1989 Mazda 626 Repeated Fuel Injector failures

1989 MAZDA 626
129,000 MILES • 4 CYL • FWD • AUTOMATIC
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SCHILSTR
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Non-Turbo

Had a #2 fuel injector failure and had it replaced with a rebuilt. It ran great about 100 miles and #2 fuel injector stopped again. It was replaced with another rebuilt. Again about another great 100 miles and failure. It was replaced with a new injector.
#2 cylinder went dead after 32 miles.

Compression is good.

Wiring diagram shows that #2 and #4 are tied common to the engine computer but #4 works fine.

All injectors make same active ticking sound.

Ignition wires and plugs were swapped. #2 cylinder remains dead. Distributor cap and rotor in good condition.

All injector resitances are in spec.

Pulling injector #4 wire does not cause #2 cylinder to fire. So engine controller is not being driven down by #4 injector.
Dec 30, 2008 at 10:15 PM
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JAMES W.
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What happens to the injectors that go bad, is it burning out the coils? Have you checked the "running" voltage of #2 injector verses #4? Please advise.
Dec 30, 2008 at 11:53 PM
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SCHILSTR
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The coils are obviously not "burned" out if they have resistances that are within spec. (spec is 12-16 ohms and the coils are around 13.8 ohms)

Battery voltage is applied to the injectors and the engine controller only grounds the circuit. The fact that the injectors are ticking indicates that they are actuating. Voltage at the connector is battery voltage.
Dec 31, 2008 at 9:07 AM
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SCHILSTR
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I have uploaded the pdf of the wiring diagram of the injector circuit from the Mazda service manual. I circled where injectors 2 and 4 are common into the controller for ground. The injectors get full voltage from the battery and the controller modulates the signal. Since injectors 2 and 4 are tied and common to ground through the controller and #4 works something else must be going on.
Dec 31, 2008 at 9:57 AM
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JAMES W.
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  • ASE Certified Mechanic
If # 2 injector coils aren't bad, what is wrong with them? Are they plugging? Let me know. This will be interesting.
Dec 31, 2008 at 1:22 PM
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