First time swap. LQ9 into 95 OBS

[Mickeymotormount]

You can use the new pump. Just be sure the low pressure(return) goes to the center of the pump. I found this out the hard way. My original pump for the 6.0 was used to power the Hydro boost brakes as well. So I had two return nipples to choose from on the pump. I chose the one on the top and brazed the center one closed. After running it, the pump whined like it had no fluid. Turned out the return nipple I chose was dumping fluid into the pump and aerating the fluid. That's when I looked at other pumps and found they all had the returns to the center of the pump. Eliminates aeration of the fluid and feeds the center of the pump all at the same time.

[kewljay223]

i hate learning lessons the hard way.... thanks for the heads up. so i should plumb the return to the center, cap off the top since its not needed, and the remaining will be the high pressure supply to the gear box correct?

[Mickeymotormount]

i hate learning lessons the hard way.... thanks for the heads up. so i should plumb the return to the center, cap off the top since its not needed, and the remaining will be the high pressure supply to the gear box correct?

Yes, cap off the top return nipple and use the one closest to the center of the pump. And plumb the pressure line right to the power steering box.

[kewljay223]

cool man. thanks alot. im gonna have to buy you a pack of beer after i get this thing started. youve been a great deal of help. too bad your on the other side of the country!!! but like i had to go to texas, maybe ill end up in PA somtime. if so ill give you a ring, we can drink some brews and maybe go race!!!! not necesarily in that order...

[Mickeymotormount]

Sounds like a plan!!!

[kewljay223]

so i was doing some double checking on my wiring to see if i missed anything and i came accross the oil pressure sensor and came up with a few questions. mostly more for learning purposes.

1) i will be using my old sensor in order to run my gauge. but i see on the escalade diagrams that the LS sensor also has 3 wires but they all go to the pcm (5v+, sig in, gnd) im assuming the pcm takes the signal and outputs it to the gauge cluster. but does it also use that signal for anything else? will it freak out when it doesnt see oil pressure and shut the motor down?

2) if i plug in a scan tool and want to view live readings, im assuming it will show zero since the pcm is getting nothing? im looking into running a digital dash by utilizing the obd2 info so im sure i will need this to work. can i just use a T-fitting and run both sensors or put one in place of a plug elsewhere or???? anyone doing this?

3) and lastly this kinda has to do with number 1. the old sensor has the "fuel cutoff" built in but the new one does not. did gm just do away with it? or is it somehow built into the pcm by taking the info from the oil sensor and then controlling the fuel circuit electronically rather than the mechanical switch?

thanks

[Mickeymotormount]

1) From what I have read, the LS PCM doesn't require a signal from the oil pressure sensor. At least on the older ones. Not sure of the newer ones. Mine is not hooked to the PCM either.
2)You can always use a "T" to use all your sensors. Not sure if your digital dash will interpret the signals from the PCM though.
3)I just hooked up the existing sensor plug on my old harness to the old sensor that I installed at the back of the block on the top. I didn't think much about the fuel cutoff since it probably goes to the old PCM and that is not used.

[kewljay223]

well if you look at the diagrams the fuel cutoff switch gets power from a fuse at all times. when the engine has oil pressure, the switch will close and supply power to fuel pump. thats how it keeps running after the initial 2 seconds from the pcm. so if the old sender wasnt used, i dont see how the pump will keep running. thats what leads me to believe its somehow now controlled by the pcm. but if people are running without the oil sensor, then maybe im wrong or they have the fuel pump relay wired differently. like i said, this doesnt really affect me since i know how im going to wire it up, it was more to gain the knowledge of how the newer systems work if anyone knew. i like learing this stuff.

and as for the digital dash, there will be a pc in the car with obd software on it that plugs into the DLC and reads all the info from pcm. it will then just send the info to a screen i will mount in front of my cluster that shows all the gauges. kinda like on a dyno computer. but thtats a whole different topic. i just figured since the software will be getting the info from my pcm, it would need the oil pressure info. and without running both sensors, how else does the pcm know what the pressure is?

[Mickeymotormount]

Since the fuel pump relay will now be powered up by the new PCM, the fuel cutoff is irrelevent. Unless, of course, the newer PCMs need the signal from the oil pressure sender. Not sure though.

The digital dash sounds cool. I would love to see pics of it when it's up and going. And as for the sensor, you apparently will need it so the PCM will "know" what the oil pressure is in order to send the signal to get the oil pressure guage in your digital dash to work.

[kewljay223]

i dont want to start a whole new thing over this but if you look at the diagram you can see once the pressure sensor reaches a certain psi (4+ from what ive read) the switch will close and let power to continue to supply the fuel pump. without it idk how else it can continually run. from what i see, all the pcm does is supply power to the pump relay (for 2 sec or so) on the dk grn wire for the initial buildup of fuel pressure to get the motor started. so either the old pcm OR the new does the same thing in respect to "just getting it stared". thats where i dont understand how the new systems run without the old sender or doing a bunch of re-wiring to bypass this.


and this is a pic of what i mean for the digi dash. but the beauty of it is that you can customize it how you want. i.e.custom colors, displaying only gauges/lights you want, placing gauges in whatever location, etc... really cool stuff