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No injector Pulse

Tiny
JIMFREY
  • MEMBER
  • 1990 MAZDA B2600
  • 2.6L
  • 4 CYL
  • 2WD
  • MANUAL
  • 100,000 MILES
Truck will start if I feed it gas, but the injectors do not pulse. I was wondering if you could start me on what I need to check?
Saturday, April 14th, 2018 AT 2:37 PM

7 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon.

I would start by verifying power to the injectors with the key on.

If you do, then you need to use a test light on the other wire and back probe it while cranking. It should flash. That will tell you if the PCM is turning the injector on and off.

Roy
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Saturday, April 14th, 2018 AT 2:41 PM
Tiny
JIMFREY
  • MEMBER
  • 4 POSTS
Can you tell me which wires to check?
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Saturday, April 14th, 2018 AT 2:49 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay.

The black yellow wire is the one that needs battery voltage. Check it with key on. The other wire is the one that needs to flash while cranking.

Roy
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Saturday, April 14th, 2018 AT 3:56 PM
Tiny
JIMFREY
  • MEMBER
  • 4 POSTS
The black and yellow doves have full voltage when the key is on, but the other wire does not flash when you spend the engine over. What should I check next? Thank you very much.
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Sunday, April 15th, 2018 AT 11:04 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay.

When you crank the engine does the tachometer move up a little? That will tell us if the crank sensor is sending a signal to the PCM.

Roy
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Sunday, April 15th, 2018 AT 11:08 AM
Tiny
JIMFREY
  • MEMBER
  • 4 POSTS
Yes, the tachometer does slightly bump up every rotation of the engine. But I was thinking this truck did not have a crankshaft sensor but did everything in the distributor. I do not see a sensor anywhere around the crank pulley. I cannot tell you how much I appreciate your help.
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Sunday, April 15th, 2018 AT 12:59 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, if you have no flash and you have a crank signal then the only things left are the wiring to the ECM and the ECM.

Check the wiring to the ECM for any damage or breaks. If you find nothing then most likely the ECM has failed.

Roy
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Sunday, April 15th, 2018 AT 1:05 PM

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