Low oil pressure

My info shows 6 psi@1000rpms. Shows 18 psi@2000rpms. MOD shows these specs. They are probably minimum specs, so the reading could be a little higher. These databases are not always correct, but, I don't carry these specs in my head, so I have to look it up.

The oil pump is the last thing to think about. First, have the oil pressure checked with a mechanical gauge to see if it really is low. If it's okay, suspect the sending unit. If the pressure is low, suspect worn bearings. The clue to worn bearings is the oil pressure will come back up when you raise engine speed a little. Typically a defective sending unit that's reading low will do it at any engine speed.

The bearings are thin curved strips of metal that sit between the crankshaft "journals" and the connecting rods, and between the engine block and crankshaft. They usually have three layers of metal. The first layer is real soft so dirt and grit embed in it rather than going around and scratching the polished surface of the crankshaft journals. The next layers are harder to absorb impact.

The gap, or "clearance" between a bearing and the metal part riding on it is very tight; in the order of.005". Oil is forced into that gap under pressure to isolate the moving parts from each other. That oil oozes out the sides, then falls back into the oil pan or gets whipped around to coat other areas, namely the cylinder walls.

The oil pressure is maintained because it's hard to push the oil through the tight clearances. Anything that makes it easier for the oil to run out will result in lower pressure. Oil gets thinner when it gets warm. That lets it run out faster, so the volume being pumped has to increase. Most oil pumps have no problem pumping enough volume, but with low pressure, those moving metal parts can start to make contact. The soft first layer of metal begins to rub off of the bearings. You can actually see that as a significantly discolored area. The missing metal results in increased clearance so the oil can run out even easier and will be less effective at isolating the moving parts. Once that wear starts, it accelerates real fast until you hear a knocking noise from the parts banging against each other.

If this is caught early enough, sometimes new bearings can be installed and the wear stops taking place. That has to be done before the journals becomes scored or scratched. Any roughness on a journal will tear up the new bearing. For a V-8 engine, the crankshaft sits on five bearings, and there's eight connecting rod bearings. It only takes one of them to be worn to allow the oil to run out too fast and cause low pressure.

Depending on the engine design, there are usually five or six camshaft bearings too. Those get oil in such a way that there's not much pressure left. They don't have to handle the same pounding forces as the other bearings so they rarely cause a problem.

Whats your engine size? 4.8 or a 5.3, also to make sure Im looking at the right picture is the oil pump mounted to the crankshaft

Yup. You got it right. For Ford products replacing the bearings is a major job because the engine has to be lifted to get the oil pan off. For yours, and most other brands replacing bearings can often be done in half a day. Once it gets bad enough that the crankshaft is damaged, the engine has to be removed, and the job is sufficiently involved that you might as well do a total rebuild.

Whats your engine size? 4.8 or a 5.3, also to make sure Im looking at the right picture is the oil pump mounted to the crankshaft[/quote:53e4c893e5][/quote:53e4c893e5]

yes you do have to prime it, you fill it full of oil and then use clean fresh white lithium grease to keep it in there( cover the holes with it )

Make sure the oil level is full. Check the oil pressure with a test gauge. If there is no pressure, replace the oil pump. If the pressure is good then goes away, check the main and rod and cam bearings. You could also check the seal on the oil pickup tube. Make sure it isn't damaged.

Yes with white lithium grease in a tub then install it, before putting everything back together see if you have pressure(turn it over), make sure the crank is turning, make sure the key is in the crank for the oil pump flange that goes into the pump off the crank

Check the oil pressure with a mechanical gauge, if normal replace the oil pressure switch. If abnormal could mean oil pump and/or engine bearing.

Could be the pick-up or the pump itself