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!!
What do you mean "#1 solenoid"?
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.
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