4200 cc, Oil pressure zero

gillis

Junior Member
Messages
77
I performed a HVAC reset today (Aircon right and middle knobs set to auto, left knob full left. Hold eco and circ button while turning ignition)
Immediately after the systems performed the reset , right after starting the engine I saw the oil pressure indicator at zero and the red oil indicator flashing. Not good!
Engine runs perfectly fine though. No ticking noises at all. Checked oil level. No issues there. Decided to do a short drive anyway. Still zero pressure at the indicator.
sticked an odb reader in my car. Nothing. Started the engine again and the pressure indicator is back to normal. No flashing lights. What the ****??
i did fiddle around with the fuseboxes to see if there is an issue there, but that cannot be it right?
Drove around for at least 10 miles. The issue did not come back.
Car is good now. But I am curious to know the cause. Anyone?
 

2b1ask1

Special case
Messages
20,220
Clearly you upset its 'Italian' temperament....

I seriously upset mine last year by taking it to the Alfa museum and it refused to give me any gears in the car park until I revved it to the redline out of frustration!
 

2b1ask1

Special case
Messages
20,220
I can just picture that :)

I thought we were going to do a Benny and have to drive home in a cr@ppy little hire car from Milan! We had been in the museum and when we tried to leave it just gave me an engine management light, refused to give me any gears and a full reset didn't work. SM/Top Gear rules applied and everyone else sodded off to Como leaving Jeanette and I with the prospect of awaiting Luigi and his low-loader! Out of pure frustration I bounced it off the rev limiter and it cleared the dash! It has been faultless ever since...
 

Zep

Moderator
Messages
9,110
I performed a HVAC reset today (Aircon right and middle knobs set to auto, left knob full left. Hold eco and circ button while turning ignition)
Immediately after the systems performed the reset , right after starting the engine I saw the oil pressure indicator at zero and the red oil indicator flashing. Not good!
Engine runs perfectly fine though. No ticking noises at all. Checked oil level. No issues there. Decided to do a short drive anyway. Still zero pressure at the indicator.
sticked an odb reader in my car. Nothing. Started the engine again and the pressure indicator is back to normal. No flashing lights. What the ****??
i did fiddle around with the fuseboxes to see if there is an issue there, but that cannot be it right?
Drove around for at least 10 miles. The issue did not come back.
Car is good now. But I am curious to know the cause. Anyone?

The sensor works with a diaphragm that moves a wiper across a resistance wire. It sounds like it jammed and might be on its way out, they are a common failure.

The main symptoms are that the needle ticks (jumps from one reading to another) or goes out of calibration (reading less than 1.25 bar at idle or less than 5 bar at over 2000 rpm. Or a mixture of both.

As to whether it is related to your AC reset, I doubt it.
 

gillis

Junior Member
Messages
77
Great feedback guys.
The sensor works with a diaphragm that moves a wiper across a resistance wire. It sounds like it jammed and might be on its way out, they are a common failure.

The main symptoms are that the needle ticks (jumps from one reading to another) or goes out of calibration (reading less than 1.25 bar at idle or less than 5 bar at over 2000 rpm. Or a mixture of both.

As to whether it is related to your AC reset, I doubt it.

Is this sensor replaceable from the outside? Any guide on this ?
 

Zep

Moderator
Messages
9,110
Great feedback guys.


Is this sensor replaceable from the outside? Any guide on this ?

As above, it’s not too tricky. Standard crows foot spanner’s can be a bit too thick to get in but I have a set of tools that I have made for the removal and install of the sender that I lend out. I also have had some adapters made to allow the use of a standard sized sender so that you don’t have to buy the expensive OEM one. PM me if you would like one.
 

gillis

Junior Member
Messages
77
Problem is back (of course :))
Now I noticed that when driving over a bump the indicator goes wild. Sometimes stays fine for a few miles and then goes back to zero with the oil indicator flashing.
To me it looks like some kind of electrical connection issue. Wonder if this is a common issue with the sensor itself or maybe some connector/wire else where.
 

allandwf

Member
Messages
10,958
Problem is back (of course :))
Now I noticed that when driving over a bump the indicator goes wild. Sometimes stays fine for a few miles and then goes back to zero with the oil indicator flashing.
To me it looks like some kind of electrical connection issue. Wonder if this is a common issue with the sensor itself or maybe some connector/wire else where.
Most likely the sender. If you have ever seen the internals you would be surprised they work for as long as they do!
 

Zep

Moderator
Messages
9,110
Most likely the sender. If you have ever seen the internals you would be surprised they work for as long as they do!

Your wish, etc etc
 

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Zep

Moderator
Messages
9,110
Problem is back (of course :))
Now I noticed that when driving over a bump the indicator goes wild. Sometimes stays fine for a few miles and then goes back to zero with the oil indicator flashing.
To me it looks like some kind of electrical connection issue. Wonder if this is a common issue with the sensor itself or maybe some connector/wire else where.

It might well be the connection, either external to the sender or internal. But it’s probably the spring in the sender being broken and causing the arm to wave around a lot.
 

gillis

Junior Member
Messages
77
With help of zeps tools I was able to replace the oil sender unit. It solved the issue.
Removing the sender wasn't easy. In my case I had 2 big bundles of wires very tightly passing the sender unit. Had to remove a bunch of clamps to push the wires away. Also removed parts of the lubrication system to get more room.
Finally I had the issue of not getting enough torque to unscrew the thing. Only after using a torque wrench I was able to get it loose.
Took some time afterwards to realign all the wires. In a better way than Luigi and mario did :)

After removal
57669
 

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