Priming dry sump pumps

[Foxy Smith]

I understand that it is common practice in starting more exotic racing engines to spin up the engine on the starter without firing up to prime the scavenge and pressure pumps and establish a supply of oil to where its needed. It strikes me that this could easily be achieved by isolating the coil and petrol pump, turning the engine over a few times on the starter and then switching pump and coil on from dashboard switches to fire up the engine. Does anyone think there is any merit in this or is it just a good way to drain your battery?

[Peter Carmichael]

What you are describing is common when first starting an engine after a rebuild but is generally unnecessary.

 

Some engines have oil filters mounted facing sideways that would drain when the engine is left for a while. These engines should be fitted with filters with anti-drainback valves and then again oil pressure will be achieved at first startup.

 

Various opportunistic merchants will tell you the importance of their snake oil/device in ensuring perfect lubrication at startup, but the big secret is that it really doesn't matter. Oil is clever stuff that leaves a thin film over the bearing surfaces. When you start the engine, the oil film is still there from the last time you ran it and this is perfectly adequate for idle running. The pressure can build up over a period of a few seconds without ill effect, but must be established before the engine is revved significantly

 

There is no special procedure for dry sumped engines.

[The Stig]

Any spinning up with no oil pressure should be done with

plugs removed and hence no compression.

 

I always do this if the oil pump, or oil pick up pipe may ahve drained.

 

Agree with Peter that it is not normally needed.

 

20-30 secs or so is usually enough to get some pressure showing,

then plugs in and fire her up...

[Paul Ranson]

If you have an engine that's difficult to start because of the ignition timing at cranking speeds then this approach may help save your starter.

 

IIRC it was required to get early DFVs going, you press the starter and then turn the ignition on. Not an issue with management or an air starter.

 

(and nothing to do with pump priming or lubrication)

 

Paul