Z3 Oil Pressure Advice

[Lee]

Morning All,

Been having a mare with Sam's Z3, Its an M54 2.2.

Been having an intermittent flashing Oil Pressure light, when it first came on the obvious thing was to shut it off but it was flickering so it started making me think it might be a faulty sensor. At this stage I also gave it an engine flush and fresh fluids for good measure.

I replaced the sensor (which closes the circuit at 0.5bar) which made no difference (still either stayed on or flickered)

Looking closer at this switch its very basic, sits on the back of the oil filter housing and has one live feed (see below)

Annoyingly my oil pressure kit didn't have the correct fittings so I went down another route. I made my own circuit using my own light. Knowing that once the switch reaches the correct pressure the light should go out and within a second it did (thank god)

Another thing worth remembering is these have hydraulic lifters so if you didn't have the correct/any oil pressure you would hear the top end getting very noisy!

Good philosophy or worth looking into some more ?

Anyone know an auto electrician in the south, It's one thing I'm not very good at.

 

[handsomejackuk]

so with the oil pressure switch disconnected does the light still flicker in the car.. ? are we talking about the light in the car or the light you rigged up for test purposes...

when you short the wires on the plug does the light flicker in the car.... ?

not sure which way the sensor works but normally short to ground one side of the switch i have a look at the wiring diagram in a minute for you

Al..

 

[handsomejackuk]

looks like the oil pressure switch switches to gorund which you probably established the other side of the switch goes to pin 26 of DME so its controlled by the ecu maybe... its page 95 of the drawing link here...

http://www.porterbility.co.uk/Files/PDF/e36z3_00.pdf

 

[Lee]

I'm mainly talking about the light In the car, It goes on/off randomly flickers if I hit a bump, lights dimly or progressively gets brighter. Almost like its a bad earth.

I haven't driven it with the switch disconnected yet.

It's a single 12v supply to the switch and the circuit is closed once the pressure is achieved.

 

[Lee]

OK looking at the diagram, there is a bunch of earth's next to the DME, I might have a go and cleaning them up and see what I get.

 

[Pingu]

@handsomejackuk makes a good point.

Rig your wire in parallel with the existing circuit so you can see both lights.

If the light in the car flickers, follow the car circuit until you find the fault. My money (10p) is on a loose bulb.

 

[handsomejackuk]

may even be a loose plug on the instrument cluster try tapping / banging the instrument cluster when the oil light is on.. engine not started.... it looks to me as though its controled by the ecu and not a simple wired oil light... you could also try disconnecting the dme and reconnecting it and spraying some contact cleaner on the dme connections..

 

[Lee]

@handsomejackuk makes a good point.

Rig your wire in parallel with the existing circuit so you can see both lights.

If the light in the car flickers, follow the car circuit until you find the fault. My money (10p) is on a loose bulb.

Not sure this would work as the oil pressure (red light) is only illuminated when the ignition is live and not running (should go out once running)
My circuit goes out right away so what would this prove ?

 

[Pingu]

It could be an earth, but it is unlikely. Most earths are for many items. If you have an earth fault, it usually affects many components.

Of course, you will only find the fault in the last place you look.

 

[Lee]

It could be an earth, but it is unlikely. Most earths are for many items. If you have an earth fault, it usually affects many components.

Of course, you will only find the fault in the last place you look.

This is also my line of thought

 

[handsomejackuk]

this is interesting...

http://www.e46zone.com/forum/topic/32188-flickering-red-oil-pressure-light-at-hot-idle/

 

[Lee]

this is interesting...

http://www.e46zone.com/forum/topic/32188-flickering-red-oil-pressure-light-at-hot-idle/

Good read that, I read that the other day. Something I picked up worth remembering is his line about the sensor:

"if the signal from the sensor to the instruments gets a short circuit to ground, this will cause the light to come on. Basically with the oil pressure at 0 the sensor has a tiny ball bearing that earths the inside of the sensor out. Oil pressure lifts the ball bearing off of It's seat breaking the circuit. If the wiring develops a short circuit somewhere. Thus will give the same effect as no oil pressure signal"

Looking like my likely culprit at this point. I think I will carry out an Oil pressure test aswell just to back all my findings up.

