26 replies to this topic

[studavis]

Quick question. Where is the oil pressure switch located in the engine bay? And secondly, would this becoming disconnected turn the oil pressure light on? Thanks folks!

[Dan]

It's on the forward face of the block, just by the dizzy. It would light up if the disconnected wire managed to earth itself but it's not likely. If the lamp is on it pretty much means either the switch is broken or most likely, the pressure is low.

[Big_Adam]

Seconding Dans comments, the light may come on from a short in the system, just unplug it from the pressure sender, if the lamp goes out, then you have low pressure (and if its BMC switch low as in 5psi or similar), if the light stays on then there is a short in the system.

[studavis]

Thanks for the info. Can I take it that if the dipstick shows a max reading it's a good chance it's the sender unit?

[mini-luke]

Thanks for the info. Can I take it that if the dipstick shows a max reading it's a good chance it's the sender unit?

No, not really as the oil pressure is generated by the pump, there could still be a blockage/broken pump.

[tiger99]

The switches often fail, and cause the light to be on. But you need to fit a new switch, before you run the engine again, to be sure. There is too much at stake, and it is just possible that you have lost pressure because of a stuck pressure relief valve, in itself trivial and easily fixed, which will ruin the engine if it is run.

Preferably fit a gauge.The pressure should be between about 30 and 70 psi, hot, when revving fairly fast. It creeps down as you get near the time for an oil change, or when the engine is becoming due for a rebuild, so it gives you lots of warning about what may be coming. A light just tells you that your engine is in very big trouble, if it is down to 5psi you are certainly going to need a crank regrind etc immediately.

[studavis]

It's weird because a new set of sparks, a new condenser and a decent clean of the dizzy has just caused it. And I just drove about 5 mile and the engine sounded and felt great, no knocking and the pickup was the best it's been. I guess the first step is to change the sender unit?

[Dan]

What colour light is on?

[studavis]

Ok, bit of an update on this one...

I disconnected the Oil Switch sender on the block and the light remained on on the clocks - so, as Big_Adam says, it looks like there is a short in the system. When the condenser was replaced I did reconnect up an electrical contact that had been taken off the ignition coil (the one on the left as you look at it). Miraculously, the oil light on the clocks now went out! So I can only assume that connecting that wire up to the ignition coil is shorting teh electrics and triggering the light.

That wire off the ignition coil had always been disconnected since I had it from the previous owner, and the car always started fine, so I guess my questions are:

a) What does that wire on the ignition coil do, and is it safe to leave it disconnected?
b) If I do the above, would it stop the Oil Pressure switch from functioning correctly?

Thanks so far for your help!

PS: The oil light on the clocks is orange.

Edited by studavis, 10 February 2012 - 10:15 AM.

[Dan]

Hard to say about the wire on the coil, telling us it's the one on the left doesn't really help. For one thing, the coil is round and can be fitted any way around! What colour is the wire? The colour codes all mean something and tell you what the wire is for. Were you connecting it to positive or negative on the coil? Someone else is currently working on an ignition wiring problem that makes the warning lamps come on too, wierd. The warning lamp should come on with the ignition, and go out with the engine running. It should come on if the ignition is on and you earth the wire connected to the sender. If it does all those things the circuit is working.

[studavis]

Hard to say about the wire on the coil, telling us it's the one on the left doesn't really help. For one thing, the coil is round and can be fitted any way around! What colour is the wire? The colour codes all mean something and tell you what the wire is for. Were you connecting it to positive or negative on the coil? Someone else is currently working on an ignition wiring problem that makes the warning lamps come on too, wierd. The warning lamp should come on with the ignition, and go out with the engine running. It should come on if the ignition is on and you earth the wire connected to the sender. If it does all those things the circuit is working.

Ah right, good point about the ignition coil - yes it's circular so could be either I suppose! The wires are all white, so presume it's an aftermarket rewiring.

The ignition light on the car works in the expected way (lights on key turn, goes out on engine starting), but the oil light is dependent on if that wire on the ignition coil is connected - if connected, always on - if not connected, never on (even on key turn). Hmmmm.....

[lrostoke]

Try connecting the wire you are putting on the coil onto the oil pressure sensor, maybe you are getting them mixed up.
Attaching it to the coil maybe giving it the earth connection it needs to trigger the light.

[studavis]

Try connecting the wire you are putting on the coil onto the oil pressure sensor, maybe you are getting them mixed up.
Attaching it to the coil maybe giving it the earth connection it needs to trigger the light.

Great suggestion, will try that when I get home from work and let you know the outcome!

[studavis]

Try connecting the wire you are putting on the coil onto the oil pressure sensor, maybe you are getting them mixed up.
Attaching it to the coil maybe giving it the earth connection it needs to trigger the light.

Ok, I tried that. It didn't really have much of an effect to be honest, all that happened was that the orange light wasn't present on the clocks, and the engine turned over as normal, with the usual ignition light behavoiur. Just so I know, when turning the ignition, BOTH the lights should come on and then go off when turning the engine over?

Anyway, I've taken some pretty bad pictures so you can see what I see. The offending wire is the one with the red connector:

[Cerberus]

That wire that's connected to the pressure switch doesn't go up to the coil does it?

Hard to tell where they're going at that angle, just that they look the same colour.

If yes, definitely shouldn't be like that.



Edit

Nevermind, forgot about the first picture,

Edited by Cerberus, 10 February 2012 - 07:20 PM.