Oil pressure gauge is showing 240 on start

If it is the oil pressure warning light showing, the next thing to do is to remove the oil pressure sender unit and screw in a gauge to see if the sender is at fault.


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After that it could be that the over-pressure relief valve in the oil pump has stuck open.

see this tips and fix it. God bless you
The oil pump supplies oil to lubricate your engine. If the oil pump is worn or is not turning, the engine will suffer a loss of oil pressure, which may result in engine damage or engine failure.
The first sign of trouble may be a low oil pressure warning light, a drop in the normal reading on you oil pressure gauge (if your car has one), or the appearance of ticking or clattering sounds from your engine.
As a rule, most engines only need about 10 PSI of oil pressure for every 1,000 RPM of engine speed. Oil pressure will read higher than normal when a cold engine is first started because the oil is thick. Oil pressure will gradually drop as the engine warms up and the oil thins out. So normal oil pressure on a warm engine cruising down the highway is typically 30 PSI up to 45 PSI.
SYMPTOMS OF OIL PUMP TROUBLE
The first thing you should do if any of these symptoms occur is to stop your car, turn off the engine, let it sit for a few minutes, then check the oil level on the dipstick. If the oil level is at or below the ADD line, add a quart of oil to bring the level back up to the full mark. Add as much oil as is needed to raise the level to the full mark. Then restart the engine. If the warning light remains on, or the oil pressure reading does not climb back up to its normal range, or the engine noise does not go away, you may have a bad oil pump.
The other possibilities include a bad oil pressure sending unit, or a problem with the oil pressure warning light circuit or oil pressure gauge.
OIL PRESSURE SENDING UNIT
If the engine is NOT making any unusual noises and seems to be running normally, and the oil level on the dipstick is FULL, but you are still getting a low oil pressure warning light or low gauge reading, the fault could be a bad oil pressure sending unit.
The oil pressure sending unit is mounted on the engine block. On some applications, there is a spring-loaded pressure-sensitive diaphragm with a switch inside the sending unit. This switch completes the circuit to the low oil pressure warning light if oil pressure drops below a certain threshold. The unit may stop working if the diaphragm inside fails, if the switch is stuck, if the small hole that allows oil to enter the sending unit becomes plugged, if there is a loose, corroded or broken wiring connector at the sending unit, or there is a fault in the wiring circuit between the sending unit and warming light.
On vehicles that have an oil pressure gauge (electronic, not mechanical), the oil pressure sending unit has a small rheostat inside that sends a variable voltage signal to the oil pressure gauge when the diaphragm moves. A worn spot on the rheostat or any of the other problems just described for the simple pressure-type oil pressure switches can cause a problem.
FORD'S FAKE OIL PRESSURE GAUGE
On many Ford vehicles that were built from 1980 through the 1990s, the oil pressure sending unit has two switches, a low pressure and a high pressure. These vehicles also have an oil pressure gauge, but the reading on the gauge is not a true indication of real oil pressure. As long as the pressure to the sending unit is between high and low, the gauge will read normal. If oil pressure drops and trips the low pressure switch, the dash gauge will now read low. Or, if oil pressure goes up and trips the high switch inside the sending unit, the dash gauge will read high. Consequently, don't rely on the oil pressure gauge for an accurate reading in these vehicles. It is only a gross indication if the oil pressure is low, normal or high.
OIL GAUGE PROBLEMS
If the engine is NOT making any unusual noises and seems to be running normally, the oil level on the dipstick is FULL, and you have replaced the oil pressure sending unit but are still getting a low oil pressure reading on the dash gauge, the fault could be in the wiring circuit between the sending unit and gauge, or the gauge itself might be bad.
Check the wiring connections on both ends as well as wiring continuity between the sending unit and gauge. If no wiring faults are found, hook up a pressure gauge directly to the oil pressure port on the engine and check oil pressure with the engine running. If the engine-mounted gauge shows normal oil pressure but the dash gauge is reading low, the problem is a bad dash gauge.
On the other hand, if the engine-mounted pressure gauge reads low and you have done all of the above, chances are the oil pump is worn, or it is not picking up enough oil because of a restriction or blockage in the pickup screen in the bottom of the crankcase.
OIL PUMP PICKUP PROBLEMS
The pickup tube has a screen on the end to prevent large chunks of anything bad that ends up in the crankcase from being sucked into the pump. But we are talking BIG chunks of debris, not normal wear particles or carbon or dust or other microscopic-sized abrasive particles that can cause pump wear over time.

replace the oil pressure senor they alway's fail on gm cars and trucks

I just recently had the same problem with my 06 Tahoe .. I replaced the oil sending
unit and fixed the problem.

When you had the pump replaced did anyone look at the rod and main bearings? 99% of all low oil pressure problems I've seen has been directly related to bearing wear, not a bad oil pump.
Replacing the pump will give you slightly better pressure temporarily but that won't last very long.
Verify the actual oil pressure using an external mechanical gauge. If it's low (likely it is) go back into the oil pan and use plasti-gage on the bearings to measure clearances.
In reality though, in an engine with that many miles, it's best to either completely rebuild or replace it though.

Seems to be an issue on mopars, i have a 92 plymouth voyager that does the same thing. had a mechanic check everything including pressure and found no problems. dont worry about it unless it drops to zero.

If the valve lifters are quiet you most likely have oil pressure even with gauge showing "0".Sounds like the oil pressure switch going bad.I would try that first.

The vehicle won't start without oil pressure. You'll need to check the oil, see if it's there, then determine where it went if gone or too low. If the oil is full & the light won't go out as you crank the vehicle, there is the possibility of the switch being bad, or internal engine problems. If you have an Oil pressure gauge also, if it's showing pressure you may want to just replace the oil pressure sending unit first

I suggest you start with just checking the area & make sure the wire to the oil sending unit hasn't become disconnected due to something striking it/breaking it. If it is intact, first choice would be to test the switch, then do a pressure test on the oil system to determine that you have pressure. If you have pressure, replace the switch.

good luck

ur oil pump may be failin-there r sensors everywhere on new cars-keepin u from starting as safety measure-computer systems r complex n things dont always show on 1 scan-they kinda hav the mindset of a pc

Hook up a manifold gauge (mechanical temporary use gauge, used by mechanics) and test the oil pressure. You probably need to replace the gauge. The computer sends info through a printed circuit board behind gauge cluster and sometimes you have to replace the whole gauge cluster.