- Location
- Charlotte NC
1988 MJ, 4.0 renix. 5 speed manual with full set of gauges.
When I purchased this fine piece of equipment the oil pressure gauge was pegged with engine running. I popped the hood and noticed immediately that the sending unit was definitely original with 193k. So being the super smart person I am I replaced it! Of course it didn't fix the issue. So I decided I should step up my brain power and check the wiring to the sending unit.
Wire to sending unit with KOEO is 5 volts, then with the KOER it reads 11.88 volts. Pretty standard I would imagine. So I began to think to myself "their is no way in hell I have been driving this thing with a pegged gauge for this long and haven't blown anything up, if the gauge is in fact accurate"
I then hop in the car and take a ride to advanced auto and pick up a sunpro oil pressure gauge to test what we got for oil pressure! I plugged the new gauge into the new sending unit and fire the engine up. Engine cold we got 40psi! perfection, I am happy with it. We draw the line from there into the interior...
Kicking the brain into 5th gear now, before removing anything I inspected all the wiring going into the gauges and the gauges themselves for tampering or burning and everything seems to be legit.
I then take out and replace the oil pressure gauge with a junkyard one (as a matter of fact I have 3 junkyard gauges to try). I do the KOEO test and the gauge sweeps to zero, I then fire the engine. Pegs back to 80 psi! So, I figure "okay, bad junkyard gauge." -Of course that's not the case, I replace it with all 3 gauges and still the same thing.
Lets move back to the engine bay area where we started. I do a little test. KOEO with the sender plugged in, the gauge goes to 0 (where it should be) I then unplug the sender and the gauge pegs to 80psi still with the KOEO. I then take a jumper and jump the oil pressure sender wire to the battery ground (koeo still) the gauge goes back to 0. This indicates to me that I have a bad sending unit. Being brand new I find this hard to believe.
IN CONCLUSION: the oil pressure gauges sweeps properly with engine not running. While engine running the gauge pegs immediately. Put new sending unit in and still had same issue. checked oil pressure at new sending unit with a manual gauge and reads 40 psi when cold which is normal. Checked wire into sending unit and voltage is fine. Swapped out oil pressure gauge and still have same issue. Rechecked brand new sending unit with simple test of unplugging and grounding the circuit and the unit failed the test.
any further tests/opinions/complaints/mockery anyone has to offer would be greatly appreciated.
Without any further opinions I will replace the sending unit with a dealer issued part and/or go deeper into the wiring schematics of this pig.
:hang:
When I purchased this fine piece of equipment the oil pressure gauge was pegged with engine running. I popped the hood and noticed immediately that the sending unit was definitely original with 193k. So being the super smart person I am I replaced it! Of course it didn't fix the issue. So I decided I should step up my brain power and check the wiring to the sending unit.
Wire to sending unit with KOEO is 5 volts, then with the KOER it reads 11.88 volts. Pretty standard I would imagine. So I began to think to myself "their is no way in hell I have been driving this thing with a pegged gauge for this long and haven't blown anything up, if the gauge is in fact accurate"
I then hop in the car and take a ride to advanced auto and pick up a sunpro oil pressure gauge to test what we got for oil pressure! I plugged the new gauge into the new sending unit and fire the engine up. Engine cold we got 40psi! perfection, I am happy with it. We draw the line from there into the interior...
Kicking the brain into 5th gear now, before removing anything I inspected all the wiring going into the gauges and the gauges themselves for tampering or burning and everything seems to be legit.
I then take out and replace the oil pressure gauge with a junkyard one (as a matter of fact I have 3 junkyard gauges to try). I do the KOEO test and the gauge sweeps to zero, I then fire the engine. Pegs back to 80 psi! So, I figure "okay, bad junkyard gauge." -Of course that's not the case, I replace it with all 3 gauges and still the same thing.
Lets move back to the engine bay area where we started. I do a little test. KOEO with the sender plugged in, the gauge goes to 0 (where it should be) I then unplug the sender and the gauge pegs to 80psi still with the KOEO. I then take a jumper and jump the oil pressure sender wire to the battery ground (koeo still) the gauge goes back to 0. This indicates to me that I have a bad sending unit. Being brand new I find this hard to believe.
IN CONCLUSION: the oil pressure gauges sweeps properly with engine not running. While engine running the gauge pegs immediately. Put new sending unit in and still had same issue. checked oil pressure at new sending unit with a manual gauge and reads 40 psi when cold which is normal. Checked wire into sending unit and voltage is fine. Swapped out oil pressure gauge and still have same issue. Rechecked brand new sending unit with simple test of unplugging and grounding the circuit and the unit failed the test.
any further tests/opinions/complaints/mockery anyone has to offer would be greatly appreciated.
Without any further opinions I will replace the sending unit with a dealer issued part and/or go deeper into the wiring schematics of this pig.
:hang: