Help with 5.3 swap!

[Clayman]

Also another question I have is my oil pressure gage... I plugged the obs sender in the hole the nbs sender came out of... with the help of an adapter but now my oil pressure gage is pegged all the way past 80 in the dash and when I turn the key on it don't move. Any ideas?!

[gagliano7]

Also another question I have is my oil pressure gage... I plugged the obs sender in the hole the nbs sender came out of... with the help of an adapter but now my oil pressure gage is pegged all the way past 80 in the dash and when I turn the key on it don't move. Any ideas?!

I had the same problem.Make sure all three wires to the sensor are wired.I had no power going to the gray wire which on my 92 goes to the fuel pump.If there is no oil pressure it will shut off the fuel pump so the motor doesn't blow.Without that gray wire connected the oil gauge won't work.

[Clayman]

The gray wires all go back to a big soldered twist it looks like and one wire comes from that cluster and went to the obs pcm... are you saying I need to hook that wire to the pcm or do I just need to make sure it has power when the truck is on?

[gagliano7]

The gray wire coming off oil temp sensor ties in to the fuel pump relay in the wiring harness in the engine compartment behind the bacck of the engine.If you eliminated the old relay and fuel pump fuse you probably disconnenected the wire.If you want give me a call 845 753 2720 ext 24412

[89sierra]

i cant say anything about the vats but i had a similar problem with my setup. if i was not running the oil pressure sensor it would not send signal to the fuel pump. it would start then die off. on the firewall on the passenger side under the black cover. or power block their is a fuel a pump relay which which you can power up or there is a fuse to, that i believe if you power up the brown wire it will send constant voltage to the fuel pump. you can test this to eliminate if its a fuel problem

[Clayman]

i cant say anything about the vats but i had a similar problem with my setup. if i was not running the oil pressure sensor it would not send signal to the fuel pump. it would start then die off. on the firewall on the passenger side under the black cover. or power block their is a fuel a pump relay which which you can power up or there is a fuse to, that i believe if you power up the brown wire it will send constant voltage to the fuel pump. you can test this to eliminate if its a fuel problem

How long would it stay running before you fixed this problem? Ill have to dig out my diagrams again and do work but im really hoping its the vats. As soon as the new ecm gets in ill see exactly what it is!!

[89sierra]

it would fire right up run for like 2-3 seconds maybe then die. fire right back up then die. but if you have a new computer coming i would wait for that and give it a try.

[00shortbox]

Yeah sounds like a VATS problem, get Nelson to delete it in the tune... as for the oil pressure gauge, use a factory 5.3 sender, should fix you up. I know my LS6 is the same, I used a CTS V sender and it is pegged over 80, just have to swap it for a truck sender to match the harness.

[Clayman]

Yeah sounds like a VATS problem, get Nelson to delete it in the tune... as for the oil pressure gauge, use a factory 5.3 sender, should fix you up. I know my LS6 is the same, I used a CTS V sender and it is pegged over 80, just have to swap it for a truck sender to match the harness.

I got those problems fixed a couple weeks ago... my new pcm came in yesterday so the vats is a nonissue now but thanks for the tips!!