66 340 Skylark w/ Autometer Oil Pressure Gauge/Sender Issue

Hi everybody,

I just installed an electric Auto Meter oil pressure gauge in my Skylark along with the remote sender and I am having a bit of an odd issue.

First, the car has the proper level of oil (just checked), the car is new-ish to me (last 6mos) and I have never tested the oil pressure before (although the idiot light never came on for what it's worth). Second, the gauge is one of three new gauges in a pod and they all share a daisy-chain pair of Ignition+ and Engine Block- and the other gauges and new tach all work fine for what it's worth.

The issue I am having is that on start up, the needle jumps up to 25psi and stays there even when I pump the throttle- at the most, it will jump to maybe 27psi under aggressive throttle but the change is so subtle you can barely see it. Other than this, the gauge behaves the way it should meaning it turns on/off with the ignition and the needle doesn't bounce around. Now I am not a smart man, but every old car I have ever had would always jump noticeable between idle oil pressure and maybe 2500RPM pressure- I want to say it could be 20-30PSI on these other cars. It's almost as if this new gauge had some kind of sensitivity setting or something where instead of reading a range of 50-75PSI, it is only reading 25-27PSI.

Any thoughts?

Thanks,
Ray

 

As additional information, I called Auto Meter and the tech suggested that I pull the sending unit, clean off the teflon tape, put teflon tape only on the back half of the threads and re-install all of it. His reasoning was that maybe the teflon was causing a grounding issue and by having the first half of the threads naked, it might ground better.

I spent my lunch break pulling the alternator and doing all that was suggested and re-installed, but same issue. One thing that I didn't tell the guy because I had forgotten about it is that I am using an adapter from what I think is 1/4" NPT at the block to 1/8" NPT on the sender nipple; I cleaned off the threads on both when I re-installed.

Yeah, I agree on the driveability aspect. I am going to get a mechanical gauge and give it all another go to see if I can rule out the ground issue. Hopefully (!), there is only a problem with the gauge/sender and I don't really have horrible oil pressure, but its an old car that might have never been rebuilt so we'll see.

[Edit]
The pressure is at 25 at start and she was sitting in an insulated garage overnight at about 40deg. When I warm the engine up to 180 and drive around the block, it is at 25 and never budges.

 

Yeah, if I put a grounded wire directly to the sender terminal, the gauge goes full sweep as soon as the ignition is on.

 

I invested in an OTC gauge that doubles as a tranny pressure gauge kit thinking that I could use it later when trying to set up a 200r:
https://www.amazon.com/gp/product/B000R5G0DO/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

The bad news is that the manual gauge gives me 27psi on fast idle after giving her about 5min to get a bit warm (not wanting to drive it now or get it really warm just yet) and if I goose the throttle a bit it ranges up to 35psi but that's it.

I am going to start a new thread for some advice on pulling the engine and giving it a light overhaul. I don't want to go crazy because it is a 340 and I could easily rack up a bill on what parts are actually available when I might be better off with a nailhead or 455 (not for $$ but for ease of finding parts).