30 Apr 08, 10:30 pm
Quote: Diagnostic Procedure for EFI Related Woe and StrifeStole it from mud, from the user jonheld. Sounds like a fusible link problem? And I should really stop procrastinating homework doesn't do itself haha.
The EFI circuit feeds +12 to the ECU, all 3 VSV valves, both O2 sensors, the ISC valve, and the load side of the circuit opening relay which feeds the fuel pump when the motor is running.
1. Motor not running; key in ON position; CEL should be on.
2. Check for +12 VDC on brass terminal screw in under hood fuse box. This terminal is located directly to the left of the main fuse and is a Phillips screw head. http://mysite.verizon.net/jonheld/im...BA/Fusebox.jpg
3. If no +12 VDC in fuse box, then check fusible links off positive battery terminal. http://mysite.verizon.net/jonheld/im...y/PosTerm1.jpg. While the one in the picture is not stock, the links are going to the stock locations. 2 to the black plastic junction box and one to the connector.
4. If +12 VDC in fuse box and no CEL, then suspect EFI relay/fuse and associated wiring and contacts. Many have said that the wire from the EFI fuse to the EFI relay is undersized and is the root cause of all these problems. I disagree with this. At idle I measured less than 1 amp across the load side of the EFI relay contacts. I believe the cause of the problems is related to the heat of the manifold combined with poor crimps on the connectors in the fuse box. Over time these connectors can become corroded and cause problems.
5. Check for +12 on pin 8 (B+) on the CHECK CONNECTOR mounted on the right side of the fire wall. If +12 on pin 8 and still no CEL, then EFI circuit OK and problem is with ECU or associated harness.