Oil Pressure Warning System

[Elsaetka]

Hi, would appreciate some feedback on the following as it may save me a lot of time and stress.

I have a 1915cc Petrol DG engine, a while ago it started with the oil light and buzzer of doom whilst driving, no problems with the engine itself so therefore after some research I learned about this common fault and the high and low pressure switches.

I decided to sort the problem once and for all, firstly I gave the actual wiring in the engine bay the once-over, especially where the wires from each sensor meet in the factory fitted white connector. I barely touched it and one of them fell out, so clearly that needed sorting. I will make a more permanant fix in due course however as a quick fix to assure myself the connections are OK I cut the rotten ends off and re-joined using a new pair of block connectors.

I started it back up and this time to my suprise when it fires the warning light now comes on immediately, even before I touch the throttle. I naturally thought fixing the rotten connectors would sort it, not make it appear worse. When I do rev it, the buzzer of doom comes on as before, so, some help needed, especially as I need it MOT'd so must sort it.

1. No doubt of course it will require two new pressure switches, any ideas about the rear one, I can barely see it let alone get it out! It looks like the only way of getting at it is to take the pullies off, what an absolute nighmare. I read some posts about bending the heatshield out of the way, but stuff that, it's in mint condition.

2. Any other tests, recommendations.
3. Worst case scenario if I cant fix it, can I extinguish the light / warning by earthing both cables, therefore bypassing the system temporarily. That way I can get through MOT and take it to my specialist. I earthed the low pressure wire and it still came on? unless I need a better connection.

Any ideas from those who know will be greatly appreciated, thanks in advance.

Paul

[itchyfeet]

Don't assume its a faulty switch it could be genuine low pressure
The low pressure switch that brings the light on is closed when no oil pressure and should open with pressure

So if the oil light comes on when ignition on but not running then that's the circuit check it should open when running and the light will go off
Earthing that wire will bring the light on
If that was the broken wire it may be that's why the light is now on at start up with a faulty sensor that's permanently closed or low pressure

The high pressure switch is the other way closed when running this can be checkekd with a multimeter with ohms to block being low check on the switch not the wire
If its not an oil pressure issue this wire or connection. Could be broken causing the buzzer over 2000 rpmif the switch measures ok change the wire

You could silence it for an mot but they will run it until hot and that could damage the engine if its a real low pressure fault don't risk it

[kevtherev]

oil pressure check first I think.
most garages will perform a wet gauge check.

[AdrianC]

1. No doubt of course it will require two new pressure switches, any ideas about the rear one, I can barely see it let alone get it out! It looks like the only way of getting at it is to take the pullies off, what an absolute nighmare.

It's not as bad as it looks, honest. Yes, the waterpump pulley needs removing - but it's easier than you'd think. Make sure the belt's good and tight, and it should hold as you crack the three bolts loose. If not, a big screwdriver jammed between belt and pulley'll lock it.

If you've been near the wiring, and you're now getting the light immediately the engine's running (but not before?) then I think you've probably just connected the sensors wrong way round. As Itchyfeet says, the low-rev is the more normal normally-closed (pressure opens it and breaks the circuit, putting the light out), whilst the high-rev is normally-open.

[itchyfeet]

If you've been near the wiring, and you're now getting the light immediately the engine's running (but not before?) then I think you've probably just connected the sensors wrong way round. As Itchyfeet says, the low-rev is the more normal normally-closed (pressure opens it and breaks the circuit, putting the light out), whilst the high-rev is normally-open.

I nearly wrote sensors wrong way around, good call
if the light does NOT come on when ignition on but engine not running then that's most likely

http://www.brick-yard.co.uk/VehicleSpec ... fo/dop.htm" onclick="window.open(this.href);return false;

The trouble with describing normally open is its confusing as normal in my book is when the engine is running but its actually when engine is not running I.e the switch in its state if tested as a seperate item

[what2do]

Has been a while since I changed mine but I'm pretty sure I didn't remove the pulley. However, removing the tinware (exhaust shield) without bending it took some fiddling with - but doable (after removing silencer of course).

For the sake of my sanity could someone else back me up here and say that they too have changed the sensor without removing the pulley - please!!!

[kevtherev]

yeah me!

[Elsaetka]

Many thanks for the replies so far, I will go back to it today.

Just for clarity a couple of further points:

I fully appreciate checking the oil pressure, which I will do. A link to a full gauge kit supplier would be a help, I see a gauge on JK however when I go to the kit it says it's for T1 / T2.

For the sake of this post I am going to assume the oil pressure is not the problem, reason being the high pressure buzzer was an intermittant fault for a long time and the engine runs perfectly. The low pressure light only started since I repaired the rotted block connection.

A further clue......

Since sorting out the corroded wiring, (i'm sure it did not do this before), when switching the ignition on engine off !), the oil light comes on for a split second and goes off, as soon as I start the engine the oil light comes on (continuously) without reving, this is 100% not oil pressure as coincided with the wire fix.

As soon as I rev it the buzzer kicks in, i.e the origional fault.

I can't remember what it used to do (ignition on engine off) before I repaired the corroded wires, no doubt the origional instructions will say.

It is one of those things where it's hard to describe and simple when working on it. I am convinced I wired it correctly as well, however if someone would tell me the wire colours I will double check to remove any doubt.

