oil pressure sending unit
Thread Starter
Advanced
Joined: Jul 2013
Posts: 86
Likes: 0
From: Yukon OK
oil pressure sending unit
Used the search function but just got back info on newer cars.
Before I replace the sending unit I just wanted to ask. I seem to have plenty of pressure running between 30-60 but the needle is not steady. It seems to vibrate or jump around erratically. The variation isn't that much, 10-15 psi but it's irritating.
Should I replace the sending unit or am I just paranoid.
Before I replace the sending unit I just wanted to ask. I seem to have plenty of pressure running between 30-60 but the needle is not steady. It seems to vibrate or jump around erratically. The variation isn't that much, 10-15 psi but it's irritating.
Should I replace the sending unit or am I just paranoid.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The sending unit wire has fatigued somewhere (probably at the connector on the sending unit) and is likely sending intermittant readings which cause the needle to jump around.
With the engine off, but key in "ON" position, have someone wiggle that wire while you look at the gauge (or vice versa). If you get it to jump from high to low, the sender wire is defective....most likely in the engine compartment.
With the engine off, but key in "ON" position, have someone wiggle that wire while you look at the gauge (or vice versa). If you get it to jump from high to low, the sender wire is defective....most likely in the engine compartment.
Le Mans Master
Joined: Nov 2006
Posts: 7,215
Likes: 1
From: Orlando FL
The sending unit wire has fatigued somewhere (probably at the connector on the sending unit) and is likely sending intermittant readings which cause the needle to jump around.
With the engine off, but key in "ON" position, have someone wiggle that wire while you look at the gauge (or vice versa). If you get it to jump from high to low, the sender wire is defective....most likely in the engine compartment.
With the engine off, but key in "ON" position, have someone wiggle that wire while you look at the gauge (or vice versa). If you get it to jump from high to low, the sender wire is defective....most likely in the engine compartment.
could be loose connection burned / frayed wire. If you are going under there the sending unit is not that expensive and easy to replace. Not sure you need to but it buys peace of mind
Advanced
Joined: Jun 2013
Posts: 64
Likes: 1
From: Lambertville Michigan
I was told that the gauge has an oil dash pot to it. The oil helps to eliminate the bouncing. This is a common thing used in race applications and often used in boats. A simple check is to turn the car to the "on" position and shake it. Does the gauge move? It could be a lose wire as stated above but I would check the possibility of a low oil condition of the gauge as well. I'm told that some of these old gauges were filled with oil or alcohol that would evaporate over time.
Let us know what you find out.
Let us know what you find out.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I don't believe that any fluid-dampened gauges have been installed in Detroit-built cars in the last 70 years (or more). Fluid-dampened gauges are common in industrial environments, where pressure spikes are present.
Advanced
Joined: Jun 2013
Posts: 64
Likes: 1
From: Lambertville Michigan
You misinterpreted me or I didn't make myself clear. Sorry. The gauge it self is not fluid filled. It is fluid damped. The back side of the unit has a damping feature. I learned this from a thread that Wilcox Corvette posted. Sorry I can't find it now but it had to do with an OEM C3 fuel gauge. I recall him stating that the fuel gauge was damped this way.
I fond a drawing that Wilcox had. See below. Note the "damping oil". I'm pretty sure that all gauges have a damping feature. I know the gauges that you are talking about that are used in factory applications. You can see the damping fluid in the face. I agree Detroit has not used that style in a long time.
I fond a drawing that Wilcox had. See below. Note the "damping oil". I'm pretty sure that all gauges have a damping feature. I know the gauges that you are talking about that are used in factory applications. You can see the damping fluid in the face. I agree Detroit has not used that style in a long time.
Last edited by Ely; Aug 30, 2013 at 09:07 AM.
