Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Volume & Pressure: Notes
Begin basic fuel system diagnosis by determining fuel system pressure.
- Remove engine cover to gain access to fuel lines. Prepare Pressure Testing Kit (135220) which consists of Check Valve (135221) and Adapter (135222). Remove dust cap from measuring valve on fuel rail. Connect check valve and gauge to fuel rail. Block (plug) fuel return line with Fuel Hose Clamp (133010).
- Remove fuel pump relay. See DME & FUEL PUMP RELAY LOCATION table. Using Fuel Pump Relay Bridging Caliper (613050) or jumper wire, connect terminals No. 87 and 30 at fuel pump relay socket. See Figure. This will turn fuel pump on.
- Disconnect fuel return line. Install extension hose and hold end of hose in Graduated Glass Container (133020). Check fuel pump delivery rate. See FUEL PUMP PERFORMANCE table.FUEL PUMP PERFORMANCE
Application Pressure psi (kg/cm2 ) Min. Vol. In 30 Sec. Pts. (L) 6-Cylinder & V8 50 (3.5) 1.85 (0.9) V12 50 (3.5) 2.3 (1.1)
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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