Finally, even though it is not as likely, if it did turn out to be a faulty unit at the dashboard end, what exactly is the part I would be looking for?

If I can't sort it soon it will be going on a truck to a VW specialist, the fact that it's SORN with no MOT is making matters that much more complicated.

Thanks again

[itchyfeet]

Lots of bodges to shut up a buzzer
On what2ds van I found it had been shorted at the dash with scotchlocks
So my point is your intermittant buzzer could have been quietened long ago and the bodged short is now broken

Then when what2ds oil light came on it was a genuine low pressure but he didn't have the benefit of the early warning buzzer

So by all means go through and check wiring and change switches but it could still be a low pressure fault


I have been looking at buying a guage myself looks fairly easy I will try and get a link up later you will need an adaptor

The ideal time to do it is when you are changing a switch

Push rod tube low pressure sensor is blue/black in loom
Rear sensor high pressure is yellow in loom

Wires over the engine can break they can measure fine with a multimeter but be broken I had this myself
Change those wires but you will need need high temp wires or sleeve , standard wire is ok for a test

[AdrianC]

Since sorting out the corroded wiring, (i'm sure it did not do this before), when switching the ignition on engine off !), the oil light comes on for a split second and goes off, as soon as I start the engine the oil light comes on (continuously) without reving, this is 100% not oil pressure as coincided with the wire fix.

I can't remember what it used to do (ignition on engine off) before I repaired the corroded wires, no doubt the origional instructions will say.

If everything was behaving, the light should come on with the ignition and stay on until the engine's started and pressure builds up (almost instantly the engine's running).

It is one of those things where it's hard to describe and simple when working on it. I am convinced I wired it correctly as well, however if someone would tell me the wire colours I will double check to remove any doubt.

Disconnect both wires in the engine bay. Turn the ignition on, don't start the engine. Earth one. If the light comes on, that's the low-rev wire. That would originally have been the one between the pushrod tubes, but it's the sensor type that's important rather than the location, so it depends which way round you've fitted them. Connect that wire to the low-rev sensor, and with the ignition on/engine not running, the light should come on. Start the engine, the light should go off. Leave the other wire disconnected. Rev the engine, the light/buzzer should come on. Earth the other wire, and rev the engine. The light/buzzer should stay off. Connect that to the high-rev sensor.

[MidLifeCrisis]

If everything was behaving, the light should come on with the ignition and stay off until the engine's started and pressure builds up (almost instantly the engine's running).

I think you mistyped here - think you meant to say ".... the light should come on with the ignition and stay ON until the engine's started ...."

[AdrianC]

If everything was behaving, the light should come on with the ignition and stay off until the engine's started and pressure builds up (almost instantly the engine's running).

I think you mistyped here - think you meant to say ".... the light should come on with the ignition and stay ON until the engine's started ...."

Yep, you're right.

[pandp38]

I had similar problem with buzzer of doom sounding. Had oil pressure checked and found to be ok. Eventually found fault was a corroded terminal in the long white connector block in the dash pod. I also managed to replace my oil pressure switch using a long reach socket (24mm I think) without removing any pulleys or tinware

[itchyfeet]

OK so this is the cheapo £20 DIY guage I was looking at getting but you would need an adaptor from the NPT thread to M10x1 which is your oil pressure switch say add another £6 ( not sure if it's male female etc until you see the guage)

http://www.ebay.co.uk/itm/Bergen-Automa ... 2c736cb881" onclick="window.open(this.href);return false;

or this kit at £39 has the M10x1 adfaptor and many more.


http://www.ebay.co.uk/itm/Engine-Oil-Pr ... 2a24972df5" onclick="window.open(this.href);return false;

Before I but one I'd be interested to see if anybody else has one and has tested their pressure, lots of advice saying 'get it tested' but never seen anybody who has their own guage and at that price it's a cheap tool for the DIY mechanic.

im sure there is something in the wiki but Id trust Aidan to be about right
http://www.brick-yard.co.uk/forum/19-dg ... 65008.html" onclick="window.open(this.href);return false;

"op stone cold will be a couple of bar at idle rising to 4 or 5 at 3000 rpm, hot 0.5-1 bar at idle and 2-3 bar at 3000 rpm"

it seems to me you just take the oil pressure switch out , thread this is and start it up.

[Elsaetka]

A massive thanks to everyone who came back with assistance with this problem, van is now repaired and perfect, worked out as follows.

Went back to it first thing and disconnected the temporary connections put in place after wiring was found to be corroded at the white connection box, which was too far gone.

Wasnt happy with the wiring, as even though I had cut off the corroded ends, the corrossion extended a little further into the cables. I trimmed the cables back to good wire, reconnected, double checking the wire colurs were correct namely Blue/ Black = Low, Yellow = High.

Started up and it is functioning perfectly again, ignition on, without the engine running- the oil light flashes, start the engine and it immediately goes out, rev the engine and no buzzer of doom either.

Appreciate the comments about the removal of the high pressure switch, which I will save should the current one ever fail. I appreciate some members say they could change it without touching the pulleys, others not. I remain in the latter camp as I just can't get near it whatever angle I come from. If you do manage it without removing pulleys, great, the only person capable of it in my view is Mr Tickle.

Thanks again.