped Band Fuel Clamp
Much like the tamper-proof screw clamp, these clamps are not intended to be reused and be removed by one of two methods. Once removed, these clamps can be replaced by a conventional screw clamp, or another crimped band clamp can be installed if the appropriate crimping tool and clamp bands are available. An example of this type of clamp can be found on the brake booster-to-intake manifold hose.
Shouldered Metal Line
The shouldered metal line fitting uses an O-ring to create a seal, and the line is held in place by a retainer, such as a flare nut or lock clip. The O-ring is installed around the line and bottomed against the shoulder and seals itself against the machined surface of the mating component. The retainer, either a lock clip or a flare nut secures the line in place. If a flare nut is used to retain the line, the flare nut is installed on the line to apply pressure to the shoulder and seat the O-ring.
An example of a shouldered metal line with an O-ring is the fuel rail feed line of the M44 fuel rail. An example of a shouldered metal line with a retaining clip, is the connection of the fuel injectors to the fuel rail.