1990 4.0 no oil pressure

[mifordguy]

i have a 1990 ranger 4.0 2wd with 170k on it, recently in Michigan it has been around 5 degrees without windchill, when starting my truck cold, oil pressure gauge doesn't move at all, i am running 5w30 oil, fram high mileage filter, and i just put a new oil pressure sending unit in, still the gauge only shows it has oil pressure once the engine reaches operating temp. could i have a clogged pump?

 

[tyler.lee132]

I'm having the same issue with my 2000 4.0 4wd with 142k on it. Any help would be greatly appreciated

 

[RonD]

Are the rockers/valve train making the "ticking" sound, if not oil pressure is OK.

The valve train has the lowest oil pressure in the engine all the time, if pressure was 0 they would be ticking like crazy.

If they are then you will need to shut down engine until you can figure out why.

If they are not ticking then either gauge is bad, wire is bad or switch/sender is bad, senders oil hole could be getting clogged up.

New no longer means "it works"
New now means it has NEVER been tested, you are the first one to see if this new part will work

 

[tyler.lee132]

Why's it only happen when it's cold?

 

[RonD]

Don't know, could be wiring or gauge, the oil pressure "sender" is an on/off switch.
It could also be the oil IN the switch is to thick to push switch "closed"

Switch is off when engine is off so the gauge shows 0
When engine starts and oil pressure is above 5psi switch is on, this grounds the gauge.
On the back of the gauge is a 20ohm resistor, which will show 40% on the gauge when grounded, so just below 1/2.

The important thing is if you hear valve train noise when engine is cold, if you do then oil pressure IS low, if you don't then it is an electrical issue or oil IN the switch is too thick.

Pre-'95 oil gauges can be converted to real oil pressure gauges, the 20ohm resistor can be by-passed and a PS60 sender($15) can be installed instead of the oil switch.

 

[cp2295]

I had that issue too. I replaced it with a mechanical oil gauge and no problems since. Gives you exact psi, much nicer