Wires/connectors I am unsure of at the moment:
Q1
Two wire connector that dumped at the front of the engine by the temp sender. Pink/black (splices into A6 IIRC) and brown I believe. Was this for air pump or something? Doesn't appear to have been hooked up anytime recently. I don't think it's AC related, looks like a different connector.
A1)==================================================================
If original harness was sourced from a 1227747 TBI truck then it is Air Diverter solenoid connector:
A6 + 12Vdc Pink-Black (Ignition hot)
C2 Air Diverter Brown
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Q2
Tan 18AWG wire that went into the cab at the bulkhead under the master cyl. Dumps near the dstrib. Don't think it was hooked on donor.
A2)==================================================================
Hard to tell, if it has a white stripe it can be an EST!
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Q3
2nd purple single wire O2 sensor connector on pass side. Ditch or keep for future?
A3)==================================================================
Pre 1992 trucks used single wire O2 - keep it as O2 used tan wire tied to D6 as O2 ground and
Purple D7 as O2 sensor input.
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Q4
VSS wires coming from bulkhead to trans, purple and yellow I believe. Where do I hook these? I assume coming from near the fuse box at least one is powered? Not sure what I need to do being a 5 spd, and wires sound different than most I have read.
A4)==================================================================
The reason for different color wires that most applications used buffer DRAC module between VSS and ECM. However all this VSS nonsense is easy to get around. If you are using 7747 ECM you need two pulse (2000 pulses per mile) square wave VSS Part # 2PRS from JTR or equivalent. Connect purple wire to ECM VSS input A10 and the other wire to electric ground –A11. VSS is done. Internally ECM has 5.1k pull up resistor on line A10 which keeps VSS line high. As speedometer cable turns VSS sensor pulls this line down and ECM is able to detect these voltage transitions. It is important to have operable VSS – ECM uses this for a number control functions!
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Q5
Neutral safety wires also go into bulkhead and not ECM. If I remember right the colors were blue, and green. I'm guessing one must have went to the clutch pedal somehow?
A5)==================================================================
That is not true - ECM pin B10 is P/N input. For automatics a simple circuit which uses relay, diode and wire can be easily configured.
http://www.painlessperformance.com/M...nstruction.pdf
For a five speed leave ECM pin B10 open – do no connect to anything.
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Q6
Lastly, there is a large red 12 or 10g wire that plugs in near the ECM under the dash. Goes to the gauges and power strip? needed?
A6)==================================================================
Hard to tell – post a picture of these wires
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Q7
So if I understand correctly all I need from the 3rd (white in my case) connector near the ECM is the diagnostic port wires, orange, white/black (data) black/white (ground) red fuel pump test wire, and brown/white SES wire (one side to a 12v light, other grounded) Am I on the right track?
A7)==================================================================
For ALDL connector you’ll need the following wires:
Pin # | Color | Function
A | Blk-White | Ground
B | White | Diagnostic enable
C | Brown | Air Diverter
D | n/c
E | Orange | ALDL serial data
F | Tan | TCC – only for A/T
For SES Pin A5 Brown-white to one side of SES light and the other side to +12 V in run/start . Make sure that your SES light does not require too much current – 20 mA or less.
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We have the 747 ECM, 88 1500 truck harness, and 5 speed manual. I don't have the service manual yet (I know) but think we can get it going off what I have dug up.
Q8
Also curious if I should wire in a 3-wire o2 sensor while it's easy to do or should I even bother? Engine does have headers and I remember reading a TBI source that recommended upgrading sensors when using headers. I know single wire o2's are slow but if the 3 wire is a waste on the older FI system we'll leave it be.
A8)==================================================================
I run four wire O2 sensor – ground return reference wire remove any possibility of a poor ground return path from O2 sensor readings, especially with long tube headers that may cool. O2 sensor must remain above 600F to provide correct voltage readings. The other two wires are used for heater coil. A simple relay tied to ignition on circuit turns on O2 heater. Use AC-Delco AFS-74 (25312179) for best results
//RF