Oil pressure

P

Paul N

New Member
3500S 1972 Has been running fine ,recent oil and filter change ,pressure ok after that
Not started for two months ,and now no oil pressure and oil light staying on
I have also taken oil filler cap off and no oil pumped up
I will get an independent pressure guage to check
but what other thoughts do you have as possible cause ?
I saw from Haynes about the pump needing priming if removed
but would it have drained down without use ?
 
Oil pump needing primed would be my guess, yes they can drain the oil back to the sump. If you can turn the oil pump enough it may prime itself.
If you have the oil filter off, fill up any ports you can get to, hopefully some may get into the pump and let it pump air until it raises the oil from the sump.
Others: Am I correct in thinking; if the filter is left off while turning the engine over, this should make it easier for the pump to raise the oil from the sump?

First: I'd remove the spark plugs and turn the engine over with the start until you either drain your battery or oil pressure appears, or pisses out the filter housing. If none appears recharge your battery and try again.

Second: I'd make or get a tool to turn the oil pump. You gain access to the pump by removing the distributor. (I'd do this first if you have a drive tool handy)
1707830537126.png
Turn the oil pump using a drill. Sorry I don't have a picture of the tool, but it has the same end as the distributor.
You'll fell the drive torque increasing as you get oil into the pump and should see oil being pumped into the topend of the engine.

Hope that helps.
 
It certainly sounds like the oil pump needs priming but I am surprised it needs it after such a short time. It usually take a lot longer for it to drain out in my experience, but all cars are different! Could be a sheared drive to the pump too I guess on the end of the distributor, but that would be obvious by removing the distributor to look.
 
Thanks for the advice ,thinking about using the distributor hole to turn the pump,
but how is the oil pump and distributor normally driven ?
I mean will it need the rest of the engine going to move ?
 
Paul N said:
Thanks for the advice ,thinking about using the distributor hole to turn the pump,
but how is the oil pump and distributor normally driven ?
I mean will it need the rest of the engine going to move ?
Click to expand...

The dist is driven by a gear on the front of the camshaft and the oil pump is driven by a dog on the bottom of the dist gear. A tip when you remove the dist, look in the hole to see which orientation is in and remember it, if you don't, it will be difficult to get the dist to go down and engage with the pump shaft.

Colin
 
Paul N said:
Thanks for the advice ,thinking about using the distributor hole to turn the pump,
but how is the oil pump and distributor normally driven ?
I mean will it need the rest of the engine going to move ?
Click to expand...
A long flathead screwdriver driven by an electric drill. Dont know what direction to drive though. You will need someone in the cabin to read your dash gauge so you will know when to stop.
 
GRTV8 said:
A long flathead screwdriver driven by an electric drill. Dont know what direction to drive though. You will need someone in the cabin to read your dash gauge so you will know when to stop.
Click to expand...

Clockwise. Careful you don't drop it into the timing cover :)

The drill will spin quite freely when you start, but will change tone as the oil pressure picks up. You should also see oil coming out of the rocker shafts if you have one of the rocker covers off.

I should have a pic somewhere
 
Paul N said:
Thanks for the advice ,thinking about using the distributor hole to turn the pump,
but how is the oil pump and distributor normally driven ?
I mean will it need the rest of the engine going to move ?
Click to expand...

This is the front timing cover from the inside. The large drive to the left is usually bolted to the front of the camshaft. The dog gear to the right is the bottom of the distributor and is driven by the cam drive. This is the later motor so is slightly different to original.

Oil pump drive.JPG

Underneath the dog gear is the oil pump drive which just slots into the bottom of the distributor, so when you remove it, the oil pump is no longer connected to the rest of the engine, and can be spun up independently.

