Oil pressure gauge stays stuck at the top...

175K911 · 10-14-2009, 07:31 AM

Once the car is warm, my oil pressure gauge stays at the top. I can tap the gauge and it'll drop to the correct place. On the track it works fine probably because it's getting jostled around, equivalent to tapping the glass. Is this something that needs to get the North Hollywood magic or is there something I can do to lube it, tweak something etc?

Formerly Steve Wilkinson · 10-14-2009, 07:51 AM

Does it snap to the top of the scale the minute you turn on the ignition? It shouldn't be going to the top (and consequently getting stuck there) as a result of actual oil pressure. If it's the former, it's a grounding problem, either in the gauge (which may be why it comes down if you tap it) or at the sender.

myamoto1 · myamoto1's Garage

+1 on what Steve said. If it pegs when the ignition first goes on (engine not running), you need to check the ground/condition of your oil pressure sender. Here's the thread I used to help w/ my replacement:

Question on replacing the oil pressure sender

DRACO A5OG · DRACO A5OG's Garage

In my situation, the wire to my connector on the oil sender was loose.

When my needle pegged up, I popped the lid and pushed the wire in to the back of the connector and it was back to normal. Couple of days later same symptoms

I pulled off the connector to discover the solder broke loose. Re-soldered and bingo no more issue. 4 months running.

kidrock · 10-14-2009, 08:41 AM

+2 on the ground. I'd pull the gauge from the dash first, and clean the connections there...because you stated that you could tap on it and it would register a change. If that doesn't work, pull the wire at the oil pressure sensor and ground it somewhere on the motor, and see what happens.

kidrock · 10-14-2009, 08:43 AM

open mouth, insert foot (again). Disregard that last post, it's actually smarter to check the wire at the sensor first. Draco A50G posted a split second before me, and I realized the error of my ways

mthomas58 · 10-14-2009, 08:49 AM

Quote:

Originally Posted by 175K911

Once the car is warm, my oil pressure gauge stays at the top. I can tap the gauge and it'll drop to the correct place. On the track it works fine probably because it's getting jostled around, equivalent to tapping the glass. Is this something that needs to get the North Hollywood magic or is there something I can do to lube it, tweak something etc?

I just went through a similar issue although my gauge pegged at 5 or 0. Sounds like you have a sender that is bad or is going bad. Replaced it and all is good now.

Ground locations for Oil Pressure Sender & Pressure Gauge?

Another Oil Pressure Sender Replacement Thread with pics

175K911 · 10-14-2009, 11:29 AM

Thanks everyone. I just rechecked the car which has been sitting for 2 days. Turn on the key and the gauge jumps to 5 without starting the car. Tap the glass and it drops to 0. Guess I'll be pulling the gauge tonight to check and clean the contacts. Doubt it's the sender since I replaced it and all other senders (including crank sensors) when the engine was out back in March.

175K911 · 10-14-2009, 01:36 PM

OK, the plot thickens. I got to the back of the gauge (one of the benefits of having removed the heat and A/C from the car) and pulled the plug off the back of the gauge. Sprayed it with contact cleaner and reinstalled.

Now if I turn on the key, the gauge pegs and you can hear the needle hit the top. Tapping on the gauge doesn't make it drop. Until I turn off the key, then tapping on it will make it drop. So I'v e actually made it worse. Go figure. Guess I better source another new sender to start with though I can't imagine it would go bad in 6 months.

McLovin · 10-14-2009, 01:43 PM

Did you try what was suggested above?

1) With the ignition on (so that the gauge is active), unplug the wire from the sender on the engine.

What does the gauge show?

2) Now plug it back in.

What does the gauge show now?

Before you do the above, clean the connector and the connection with contact cleaner. You should also be sure you are getting a tight "snap" fit on the connection.

myamoto1 · myamoto1's Garage

Read the post I linked for details, but here's the Reader's Digest version:

Turn car on (not start car)
Pop engine lid
Pull wire off of sender
Grab any spare wire you have laying around the garage (I used 12 agw)
Ground the spare wire to the engine (just touch it, nothing fancy)
Now touch the sender wire w/ the grounded wire.
If your needle drops - your sender is shot
If not, you've got a bad sender wire and need to start looking for breaks.

mthomas58 · 10-14-2009, 06:40 PM

Quote:

Originally Posted by 175K911

OK, the plot thickens. I got to the back of the gauge (one of the benefits of having removed the heat and A/C from the car) and pulled the plug off the back of the gauge. Sprayed it with contact cleaner and reinstalled.

