Oil pressure put a T and manual gauge on it and early in the morning and first start off runs good and normal later in the afternoon the oil pressure on the dash hits rock bottom but my manual gauge is reading right and gauge inside the tractor has recently been changed and it messes up the lift functions what could be the problem after you let sit awhile it goes back to running normal on a 8970 new holland tractor

No this is not a "computer running a test" You need to have the fuel pressure tested when you have these no start or hard start events.

so where your eyes look at to see 60, ?
the dash?
or a real gauge , at the block, port. (gallery)

you must learn 2 things, about dash gauges

1. they are not really instruments. not even close, more toy like.
2. and some return to zero others do NOT.

many cars made, you key off and the gauges, freeze.
this is nothing new and is normal.

use the scan tool yet and look for DTC errors from the cluster?
in any event.
id concerned about engine oil pressure , try a real gauge.
if concerned about just the dash gunge?, then scan it first. then do the self tests shown in the FSM.

this car the PCM sense oil pressure data via the PCI bus
to the cluster and then it displays this data.
im not sure which years return to zero.
the PCM gets its DATA from the oil pressure sender.
if the pCM shows the data to bee good using a scan tool
then we check for errors on the PCI buss. if that is good
the display is bad, if the data is wrong. there.

here is the path of data. in text
sender>>> pcm>>> pci bus>>>> cluster.>>> gauge.

see the FSM page , 1 or 9 pages just for the cluster. page 7

factory service manual or alldata.com
either.

Well it could be the sending unit for the gauge.
But odds are the oil pump or engine bearings are worn out.
As the engine warms up, the metal spaces expand and the oil gets thinner. The oil pressure drops some under normal conditions, but not more than 10 or 15psi. Normal idle pressure with the engine warmed up is probably 25psi.
You could check oil pressure with a mechanical gauge to make sure its not the sending unit.
Once the oil pressure starts staying below 20psi for long periods you'll start hearing noises.

Check fuel pressure at motor

Run some tests on fuel pump

Fuel pressure,volume,current or scope it
& check armature pattern for failing pump

• You have an oil pressure sending unit on your oil pan, just above the oil filter that could be going bad. Of course the oil pump could be going bad also but you can check the sending unit at home.

1. First check your oil level to make sure enough oil is circulating.
2. Now look at the oil sending unit and inspect to make sure the wires and connector look good.
3. Note that in the next step when you remove the connector, turn the car to on NOT START JUST ON and have a quick look at the gauge inside the cabin. It should be all the way up. If not you could have a connector problem.
4. To remove the oil sending unit by removing the connector and putting the proper deep socket on and twisting it out.
5. Now put an oil pressure gauge in where the sending unit was and start the car. Make sure there are NO leaks and now watch the gauge.
6. Now start the car and wait two minutes (roughly). If the pressure goes up to 50lbs (roughly) and stays then the sending unit itself is bad and needs replaced. Only let the car run lon enough to get a good reading then turn it off.
7. If the pressure is low and won't come up after a couple minutes of running then your oil pump could be failing.

• Hope this helps and thank you for using FixYa.

Regards, Tony

ur oil sending sensor is bad it reeds the oil pressure

Did you compare what your dash gauge read when it was acting up and compare it to the manual gauge at the same time? I know you said you used the manual gauge and it read fine so if you get a proper reading out of the manual gauge and an improper reading out of the dash gauge then your dash gauge needs addressed.

You need to have the oil pressure checked with a manual oil pressure gauge you may have a bad sending unit. If the you oil pressure is the same with the manual gauge then you have a oil pressure problem.

Sounds like an engine sensor, EGR valve or O2 sensor has failed. First thing to do is to look at the engine trouble codes to pin down the failure. You can usually borrow an OBD1 code checker from your local parts store.

HEY,
YOU SEEM TO BE ON THE RIGHT TRACK. I WOULD START WITH THE SENDING UNITS. GM LOVES TO PUT TWO OF THE ON A CAR. ONE FOR THE GUAGE AND ONE FOR THE DASH LIGHT. UNLESS YOU HAVE NOTICED ANY BIG CHANGES IN OIL PRESSURE I WOULD THINK IT IS THE SENDER(SWITCH) FOR THE LIGHT. THEY ARE NORMALLY LOCATED AROUND THE AREA OF THE OIL FILTER HOUSING.