SiV6Qcoupe

I've had a long term problem with my oil pressure on starting the car both cold and warm (2.8 12v AAH '94). I get zero oil pressure on first starting the car cold and can only raise the pressure by reving the engine - oil pump is crank mounted. Even when the car is well into operating temperature leaving the car for 10-15 mins it can take up to 3000rpm to see pressure which will come on instantly and stay at the correct oil pressure throughout the journey untill the engine is turned off.

This situation has given me grief once in that it starved the engine of oil for a moment too long and spun the no.1 main crank bearing and lost me 1.5bar of pressure across the range but now with new bearings I'm extra careful.

Previously I checked with a mechanical oil gauge and this confirmed no pressure only on startup prior to raising the revs. The gauge is installed on the electric gauge tap point which is on the oil channel coming from the oil pump output to the oil filter. I've installed a new oil pump with gaskets and this has made no difference also new oil pressure relief valves in the cylinder heads - no difference.

The suction tube from the sump to the oil pump is my only part I haven't replaced, the strainer mesh was clean and the sump showed no sign of sludge only slight oil varnish. The strainer is held to the steel suction tube by a rubber cup and retaining clip, these three separate parts have now been superceeded by one single part according to ETKA so I can only take a guess that everytime the engine is shut down the suction tube assembly is leaking oil so draining the pump and leaving a volume of air somewhere and that's why it takes so much effort for the pump to actually move the oil from the sump to the oil galleries. The anti-drainback valve in the oil filter should stop the oil draining back to the sump on the output side of the oil pump and yes I have tried various filters including the Audi OEM filter.

I've never come across this type of problem and it sounds very uncommon, it would be great if someone could verify my theory but I can't tell untill I order a new suction tube from Audi.

Thanks for any help!