Oil Pressure Indication

[aj81spider]

I'm not sure I have a problem, and if I do it's not clear if it's engine or electrical. However, when I first start the car (1974 with newly rebuilt engine) the oil pressure guage shows a reasonable pressure (around 20). While I'm driving it also shows reasonable pressure. However, once I warm up - i.e. the temperature guage reaches running temperature, the oil pressure guage shows 0. The warning light never comes on, and the car seems to be running fine.

This doesn't seem normal, and looking for any thoughts or feedback.

[narfire]

I have a mechanical oil pressure gauge installed on my 2L. At start cold I show around 70psi, settles to around 50-60 at idle and then when warm down to around 50psi. 20-50 oil, outside air around 17-22 deg C. When driving it moves up or down depending on rpm as it should I suppose.
20 at start is low in my opinion. Oil level? , no crunched oil pan?
Chris

[azruss]

Sounds like a sender issue. there is a jet in the intake hole and that can be unscrewed and cleaned. Not uncommon to have gunk in this tiny orifice. Hard to remove with the oil filter in place, but the oil doesnt have to be drained.

[carl]

The oil pressure senders for the gauge and the light are separate units so if your gauge reads too low but the light does not come on it is probably the sending unit for the gauge. With no oil pressure you would have had serious damage with any run time so we can assume you have OK pressure. If you want to see what pressure your engine really has then you should get a mechanical gauge.

[aj81spider]

Thanks for the replies. I'll add the sender to my list of things to do. It just seemed odd that the readings changed after the engine came up to temperature.

[DanD]

What oil are you running ? A drop in pressure can indicate a loss of viscosity.

0/20 won't cut it in these engines. 5/40 0r 10/40 used to be standard in the old days and a lot of us ran 20/50 in the summer.

I'm not saying that this is your problem, but it is always good to look at the whole picture.

[aj81spider]

Hi Dan,

I'm running 15W-40. Basically that's what my owner's manual calls for, and it seems that a lot of people are running that wieght, so I settled there.

[aj81spider]

Ordered a new oil pressure sensor and tried to install it today. Unfortunately I could not get the old sensor off. I can only fit an 8" crescent wrench into the space around it and could not generate enough leverage to move the old sensor.

Short of pulling the engine any thoughts on how to get the old sensor off?

Thanks for any ideas you can provide.

[sptcoupe]

It is normal for oil pressure to drop as it warms up.

[spiderdan]

the oil pressure guage shows a reasonable pressure (around 20). While I'm driving it also shows reasonable pressure. However, once I warm up - i.e. the temperature guage reaches running temperature, the oil pressure guage shows 0. The warning light never comes on, and the car seems to be running fine.

Hi aj81, your observations above are exactly how my 68 runs. I always use 20-50, and over the last 13 years my gauge reads like yours. I have never had the engine rebuilt and it just turned 160,000 miles. I asked my Fiat mechanic about it years ago and was told, lots of them are like that. He said you can spend time replacing gauges, senders, etc...or just leave it alone.
Now when that little red light goes off, different story...

I thought my gauge did that just because it was old, but hey, at least it's original and it works, kinda....

[seabeelt]

I'm running 20/50 rotella. I get 40-50 psi when cold at start up, normal when warm and at speed is 20-30 and just above 0 when at idle. If you look at some of the early road and track articles for the new model years, this happend even when new. When I first got this car, the PO had a resistor wired in parallel to the sender to make the gauge read higher.
R/

[sptcoupe]

The Veglia oil gauges are famous for showing zero or very little pressure at idle. In the 60's and 70's, even in the new cars I owned then, it was common for the light to flicker at idle. Of course, that meant a trip to the dealer, who would put a mechanical gauge on the car and show us we had pressure, and tell us not to worry about it. I had a '72 spider and a 124 coupe that both had this issue. In fact, it was such a problem that, as you know, they finally removed the gauge. I was told they did this because whenever a customer came in for service because the oil light was on or flickering at idle, it counted as a service call and was included in the consumer surveys of how many times your car was in for repair in the first 90 days etc, making the reliability appear much worse than it was.

[BEEK]

the gauge and the light are handled by completely different sending units. While the the sender that runs the gauge is most likely inaccurate, the one that runs the light will not be. when that unit reaches less than 5lbs it turns on the light, at that point stop and figure out why! the early light sending units did leak from the center post, which would cause a false reading, but those units have been gone for years.

[Exit98]

Ordered a new oil pressure sensor and tried to install it today. Unfortunately I could not get the old sensor off. I can only fit an 8" crescent wrench into the space around it and could not generate enough leverage to move the old sensor.

Short of pulling the engine any thoughts on how to get the old sensor off?

Thanks for any ideas you can provide.

But no one answered AJ's question, which is the same one I have, how do you get the damn thing off?

AJ mines the same as yours and my engine runs like a top. I just know the pressure is good. But I want my gauge to tell me that. If I can figure out how to get it off I'll clean it up or replace it.

[seabeelt]

I used a big pair of channel locks to get the old one off. Expect to mangle it some. I think it's either a 17 or 19 mm wrench that might fit. I haven't tried the one from the tool kit as it is a little thinner than the standard combo wrench but would be interested to know if that works.
R/