Abstract: A tamper-proof adjustment screw arrangement for a vehicle fuel supply system for preventing tampering with the setting of an adjustment screw that is situated in a common recess with a component requiring the availability of continued access. In a preferred embodiment, a tamper-proofing shield coacts with the configuration of a portion of a recess having a stepped bottom wall and with a spanner jam nut on the adjustment screw to create a press fit mounting of the shield that makes it exceedingly difficult to pry off the tamper-proofing shield. As an additional safeguard, the spanner nut is designed to require a special tool for loosening thereof.

Abstract: A system is provided for controlling fuel flow within an internal combustion engine having a plurality of cylinders. The system includes a fuel source; a fuel pump responsive to the engine speed; and a multimode adjustable control valve connected to the fuel pump and a predetermined number of first cylinders. The control valve, when in a first mode, substantially shutting off fuel flow to the first cylinders, except for a minimal amount of fuel leakage from the valve to the first cylinders for lubricating purposes. When in a second mode, the control valve allows substantial fuel flow to the first cylinders. The control valve assumes its first mode when the operating temperature is below a predetermined amount and/or the engine is operating under a predetermined load.