Low oil pressure?
08-26-2014, 05:26 PM
#11
Senior Member
The oil pump is driven directly by the turning of the engine. When you first turn on the ignition, there is no oil pressure because the engine is not turning. When you crank the engine it is turning but very slowly compared to running so it may still not register any pressure. Once it starts, it should show oil pressure within a few seconds at idle. It is customary to let the engine idle for a few seconds to be sure oil is circulating well before we drive. The gauge will stop increasing when full pressure is reached.
As you drive with the engine speed above idle, there should be an indication of more oil pressure. Each engine is a little different but the gauge should read somewhere around the mid point with no large and sudden fluctuations. As the engine warms up to operating temperature the oil pressure should drop some. It may seem quite low at idle but the light/ message should not illuminate with the engine running.
As you drive with the engine speed above idle, there should be an indication of more oil pressure. Each engine is a little different but the gauge should read somewhere around the mid point with no large and sudden fluctuations. As the engine warms up to operating temperature the oil pressure should drop some. It may seem quite low at idle but the light/ message should not illuminate with the engine running.
08-26-2014, 10:41 PM
#12
Low oil pressure warning during start up is not normal. It may not be indicative of a real lubrication problem but it certainly isn't normal or we'd all be seeing it. I have an 04 that has **** down 4 times while driving over the last 90k because of a low oil pressure warning. The cause is unknown. I can oddly enough make it stall by leaving it running with the gas cap off. It will give me a low oil pressure warning. What does fuel tank pressure have to do with oil pressure? I don't know but would love to hear a theory on that one.
08-27-2014, 06:35 AM
#13
Senior Member
08-27-2014, 07:52 AM
#14
What oil filter and viscosity/type of oil are you using? If you are using "thick" oil, it could be taking a second long to bring up pressure. The 5.4l recommends 5w20 - which is quite thin.
That said, you really should have it professionally checked - real/actual low oil pressure is nothing to ignore.
That said, you really should have it professionally checked - real/actual low oil pressure is nothing to ignore.
08-27-2014, 11:44 AM
#15
Senior Member
That indicator comes on when the ignition is first turned on, even before starting the engine. That is to test that it works. This indicator is controlled by the oil pressure sending unit by the oil filter. The sending unit is a mechanical switch that trips when it is actuated by 7psi of oil pressure. It doesn't indicated anything but "less than 7psi" or "more than 7psi". While you are starting the engine it isn't getting more than 7psi of pressure and the indicator will light. When it is running the light will turn off once the pressure builds to more than 7psi. The self test and boot sequence of the dash controller can take a few seconds, where the light is on for testing mode, and if you start the truck quickly, the dash can still be in test mode once the engine is running. This can explain part of what you are seeing. If you are running a filter with a silicone anti-drainback valve, you shouldn't hear more than a 1/2 second or so of valve clatter on start. If that's what you hear, chances are everything is good.
There is no actual variable oil pressure sending unit (0-100psi) in these truck engines. The gauge is just a dummy light with a needle. If pressure drops below 7psi the needle drops to zero and the warning light comes on.
The actual pressure can be checked by removing the switch and installing it in a tee, then adding an actual sending unit to the second part of the tee and installing it into the original port, but if it's just coming on a second or two when you start the truck, that's pretty much normal operation.
There is no actual variable oil pressure sending unit (0-100psi) in these truck engines. The gauge is just a dummy light with a needle. If pressure drops below 7psi the needle drops to zero and the warning light comes on.
The actual pressure can be checked by removing the switch and installing it in a tee, then adding an actual sending unit to the second part of the tee and installing it into the original port, but if it's just coming on a second or two when you start the truck, that's pretty much normal operation.
08-27-2014, 12:59 PM
#16
Mine does that on start up, and has for 10s of thousands of miles.
If it ever causes an issue, I'll let you know.
I'm my opinion, if it only comes of for a split second (literally less than one-one-thousand) when its turning over, that is NOT an issue. You can't expect the thing to have full oil pressure the second it begins to crank.
The "issue" lies in the fact that Ford didn't program the display to crank time into account.
If it ever causes an issue, I'll let you know.
I'm my opinion, if it only comes of for a split second (literally less than one-one-thousand) when its turning over, that is NOT an issue. You can't expect the thing to have full oil pressure the second it begins to crank.
The "issue" lies in the fact that Ford didn't program the display to crank time into account.
08-27-2014, 09:47 PM
#18
I have a 05 f150 lariat 4x4 with the 5.4, and it as well will flash Low Oil Pressure for a brief second at startup but only if i put the key in accessory position for a second or so before actually cranking it. It has 7qts of fresh 5w20 valvoline next gen conventional oil and a wix oil filter, I'm going to be changing out the solenoids and the oil switch in a few days, waiting for shipment to arrive and will report back. Truck has 241xxx miles, yeeeyeee!!!
