Both oil gauge & oil light read no oil pressure

Have you had a failure before?
Have you re-read (and digested) the link you posted as a source which explains quite clearly that oil pressure doesn’t disappear completely and immediately?

What, the link that says?

"A question about the oil pressure relief valve. I started my 3.8 engine for the first time this year, and had no oil pressure. And stopped the engine."

Perhaps you only read the first part of the first link and assumed that the relief valve always returns to closed, then opens again under the pressure of the oil.

A stuck relief valve, or one with a foreign body in it, will always flow.

To the O/p.
Perform the oil pressure test then if found to be no oil pressure, investigate the cause.
It can only be;
No oil
oil pickup blocked
oil pickup split so sucking air
oil pump not turning
open pressure relief valve.

Hopefully, it’s the transducer has failed on both circuits simultaneously.

Maybe bolding helps you read the whole thing.

[…] will fire up as normal and show round 60 PSI oil pressure, but within a minute or less, pressure drops to somewhere between 0 and 5 PSI. Sometimes it will read closer to 5 or 10, but usually its just a hair off the lowest marker on the gauge. If I let the car warm up, shut her off, and then restart say in 15 or so minutes, the gauge will read a more normal 45 PSI - but again drop off quickly to the same low reading as when cold.[…]

To the O/p.

I’m out of this thread.

Good luck with fixing your problem. :slightly_smiling_face:

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Thank you very Dieselman your help was much appreciated. I borrowed a pressure test from a mechanic mate, weird bunch of fitting so I’ve brought a pressure gauge set from Supercheap $70 and screwing the fitting together start do a start up. If the oil pressure can match my current blood pressure everything would be find.
It’s a bit like walking thin ice wait to fall through in this case it’s bottom the bankcard

One easy thing you can do to reassure

take of dizzy cap, and turn over motor very briefly

If the rotor turns (and there is no crunching noises) your oil pump is almost certainly functional

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Good point but one could argue that the rotor turns, because the engine has started and ran.
Maybe the inlet hose tube is leaking or broken, which is a point the Dieselman made. It would be extremely unlikely. I don’t think it’s a mechanical issue…

Goodness gracious me, Thomas - your blood pressure is measured in millimeters Hg, and should not match…:slight_smile:

But if you read an oil pressure you are accustomed to; the engine oil pressure is of course OK. With the transmitter our anyway; clean its port and retry - sometimes it clogs up.

But whether the fault is then the transmitter or something else can easiest be solved by replacing the transmitter.

With no oil pressure it gets more intricate - and really urgent.

As asides; there are to oil pressure devices; the fuel safety oil switch, green/yellow wire - grounded with oil pressure (fuel pump keeps running). And transmitter, white/brown, grounded with no oil pressure - lamp lit, gauge at ‘0’ or thereabouts. Crossing the two gives misreads…

xj6 85 Sov Europe (UK/NZ)



Well it’s Anzac Day tomorrow.
Only going to do a little bit on the Jag, out of respect for the Aussie diggers

After reading all your replies, thank you so much

I’ve decided to use my stethoscope, remove dizzy cap & rotate the motor listening for grinding noise & anything else that shouldn’t be making noise.
That the same watching the new pressure gauge kit for any pressure
Last hope start the engine & see what happens hopefully I about 70 psi oil pressures, then look for the lose wires

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You simply have to run the engine with the external gauge connected, Thomas - for certainty. Apart from the rather improbable sudden loss of actual pressure; there is little risk of further damage with a brief engine run…

You can also use the fuel safety pressure switch as an indicator; not grounded before starting - and grounded with oil pressure. And the fuel pump will not run without oil pressure…

xj6 85 Sov Europe (UK/NZ)

hehe…you could just back off the oil filter a bit, and start the engine

Make sure you have an oilpan and plastic tarp, especially if you do it on a new concrete driveway

I know this will work, as not so long ago, I did a hurried filter change on the new council driveway, and blow me down left the old washer on (not Jag), OP does not come up on gauge, quick look underneath, and to my horror, oil all over the new concrete

Been a while since I did that dumbass thing

Would show you have oil pressure, minimal mess if done right