[DeTomaso] Oil Pressure Gauge

[Joseph F. Byrd, Jr.]

Just saying....When I google NAPA OP6091, I get a SWITCH.  
You could use a DMM and see if not running you have "open" and once cranked
"closed".  A sender would have about 70 ohms not running and approaching 0
running.

I would still want a mechanical gauge locally.  ( I like Marshell's for
automotive)

Joe/NC

-----Original Message-----
From: DeTomaso [mailto:detomaso-bounces at server.detomasolist.com] On Behalf
Of Mike Drew via DeTomaso
Sent: Wednesday, August 31, 2016 20:37 PM
To: mbefthomas at comcast.net; detomaso at server.detomasolist.com
Subject: Re: [DeTomaso] Oil Pressure Gauge


In a message dated 8/31/16 17 26 15, mbefthomas at comcast.net writes:


> I'm trying to figure out why I'm getting a pegged reading on my oil 
> pressure gauge.  It will show normal pressure as the car starts, but 
> soon after pegs to the right and stays there.  Everything runs fine 
> otherwise.  I've swapped out the pressure sender, NAPA OP6091, and 
> it's still pegging, so I'm suspecting the gauge.  Anything else I 
> could check?
> 

>>>Calling Bill Taylor!   That is, assuming it's an electrical.   You can't 
make that assumption though.

I *think* I may have stumbled across something.   Doing some primitive 
Google research, I confirmed what I thought I knew, which is that the oil
pressure gauge works by taking 12V power in, which runs across the gauge,
then out 
to the sender unit, which is a variable ground.   The reading given by the 
gauge depends on the resistance of the sensor unit; this in turn is
determined by the engine's oil pressure.

Extremely high readings after a cold start, if they are accurate, mean the
pressure relief valve near the pump and filter has probably stuck. The
engine should be switched off or the oil filter could burst.

I have a mechanical oil pressure gauge which threads into the hole normally 
occupied by the electric sender.   It is used to 'sanity check' the 
readings on the gauge.   It's the first troubleshooting tool; if the
mechanical 
gauge reads high, you have an engine (or at least oil filter) problem.   If
it 
reads normally, you have an electrical problem.

I could mail it to you tomorrow and you would have it by the weekend?   Let 
me know if you would like to try it out.

Mike