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.
1991 BMW 735iLFACTORY OEM SERVICE PROCEDURE
Fuel Pressure: Notes
Basic fuel system diagnosis should begin with determining fuel system pressure.
- On 318, 325 and 525 Series, remove air intake duct to gain access to fuel lines near throttle body. On all models, connect Pressure Gauge (13 3 060) and "T" Fitting (13 3 064) in fuel lines in front of fuel pressure regulator. See Fig 1 . Block (plug) fuel return line with Fuel Hose Clamp (13 3 010).
- Remove fuel pump relay. See DME & FUEL PUMP RELAY LOCATION table. Using Fuel Pump Relay Bridging Caliper (61 3 050) or jumper wire, connect (bridge) terminals No. 87 and 30 at fuel pump relay socket. See Fig 1 . This will turn fuel pump on.
- Check fuel pump delivery pressure. To check fuel pump delivery rate, disconnect fuel return line. Install extension hose and hold end of hose in Graduated Glass Container (13 3 020). See Fig 1 . Check fuel pump delivery rate.
FUEL PUMP PERFORMANCE
| Application | Pressure psi (kg/cm2 ) | Min. Vol. in 30 sec. Cu. In. (cc) |
|---|---|---|
| All Models | 43 (3) | 53.38 (875) |
Factory Service Tools
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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.