My oil pump has a tongue on the end of it (later unit) but yours should have a slot in it so a long screwdriver bit in a drill can be fitted into it and the pump can be spun with the drill.

oil pump drives.JPG
 
This used to happen on my 3500S when left for 2-3 months without use. Always had to prime the oil dump, which I found was a real pain. Eventually raced to the oil filter being the 'wrong type' I was told that some filters have a non-return valve to stop he oil draining back to the sump, iobviously other do not.
I do not know how you identify a 'good filter' but now I buy mine from a specialist and not Halfords who used to stock V8 filters.
NB you will need a special Trox socket to get the bae pump. Priming pump is dealt with in Haynes manual. Not difficult but a pain if you cannot get access under the front of the engine. Vaseline from Boots.
I always changed the oil after doing this as I did not think that Vaseline in thee oil was good for the engine.
 
The oil pump bolt heads are 5/16" AF or 8mm 12 point ring or socket, you will need the spanner because you can't get the socket on all the bolts. Vaseline is a trade name the product is petroleum jelly and will mix with the oil OK, in the ratios concerned it will not be detrimental.

Colin
 
How can oil drain from the filter when it slopes down from the pump, and the gallery that feeds oil from the sump is above the pump? In the 4 cyls an anti-drain filter is vital, but not the V8s. I have had my sump off twice, and never had to prime the pump.
mjwhrX6.jpeg
 
JP 928, I will leave it to you to explain the how the oil drains, but the fact is, that 3 times I had to prime the oil pump when starting the engine after a 3 month lay up. I changed the filter supplier and never had the problem again. I only report what happened so hat others might benefit.
 
Having never seen this problem I dont need to explain it. If more owners of P5Bs, P6Bs and Rangys and discos also echoed your experience its credibility would be enhanced. All I can suggest is something like a leak at the filter joint allowed the pump to drain, thus requiring a prime. Gravity prevents the oil climbing the inlet line and draining back, unless there was a vacuum in the sump sucking it back, and that should happen in a fairly short time after shutdown. Maybe a vacuum could occur with blocked flame trap breather lines? I have had 2 Disco V8s with many miles on them, and spent at least 1 month laid up each year, and never had any trouble with oil pressure.
 
I seem to recall that the difference between a Ryco Z79 filter and the Z79A used in the rover is just that valve. The problem does occur quite a bit but seems to be specific to some engines. Note that while the filter is below the pump, the lowest point is the pickup and the sump level is below the top of the filter so gravity causes the level in the system to drop till it gets to sump level leaving only air in the pump (though the filter may or may not still have some fluid in it. When the pumps wear a bit they lose there self priming ability at cranking speed as pump turns at half engine speed as it comes from the distributor drive.
 
Yes it could siphon back, but what would start that action? Low pressure in the sump? Caused by blocked flame traps? They do get pretty bad - when I got the car they were bad, and I cleaned them in an ultrasonic bath in petrol, they came up very nicely. Be interesting to know if an engine with blocked traps makes any strange air noises at shutdown.....
 
What can happen is a failure of the timing case gasket around the oil gallery from the sump, if this happens it can draw air into the gallery and it won't prime.
 
Many thanks to all who have contributed to this discussion,all very helpful.
I think I will try the distributor removal option first .
I will update when done
Thankyou all
 
My 3.9 engine has a remote oil filter mounted fairly high up on the inner wing, also an oil cooler mounted lower down in the nose. There is a problem getting oil pressure up on start up. Firstly I just crank the engine until the oil pressure light goes out ( it won't start without me adding fuel there is no choke ) Then a couple of pumps on the throttle and the engine will fire, I then tickle it along at 3-4 hundred rpm until the oil pressure gauge moves, then warm up as normal.
I think the only way I am going to find out which bit is draining down is to temporarily fit clear tubing to the filter and cooler runs. This might tell me if it is worth re locating things height wise.
I thought of the filter siphoning scenario, but as the filter head outlets are at the top of the filter and there is no dip tube going down the filter I cannot see it emptying.
 
The lowest 'open' point is the oil pickup pipe at the level of the oil in the sump so regardless of how high or low the filter is, if air leaks in then oil starts draining back into the sump unless something physically stops it. On my old (and worn) engine I once fitted a filter without an anti-drain valve and the oil pressure light wouldn't go out until the engine started. When I replaced it with a filter with an anti-drainback valve the light went out almost straight away the starter turned.
 
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