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MG MGB Technical - No Oil Pressure

After winter sleeping I find some time to check brakes, replace worn diff, drain out oil, fill in some fresh, replace oil filter and at that opportunity I change also oil pipes I bought time ago but didn’t find time to install them.
After refilling oil I disconnect spark plugs and power from coil and spin engine with starter motor to build pressure before cranking - but needle on oil pressure stayed at zero. I checked for oil leaks if is oil filter on place but everything seems fine so I repeat procedure but still no pressure.
At that point I was already very concerned so I thought maybe were new pipes jammed so I decide to remove that one at filter and tried again. No oil came out of block!
My diagnosis is that oil pump died. But on other side engine made only over 6.000 km after total rebuild and when I parked car at end of October engine runs fine and otherwise there was always good pressure. What I do remember is that I had to move car in January so I stated engine for maybe 1 minute, just to move car from one part of garage to another. At that event oil pressure was just over 30 PSI. I thought that was reason for that cold and didn’t pay any attention to that.
Can I check something else before I pull engine out and open sump?
Toni Kavcic

Try priming the pump with oil - pour some down the oil cooler hose to block connections - can't remember if the B engine has a priming plug ?

Take out the oil pressure relief and check not stuck open.

Even when an engine is fairly worn / bearing shot it will still have some pressure - so I go for priming first.

R.
richard boobier

Sometimes it can take a long time to raise oil pressure on the starter. I had the same problem when I rebuilt my roadster and had to resort to starting the engine to raise the oil pressure. I'd be inclined to start it and keep it at low revs and at the same time keep an ear out for the bearings rattling which you really do not want to encourage, When you moved the car and got 30psi I wouild say that that is a bit on the low side. What pressure does your engine normally run at as it should be between 50 and 70psi.
Iain MacKintosh

Do you have the inverted filter with the anti-drainback tube up the middle? If the filter is too short it will close that off and you will get no oil pressure. My tube is 2" long so the filter needs to be at least 2 1/2" internally. If in doubt I'd be inclined to crank with the filter off just to be sure it isn't that. A bit messy, and you need to be watching like a hawk i.e. bridge the starter relay or solenoid contacts from that side of the engine rather than leaning in the left-hand side if LHD.

I don't know how cold Slovenia was in January but if you use 20W/50 and it was very cold 1 minute may not have been enough to develop full oil pressure. having said that whilst my V8 has a slow rise-time once the 4-cylinder starts it rises to full pressure pretty quickly. My roadster takes about 8-9 secs to build pressure after an oil and filter change, about 2-3 secs after standing a few days, pretty-well instantaneous overnight.
Paul Hunt 2010

Normally oil pressure never dropped below 45 PSI even if engine just idle so I would say engine had healthy oil pressure most of the time over 50 PSI.

I use spin on oil adapter but if would be problem a filter the oil should came out of block when I spined engine without attached filter. Otherwise I use 20 W 50 oil and as far as I remember pressure always build up after few seconds. Pressure relief valve looks fine I didn’t notice that is anything wrong with it.

I tried Richard’s idea and fill some oil down the oil hose. I have to say that oil does not flow at all. I had first to fill hose with oil and then use pressure from compressor to push oil to engine. I filled approx. ½ liter that way and started engine after that. Oil pressure jump to 10 PSI but quickly disappeared. I am not brave enough to make any further experiments so I booked Saturday for garage, only if I get any good hint here.
Toni Kavcic

Toni,
Go to the website www.mgaguru.com
Barney has a good amount of information on priming the oil system on B series engines.
I believe it is in his tech section under "starting a dormant engine" or "priming the oil system".
Good Luck,
Ralpjh
Ralph

Ralph, thank you for a good hint. Statement on MGA-guru site that oil pump just do not die from one to another day forced me to rethink again. So at the end I have to confess that I created problem. I usually pre-fill filter with oil to speed up pressure built (you will not believe how much oil goes in filter cartridge) and since I have real mess in my garage I stick over a filter a thin foil (transparent) to prevent oil leak. I followed Paul’s idea (even if it seems to me not very likely, but still better than take engine out) and of course you can guess now - I forgot to take it off :)

Happy end
Toni Kavcic

Ah, Toni, we have all made silly mistakes like that, and have the red faces to show for it. Well done for finding the problem before you did any damage or paid out lots of money to a garage without need.
Mike Howlett

Commendable honesty on your part Toni, and a lesson to us all to make the simple checks first no matter how unlikely they seem.
Paul Hunt 2010

This thread was discussed between 27/04/2010 and 29/04/2010

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