Now if I turn on the key, the gauge pegs and you can hear the needle hit the top. Tapping on the gauge doesn't make it drop. Until I turn off the key, then tapping on it will make it drop. So I'v e actually made it worse. Go figure. Guess I better source another new sender to start with though I can't imagine it would go bad in 6 months.

These symptoms are now identical to my bad sender problem.

175K911 · 10-15-2009, 05:31 AM

I've tried all the suggestions related to the sender. With sender unplugged it stays at zero, with it plugged in, the gauge acts up. Grounding the wire to the sender everything stays the same, i.e., gauge pegs, but tapping the glass makes it drop. So I'm going to have to pull the gauge and check internal contacts. The fact that it works fine when being jostled around at track speeds and when tapping the gauge glass really makes me think gauge, but it's always worth checking out all the possibilities

175K911 · 10-16-2009, 06:53 AM

Thanks everyone, the problem is now fixed. After pulling the gauge, checking the connections at the sender and everything else, turns out it was the wire into the plug at the back of the gauge. The wire was broken right at the crimp inside the plastic plug at the back of the gauge. Quick repair with a new crimp end and all is well.

That's what's great about this site. Thanks to Wayne for hosting it.

kidrock · 10-16-2009, 11:10 AM

Sweet. I love an easy fix.

dictoresno · dictoresno's Garage

sorry to revive an old thread.

my oil pressure gauge pins at 5 bar when I turn the key to on before starting the engine, and stays at 5 during idle, warm up and while driving. I had the gauges out recently to dismantle and clean them and they are wired properly. would this likely be a ground issue at the gauge or the sender being bad? temp gauge works no problem, so im assuming maybe the sender. this was my dads car that he gave to me recently that im sorting through and fixing up now so asking for a proper history of when it was last working properly, he has no idea.

917_Langheck · 917_Langheck's Garage

Quote:

Originally Posted by dictoresno

sorry to revive an old thread.

my oil pressure gauge pins at 5 bar when I turn the key to on before starting the engine, and stays at 5 during idle, warm up and while driving. I had the gauges out recently to dismantle and clean them and they are wired properly. would this likely be a ground issue at the gauge or the sender being bad? temp gauge works no problem, so im assuming maybe the sender. this was my dads car that he gave to me recently that im sorting through and fixing up now so asking for a proper history of when it was last working properly, he has no idea.

The meter is a negative (or inverse) coefficient type, which means when it is not connected to the sender it pegs at the top.

But also, always check the ground points.

dictoresno · dictoresno's Garage

Quote:

Originally Posted by 917_Langheck

The meter is a negative (or inverse) coefficient type, which means when it is not connected to the sender it pegs at the top.

But also, always check the ground points.

The ground on the back of the plug on the gauge seems in tact. The oil temp gauge works just fine. I also found that when I tap the gauge, the needle drops back to zero. Ordered a new sender just in case. When I activate the key, the gauge pegs from 0 to 5 and stays there until I tap it back down after turning the car off.

Sent from my iPhone using Tapatalk

917_Langheck · 917_Langheck's Garage

When I start my '84 the meter does not move until pressure is made, so no key on jump.

I will run a test with the wire off to see if that changes.

wazzz · wazzz's Garage

Quote:

Originally Posted by dictoresno

The ground on the back of the plug on the gauge seems in tact. The oil temp gauge works just fine. I also found that when I tap the gauge, the needle drops back to zero. Ordered a new sender just in case. When I activate the key, the gauge pegs from 0 to 5 and stays there until I tap it back down after turning the car off.

Sent from my iPhone using Tapatalk

Issue is probably not related to the sender. Otherwise you wouldn't be able to make the needle drop back to zero by tapping the gauge. It certainly lies in the gauge itself or the signal wire that connects to the gauge. Clean the contacts and check.

When the needle pegs to max with ignition on and engine off, that means the circuit to the sender is open somewhere. The sender is a 2-pole component connected between ground (from engine case) and signal input at the gauge. It is like a potentiometer, with its resistance varying between near zero ohm (when pressure is nil) and 130 or 150 ohms (can't remember the exact figure) when pressure is at max. So in your case it is like having max pressure => infinite resistance.