Hello all,

I have an 87 Iroc that I'm removing the computer from because I'm putting an older 350 in, along with that, I'm removing all of the associated wiring that came from the computer. I am looking for a complete wiring diagram because 7 of the wires are spliced into the wiring harness that runs towards the drivers side under the dash, and so I can wire the dual fans and fuel pump from scratch. I have done allot of research on here, but maybe not enough. I have read many posts about people running their factory fuel pumps to a 3 way valve with regulator, my question is, do you leave the fuel pump running the entire time the car is on (I don't want the pump to smoke itself by not shutting off at pressure)? Or does the computer have a built in cutoff point that I'll be removing? I plan on wiring the fuel pump to a hidden switch. Years back I bought what was suppose to be a complete wiring diagram from some guy on ebay, but it doesn't come even close to covering all the wiring. Thanks allot for any input you guys may have.

 

A smart person would use the factory oil pressure switch so that as soon as the engine is cranked over ,
the pump runs and as soon as the engine stops so does the fuel pump.
A carb engine doesn't need the pump to prime 1st like injection does , the engine will fire on the fuel
in the carb bowl , just like a engine with a mech fuel pump does
Secret cutout switch can still be used anywhere in the fuel pump wiring between the battery and the pump

If you have a auto need to read this
https://www.thirdgen.org/newdesign/t...ueswitch.shtml

 

That is a smart idea. Just one question, the oil pressure switch runs the gauge pressure right? So, will the oil pressure switch give a strong enough signal to activate the fuel pressure relay? It's smart people like you that make me come here, I'm forever learning, thanks.

 

So is that link how we hook out torque converter lockup back up?

 

Oh ya, I meant to comment on that too. I'm good with that, I have reviewed that post berfore as well. Thanks for pointing it out though. Wish someone had an answer to whether or not the oil pressure switch which controls gauge signal will work for the fuel pump relay? Or, I'll just wire it up, put 40 psi to the switch via my air compressor and see if it works. Any body have any other ideas? I'll take any help I can get. Thanks again for the help.

 

No
Early cars had a OP switch (2 wire ) for the fuel pump and a separate gauge sender unit (1 wire )
Later cars combined both in a single 3 wire unit but they are still completely seperate circuits unrelated to each other

It would but you don't use or need a relay , ( something else to stuff up on the road )
just run fused 12V power through the OP switch to the pump ( and install your cutout witch somewhere on the circuit )

You only need the OP switch wiring , check out the circuit diagram here
https://www.thirdgen.org/forums/post...612-post2.html

 

Bumb

 

You guys are awesome, but I read several times that using relays is better than running hot eleictrical leads into the car. What is your stance on this?

 

Yes you do not want to be running hot wires around like that.

Use ground trigger wires to relays.

You wouldnt be interested in a complete custom harness for your setup would you ?

 

Not for what I'm doing. Only reason for getting rid of all the old wires is just to clean up the place a bit. What I am interested in is a complete wiring diagram of the entire car. The 3 page one from autozones website cannot be the whole thing, way too much missing off of it.

Ground trigger wire? Sorry, no clue.

 

well i hope i can help u whit the wires...i resently remove my ecu wires but my car was ecu controled rochester...any way all cabels that got to passinger side fender are gone exsept 2 that are coming from the transmision swich for reverse lights...now i did not had any cables going to the driver side but i would folow them see where they go...about the fuel pump i would make it whit the oil swich like sug above...its a good fail safe too

 

Relays use a ground and hot wire to make the connection.

You wire the relay coil side so that the hot is ignition hot from another wire under the hood, then your switch is hooked up to the relay on one terminal, and ground on the other. that way you arent running hot wires all over the place.

 

Ok, that makes sense. I seen some wiring diagrams for that already. That is what I was planning on doing. Thanks for the help.

 

No different than the original factory wiring,
the pump relay is only there so the ECM can operate the pump to prime the rails when the key is first turned on

 

The relay stays hot it doesnt just prime, the fuel pump pressure switch is a redundant safety that was done away with on newer cars.

Yes indeed the factory fuel pump wiring, which is routed through a factory grommet and factory protection is activated by a hot wire.

However fan relays and a/c relays are ground actuated, as well as most vehicles relay systems.

When adding something in, people dont often follow the best protection and routing practices, and it is best to just use ground to trigger the relay, then if something gets shorted out due to poor routing, its just going to turn on, rather than test if someone fused things properly.