Thread: 4.0 V8 Oil Pressure

The last crank pump engine that I assembled (a 4.6 in an RRC) got primed by pumping 2 litres of oil slowly into the oil pressure switch port. From memory the light still took a little while to go out on starting but at least all the galleries were full.

Thanks Jilden

I also filled the oil filter and the oil cooler hoping it would help. Your suggestion sounds the way to go - just a messy proposition without the right connectors.

Not sure how much I can crank the engine with just the assembly lube - I guess it is not so bad as the engine is not getting hot.

Cheers

garry

hot or cold I reckon less than two secs,,
I always thought these would not start without oil pressure,, but have seen it happen---

Originally Posted by Pedro_The_Swift

hot or cold I reckon less than two secs,,

I assume that is an engine that has been running and already primed - this is a fresh build so the empty oil pump has to suck up cold oil for the first time and prime itself.

I am going to pull out the oil pressure switch and check it again and maybe pump in some oil as suggested by bee Utey

Pulled the oil pressure switch out - no oil is there whatsoever so the oil pump has not yet primed.

I will pump in some oil as suggested and see what happens.

No more oil would go in the port and the oil pressure switch was working. Cranked the engine with out the switch in and a little oil came out so at least some oil was getting pumped.

Put everything back and cranked and it took another 30 secs before the light finally went off - so from dry it takes a few minutes cranking to get oil pressure.

There really need to be a better way to prime these oil pumps - but is all done now so I can move on.

Thanks for the input.

Garry

If i drain the hot oil overnight mine looses prime and it is the most heart stopping time i have had.300000 km though

I think that you will find is that it is not actually loosing prime - the oil pump sits at the bottom of the engine on the crankshaft and has to pump oil all the way up to the rockers etc - so the oil drains down out of the top of the engine - so when you start up after a period of being shut down the oil pump has to pump the oil all the way up to the top and it is only when these oil ways and pipes etc are filled up that oil pressure is achieved.

My old 3.5 engine (different oil pump arrangement) sat for 10 years and not used and did not require any priming so once primed the oil pumps stay full of oil way unless they have been tinkered with.

Garry