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91 Legacy, baffling electrical problem


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Greetings all -

 

My son's 9 Legacy died on the road, and initially thought it just was a jumped timing belt.

Did the whole rigamorale of installing a new belt pulleys etc..however...

 

After reassmbling everything, found that when the ignition\power was turned on we got these symptoms :

 

  check engine light on, no flashing

 
  purge control solenoid clicking
 
  a\c sub fan relay clicking
 
  blower fan relay clicking
 
  fuel pump cycling on\off rapidly
 
  radiator fan cycling on\off
 
The alternator, starter & battery have all been tested and came back good.
Checked and double checked the grounds & battery connections.
Replaced the main relay, swapped out the ECU with a known good one, and inspected the fuse box.
Replaced the voltage ballast.
 
Nada.
 
Any suggestions?  I'm at a complete loss here.....
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There is a pair of connectors under the dash on the drivers side, 1 green set, 1 black set.

When the greens are connected it puts the ECU in test mode which causes the ECU to cycle all of the solenoids and relays. Useful for testing certain components.

The black connectors are for read/clear memory. They allow you to read codes from the computer and clear them. I don't remember the exact procedure on the Obd1 cars, but some combination of having those two connectors plugged in erases stored codes in the computer.

 

Make sure both of those connectors are Unplugged! I don't know if this will cause your no-start, but those connectors are not to be plugged in except for testing purposes.

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There is a pair of connectors under the dash on the drivers side, 1 green set, 1 black set.

When the greens are connected it puts the ECU in test mode which causes the ECU to cycle all of the solenoids and relays. Useful for testing certain components.

The black connectors are for read/clear memory. They allow you to read codes from the computer and clear them. I don't remember the exact procedure on the Obd1 cars, but some combination of having those two connectors plugged in erases stored codes in the computer.

 

Make sure both of those connectors are Unplugged! I don't know if this will cause your no-start, but those connectors are not to be plugged in except for testing purposes.

 

Kudos to you Fairtax4me, had my son look underneath the dash - and sure enough both sets of the connectors you mentioned were plugged in.

After disconnecting them, the clicking relays etc went away.

 

Now we'll move on to troubleshoot the no-start...

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A no crank condition? Or a no-fire condition?

 

If a no crank, (And A/T) throw it into neutral and see if it cranks. If manual, look for the Clutch safety switch, unplug and jumper it on the car-harness side.

 

If a no fire, give it a shot of starting fluid and see if it responds. Yes, then fuel issue. Look at a dead/dying cam sensor or blown ECU/INJ/IGN fuse. If no, then consider a no-spark condition. Crank sensor, coil, blown fuse..

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