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408cuda · 01-31-2009, 12:05 AM

Sorry for the dumb questions guys. I looked the thread over again start to finish and it covers most of all of it, great info! I have been reading about it so much my mind is numb. Anyway, I have a wiring schematic for a 90 that seems to be pretty accurate to our 88 that has helped. We stripped the harness down today and unloaded the known unnecessary wiring but....

Wires/connectors I am unsure of at the moment:

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.

Tan 18g 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.

2nd purple single wire O2 sensor connector on pass side. Ditch or keep for future?

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.

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?

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?

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?

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.

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.

Thanks in advance! Sorry for the laundry list of dumb questions.

01-31-2009, 12:05 AM	#58
408cuda Registered User Join Date: Jan 2009 Location: White Creek NY Posts: 14	Re: Tbi swap build thread Sorry for the dumb questions guys. I looked the thread over again start to finish and it covers most of all of it, great info! I have been reading about it so much my mind is numb. Anyway, I have a wiring schematic for a 90 that seems to be pretty accurate to our 88 that has helped. We stripped the harness down today and unloaded the known unnecessary wiring but.... Wires/connectors I am unsure of at the moment: 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. Tan 18g 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. 2nd purple single wire O2 sensor connector on pass side. Ditch or keep for future? 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. 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? 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? 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? 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. 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. Thanks in advance! Sorry for the laundry list of dumb questions.