No oil pressure

[100 OCTANE]

Please can anyone help me. I have a kit car fitted with a BMW 1200s K40 motorcycle engine, it has a dry sump and a front mounted oil cooler. The problem is, after draining down the oil and re-filling it, takes about 30 seconds to build up pressure, and the engine knocks badly. Please don't advise to prime the system, as this is not possible.

[100 OCTANE]

The problem occurred after its first fully oil drain down.

[100 OCTANE]

Unable to prime as I can't remove the spark plugs without removing the engine.

[100 OCTANE]

stevieturbo said:

you say it's a dry sump....how is the pump driven ?

And cranking the engine over with plugs in to prime, is better than running the engine with no oil pressure until it knocks

Or get an electric pump and hook up to an oil gallery and prime it eternally before starting.

Nothing in the BMW workshop manual about priming the system after an oil change.
I don't want to spend time faffing around priming the system, ever time I change the oil.

[100 OCTANE]

227bhp said:

You've got more issues than you realise if that is what you think is happening. A bit more explanation is needed as to what you did and what has happened.

I did no more than just change the oil.

[100 OCTANE]

227bhp said:

No we need to know more.
What did you do then, change all the bearings or has it run ok?
Have you got an oil pressure gauge fitted?

I've not done anything to the engine. It took about 30 seconds before the oil pressure came up that's it, end of story, it's now running fine

[100 OCTANE]

227bhp said:

So it knocks its tits off and then runs fine

Yes that's one way of putting it. It's a complete mystery as the pump is gravity feed, however the return feed via the front cooler that's an area where a lot of air can collect, but not sure if that would effect the pressure?

[100 OCTANE]

227bhp said:

If an engine does that it's fked, it doesn't suddenly repair itself so I have to refer you to my first post.
Again; oil pressure gauge? Yes? No?

No oil pressure gauge fitted, I'm not sure if it's possible to fit a gauge as it has a cambus electrics, I know nothing about electronics. BTW the engine has only done 18,000 miles, as I said before the problem only occurs after a oil change, I would have thought if there was a oil pressure problem, it would have knackered the engine by now, given I've done a track day.

[100 OCTANE]

wutschel said:

Did you change the oil filter? If yes, did you use a good one(In the US it normally should be AC Delco or oginial BMW stuff). Are ou shure that you used the right oil regarding viscosity range? It can even happen that there is the wrong stuff in the canister. Normally the oil pressure should rise in seconds after starting.

To me it looks like something in that direction.

But it also can be that the oil pump is broken. And: If this is not the case: Even worn down or not well connected spark plugs can lead to such behavior. Just because they can suffer from a weak spark.

Greetings from Peine/Germany

wutscherl

Yes I did change the oil filter, with a original BMW. I used a 10-50w oil, BMW recommend 10-40w so could this cause the problem?

[100 OCTANE]

Boosted LS1 said:

So, we're still left with the knock that's sorted itself out. Tiz bizarre this.

I think the problem lies with the gravity feed, is too low from the oil tank, I've no idea how to check it.

[100 OCTANE]

Blaster72 said:

I'm not really understanding why you can't prime the system just because you can't take the plugs out.

Surely you just pull off the plug leads or pull the fuse for the fuel pump and turn it over until pressure builds up?

I'm also struggling with your current problem - is it still knocking? Did it just tap a bit until the pressure built up?

You've done a track day since, surely you didn't do this with the engine knocking.

Pretty confusing.
If it's just the oil pressure light that takes ages to go off, I'd change out the pressure sensor first and see how it goes.

It's not possible to prime the system on the starter, cambus electronics, if it was possible it would take to long, as the starter is very small it would most probably over load it, as it 30 seconds running the engine before the oil pressure comes up after the oil change. It only knocks for 30 seconds after the oil change, after that it runs fine

[100 OCTANE]

Blaster72 said:

Trust me, 30 seconds won't overheat or overload a starter.

Canbus wiring makes no difference, pull the fuel pump fuse and it'll still turn over.

I don't think the starter will turn the engine over at 1100rpm so it will take longer than 30 seconds.