Erratic to no-existent oil pressure - diadnostic help wanted

[bcmc33]

I agree with the comments about the usefulness of an oil gauge . It is astonishing how quickly you notice a change even if you don't think you are looking

In response to a previous thread, I am in the process today of fitting an oil light next to the brake light with a 15 psi switch on the basis that it can be easily seen with peripheral vision when driving.

[GrUmPyBoDgEr]

I agree with the comments about the usefulness of an oil gauge . It is astonishing how quickly you notice a change even if you don't think you are looking

In response to a previous thread, I am in the process today of fitting an oil light next to the brake light with a 15 psi switch on the basis that it can be easily seen with peripheral vision when driving.

Brian,

isn't 15 psi being a bit overcautious? Low pressure switches usually actuate around 0,5 bar (7,5 psi)
I've read that Twincams can run pretty low pressures with hot oil at tickover.

Cheers
John

[bcmc33]

isn't 15 psi being a bit overcautious? Low pressure switches usually actuate around 0,5 bar (7,5 psi)
I've read that Twincams can run pretty low pressures with hot oil at tickover.

John,

I took advice on this from two major Twink engine builders and bought a 15 psi switch. If that does turn out to be the wrong mumber, then I will fit the 10 psi switch I already had.

Tickover pressure was not the incentive for the switch - I simply wanted to have a better indicator for seeing if my pick-up design works on fast RH bends.

[bcmc33]

Do we all remember this debate from a year ago? Well...............................................................................

VERY
My new engine has no oil pressure when spun over without plugs.

All new parts apart from reground crank, conrods, flywheel, sump and pick-up.

New pump from QED - no pressure. Pump from old engine - no pressure. New Ford pump - no oil pressure. (Rotors liberally coated with thick assembly lubricant)

Clear passage from pump to pressure gauge connection.

Dipped down through pump pick-up hole in block showed good depth of oil at bottom of pick-up tube.

I recalled the issue of different sump depths, and the sump is 170mm deep compared to the 160mm on the old engine where the pick-up tube came from. So, if anything, the bottom of the pick-up tube has a greater than optimum gap, but should not relate to a no pressure situation.

I have now dropped the sump, and will give it some serious consideration in the morning.

All comments welcome.

[robertverhey]

Before dropping the sump (oops too late?) try pumping some oil into the oil pressure gauge threaded hole in the block. Sometimes there's an airlock created there

[512BB]

Brian,

I have posted this before on another thread about no oil pressure.

On servicing one of my Elans, after changing the oil and filter, I always spin the engine over without the plugs in, having filled the filter with oil prior to fitting. Oil pressure never registers on the gauge no matter how long I turn the engine over for on the starter.

On fitting the spark plugs and firing up, oil pressure comes up within 3-4 seconds. Obviously, with a newly built engine, you cannot 100% guarantee that everything is fine until you fire up, but have faith in your abilities.

On a different Elan of mine, oil pressure comes up whilst spinning over on the starter. I can only put this down to differences in the type of oil pump fitted to each engine.

Hope this is of some comfort if you deceide to give it a go.

Leslie

[GrUmPyBoDgEr]

Hi Brian,

from the described symptoms & assuming that you're talking about a freshly rebuilt engine, I strongly suspect a leak on the suction side.
Even a small air leak will lead the oil pump to seek the easiest route & subsequently suck air rather than oil.
You also mention the deeper sump & that the suction pipe is subsequently further away from the bottom of the sump.
I strongly recommend that you make changes to get that pipe lower down in the sump; a subject dealt in, in depth a few years ago on here.
That alone will reduce the effect of oil surge & improve cornering ability.

A quick fix which may work would be to fill the oil filter with oil & whilst it's loose on the engine, spin up the engine until it throws oil out at that point.
Although I've never heard of Twincams suffering with priming difficulties, this technique has proven not only useful but necessary on some other cars.

Cheers
John

[bcmc33]

Before dropping the sump (oops too late?) try pumping some oil into the oil pressure gauge threaded hole in the block. Sometimes there's an airlock created there

Tried that, and it just spat it out with no follow-up.

On a different Elan of mine, oil pressure comes up whilst spinning over on the starter. I can only put this down to differences in the type of oil pump fitted to each engine.

My first thought was a duff new oil pump ? so the easy option was to fit a known good pump from the ?old? engine - without success. A friend found a new Ford pump in his garage, which was again unsuccessful.

I strongly recommend that you make changes to get that pipe lower down in the sump; a subject dealt in, in depth a few years ago on here.
That alone will reduce the effect of oil surge & improve cornering ability.

This is one of the reasons that I dropped the sump. When I realised that the ?new? sump (given to me by Alex as a leaker) was 10mm deeper than the sump that the pick-up originally came from, it was obvious that it would give me problems on RH bends despite the revised baffle I devised. I shall make a new pick-up tube from ?? x 18g copper pipe.

