oil pressure light on HELP!!!

[waggy]

94 500HC pre serp,, on way to griff growl after 60 miles my oil pressure guage dropped to zero ,, stopped and checked oil level ok,, thought it must be sender unit playing up, as engine sounds ok,, then on way back after about 50 miles the yellow light started to flicker on and off , rechecked oil level and all ok on max line,, oil still clean since oil change 5000 miles ago,, is this the oil pressure switch causing this or something more fatal,, engine sounds alright no rattles ,, guage still zero and oil light flickering on and off,, normally the guage stayed at 30psi and moved a little from this when accelerating,, checked the bible and previous posts but no info on oil light,,

worried!!!

Edited by waggy on Tuesday 21st August 15:07

[TVRleigh]

Take the sender off the car, connect to a foot pump, and use a meter to test the resistance of the gauge when you aply pressure to the gauge.
The resistance should change with pressure, this will tell you if the sender is working, if can then get a varible resister and connect this to the wires of the sender to test the gauge. with the same values of resistance, and PSI noted on the foot pump.

Some sender have twin outputs 1 for pressure and one for low pressure, if this is the case and the sender is faulty this could cause both your problems.

[Johno]

Waggy,

I'm not certain, but i am 99% sue than on the pre serp there are 2 senders for oil pressure.

One is for the gauge, and there a seperate one for the oil light.

The seperate oil light will only come on at around 5psi. The sender is a seperate unit.

It may be different on the Pre Serp, so if so sorry for sucking eggs comments . .

[waggy]

if there is a seperate sender for the oil light this means im low on pressure,, could this be a broken spring in the relief valve or maybe its stuck,,, how can i check the relief valve is working ok,, i drove 40 miles like this so i must have some oil pressure or it would be seized by now,,
any help is appreciated,,,

[waggy]

TVRleigh said:

Some sender have twin outputs 1 for pressure and one for low pressure, if this is the case and the sender is faulty this could cause both your problems.

how can i tell if this has a twin output ,, does it have 2 wires as opposed to 1 wire,,,
will the light come on even though my oil pressure is ok,, sorry to be a pain but i need the car for next week and dont want to run it with no oil pressure,,

thanx

Alex

[spend]

Its a pain to try and get the pressure relief spring out, just as quick (well!) to drop out the oil pump cover. That way you can inspect the oil pump & idler + the dizzy gear. Not hard just fiddly...

Dave

[Johno]

spend said:

Its a pain to try and get the pressure relief spring out, just as quick (well!) to drop out the oil pump cover. That way you can inspect the oil pump & idler + the dizzy gear. Not hard just fiddly...

Dave

A pain, but I've had a mate do it in the pitlane at Zolder and then another time at Calais ferry terminal. Best way forward given the symptoms. I certainly wouldn't drive it any more.

Don't panic though, 40 miles isn't a huge amount, and you were being gentle. If it had been terrible the temp would have gone off the scale if oil wasn''t getting round the engine.

[TVRleigh]

waggy said:

TVRleigh said:

Some sender have twin outputs 1 for pressure and one for low pressure, if this is the case and the sender is faulty this could cause both your problems.

how can i tell if this has a twin output ,, does it have 2 wires as opposed to 1 wire,,,
will the light come on even though my oil pressure is ok,, sorry to be a pain but i need the car for next week and dont want to run it with no oil pressure,,

thanx

Alex

Yes if its a twin sender it will have 2 wires comming off it. as posted most are seperate. also if the light is flicking on/off then you are getting aprox 5PSI, the RV8 will be ok if not driven hard at 5PSI, as they need flow not pressure.but not a good idea to keep driving it, as it could get worse, also not a good idea to put too much load on the car. best get an ohm tester, and test the sender with a foot pump, as the sender should come out by hand.

[Pupp]

With 'really' low pressure, the lifters will clatter too.

[waggy]

spend said:

Its a pain to try and get the pressure relief spring out, just as quick (well!) to drop out the oil pump cover. That way you can inspect the oil pump & idler + the dizzy gear. Not hard just fiddly...

