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MG MGB Technical - rebuilt engine oil pressure

rebuilt my mgb engine have no oil pressure not trying to start engine just turning over without spark plugs, any ideas rhanks les
les

Les, how long did you try to get pressure. I rebuilt mine a few weeks back and with the plugs out it took 30 seconds or more before pressure built up. If that's not the problem then it could be any number of things, the most common I have read about is fitting the wrong gasket to the oil pump when refitting it to the block.

If you are a member just have a look at the archives, stacks of info there.

Cheers

Tony
Tony Oliver

les. Please let us know what engine you are writing of. As Tony notes, it is not uncommon to fit the three main bearing oil pump gasket to a five main bearing engine, resulting in no oil pressure. This can be corrected with the engine in place, but is a pain in the neck to do so. The two oil pump gaskets are not marked as to which is which on either the Rover, nor the Fel-Pro gasket sets I have used.

Les
Les Bengtson

this is a 73b with 5 mains. ive tried to push it in gear with the plugs out. do not know how far.
les

Usually it takes 30 seconds if the pump is getting prime. I had trouble with a Ford engine I rebuilt getting oil pressure prior to startup. I finally disconnected the oil pressure sender and vented out some air. Then full flow almost immediately. You could disconnect the oil pressure line and do the same thing.

Of course there is the gasket issue described. If that's the case the oil pan has to come off.

You should be able to spin the engine easily with the starter especially if you remove the spark plugs. If you can't something is wrong.
Robert McCoy

You have to make sure the rebuilder used the correct oil pump gasket. Gasket kits usually come with two, one for the older motors and another for the 18V motors.

I had the same problem with mine after a rebuild. They installed the wrong gasket and could not get oil pressure. Had to drop the oil pan and install the correct gasket.

Got oil pressure after about 20-30 seconds.
Steve Rechter

Just a thought... Is is not a good idea to fill the oil filter with oil before cranking the engine to generate oil pressure? Is this a good precedure to follow when changing oil?

Frank Grimaldi
Frank Grimaldi

Frank. Maybe. If you have an oil filter system where the oil filter is hanging downwards, it can be filled with oil and fitted to the engine. If the oil filter is sideways, as some cars have, it may be partially filled with oil and fitted to the engine. If you have the 18V engine with its inverted oil filter, any oil inside the filter will run out as the filter is fitted to the engine--just as it does when the oil filter is removed from the engine during an oil change.

Good idea you had, but most of us cannot take advantage of it.

Les
Les Bengtson

It's not neccessary. For just an oil change the system will pressurise in just a second or two longer than normal. If it's not neccessary when starting a rebuilt engine for the first time i.e. no oil anywhere except the sump then it isn't neccessary any other time. I recently examined the mains and big-ends on my V8 after switching off hot and leaving it for a couple of days to stop dripping, and the bearings and crank were still swimming in oil. Having said that the V8 does have the beautiful arrangement whereby one can remove the distributor and put a drill on the oil pump shaft to get full flow and pressure before the crank is ever turned on the starter.
Paul Hunt

This thread was discussed between 12/07/2009 and 16/07/2009

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