Sudden oil pressure disappearance

[StescoG66]

Experienced a sudden loss of oil pressure. Can't put an exact time it happened but seemed to coincide with about the time my son started the car and revved it a bit too high, but only for a few seconds and not overly excessive. He's not used to the responsive, revvy nature of the boxer engine.
Anyway I actually suspect the problem is a stuck non return valve in the oil filter. Could this be possible or am I talking pish again
Pics below, I tried to show the valve position. The first one is the filter that was on the car - you can see the valve is set well in to the housing. Second pic is new boxed filter of same OEM part number 004680828. The valve appears to be in a different position.
Could it be oil has been getting pumped in to the filter, but not getting back out due to the valve? Your opinions are appreciated as I am truly stumped, plus the sudden nature of its occurrence makes me think it's something daft to cause it.
I have put on a Bosch P3350 0 451 103 350 now, have dropped the sump and going to pull the oil pump out to check it. I read on here about shimming the oil pump - how do you do that? Is it the washer under the spring?
Also had 15W-40 in there, going to put in either 10W-50 or 20W-50

Exist filter non return. Stuck?

New boxed filter same part number

[alfadave]

Was there any reading at all on the gauge? Could be a faulty sender.

Also did the oil warning light go out?

[alfadave]

........also my Jaeger OP gauge quite often shows zero reading......until I give it a tap, and it springs into life!

[StescoG66]

Tried another sender so it's ok - although it does give a reading of 0.5 bar with no engine running............ Low warning light comes on at tickover but even tiny gentle blip of the throttle makes it go out. I think there is some oil pressure there, just not enough.....
As I say - it was all ok this just happened suddenly
Both sensors are new

[KevJTD]

There are a few posibilties, could be that the pressure relief valve in the oil pump has stuck open, a sudden surge of oil with the engine being revved especially if not warmed up could have caused the valve to open to relieve the high pressure and it didn't fully close. Had that happen once on our Rally Astra, the night before a Rally of all times! Had to strip the pump down, remove the pressure relief valve and clean it up with emery paper so the plunger could return smoothly.

There's also core plugs within the oil galleries, from memory I can't recall if any lead back into the sump chamber area so if they have blown out would be undetectable, although if that had happenned you'd have so little pressure it'd be the death throws, unless a pinhole in one, but unlikely .

Again I can't recall the oil flow route from the pump, but doesn't it go from the N/S of the engine where the pump is, across the block (via the central pressure gauge port) along that raised channel before reching the oil filter housing. Filter first before low pressure warning light sender?

Can you fit a known capiliary pressure gauge into the sender fitting? One from a Mini or something? Get an accurate reading to see what you have, sometimes the electric ones aren't all that accurate.

Another possibilty, have you had carb trouble? If one carb has flooded fuel down the bores it would get past the rings and into the sump diluting the oil and casuing pressure issues, is the oil level up on normal? Does it smell of petrol?

[alfadave]

I wondered what mileage your oil pump had done.
I think they quite long lasting items. I've never shimmed one, but someone on here will have.
New ones very rare. 300 euros on ebay.it.

I think 16v oil pumps give more flow. Maybe get hold of a decent used one?

[LooLooSud33Spider]

Hi all
I regularly shim oil pump relief valves. The other option is to fit a stiffer spring. But i find putting a .20 thou (0.5mm)washer under the valve usually does the trick if you go too thick you’ll just end up popping seals all over the shop.
It doesn’t sound much but it’s usually enough to raise the pressure to a more comfortable level
Lou

[StescoG66]

Well it seems that KevJTD hit the nail on the head. Pressure relief valve stuck ever so slightly open......

I had a spare pump thankfully, so a little washer to shim and have put back in. Runs smooth with no free play. I think the spring in the pump I had in was goosed too as it was a good 5mm shorter than the spring in the pump I have now used.. Took the opportunity to set the distributor up in the correct position too.
The gears in this other pump are ok, so I may refurb and keep as a spare if I can get hold of a good spring and plunger

New oil filter on (Bosch with 2 non return valves), will refit the sump and fill with 10W-50. Wish me luck.......

[StescoG66]

I stuck this oil in. Anybody tried it??

Spec seems correct at API SN, but just noticed it says suitable for motorcycles...... Presumably not an issue if the spec is right

[alfadave]

Never used it.
How is the oil pressure!

[StescoG66]

Tell you later. Didn’t start her up as no fuel. But will try today.

[StescoG66]

Bingo!! Spot on now. Thanks all x

[alfadave]

Maybe someone could do brief notes of how to refurbish an oil pump?
Personally, I've never done it.
Haynes is very sketchy, and no photos.

[Veesix75]

That oil will be more than fine, oil is oil……so long as it is high quality in the first place which most top brands are.

Think I’ve posted on here before that a mate worked for silkolene and castrol and he was adamant that so long as it was a top brand, hence refined well, Ester based, then other than the odd additive a brand would include it was all the same.

Rest is marketing as usual.

I use Castrol Edge fst 10/60. You don’t need 60 for road use tho. Brand affinity more than anything as said mate used to get it cheap for me and I stuck with it.

Glad it’s fixed .

[StescoG66]

Maybe someone could do brief notes of how to refurbish an oil pump?
Personally, I've never done it.
Haynes is very sketchy, and no photos.

Happy to take pics of the innards of the spare one I have. Trouble is the internal parts are largely no longer available, however they are reputed to be pretty hardy.