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Discussion Starter #1
Evening team,

I have a 1986 75 1.8. The oil pressure gauge was functioning intermittently but seems to have stopped altogether now. I'd like to get it working again.

My reckoning is that it is either the sender, the wiring, or the gauge. I want to start with the sender but I'm not sure I'm looking in the right place. I have plenty of manuals of 75 TSs but nothing on the older 1.8.

I think the sender is the one located just under the distributor. It is a 2 wire unit, both are orange/grey and run back into the dashboard console from what I can see.

I assume that one wire is for the gauge and the other for the low pressure warning light.

I'd like someone to confirm my assumptions regarding the sender position and the wiring are correct so I can be sure I'm tracing the fault correctly. And if someone has a wiring diagram for this model that would be much appreciated.

Thanks in advance.
 

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sender is under the intake to the rear of the head. It's a round "can" kinda thing with one wire coming off of it. About the size of a shot glass and IIRC 15mm open end will get it off. change it first, they usually are the issue. I used a SunPro unit on mine and am pleased with the result. See Roadtrips posts on the 164 side for details. ciao, jc
 

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Discussion Starter #3
Thanks JC. It's very well hidden under the carbs, no wonder I didn't see it. That's going to be fun to get out.

Cheers,

Mark
 

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easy, it's a 5 minute swap, 10 if the engine is hot. There is a very small copper gasket (sealing ring) that you dont want to lose. I used a wee bit of grease to hold it in place while reinstalling. ciao, jc
 

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Discussion Starter #5 (Edited)
I have a follow up question with regards to gauges and senders, switches and warning lights, and oil pressure.

I've followed the advice above and replaced the oil pressure sender which got the gauge working. It's a new sender from a reputable supplier. On start-up it jumps to 6 bar cold and stays there. I'm thinking that's not right.

The low pressure light also comes on red, and after a minute starts blinking.

Also did an oil change.

The engine sounds and runs absolutely perfect - although I haven't taken it for a drive, I'm too scared.

Also I've read quite a few threads referring to low oil pressure switches having one wire. Mine has two - both grey/red from memory. Wiring looks fine.

Any thoughts?

Much appreciated.
 

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my thought keeping in mind the engine I have is 1.6 carbed, but I think they are the same for our discussion. The 2 wire switch near the fuel pump/distributor on the block is for the low oil level signal to the computer in the dash. The low oil pressure switch is on the other side near the dipstick and rear of alternator. The pic I'll put up is the oil level sensor. I'd give thought to changing the oil switch as they are very cheap and easy to do. At a minimum, take the cable off it and clean it and the terminal on the switch. Mine did the same thing and I dont recall the "fix" but in the course of the car being new to me, I changed the sender and switches and everything functions as it should.

as far as being 6 bar and staying there, mine goes up to somewhere around there then as the engine warms it goes down and then rises and falls with the engine revs as I'm driving it. I think the gauge is not more than a guide with accuracy of the numbers being "suspect" - this is Italy and an Italian car afterall!! It takes an age for the oil to come up to temp and then it thins and changes the readings. I've never seen an Alfa 4 with an oil pressure problem that couldn't be chased down to the sender. Street cars, race? No idea what they do as far as OP goes.

From what you say, I'm led to think you've not driven it far or enough to warm it fully and see what the guage is doing. If it were mine and based on what I read you saying, I'd drive it and see where you are engine wise. ciao, chris
 

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Discussion Starter #7
Thanks JC96 - you beat me to an update and you're absolutely correct.

I went and had a beer and read some more posts on the forum and came to the conclusion I'd been looking at the wrong sender. The reason I didn't identify the correct one early was the PO had removed it and replaced it with a bolt which looked like it was supposed to be there. I then found the stray connector which I assume must have been earthed to the body to stop the warning light.

So in my case there have been two untimely coincidences. (1) the oil pressure sender failed, and (2) the switches earth came away from where ever it was. Result was a gauge showing zero and a red flashing light. Then I replaced the sender, changed the oil, and ended up with a working sender (but reading higher than I remember - perhaps the new sender reading more accurately?) and a flashing light. What are the chances?

Thanks for your help.
 

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Good to hear. Somewhere on the BB is a thread I did a few years ago where I cut up a sender and exposed the guts. In a nutshell there's a diaphragm that stiffens and the new sender is more flexible thus the different readings. On the 164 side of the BB a guy "Del" who also peruses here on the Milano side, has a method where he drills a hole in the sender and inserts a screw to calm any leak and this sort of vents the backside of the diaphragm so it can do its thing. I've tried this on 2 of them but no luck as they're 25 years old at this point the sender is/was too far gone. I can only hope 25 years from now, stiffness is a "problem"....ciao, jc
 
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