Oil pressure gauge problem?

[mwood65]

I have always had good oil pressure in my 74 Cherokee and the stock gauge worked fine.
4 days ago the gauge quite working and I am sure I have oil pressure still.
After the Jeep sits a few day and I start it the top end clatters for a few seconds after I start it then after about 5 seconds it quits making noise once oil gets up there. It still does and when driving it makes zero noise and runs perfect.
I replaced the sending unit and still no gauge action except it starts pegged at the bottom and when I start it it goes up to just above zero (1-5 psi?)
and it jiggles around a tine bit.
I pulled the dash out and the plug on the back is tight and seems fine.
Is there a way to test the gauge itself?
On the wiring schematic it shows the circuit goes to the dash then to the radio noise suppressor or am I reading it wrong, and why the radio noise suppressor? Is than just where it grounds to?

[wiley-moeracing]

Are you using a oil filter with a check valve in it?

[Tripwire]

buy a cheap ass mechanical one for a test...then run from there? clattering is a bad sign, could be as simple as lifter bleeddown?

[mwood65]

Are you using a oil filter with a check valve in it?

??? Using a Wix filter

[mwood65]

buy a cheap ass mechanical one for a test...then run from there? clattering is a bad sign, could be as simple as lifter bleeddown?

I guess I will just get a set of guages and mount them under dash. And yeah, I think one or more lifters are bleeding down when it sits for a few days or weeks

[babywag]

easy test to check wiring is good/gauge functional...
@sending unit wire should have ~6v key on engine off.
if yes wiring to sender from gauge probably good
if no have an issue with cluster/gauge/wiring

if voltage is present @sender wire momentarily grounding it should peg gauge.
do not keep it grounded only momentarily!!

[mwood65]

easy test to check wiring is good/gauge functional...
@sending unit wire should have ~6v key on engine off.
if yes wiring to sender from gauge probably good
if no have an issue with cluster/gauge/wiring

if voltage is present @sender wire momentarily grounding it should peg gauge.
do not keep it grounded only momentarily!!

Alrighty! I will check it out but still am going with new gauges I believe, mechanical ones not electric.

[letank]

check the TSM, section 3 (the second part)

https://oljeep.com/edge_74_tsm.html

The 78 manual has much better schematics for debugging, page 353 for the oil pressure

https://oljeep.com/gw/78_tsm/1978_JeepShopManualComplete.pdf

[letank]

Otherwise the quick and dirty is to connect your DVM on ohm scale directly to the sender unit on the engine, one probe to ground the other to the top of the sender signal pin output (yes disconnect the oil sender wire). Secure your leads away from moving parts such as fan and belt... crank and start the engine... depending on oil temperature, at 50ish you should read around 28 ohms which is the mid range of 40 psi, 15 to 18 for the higher pressure of 60 psi