The 'E' Type Forum

Ive just rebuilt my heads and installed new rings and shells, honed the bores and installed new spin on oil filter.

On cranking the engine (plugs removed) ...I get no oil pressure at gauge...tho I did get oil issuing from slackened cam feeds. A friend of mine (who worked in engine development) suggested firing her up which I did. Sure enough gauge read 50psi at 1000 revs. However I still get no reading on cranking alone and I seem to remember before the rebuild I did get a cranking reading.

Should I be worried?!!

Thank you

David

Hi....almost all the oil drains back into the sump when engine is off.....as you crank the pump starts to suck up oil and build pressure.....engine fireing speeds this up..
but on cranking alone it can take quite a while a minute isn't uncommon or even longer....Steve

I don't think it'd take a minute or longer to get oil pressure.

The sender is a bimetallic type and so is the gauge. That means they will respond very slowly when initially fed a signal. Prolonged cranking without a start will also deplete the battery somewhat and so the gauge will not have sufficient voltage across it to register very much, exacerbating the problem.

By contrast, a mechanical gauge will probably pick up very quickly, dependent only on how much oil was left sitting in the feed lines and galleries.

kind regards
Marek

You could try an Accusump. It stores oil under pressure and releases it into the engine on startup. I've never used one but the theory is good and folks who have them support that. They're probably a good idea especially on engines that sit for a long time.

Your oil pressure with the engine running looks fine. I would not be concerned.

Thanks guys for your replies!
My car does certainly have a lazy cranking speed. I was just concerned that when cranking for e.g compression testing... that oil might not be circulating. I will get hold of a mechanical gauge to check.

best

David

If you are worried about lubrication during extended cranking when doing a compression test, get a garden sprayer and decant some of your oil into the sprayer. With the nozzle removed, these sprayers will have the same thread as the oil pressure sender and you can thus easily pump oil into the galleries and bearings with the main oil sender removed. With the ignition key in the second position, you'll have the bonus of seeing the oil light go out as you do it, demonstrating 3-5psi of oil pressure. You'll also hear the oil hissing out of the camshaft bearing caps from whence it drains back down into the sump.

kind regards
Marek

Thank you Marek.

Are you saying that with extended cranking on a car with no lubrication problems, oil pressure might not be sufficient to lubricate bearings?

Regards

David

No, I merely outlined a procedure explaining how to lubricate the bearings without having to crank the engine, plus a method that demonstrates that the garden sprayer produces in excess of 2-3psi.

kind regards
Marek

Just to add, because of the reasons Marek has outlined, I would avoided pressing the clutch pedal whilst cranking a cold XK engine (exactly the opposite of what you have to do in many modern cars).

Disengaging the clutch puts a huge thrust on the crank, the reaction to this push being the thrust bearings.

If you roach your (dry) thrust bearings, you will have no oil pressure, its an engine out job. All the oil in the crank will just pour out of the crank once the bearings have vaporised.

You will also not be able to select gear, as the lack of thrust bearings will allow the crank to move forward a few mm every time the clutch pedal is depressed instead of the clutch diaphragm working properly.

Ask me how I know.