fuel injectors not firing

I have a 1988 Thunderbird with a 3.8L. It has good fuel pressure on the feed rail. However, the engine will not start because the signal to the injectors is incorrect. With switch on run, engine not running, I have about 12V on both the tan and the red wires to #1 solenoid. When I crank the engine the voltage alternates between about 6.5V to 12V on BOTH wires. I believe one wire should remain at 12V, and the other should alternate between ground and 12V. Also, I cannot get the ECM to download the engine trouble codes to read out on my Sunpro.

Any suggestions where I should look next? Help!!

  Pat Bennett

What do you mean "#1 solenoid"?

  DodgeRida67

The injectors pulse so quickly that a voltmeter won't be able to respond with the same speed...keep in mind injectors are kept open for only a few milliseconds...chances are, your meter can't bottom out at zero then get back up to 12v quick enough so you're getting a reading somewhere in between. Are you using a digital or analog voltmeter?

If you can't get the codes to come up on the Sunpro...you could try using the check engine light to get the codes(refer to repair manual for proper procedure). If that fails to work then I would assume that the ECM went to lunch and isn't coming back.

  Sick88Tbird

The EEC-IV system on the 88 T-bird will identify the weak cylinder but will not diagnose why. The test procedures for pulling the codes will allow the computer to do a cylinder balance test which will isolate the weak cylinder and alloe troubleshooting to go from there.

A special node light is required to determine if the injector is getting the signal to fire (autoparts store $6) due to the short but variable duration of the electrical pulses as described above

  tbaxleyjr