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1990 Subaru Legacy no power to injectors

Tiny
RANDALL1965
  • MEMBER
  • 1990 SUBARU LEGACY
  • 200,000 MILES
Car was running with a miss and after listening to injectors with scope, I heard two that were not making the usual sound. I rented the noid test lights and checked the injectors. I found two of the four were not getting power. Therefore it has basically two dead cylinders. What would cause only two injectors to fire and not the others?
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Sunday, July 7th, 2013 AT 9:30 AM

8 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
One of the wires to the injector must have battery voltage when ignition is turned on. If power is not available, something is wrong with the wiring.
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Monday, July 8th, 2013 AT 5:55 PM
Tiny
RANDALL1965
  • MEMBER
  • 5 POSTS
With the noid light installed, there is only power for a brief moment when the ignition is turned on. The engine was recently replaced and it had no problems before. The wires were unplugged at the connectors by the battery so nothing should have changed. It did set for almost a year before the engine swap. Would that possibly have something to do with it? The new engine ran fine in the car it came out of.
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Tuesday, July 9th, 2013 AT 11:42 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
The noid light is for testing whether the injector circuit is pulsing but it does not tell you if power supply for the injectors are interrupted.

Did you test the circuit for battery voltage when engine is running?
Which are the 2 cylinders not firing?
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Tuesday, July 9th, 2013 AT 5:32 PM
Tiny
RANDALL1965
  • MEMBER
  • 5 POSTS
It is cylinders 1 & 2 that are not firing. However I have not checked for battery voltage yet. I will do so a.S.A.P and get back to you. Thank you
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Wednesday, July 10th, 2013 AT 8:25 AM
Tiny
RANDALL1965
  • MEMBER
  • 5 POSTS
After testing the wires like you suggested, I found there to be power on one side while the engine is running. Does this indicate a problem with the ecm or is it a simple fix? Again thank you.
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Thursday, July 11th, 2013 AT 8:51 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
If there is power to one of the wires and the circuit is not pulsing, you would need to test the wire for continuity to the ECM. If continuity is available, the problem would be with the ECM.
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Thursday, July 11th, 2013 AT 10:28 AM
Tiny
RANDALL1965
  • MEMBER
  • 5 POSTS
I will run a continuity test as soon as I get a chance. Thank you for all of your help. I appreciate you taking the time to help figure out this problem. Again thanks
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Thursday, July 11th, 2013 AT 2:04 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
You're welcome and good luck.
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Friday, July 12th, 2013 AT 7:09 AM

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