Oil pressure gauge install headaches

Messages
3,228
Location
Richmond, VA
My 07 Mustang GT with a 4.6L has a dummy oil pressure gauge in the cluster so I wanted to be able to see the actual oil pressure. Ordered a cheap electric oil pressure gauge with sender from Amazon and installed it today -- it took me 5 hours🙈. First when i took out the factory sender I immediately noticed the bolt that screwed into the engine block was bigger than the one on my sender. Luckily Home Depot had a perfect adapter that soleved that problem, but created an new problem. Now with the adapter the sending unit will not screw in because it is too long and the electrical connector is hitting a part of the frame- but barely. Remember this is a $20 part so I am not to afraid to modify/break it in an attempt to make it fit. Since the clearance is so close, I attempt to grind down the connector. All is going well UNTIL the entire connector rips off from the vibration of the grinder. The good news is that the wire is now exposed from the back of the sender. I grab a razor blade and strip away some insulation then solder a wire that goes to the gauge. To fill in the small hole that has been created by the connector exploding I put a generous amount of silicone and decide to procede. Now I screw the sender into the block after applying a small amount of red locktite to the adapeter and the send unit threads.
Connecting the gauge itself took some time because i had to pull apart the area around my stereo since I wanted to use the switched 12v signal that my aftermarket stereo sends out to power the gauge. I connect the wire from the sending unit and ground the gauge to a good spot behind the dash.
I plan to later ground the original connector that powers my dummy gauge which scares me and brings me to my first question. Since the ecm will always think there is oil pressure, will the fuel pump always be running?
I turned the key and the new cheapo gauge lights up and registers 0 psi, I crank the engine and the gauge says 60 psi, I drive around the neighborhood and the pressures go up and down just as anticipated (thats the good news). The bad news is that there is a terrible hum coming from my car stereo speakers. Question 2, do i need a different switched power source? I was confident that I had a good ground but went ahead and ran the ground to my trunk where i have a grounded distribution block for 3 amplifiers. The sound is still there.
Anyways, there are no leaks and the gauge works...but that hum is going to drive me nuts. Luckily i have not mounted the gauge permanently and can easily disconnect it and the hum stops immediately.
Question 3. Since my message center is giving me a message that says low oil pressure (because i disconnected the factory sender), is that info going to the ECM? I dont want the car to go into limp mode tomorrow on my way to work.
Question 4. Since i used locktite is it possible that I dont have a good ground?

Here is the unit I purchased which also has in the pictues, a diagram that is included in the pictures
thanks for any insight, i am tired
 
Messages
4,917
Location
Southeast
nice job and perseverance.

when confines are tight, you can use tubing from the engine port, to a Tee, which can then feed both the gauge and the factory sender. You need to ground the Tee, which ive done by soldering a ground lead onto it, using electrical solder and a small propane or butane torch.

regarding the humm, that stinks. You can try buying a 12v noise filter from amazon and installing the gauge downstream of that. The filters vary in complexity and effectiveness but id give that a shot since they are pretty inexpensive, compared with playing with all sorts of grounding ideas and such. If nothing else, move to an analog gauge. Real oil pressure gauges are useful!
 

Barkleymut

Thread starter
Messages
3,228
Location
Richmond, VA
Answered one of my own questions, the car will not go into limp mode if the oil pressure gauge is red and pegged at 0. But my message center keeps on telling me that oil pressure is low. I point to the new gauge and tell it no its not, see right there we have 47psi but I'm convinced that the voice recognition is broken.
 
Messages
36,465
Location
ME
Ditch the feed coming out of your stereo, that will clear up your hum. There must be an ignition-on fuse you can tap.

If you can tee in the original sensor you'll probably have a happier car. This present situation sounds like it'll scare off anyone that borrows the vehicle.
 
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