From the described symptoms & assuming that you're talking about a freshly rebuilt engine, I strongly suspect a leak on the suction side.
Even a small air leak will lead the oil pump to seek the easiest route & subsequently suck air rather than oil.

This was probably the main reason to drop the sump. Although there was no obvious scoring or other reasons to think that the fit between the tube and block was not complete when I did the assembly ? I could not think of anything else to prevent the pumps sucking up oil.

[rgh0]

Friend of mine recently fitted a new pump at a race meeting because of a leak. He could not get any pressure with the new pump to prime and push oil our the oil guage tapping point despite all his attempts including fill the pump rotor with oil and then grease at the time in the pits

In the end he went back to the old pump as he ran out of time before the next race which worked ok

After a close inspection back in the workshop after the race meeting he could find nothing wrong with the pump and installed it on another engine. He cranked the engine over with the filter renmoved until he got oil coming out then he reinstalled the filter and kept cranking and had no problem getting oil presusre.

Clearly you can have problems priming a new pump on a twin cam if the pump system up to the filter not full of oil
Priming the whole oil system via the pressure guage tapping and a pressure bottle full of oil generally solves this
cheers
Rohan

[bcmc33]

Priming the whole oil system via the pressure gauge tapping and a pressure bottle full of oil generally solves this

Thanks Rohan - you're the second person to tell me that. However, realising that the pick-up tube is too short for my needs anyway, I bit the bullet and removed the sump. Normally I take great care in making sure that the pick-up is correct each time I build an engine --- BUT this time I didn't give it any thought. How stupid and embarrassing is that?
Maybe dementure is all some people say it is.

[GrUmPyBoDgEr]

Before dropping the sump (oops too late?) try pumping some oil into the oil pressure gauge threaded hole in the block. Sometimes there's an airlock created there

Tried that, and it just spat it out with no follow-up.

On a different Elan of mine, oil pressure comes up whilst spinning over on the starter. I can only put this down to differences in the type of oil pump fitted to each engine.

My first thought was a duff new oil pump ? so the easy option was to fit a known good pump from the ?old? engine - without success. A friend found a new Ford pump in his garage, which was again unsuccessful.

I strongly recommend that you make changes to get that pipe lower down in the sump; a subject dealt in, in depth a few years ago on here.
That alone will reduce the effect of oil surge & improve cornering ability.

This is one of the reasons that I dropped the sump. When I realised that the ?new? sump (given to me by Alex as a leaker) was 10mm deeper than the sump that the pick-up originally came from, it was obvious that it would give me problems on RH bends despite the revised baffle I devised. I shall make a new pick-up tube from ?? x 18g copper pipe.

From the described symptoms & assuming that you're talking about a freshly rebuilt engine, I strongly suspect a leak on the suction side.
Even a small air leak will lead the oil pump to seek the easiest route & subsequently suck air rather than oil.

This was probably the main reason to drop the sump. Although there was no obvious scoring or other reasons to think that the fit between the tube and block was not complete when I did the assembly ? I could not think of anything else to prevent the pumps sucking up oil.

Please use steel tubing for the new pick-up pipe. Copper will give up after a very short time.
Don't underestimate the vibrational forces present in a 4 Cyl. Engine.

I really recommend you trying the priming methods described by Rohan & in my posting.

Good luck
John

[alexblack13]

Hi Brian,

Sorry to read of the oil issues. I had the same problem when I put everything back together recently (this year) and did all of the things suggested. (I do most of them anyway) Drove myself nuts! No Oil pressure no matter what I tried. Eventually bit the bullitt (as Les' suggested) and just started the bugger up. Oil pressure was up in less than 5 seconds.

Hope you get it sorted soon... You will!

Al' .......

[Allison]

Following up on Rohan's point; certainly the old style pumps have metal rotors spinning round to provide pressure. If the pump has dried out they just spin and do nothing - its the oil film between the rotor and their cylinder which provides the suction. I doused the pump in oil - problem solved.

Peter

[paddy]

Do you have a short jackshaft, and are the oil holes blanked off in the spare journal?

Paddy

[bcmc33]

Following up on Rohan's point; certainly the old style pumps have metal rotors spinning round to provide pressure. If the pump has dried out they just spin and do nothing - its the oil film between the rotor and their cylinder which provides the suction. I doused the pump in oil - problem solved.

Pump and all bearings liberally coated with assembly lube.

Do you have a short jackshaft, and are the oil holes blanked off in the spare journal?

Yes & Yes, Paddy.

Looked closely today at the pick-up tube for the 40mm length that goes into the block and there were signs that full contact was not made all around for the full length. However, there was good contact for about 3mm at the top and bottom of the contact length.
I made some effort to calibrate the bore of the tube before it was reassembled with some sealer in the hole and on the tube. So, if nothing else, there should be some sort of seal at the top and bottom of the tube/hole.

I shall put the sump back later today to see how successful I've been.