1988 tbi harness wiring/plug questions

[stackz]

couple more questions.

harness is from a 1988 4.3 manual truck. I'm down to the last couple of things.

The blue wire coming off the ESC at terminal E:
http://www.gearhead-efi.com/gearhead...ng/747ecm5.jpg
is cut on my harness. do I need a knock sensor? can I bypass it if I need it or will it run regardless as I will need to harvest a plug from the u-pull which will be a bit before I can get back there.

second, I think this two prong plug with a pink/black wire and a cut (either brown or gray, I honestly cant really tell it seems to change in the lighting) is for the EAC solenoid. the brown wire is cut so no clue. I will try to finish ohm'ing the pink/black wire tomorrow as well. just seeing if anyone recognizes this plug. If it is the EAC, what is this sensor? do I need it? can I leave it out? I cant even find a pic of this thing online lol.
20240416_144503.jpg20240416_144622.jpg747ecm5.jpg

next, the fuel pump relay...again....I cant figure out what happens with the red/white strip wire? no clue as it is cut. I believe its the same as the "red" wire here though?:
http://www.gearhead-efi.com/gearhead...ng/747ecm4.jpg

the one coming from terminal C of the fuel pump relay in the diagram that goes I think to ALDL terminal "G"?? is this correct? If so, it looks kinda off but at the same time I'm really not sure how to read this relay diagram (I did not mess with the wiring to it though just fyi). when I look at the back of this thing as opposed to the front, it looks like the red/white is coming from terminal D? ugh.
20240416_144405.jpg20240416_144401.jpg

and finally, a pic of my mocked up mess that is hopefully about ready to test fire (59 chevy 235 inline-6):
20240416_114937.jpg

[MO LS Noobie]

EAC=Electronic Air Control - it controls the solenoid that controls the air pump flow, it can be safely eliminated for your application, I am assuming you have eliminated the air pump.

You can safely run the vehicle without the knock sensors, but it will turn on the check engine light. You can modify the ECM to eliminate the knock sensors or you can run it as is for initial testing and add a knock sensor later, but for it to function correctly it would need to be the right sensor for the engine, not likely to happen.

In as far as the red and white wire you would need to trace and out and see where it originates, possibly the fuel pump test connector (ckt 490) which is only used to bypass the oil pressure switch and the fuel pump relay to send power directly to the fuel pump.

[stackz]

ok, its definitely the EAC solenoid. per the wiring diagram, I probed the B terminal of the ESC (pink/black) to the pink/black at this connector and they have continuity. I then chased from the egr plug to the ecu connector and it plugs into A6.

From the EGR I traced the gray wire to the ecu and it does connect at A4 and does have continuity. Then while doing this, I thought to look through the box of parts I grabbed on my last upull trip. They had a 1990 truck that had just been dropped and I grabbed all of the sensors from the top half of it, I guess this is the EAC solenoid? it plugs in and has vacuum connectors on both sides. I will just cut it out of the harness and put shrink wrap on the end.

for now I will just label the blue knock sensor wire and tuck it away.

now I guess its time to finally figure out the fuel pump relay finally. thats about all I have left to do aside from pull signal for the computer from the msd 6a box.

[MO LS Noobie]

Relay can this be an ordinary relay with a suppression resistor built in, a normal ice cube relay that has is 5 terminal is all you need. The wiring diagram is correct, but confusing.

https://www.amazon.com/Recoil-Automo...s%2C130&sr=8-8

Take normally closed contact and make that the "test" terminal if desired. The common terminal to the fuel pump and the normally open contact to B positive (fused).

[stackz]

yeah I've got a couple of them with plugs I snatched from other cars and will go that route if I cant stick with the oem pre-wired relay.

on another note. I have this diagram I found as well:
0996b43f80231a25.jpg

A6 (pink/black) is switched ecu power. is B1 (orange) constant power or memory power? do these computers retain constant power?

and do I need to worry about whatever the hot fuel module is? I want to say I dont as I think that just power the oem dash gauge??

I see how the starter has a purple/white coming from it going to the ecu. purple/white at the ecu is B5. do I tie into this?

I also see the purple from the ignition switch. I assume that is the "ignition switch on" position so I would tie from the ignition switch to all of the following: pink at coil, A6, B1 right?

[MO LS Noobie]

yeah I've got a couple of them with plugs I snatched from other cars and will go that route if I cant stick with the oem pre-wired relay.

on another note. I have this diagram I found as well:
0996b43f80231a25.jpg

A6 (pink/black) is switched ecu power. is B1 (orange) constant power or memory power? do these computers retain constant power? YES, "ECM B" FUSED B+

and do I need to worry about whatever the hot fuel module is? I want to say I dont as I think that just power the oem dash gauge?? CORRECT

I see how the starter has a purple/white coming from it going to the ecu. purple/white at the ecu is B5. do I tie into this? NO, IGNITION SWITCH "S" TO STARTER PRPLE WIRE. P/W WIRE IS FEED TO ECM FOR CRANK SIGNAL.

I also see the purple from the ignition switch. I assume that is the "ignition switch on" position WRONG, SEE ABVE. so I would tie from the ignition switch to all of the following: pink at coil, A6, B1 right?

"ECM 1" is only hot in start/crank. Make sense?

[stackz]

"ECM 1" is only hot in start/crank. Make sense?

Yeah I get that,I can't tell if the hot in run by ecm b is for that or the hot fuel module. If it's not then that would be 10a memory power

[MO LS Noobie]

Keep Alive, Memory Power, B+ all mean it is fused battery positive.

Hot in run/crank is the ignition/injector power that is only hot with key in crank or run position. Not ACC or OFF.

See reply above with in quoted text IN ALL CAPS.

HTH, Jeff

[stackz]

Keep Alive, Memory Power, B+ all mean it is fused battery positive.

Hot in run/crank is the ignition/injector power that is only hot with key in crank or run position. Not ACC or OFF.

See reply above with in quoted text IN ALL CAPS.


HTH, Jeff

Thanks, didn't even notice you modified the quoted text on my phone lol