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.
1990 Audi 100 Base, AutomaticFACTORY OEM SERVICE PROCEDURE
System Pressure
- Using Adapter Fittings,connect Pressure Gauge (VW 1318) between line from fuel distributor to cold start valve and test port connection on lower chamber of fuel distributor. See Figure
. Test port is sealed by a threaded plug. Bridge fuel pump relay (located on fuse/relay panel) with Jumper Switch (US 4480/3). See Figure
for fuel pump relay terminal identifications.NOTE: Fuel pump may also be activated by jumping 12 volts to by-pass terminal on fuse/relay panel. See the appropriate WIRING DIAGRAMS article.
- Open valve on pressure gauge (points to cold start valve line when open) and activate fuel pump. System pressure must be 68-78 psi (4.7-5.4 kg/cm2 ). If pressure reading is low and fuel pump delivery quantity is good, adjust or replace regulator assembly.
- If pressure reading is high, disconnect fuel tank return line from fuel distributor. Repeat test. If reading is correct, check for plugged return line. If reading is incorrect with line open, replace regulator assembly.
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.