For a quick check of pumps, jumper +12V from LEFT contact of any fuse 6—10 to the LEFT fuse 4 contact. Both pumps should run. To test just the Main pump, pull fuse 4 and apply the +12V as before. Putting the +12V to the RIGHT fuse 4 contact (with fuse removed) should only run the Tank pump.

• "Can some one let me know how to check this problem?"

1) Begin at the 25 Amp blade fuse in the coil/battery area. Could be corrosion problems in the fuse holder or wiring—especially the connection at the Battery + terminal.
(Or the fuse may have blown when the pump wires shorted.)

2) If still a no-start, use a 12V test light to see if that 25A fuse is sending good current to Fuel relay terminal 30. "Back-probe" the big Red wire in the relay harness plug. Should be a good +12V there all the time.

3) If relay 30 has +12V OK, back-probe relay 87-1 (Orange and Brown wires) and turn the key to On. The Test light should come ON when key goes On. That means the FI Main/System relay is energized.
(The Fuel relay is separate.)

4) If relay 87-1 voltage is there, back-probe relay 87-2 (Fuel relay) and try starting.

5) If no relay 87-2 voltage when cranking, the 87-2 relay contacts might be burnt from the shorted pump wiring. Or, it could be an ECU problem (see 6).

6) To see if the ECU is energizing the Fuel relay, back-probe relay 86-2 (Blue-Green wire). The test light should come ON when the Key is turned to ON, then go OFF when cranking the starter (ECU grounds B-G wire to energize Fuel relay).

7)If still no start, and the test light stays ON, it could be the ECU failing to ground the B-G wire.

BUT if the engine starts with the test light probing 86-2, the test light may be supplying the needed relay ground.

See if it starts without the test light probing the relay 86-2 wire. If not, it could be a bad ECU — or the ECU is not getting the "OK" signal from the Ignition CU (not too likely).



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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.