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No Oil Pressure!


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#16 DomCr250

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Posted 11 January 2019 - 11:08 AM

How are you measuring the oil pressure ...with a gauge or on the light?

 

The reason I ask is based on my 1st ever engine rebuild ...1969 1275GT I had at 17 (they were worthless then) - full engine rebuild at the machine shop with me assembling - back in the car plugs out no pressure with the light, so a quick tow with the plugs still out, still oil light on - royal bollocking from my Dad 'you prat, you've put it together wrong and missed out the spider' - me practically in tears ...then I swapped out the sender unit and hey presto we had pressure ...the sender was faulty not my workmanship - my old man 'you should have checked that earlier'!  You cannot win with him.


Edited by DomCr250, 11 January 2019 - 11:08 AM.


#17 mini13

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Posted 11 January 2019 - 07:22 PM


If the pump badly worn or not sealing the oil will drain down easier and the pump will have a hard time sucking oil up from the sump.

Just because you have oil coming out the oil filter pipe doesn't mean that it will make good pressure once there is a load in the pump.


Forgot to ask if there’s is any reason for the temporary pressure then after letting sit for 10 mins no pressure?



#18 Homersimpson

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Posted 12 January 2019 - 09:30 AM

I saw one once where the engine and box had been rebuilt and where the oil pickup bolted to the gearbox case the gasket had been made without a hole in it.  The clue was when the engine was separated there was still oil in the oil feed hole in the gearbox from the oil that had been put in from the banjo in an attempt to prime the pump as it couldn't drain back to the sump.

 

I would be looking at whether;

 

1. is the pump able to suck oil up from the sump (gasket as above, fault in oil pickup pipe, blockage etc.).

2 is the output from the pump going somewhere else (as mentioned above is the pump seated correctly, bolts too long etc.



#19 Rorf

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Posted 13 January 2019 - 06:00 PM

Is the engine correctly assembled and all clearances checked - plastigauged. You mentioned big end caps on con rods might be incorrect. So many things that could be wrong unfortunately.



#20 Homersimpson

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Posted 13 January 2019 - 06:30 PM

Is the engine correctly assembled and all clearances checked - plastigauged. You mentioned big end caps on con rods might be incorrect. So many things that could be wrong unfortunately.

True but even engines with big ends knocking tend to have some oil pressure, if the OP has none that points to something more fundamental (assuming their pressure gauge is working!).



#21 mikal

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Posted 14 January 2019 - 03:55 AM

I had a problem a few years ago. I had an engine and gearbox reconditioned. I assembled and installed everything myself and had oil pressure and the car ran well. However, it soon became apparent there was a problem with 2nd and 3rd gear synchro's (at speed couldn't down change cleanly without double declutching). Gbox "specialist" said bring the gbox back and I'll take a look (Great, got to remove the bloody thing myself..). Got the gbox back, put everything back together and NO oil pressure despite trying everything under the sun. It was weird because I knew everything was fine engine wise and I was certain I had installed the O ring between the engine and gbox. So I took everything out, again, split the gbox. Found nothing wrong so I put in a new O ring and everything back together. This time, oil pressure almost straight away! Don't know what was wrong with the first O ring but it seems it was sucking air...

 

Re the sychro problem, the "specialist" blamed the poor quality synchro rings these days. I suspect it was poor quality something else....






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