Dave

does that mean you have to prime the oil pump afterwards like wen you do an oil change and let the pump drain out,, also how do i tell if the pressure relief valve is ok , never seen 1 b4 ,,

alex

[Johno]

The releif valve lies in a channel in the front cover/oil pump. My experience is that they get stuck in that channel, normally when bur is developed and gets between the plunger and the channel wall. It may even be a broken spring.

It should be obvious once you have the pump off. Parts available easily enough and i think Rimmer bros used to do an upgraded spring for additional pressure.

If it is a dual outlet sender, then make sure you test it first and check the wiring as well.

You will have to re prime the oil pump, and it seems the easiest way is with a priming tool, available on ebay etc . .

[waggy]

im thankful for all the knowledge given,, my weekend will now be spent under me griff in the rain removing and testing the oil pressure switch,, then if thats ok remove the oil pump cover and check the relief spring, and valve ,, found a couple of photos from an old posting showing the relief valve in the stuck open position,, wheres the best place to get the bits if needed ,, ie pressure switch relief spring or valve,, reasonable priced

alex

[TVRleigh]

RPI IIRC do a replacement pump thats of the new style, and only a bit dearer than the stanard one. it has the remote oil feeds also.

[Dave 500]

If your going through all the hassle of jacking the car up etc etc I would get a new sender/switch they are only a few pounds and easy to fit. I would also give the pressure sender spade for the gauge a good clean up at the same time

[spend]

It may be worth just getting new pump internals, I think they only cost @£20. You will need a gasket anyway, there are also some options for the pressure relief valve IIRC.

Yes the pump will need to be primed after removal (3/4 methods, well described in past posts) if you only pull the pressure relief valve probably wont need priming.

Johno: are you referring to a serp or pre-serp engine?

Dave

[Johno]

It's a pre serp isn't it ?

I run my serp on the starter with no HT lead to the coil to build up my pressure after a change, ut this ain't gonna work on a pre serp.

Drills and vaseline aside, the best I've seen is the tool .. . .

[waggy]

sorry, i had to go out and missed the last postings,, it is a pre serp and according to bible there are 3 ways of priming the pump,, i like the method where you fill the pump from the oil filter hole and quickly put the oil filter on ( filled with oil of course ). when you mention vaseline my mind wanders,,

where can u get pump parts for £20, i like the sound of that,, easy on the wallet,, i just hope i havnt damaged the engine,, its only done 28k since new ,, was laid up by previous owner for 6 years ,,

cheers

alex

[spend]

Paddock are 24.40+dreaded, v8tuner 29.95inclusive. 50p gasket & £4 for Pressure Release valve & spring. Its up to you, but its easier to have the parts at hand (particularly if you do it at the weekend), and non of the parts are expensive compared to the cost of 6 litres of amber nectar!

You are sure its not just really crap oil thats been put in, aren't you? I used some Halfrauds bargain fully synth to give mine a flush out & the oil pressure light flickers when warm (not thrashed) on an engine which never goes below 30psi hot idle with Mobil1 racing.

Dave

[waggy]

it had its last oil change a couple of years ago using mobil 1 5/40, ive only done about 4k since and it never uses much oil,, i top it up with carlube tripleR 10/40 fully synthetic ( which was recommended by tvr when they dropped Mobil ) i read that you shouldnt use 0/40 as its too thin,,, it always has 30psi on the gauge, last year i drove to devon non stop 230miles at 80mph and it never missed a beat, i think something has happened suddenly such as oil pressure gauge giving up or the relief valve sticking or broken spring,, i'll check the pressure valve first and then take pump apart,,

alex

[spend]

The Carlube wasn't allowed to stay in my engine for more than 40 miles!, these oils which purportedly adhere to accepted standards do seem very different The mobil1 I was referring to is the 15w/50 version, quite a lot of us used it, but I think Silkolene may now be the more popular choice. It seems to me cheap oils = fast drop in oil pressure thats all .

Dave