No Oil Pressure

[4129R]

I am getting a 1558 Lotus Twin Cam started, and I have got no oil pressure.

I have changed the pump and filter, packed the pump with Vaseline, filled the oil filter, taken the spark plugs out to get fast turn over, and still no pressure.

Oil comes out of the oil pressure union hole on the block when I undo the 5/8" union connector at a dribble, but nothing registers on the gauge, and nothing comes up the clear gauge plastic pipe when the pipe is connected to the union and the gauge is disconnected.

I have run out of ideas. What could cause the primed pump to go round normally, and produce no pressure at the hole in the block to the oil pressure pipe connection?

There was 7 pints of new oil in the sump.

Any ideas as to what is wrong?

[jbcollier]

At this point I would drop the sump and check the pick up carefully.  Perhaps the screen is plugged or the "press-fit" into the block is loose allow the pump to suck air.

[4129R]

At this point I would drop the sump and check the pick up carefully.  Perhaps the screen is plugged or the "press-fit" into the block is loose allow the pump to suck air.

Having just driven into town to buy a gallon of new oil, I have come to the conclusion that there must be a fault with the pick up pipe, either a blockage, or something else that is not right.

Next I drop the sump expecting to find the cause.

Thank you for your help, to be honest there is not really much else left that it can be.

[4129R]

Sump removed, all oilways perfectly clear. I took the pump off to check.

I checked the pick up pipe to the oil pump by pushing a small plastic pipe up all the way (windscreen washer pipe), and the oilway from the pump through the block to the oil pressure pipe mounting which is 2 oilway holes at right angles to each other. I could see a wire I pushed in from the mounting flange from the oil pump oilway.

The oil strainer was perfectly clear too.

So no apparent fault with the pump, and everything up to the oil pressure pipe take off on the block. It is a mystery.

[EuropaTC]

Is the oil being pumped around the engine, for example is the cam cover full of oil ? I remember not fitting the cap on the cam cover once and oil certainly comes out then ! 

If it's not going round, is the relief valve in the pump stuck open somehow ? (no idea how that would happen, straw clutching time)

Brian

[4129R]

Is the oil being pumped around the engine, for example is the cam cover full of oil ? I remember not fitting the cap on the cam cover once and oil certainly comes out then ! 

If it's not going round, is the relief valve in the pump stuck open somehow ? (no idea how that would happen, straw clutching time)

Brian

The exhaust cam side was very oily, but it would be as you fill that side. The inlet cam side was only oily at the chain end, as the chain drags up lots of oil. I had the cover off with the engine turning.

I have tried two oil pumps, both stuffed full of Vaseline, with the filter filled to the brim.
 

[EuropaTC]

I must admit I am clueless on this one. If you've had 2 oil pumps then I think I'd rule out the relief valve. From memory the oil pressure take off is next in line after the pump as it splits to the rest of the circuit, so if that is clear and only a dribble coming out, I've got to go back to the pump. I've never had to use vaseline, all I've done is to take off the cover, pour in some oil around the lobes and then fit it.

As we're contemplating which straw to pull at next, are we 100% certain that the jackshaft is actually turning and the pump rotating ? given how lost I am I'd be tempted to remove the oil pump cover & turn the engine by hand to see if it's actually moving !

[FourLoti]

May or may not be relevant thread from the Elan world. Says he found the problem in the 5th post. https://lotuselan.net/forums/viewtopic.php?f=39&t=1804

Curious that in his case it came on suddenly, but might be worth measuring for clearance in the bottom of the sump?

Ron

[4129R]

As we're contemplating which straw to pull at next, are we 100% certain that the jackshaft is actually turning and the pump rotating ? given how lost I am I'd be tempted to remove the oil pump cover & turn the engine by hand to see if it's actually moving !

I thought that, but as the jackshaft drives the distributor, and the engine fires up, I concluded that the pump must be rotating.

Tomorrow, I pretend all is in order, bolt it all back together, fill it with 7 pints of new oil, cross my fingers, and all will work perfectly.

[4129R]

May or may not be relevant thread from the Elan world. Says he found the problem in the 5th post. https://lotuselan.net/forums/viewtopic.php?f=39&t=1804

Curious that in his case it came on suddenly, but might be worth measuring for clearance in the bottom of the sump?

Ron

You may have something there. The gauze was rather gooey at the bottom, and if it was pressing against the suction pipe, it would have prevented the pump sucking properly.

Tomorrow, I will tap the pipe to make sure it is seated fully to give the right clearance, gauze to pick up pipe. I have thoroughly cleaned the gauze.

Thank you for that. Much appreciated.

[jbcollier]

Measure how low the oil intake sits and compare that to the depth of the sump.  No specific spec comes to mind but anything under a 1/2" would have me concerned.

[4129R]

Measure how low the oil intake sits and compare that to the depth of the sump.  No specific spec comes to mind but anything under a 1/2" would have me concerned.

I thought exactly that. It was first on my list to do this morning.

It may be that the tube is not fully up into the block, and the gauze is touching the end of the pick up pipe preventing a free flow of oil being sucked up the tube into the pump.

The oil had been sitting in the block for about 3 years, and was a bit creamy. The gauze was creamy along the bottom about 5mm, and it would not need much to stop the flow of the oil into the pump as the suck is not very powerful compared to the pressurised output if all is flowing freely.

Thanks again for your help, it is good to share problems to think logically through to the answers. They are very simple engines so whatever is wrong cannot be that difficult to find and cure. 

[4129R]

Length of pick up pipe, 6 1/4" to 6 3/8". Pipe is slightly slanted.

Depth of sump 6 3/4". Therefore 1/2" gap.

I tried tapping the tube further into the block, but it was all the way in.

But, after draining the sump, there was a creamy slurry in the bottom, which would not drain out of the sump plug, so I have thoroughly cleaned the sump and about to replace it.

My theory is condensation over standing 3 years with new oil in the sump has made water mix with the oil, form a thick cream, this has surrounded the sump sieve gauze and created a dam, which has prevented further oil from being sucked up the feed tube to the pump.

All is now clean, new oil ready to put in, new filter, primed pump, and fingers crossed soon.

[4129R]

It is all back together now, oil comes out of the oil pressure pipe take off union, but not at sufficient pressure to make it to the end of the 5ft long pipe to the gauge, and the gauge does not move with the spark plugs out when the engine is cranked over for 10-15 seconds.

I don't want to run the engine for more than 10 seconds with no recordable oil pressure.

I cannot understand why everything seems to be working correctly, but there is no apparent pressure being generated by a completely normal looking oil pump, which is primed, rotating on the starter, and cannot push the oil up the pressure gauge pipe.

How long would you run the engine for with no recordable pressure, just to see if the pressure builds up as the engine fires at say 2000 rpm? What am I missing here?

[Pfreen]

Was the engine rebuilt immediately before you are attempting to get oil pressure?
Maybe an oil gallery pipe plug was left out.
Another idea is to get a pump to pump oil into the gauge port to pressurize the oil gallery.
I found the new oil pumps they sell have a hard time priming, probably due to greater rotor clearances.