Oil Pressure Gauge pegged engine off ignition on - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 7 (permalink) Old 05-05-2011, 06:46 AM Thread Starter
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Oil Pressure Gauge pegged engine off ignition on

Aynone know what I did to get my oil pressure gauge to show pegged pressure with the key on and engine off? I know the sensors run on resistance so suspect
a miss wire? The isolated oil pressure connection goes directly to the sender so I suspect somehow I am "Powereing" the gauge? 66 GTV.
Can someone explain how these sensors work? does the guage need power?
I would welcome any suggestions.
Thanks,
Shayna
email: [email protected] for direct contact or 603-863-6480
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post #2 of 7 (permalink) Old 05-05-2011, 08:00 AM
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Yes the gauge gets 12V from fuse box on one side, then the reading from the sending unit comes in the other side. Plus there's a ground. I wonder if you have the 12V and sender wires crossed? Or if the sender wire is grounded it'll peg the gauge, but that should happen only with the key on. Is it getting power with the key off? A test light or voltmeter will tell.
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post #3 of 7 (permalink) Old 05-05-2011, 08:03 AM
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I re-read and see you say with key on. Your sender wire is probably grounding somewhere, or the sender is bad and making no-resistance contact all the time. At least I think I have that right. Does the gauge change when you start the engine?
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post #4 of 7 (permalink) Old 05-05-2011, 08:22 AM
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Try pulling the wire off of the sending unit. If the gauge drops, the sender is likely bad. If the gauge stays pegged, the wire is grounding out someplace between the gauge and the sender.
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post #5 of 7 (permalink) Old 05-05-2011, 08:31 AM
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Quote:
Originally Posted by Shayna Malool View Post
Aynone know what I did to get my oil pressure gauge to show pegged pressure with the key on and engine off? ..66 GTV.
Shayna:

Tell us more. Did your oil pressure gauge ever work? Was it working OK one day, and then just showed "max" the next? Or has there been some work to the wiring, a change in the pressure sensor, or an engine swap recently?

A "red flag" is your mentioning that this is on a '66 Sprint GT. The early cars like yours use a different system than the later cars - the early sensors work backward from the later ones. So a common problem happens when you install a later engine (with its O.P. sensor) into an early chassis, hook up the gauge, and get weird readings (ask me how I know). A few threads have discussed this - you could start with the one at: http://www.alfabb.com/bb/forums/gt-1...veglia-gt.html

If this is your problem, Centerline sells the early-style sensors.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 05-05-2011 at 08:34 AM.
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post #6 of 7 (permalink) Old 05-14-2011, 01:22 PM
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Good catch, Jay. Like you, I've been there.

Gary Williams
Washington State
'67 GTV
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post #7 of 7 (permalink) Old 05-16-2011, 04:53 AM Thread Starter
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Hi Jay, I had the pressure guage reading backwards years ago then parked the car till I could aford restoring it completely. No blown fuses so I suspect an earlier sending unit was installed, getting an earlier one.
Thanks,
email me at [email protected] and I will forward you a picture of the GTV on Road America.
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