Oil pressure

[street]

Would anyone expect oil pressure when cranking the engine over, trying to start after full rebuild.

Noting showing at all, so a little concerned. I remember the oil pressure tube was not a fantastic fit so thinking of dropping oil and putting the bore scope in and having a look.

[vstibbard]

A few steps to take, prime the main gallery, oil pump with oil and ensure the filter is also full of oil.

I also remove oil pump end cover and fill the space with grease, this increases the suction for the short period helping lift oil from the sump.

Cheers

V

[UAB807F]

If you take the plugs out and spin it over you should get some pressure. I normally do that anyway if the engine has been apart for any reason or I've changed the oil.

If you fitted the oil filter without filling with oil first, that might be the reason. Before you drop the oil I would imagine if you unscrew the oil filter and it's still dry then it's either the pump or pick-up.

If the filter is full and there's oil in the cam cover then is the gauge right ?

Brian

[2cams70]

100% normal and 100% waste of time trying to get oil pressure using the pump before you start the engine. Make sure you have the pump primed with regular engine oil - don’t use grease and have the oil filter pre filled with oil before you attach it. If you have any doubts whatsoever about the state of the oil pickup however this must be sorted before you attempt to start the engine. Give the cams a covering of oil too before you replace the cam cover and attempt to start the engine. Once started should only take a couple of seconds to reach proper oil pressure. If not shut it down quickly. Oh - and check the PRV valve on the pump for freedom of movement before you fit it

[street]

Prv valve?

[Billmack]

PRV is pressure relief valve. Its a steel cup with a spring behind it that will vent excess oil presure back to the sump. They are supposed to be a close slip fit in the bore in the pump body but not uncommon to be tight or hungup by a tiny piece of crud and will then vent all the oil peressure back to the sump.

[joe7]

Has a problem recently after changing oil, I couldn't get any oil pressure. Did the usual start and die, but the pressure didn't come up. So usual approach, what did I change last? The oil filter. I had been using Fram filters for the last 25+ years without any problem. The ones I previously used had been discontinued or superseded. The cross reference to the new ones had the same part number. Since I bought 2 oil filters, I took a very rudimentary approach and attempted to "blow" through the extra filter NO LUCK! The filter was filled with oil before installation. Removed the filter and no sign any oil had made it to the filter. Bought a Gold Pro NAPA and amazingly I could easily blow air through and get the relief valve to pop! (No comment here please!) Installed the Gold Pro filter filled with oil, did the start and its dies, the pressure started to come up immediately!

[mbell]

It's very common for the engines not to build oil pressure in the starter, some do some don't.

Mine is one that won't. So I used the oil pressure gauge take off and a garden pressured spray bottle to pump oil in to the engine and then started it. This ensure there is oil in the bearing surfaces and pump is primed.

[Donels]

I have rebuilt several cross flows, and one twincam and agree with 2cams. You can’t get oil pressure with the starter. If you’ve done everything right, primed the pump and filled the filter then go for a start and the pressure will come up after a few seconds.

[street]

Prv valve anyone got a picture?

[oldelanman]

Prv valve anyone got a picture?

This is the paper element type pump and the spin-on will be similar. With the filter removed use a screwdriver to check the plunger moves freely against the spring.

[rgh0]

I have rebuilt several cross flows, and one twincam and agree with 2cams. You can’t get oil pressure with the starter. If you’ve done everything right, primed the pump and filled the filter then go for a start and the pressure will come up after a few seconds.

I believe "Can't" is somewhat of an overstatement. You can and plenty of people have done it. Whether you need to or not is another question

cheers
Rohan

[skelteanema]

I recently removed and re-installed engine for a water pump replacement.
I could not get any oil pressure on cranking, even with plugs out, filter filled and pump primed.
I noted some reports of getting pressure on cranking and others with no pressure.

I bit the bullet and fired her up, and was pleased to see the pressure rise almost immediately to a nice and steady ~40psi level.

Car has been running beautifully since rebuild, and is "almost" oil leak free, even with a rope seal!

[UAB807F]

This has been one of those "every day's a school day" topics for me, I'd always thought that everyone built oil pressure before starting an engine that had either stood for a while (over winter) or just been apart.

It got me thinking and maybe it's not such a binary "can/can't" answer. Bearing clearance, oil viscosity, crank speed must all have an impact on whether it works or not. There's no doubt that 1000rpm when it fires up has got a much better chance to develop pressure than 2-300rpm (?) on cranking though.

Brian

[2cams70]

Just ask yourself the question why on earth an engine designer would find it necessary for the oil pump to be configured to supply oil pressure under cranking conditions and there’s the answer! It only makes sense to pre-fill oil galleries if there’s a lot of volume there to fill. In a LTC there isn’t.