Sending Units, Checking
Test Requirements^ Fuel tank full of fuel
^ Observe all safety precautions --> Group 20 of appropriate Repair Manual.
^ Observe rules of cleanliness --> Group 20 of appropriate Repair Manual.
^ Always complete checking procedure (check all 3 sending units).
Starting with tank full:
- Check fuel gauge sending units as described on pages 5-7.
After checking fuel gauge sending units with full tank. Drain fuel tank as follows:
- Remove fuse 28 from relay panel (left-row, fifth large fuse from top).
- Start and run engine until engine runs out of fuel (relieves pressure in fuel system).
- Switch ignition OFF.
- Remove fuel supply hose from sending unit -0- and connect to VAG 1433A fuel cart or similar approved equipment.
- Connect VAG1348/3A remote switch with VAG1348/32 adapter to cavity for fuse 28 (arrow).
- Connect test probe to Battery Positive Voltage (B+).
With remote switch connected:
- Operate switch and pump fuel into fuel cart until tank chambers for sending units -G237- and -G- are empty.
- Switch OFF VAG1348/3A remote switch and remove VAG1348/32 adapter from cavity for fuse 28.
- Remove test probe from Battery Positive Voltage (B+).
Note:
Chamber for sending unit -G169- will still be full of fuel, remove fuel as follows:
- Reconnect fuel supply line to sending unit -G- with appropriate clamp.
- Reinstall fuse 28 in relay panel.
- Start and run engine for approx. 15 minutes.
Note:
^ Remaining fuel from chamber for sending unit -G169- will be siphoned into chamber sending unit -G-.
- Switch ignition OFF.
- Remove fuse 28 from relay panel again.
- Start and run engine until engine runs out of fuel (relieves pressure in fuel system).
- Switch ignition OFF.
- Remove fuel supply hose from sending unit -G- and connect to fuel cart again.
- Reconnect VAG1348/3A remote switch with VAG1348/32 adapter to cavity for fuse 28 (arrow).
- Connect test probe to Battery Positive Voltage (B+).
- Operate switch and pump fuel into fuel cart until tank chamber for sending unit -G- is empty.
- Switch OFF VAG1348/3A remote switch and remove VAG1348/32 adapter from cavity for fuse 28.
- Remove test probe from Battery Positive Voltage (B+).
- Reinstall fuse 28 in relay panel.
- Check fuel gauge sending units as described on pages 5-7
- Reconnect fuel supply line to sending unit -G- with appropriate clamp.
Fuel gauge sending unit -G-, checking
- Check resistance between pin 3 of sending unit -G- and pin 2 of sending unit -G169-.
Specified values:
^ Tank empty: approx. 20 Ohms.
^ Tank full: approx. 70 Ohms.
If specified values are not obtained:
- Check wiring per diagram --> illustration 97-A492 (checks wiring inside fuel tank between sending units).
If wiring is faulty:
- Remove sender from fuel tank.
- Repair wiring.
If wiring is OK:
- Remove sender from fuel tank.
- Test sender.
If specified values are not obtained:
- Replace sender.
Fuel gauge sending unit -G169-, checking
- Check resistance between pin 2 of sending unit -G- and pin 1 of sending unit -G169-.
Specified values:
^ Tank empty: approx. 20 Ohms.
^ Tank full: approx. 118 Ohms.
If specified values are not obtained:
- Check wiring per diagram --> illustration 97-A492 (checks wiring inside fuel tank between sending units).
If wiring is faulty:
- Remove sender from fuel tank.
- Repair wiring.
If wiring is OK:
- Remove sender from fuel tank.
- Test sender.
If specified values are not obtained:
- Replace sender.
Fuel gauge sending unit -G237-, checking
- Check resistance between pin 1 and 2 of sending unit -G237-.
Specified values:
^ Tank empty: approx. 30 Ohms.
^ Tank full: approx. 82 Ohms.
If specified values are not obtained:
- Remove sender from fuel tank.
- Test sender.
If specified values are not obtained:
- Replace sender.
- After procedure is performed, check and erase any stored DTC's using VAG 1551 Scan Tool.