Oil pressure gauge reads low - machanical measurement is within spec

[86tona]

I rebuilt the 2.2 in my Turbo Z about 5000 ago. When I started it I freaked out because the electrical gauge read low.

I then tested the pressure with a mechanical gauge and I have good pressure 'hot' at both idle and at 3000 RPM as per the FSM tests. All these tested within spec or a bit above.

Has anyone had a problem with the electrical pressure gauge reading low?

I've changed the sending unit and the gauge with my other Daytona which reads 'normal'.

The other car is a 2.5 TBI and the Turbo Z of course has a turbo. I've installed the Turbo's Unleashed braded hoses for both coolant and oil feed and the turbo was rebuilt before being installed.

The measurements on the bearings were well within spec (complete article of the build is published if interested please let me know and I'll post a link).

Any thoughts?

[tryingbe]

Most common cause is the bad sensor. Buy a new sensor and be done. You want to change the big one.

[86tona]

I did that by swapping with a known good one. My other car also a Daytona has the same sending unit. The problem didn't change. I suspect a wiring issue like perhaps a bad ground or weak 12v feed.

[Force Fed Mopar]

What is the mech oil pressure reading? Mine runs about 5-psi at hot idle, I think I'm missing the restrictor in the block.

[86tona]

Mine runs between 5 and 8 at idle and over 45-55 at 2500 RPM. At idle cold, the gauge reads above the second line from the bottom. When it's running at 2500- 3000 RPM hot it's at the line or slightly above it most of the time.

I'm not sure about a restrictor block. I have to believe the guy who rebuilt it installed that though I'm not sure. I was unaware of 'restrictor' block when I built assembled the engine. I'll check to see where it goes and see if I have one.

[135sohc]

Thr restrictor block goes in the vertical gallery that feeds the cylinder head. Slightly bigger than a 22 caliber casing with a hole drilled in one end.

[86tona]

Thr restrictor block goes in the vertical gallery that feeds the cylinder head. Slightly bigger than a 22 caliber casing with a hole drilled in one end.

The head is fed via the pump, through the block and into the head. Where does this 'restrictor' block go?

Keep in mind I'm getting 'normal' pressure when mechanically checking. It's only at the electronic gauge that I see low pressure readings.

[turbovanman²]

Why are you worried about the factory oil pressure gauge? Its dodgy at best. If you know you have good oil pressure, then simply use your current gauge position and note that for future use.

Your not missing the restrictor if you have good oil pressure when using a real gauge.

[86tona]

Why are you worried about the factory oil pressure gauge? Its dodgy at best. If you know you have good oil pressure, then simply use your current gauge position and note that for future use.

Your not missing the restrictor if you have good oil pressure when using a real gauge.

I'd like the interior gauge to read accurtely. It is my only indication regarding the pressure when I'm driving. I know I have good pressure and it indicates low on the gauge. Still, I'd like to know when something or should something change so I can shut down before too much damage is done.

[tommyturbo]

I know on one of my cars, the wiring was finiky where it plugs into the sensor, depending on which way it was bent / twisted would change how the gauge read. Yours should be the single wire kind, where as the one that was giving me trouble was a later style two wire.

[turbovanman²]

I'd like the interior gauge to read accurtely. It is my only indication regarding the pressure when I'm driving. I know I have good pressure and it indicates low on the gauge. Still, I'd like to know when something or should something change so I can shut down before too much damage is done.

If you know how it reads now, then you use that as your baseline. Factory gauges are notoriously inaccurate, and should be simply used accordingly. I got fed up with mine and put a real gauge in. If your sender is good, which I find OE is better, then the wiring or gauge is bad.

[86tona]

If you know how it reads now, then you use that as your baseline. Factory gauges are notoriously inaccurate, and should be simply used accordingly. I got fed up with mine and put a real gauge in. If your sender is good, which I find OE is better, then the wiring or gauge is bad.

I believe the wiring at the cluster or a ground is bad. When I get the chance I'll measure the mechanical pressure on my 2.5 and compare that with my 'new' 2.2. That should help understand what if any difference pressure makes on the reading at the gauge. I understand that factory gauges are not all that accurate. But in my nearly 40 years of working on these things this one stumps me. I've had a Daytona for going on 26 years as I bought my first one in December of '85. It doesn't show me actual pressure but I like to see half or higher on the gauge as 'normal'. So I'll compare the voltages at both my 2.5 TBI and my 2.2 when I get around to it. In the mean time I thought I'd ask if anyone has experienced this issue and solved it rather than replacing the gauge with a mechanical one. That is not an option for me on the TurboZ as it is used primarily for show and I want everything in the interior to be as stock as possible.

[turbovanman²]

What are the readings cold? You said 5-8 psi hot? For a rebuilt engine, that is kinda low, I see 25 psi on my van and 75 psi at 3000 rpm but I do have the MP spring in, which raises the max pressure 10-15 psi i believe. I also run 5w40 synthetic. What oil do you run? Post up your cold pressures idle and 3000 rpm, that will help us pinpoint it. Sorry, I missed you posted up actual pressures earlier.

I understand your wanting to stay stock, so if everything checks out, then you'll have to adjust your brain,

[tommyturbo]

Like I said i went through this with my 89 GTC conv. The oil pressure gauge would read very low and drop to 0 at idle. That's part of how I got the car so cheap, as previous owners though the engine was dead. He had even had the rod bearings replaced thinking that was the problem. With a mechanical gauge verified engine was ok, drove around and got the thing good and hot, and saw that oil pressure was very good and within spec. Checked all the wiring behind the cluster by wiggling around the wires while the engine was on and the cluster was half out of the dash and found no changes. Looked under the hood and noticed more closely that the oil pressure sending unit had been replaced but they had broken the clips in the plug. Harness was a bit loose. Played with the wires while a friend sat in the car, and noticed it did change the readings substantially. Then once the wires seemed to be making good connection ( wires had been twisted somewhat at the plug like they had tried to unscrew the sending unit with the wiring attached) I replugged in the harness and secured it with a zip tie. Oil pressure gauge works pretty good now, although each of my cars have their own personalities with regards to readings on oil and water temp. Keep in mind these sensors and gauges all work off of electrical resistance and over time things can get corroded, loose, etc. your 86 is 25 years old.

I totally get the trying to keep things original...I'm very much doing the same thing with my cars.

[Force Fed Mopar]

The restrictor is not a block, it is a small round metal sleeve that goes into the oil feed galley in the block that feeds the head. It has a small hole in the downward end and the top end is completely open. The cyl head has to be removed to check for and install it.