Oil pressure guage

Hi to all
Still working on my 1979 ta 403 k code with rally guages
The oil pressure guage is not working, temp guage works normal, the rest of the center cluster works normal.(engine has oil pressure)
I have replaced the oil/temp guage assembly, the printed circuit board, and even tryed a new sender.
Battery is grounded to engine, engine to firewall,transmission to frame,dash to firewall.
When I remove wire off sender, guage pegs to the right, when I ground the wire the guage goes to zero. When connected the needle just sits there, key on,off engine running or not.
I have seen guage work before, all I am doing is replacing dash light bulbs.
Has anybody been thru this and corrected it
Any help is greatly appreciated Thanks  

do you have a ground strap between the engine and the firewall????

because the ground is half the circuit..



but..  you probably have too much teflon tape on the threads of the sender.. so the body is isolated from ground..



i will be back with the resistance readings...

i am taking that you have an ohm meter..


0 to 3 PSI    0 to 5 ohms of resistance...

7 PSI       13 to 26 OHMS

60 PSI    58 to 83 OHMS

80 PSI    70 to 105 ohms...

this unit only reads to 80 PSI..

the terminal is grounded through the housing and the threads into the block...

so.. either the sending unit is defective..

the  sending unit is not properly grounded via the threaded connection..

or

the sending unit is NOT grounded through the oil filter adaptor..  as the oil filter adaptor might be isolated by the gasket or the amount of paint on it..

OHM the sending unit terminal to the block...  digital volt meter set to 200 ohm scale..

0 to 5 ohms with the engine off.. .

you should have somewhere between 20 and 60 ohms at idle..  

Hello
Thank you for your time this is the 403 k code(olds engine) which means the op sending unit is up front with an extension tube, (factory)
I removed the teflon tape and the sending unit is secured to engine by a strap bolted to block.(factory) Is that the ground?
The grounds I found out are extemely important.
I have new ground from battery to engine, cleaned both ends of ground strap, engine to firewall, witch is back of engine, cleaned ground under car, trans to frame.
and added a new ground from center cluster to firewall
I also added a ground wire to my power window motors both sides,and that helped so much that I do not need the 4 relay set up at this time (thats another story)

I am getting a colored wiring diagram to verify
I am getting battery voltage at sending unit end of wire.
Sounds like my testing sending unit wire is working opposite from what you stated
Not sure why
I have 2 sending units now 1 new 1 orignal
I will do ohm test next
These cars a simple compared to... Anyway Thank you again and I will check back.