Starting engine after oil change, no oil pressure for 7 seconds

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Anders_P42

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I watched engine oil being changed today. After it had been filled up and engine started I noticed it took 7 seconds to build oil pressure. I wondered with all the electronic wizardry in the ECU and Vodia tool, why the engine would be allowed to start before sufficient oil pressure has built up? Running 10-15 seconds on the starter motor must be better than running an engine will no oil in mains and big ends? You can hear slapping going on with no oil pressure and how much quieter it runs with oil pressure doing it's job.

Anders

 
i wouldn't worry too much - the oil film will still have been there and the pressure would ave taken time as the oil circulated. Mine always does take some time before the alarm goes off. I've never worried about it.
 
Big big engines have provision for getting lub oil up to pressure before starting. For our boat engines, either don't let it worry you, or fill the filter before fitting it. Mind you, if it's anything like mine, that is impossible.
 
My old Perkins engine takes as long as 15 seconds or so to get up some head on the first start after de-winterizing. I've taken to pulling the kill control and cranking it for 2 or 3 10 second cranks before I make a proper start. For the rest of the season the oil pressure comes up in about 5 seconds.
 
nimbusgb said:
My old Perkins engine takes as long as 15 seconds or so to get up some head on the first start after de-winterizing. I've taken to pulling the kill control and cranking it for 2 or 3 10 second cranks before I make a proper start. For the rest of the season the oil pressure comes up in about 5 seconds.
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I use the decompressor if there is one.
If my motorbike's been standing a week or two, I crank it a couple of times with the kill switch killed.
Probably makes no odds, but I feel I'm doing what I can....
 
Be very careful of cranking a marine engine over without it firing if it is connected to the sea water cooling. The cooling system needs the exhaust pressure to clear the water from the exhaust. If the sea water is not cleared away it will go into the cylinders!!!! Then you really will have trouble if you have not got a decompressor valve.
Much better to start as normal with low revs.
 
Probably worrying about nowt then :)

The oil filters have valve in them to stop old oil pouring out.

Good point about exhaust filling up with water, that would cause a mess in cylinders.
 
If you have a Yanmar like mine the oil filter screws on in a horizontal position, so you cannot fill it before fitting. I always press the stop button and let the engine turn on the starter for about five seconds before letting it start, The Yanmar manual for my engine actually tells you to do so. As for water getting into the cylinders. it would have to fill a big plastic exhaust box and a length of three inch exhaust hose between the mixing elbow and the box first, and I could crank the engine for much longer before that happened.
 
TRUNDLETRUC said:
Be very careful of cranking a marine engine over without it firing if it is connected to the sea water cooling. The cooling system needs the exhaust pressure to clear the water from the exhaust. If the sea water is not cleared away it will go into the cylinders!!!! Then you really will have trouble if you have not got a decompressor valve.
Much better to start as normal with low revs.
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Good point. I should have added that the boat is ashore after de-winterising so no water being put into the system. Alternatively simply loosening the cover to the water intake basket will stop water being drawn up!
 
TRUNDLETRUC said:
Be very careful of cranking a marine engine over without it firing if it is connected to the sea water cooling. The cooling system needs the exhaust pressure to clear the water from the exhaust. If the sea water is not cleared away it will go into the cylinders!!!! Then you really will have trouble if you have not got a decompressor valve.
Much better to start as normal with low revs.
Click to expand...

Good thing to be aware of, but it takes a lot of cranking to fill most exhausts.
There are a few boats with badly designed exhausts where it can be an issue.
 
nimbusgb said:
Good point. I should have added that the boat is ashore after de-winterising so no water being put into the system. Alternatively simply loosening the cover to the water intake basket will stop water being drawn up!
Click to expand...
Now you are in danger of burning out your impeller!
 
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