Oil Pressure warning light

[jswagger]

Hi,

I've had the oil pressure warning light (with no buzzer sounding) come on a few times. Each time it has come on I have straight away turned the engine off and waited for a while and then restarted the engine. I have then been able to drive for differing periods before the light came on again. Oil level is fine. I managed to get home and changed the pressure sender on the passenger side bank only for the same thing to happen again.

From reading the wiki am I correct in saying that as the buzzer is not coming on it is the sender (high revs /low pressure) near the waterpump that is turning the light on? (I didn't realise I had 2 senders!). If so I will change that but any other tips?

Thanks in advance.

[ewenmaclean]

Hello,

what revs is the oil light coming on at? If it's under 2000 rpm then it's the 0.3 bar low pressure sender, if not it might still the high revs sender and someone has disabled the buzzer. When it comes on, does revving the engine make it go away? Is it worse under braking or anything like that?

To test the high revs/low pressure circuit, disconnect the wire to the sender and rev above 2000 rpm - you should hear the buzzer then.

If your oil level is ok, I'd get the oil pressure checked with a "wet" gauge, to check it's not anything scary if you're worried. I wouldn't rule out an electrical fault, such as an intermittent earth leak, or indeed the 0.3 bar pressure switch itself.

Hope that helps a bit

Ewen

[jswagger]

Hi,

I'm afraid I don't know what revs it comes on at no rev counter. Also, as I turn the engine off as soon as the light comes on I don't know if revving makes it go out but will try this next time.

I have changed the low revs/low pressure sender so hopefuly it is the other one? Will get down and try and see if disconnecting the wire makes a difference.

Thanks again.

[ewenmaclean]

Hello,

sorry - I might not have been very clear. With regards to revs rough estimation is probably good enough for the purposes of diagnosis of the switch.

When I suggest disconnecting the switch, I don't mean drive around with it disconnected - I mean disconnect it then find out if the buzzer comes on when you rev it up above 2000 and keep it there for a few seconds. If the buzzer sounds then the switch causing the oil light is not the high revs/low pressure switch, and it might be the other one.

You can check the wiring to the 0.3 bar switch by disconnecting it and holding the spade connector against the engine block - this should light up the oil light.

I'd start with these two sanity tests - the first test will tell you if you the high revs/low pressure switch is working ok, and that the electics are ok, and the second one will check the electrics.

If both of those tests check out ok, then think about the 0.3 bar pressure switch as a culprit, but I would definitely check the oil pressure to, to make sure it is not a failing oil pump or something (assuming your levels are defnitely ok).

Ewen

[jswagger]

Thanks for the reply. I have taken the bus for a short drive and when the light comes on tried revving it with no joy.

With the help of an assistant I have managed to check the circuits:
Engine idling and shorting the low revs/low pressure circuit: Light flashes with no buzzer
Engine revving past 2000 and just disconnecting the high revs/low pressure sensor: Light flashes with no buzzer

So buzzer does not sound at all. Does what I have done confirm the circuits are ok? I have changed the low revs/low pressure sensor already so will change the high revs/low pressure one anyway.

On the subject of the buzzer not sounding could this be anything to do with the multiplug in the engine bay which both sensors plug into? I ask as a couple of years ago I found that the wiring for the low revs/low pressure side had what I thought come apart so just I remade the connection at the time. Looking at it now it looks like it was cleanly cut! Perhaps trouble in the past?

Thanks again

[Ian Hulley]

I take it this is a 1.9 wbxer ? What year ? ... Early ones didn't have the Buzzer of Doom just the warning light controlled by the sensor between the left bank cylinders.

What oil are you using ?
Where did you get the sensor from ?

Ian

[jswagger]

Hi,

Sorry, I shgould have mentioned it is a 1988 1.9DG auto. Sensors are from GSF. THe oil is 15w40 but I'm afraid I can't remember the brand. Is it worth changing it?

Thanks

[Ian Hulley]

GSF sensors have been known to have issues, I'd be inclined to buy the correct one from here ... http://www.brickwerks.co.uk/shop?catego ... 0&start=20

15/40 mineral oil is what's required.

At '88 you should have both sensors BUT it doesn't mean to say a different, earlier engine has been fitted. Look for a brown wire crossing the left side and dropping down between the water pump and the oil pump behind the crank pulley. If it's had 'issues' before this may have been earthed somewhere.

Hope this helps, Ian.

[jswagger]

Thanks.

Both sensors are physically there and the wire for the high revs/low presssure is there and it is all connected up in the engine bay (i.e. at sensor and at multiplug near thermostat). Also the sensor that had been cut was for the other circuit. If high revs/low presssure was earthed elsewhere then would the light still come on when the sensor was unplugged (like earlier)?

Will change the oil as it's due for a change soon anyway.

Point noted about GSF sensors.

[Ian Hulley]

I believe the 2 sensor system (DOPS) needs both sensors to function correctly. The one near the pump is the one that sets the B.O.D. off if the pressure is below 'X' and the revs venture above 2,000rpm.

With us running on lpg I change my oil at 4,000 mile intervals religiously, with a filter every other change, for what it costs it doesn't hurt.

Ian

[jswagger]

Thanks for that.

I now need to change the coolant too so will do the oil at the same time....