 

[Dino D]

When I needed an auto elec to sort my damaged loom I had to look at classic car restorers, regular garages didn’t like wiring work!

The guy I ended up using is based in Sandwich so a bit of a trek but put you in touch if needed.


Although you’d probably be better off just doing an engine transplant if you going play with wiring anyway, whilst you in there and all that, probably take you a weekend!

 

[Lee]

When I needed an auto elec to sort my damaged loom I had to look at classic car restorers, regular garages didn’t like wiring work!

The guy I ended up using is based in Sandwich so a bit of a trek but put you in touch if needed.


Although you’d probably be better off just doing an engine transplant if you going play with wiring anyway, whilst you in there and all that, probably take you a weekend!

Don't you start, Sam is trying to use this as an excuse for me to drop the M54B30 in it, can be done in a afternoons work.

 

[BMBabe]

@Mnbrennan

 

[handsomejackuk]

yes look like it works in reverse of what we normally think, the control signal is inverted by the dme basically as you probably know the dme can be programmed to use any input or output to make a light come on or off so someone that could program the dme could in efect use a different light for the oil pressure light ( i dont know why you would )....

it might even be that the dme could have some sort of algorithmn programmed in it to say that if the engine revs or some other thing is low.. that the oil light flickers.. just hoping that what you will find is easy fix and a loose connection...

@colb has retrofitted a oil pressure guage on his 1.9 quite a nice little mod if you want a real oil pressure guage... so many of the guages on modern cars are ecu / dme controlled and not "real world" hard wired gauges...

 

[Pingu]

Not sure this would work as the oil pressure (red light) is only illuminated when the ignition is live and not running (should go out once running)
My circuit goes out right away so what would this prove ?

It can only be one of the following...

1. Faulty feed
2. Faulty component
3. Faulty earth

a. Pin 19 of the Instrument Cluster (page198) supplies the oil pressure switch with a voltage. I'd use a voltmeter to confirm that this is 12v, but you have put a bulb on there and jumped that stage. When confirmed that it is 12v, run a fused wire with bulb from the connector to earth and test. This will test the wire from Pin 19 to the oil pressure switch. This is the test that you have done. (Faulty feed and faulty earth tested)
b. The oil pressure switch is 12v. You have confirmed this. Disconnect the switch. Connect a fused wire with a bulb in series from the 12v terminal in the engine bay to the oil pressure switch, and test the switch by starting the car. Your bulb should do the opposite of the engine off state. That will confirm the switch and the earth are good. You can do this test with a "beep" diode tester, but it will beep with just a single wire strand - better to use a bulb. (Faulty switch tested)
c. Your next test is the cluster itself. Take the cluster off and check for damage to the tracks and make sure the bulb is secure and the contacts are clean. Find the earth and the bulb tracks, connect the earth track to the negative pole of a battery and connect a fused wire from the bulb track to the positive pole of the battery. (Faulty bulb tested)

 

[Lee]

It can only be one of the following...

1. Faulty feed
2. Faulty component
3. Faulty earth

a. Pin 19 of the Instrument Cluster (page198) supplies the oil pressure switch with a voltage. I'd use a voltmeter to confirm that this is 12v, but you have put a bulb on there and jumped that stage. When confirmed that it is 12v, run a fused wire with bulb from the connector to earth and test. This will test the wire from Pin 19 to the oil pressure switch. This is the test that you have done. (Faulty feed and faulty earth tested)
b. The oil pressure switch is 12v. You have confirmed this. Disconnect the switch. Connect a fused wire with a bulb in series from the 12v terminal in the engine bay to the oil pressure switch, and test the switch by starting the car. Your bulb should do the opposite of the engine off state. That will confirm the switch and the earth are good. You can do this test with a "beep" diode tester, but it will beep with just a single wire strand - better to use a bulb. (Faulty switch tested)
c. Your next test is the cluster itself. Take the cluster off and check for damage to the tracks and make sure the bulb is secure and the contacts are clean. Find the earth and the bulb tracks, connect the earth track to the negative pole of a battery and connect a fused wire from the bulb track to the positive pole of the battery. (Faulty bulb tested)

That sums it up nicely, I'll take the binnacle out and have a look. Failing that it looks like that single wire somewhere has a break.