rebuild status: oil pressure gauge shoots to the top...
03-27-05, 04:42 AM
#1
rebuild status: oil pressure gauge shoots to the top...
we finally got my rebuild all completed, got the blackmagic efan installed, and go the engine started tonight... all seems well after we get it idling at about 1500 then i notice that my stock oil pressure gauge is off the top of the gauge OH GOD WHAT HAVE I DONE. however, before the car was running, i was watching the gauge sit at about 30psi during cranking (while cranking for 10 seconds or so) so i thought nothing else of the gauge until i saw it sitting at like 150psi, and the car had been running for like 5 minutes prior to me noticing the gauge off the scale.
has anyone had this problem with the stock gauge or did i seriously eff something up with my rebuild? i didnt touch my oil press regulator, i used the stock s5 oring/teflon retainer in the front cover, and didnt mess with the relief valve.
edit: also thought, i'd mention the engine is idling without very much smoke out the exhaust at all. there is a good amount of smoke coming from the center section of the turbo (prolly had oil, vaseline, a plastic connector or something resting on it), but nothing out the exhaust...
has anyone had this problem with the stock gauge or did i seriously eff something up with my rebuild? i didnt touch my oil press regulator, i used the stock s5 oring/teflon retainer in the front cover, and didnt mess with the relief valve.
edit: also thought, i'd mention the engine is idling without very much smoke out the exhaust at all. there is a good amount of smoke coming from the center section of the turbo (prolly had oil, vaseline, a plastic connector or something resting on it), but nothing out the exhaust...
Last edited by jacobcartmill; 03-27-05 at 04:50 AM.
03-27-05, 08:12 AM
#2
Did you check the connection to the pressure sending unit on the rear iron? When it is fully grounded, the gauge will go to the top like it is for you, so make sure it has a good connection to the sending unit, and is not being ground out on something else.
03-27-05, 08:17 AM
#3
Check to be sure capacitor is attached. When car running hit the sending unit and see if the gauge moves. Hook a mechanical pressure gauge to see what the actual oil pressure reads. Go from there.
Years ago a neighbor of mine blew the sides out of 2 oil filters (piston Engine). Checked it out and relief valve was stuck. Opened it up, freed the valve, and it was good to go.
Years ago a neighbor of mine blew the sides out of 2 oil filters (piston Engine). Checked it out and relief valve was stuck. Opened it up, freed the valve, and it was good to go.
03-27-05, 08:52 AM
#4
The mystery of the prize.
like the guy said above, when the wire going to the sender is grounded the gauge will peg, when it's disconnected altogether you get no movement @ the gauge.
Since it's pegging you either have faulty wiring, a faulty sender (the internal electro-thermo-mechanical PWM b.s. is stuck in the closed state) or ridiculous pressure (unlikely IMO).
I've had the wire short to ground on my old setup and it shot so far up it rotated the shaft inside the needle causing it to be shifted at all times even after fixing the wiring, the gauge had to be disassembled and the needle zero'd.
I wouldnt sweat it, put an aftermarket sender & gauge on the car and see what it says, the stock oil pressure sender & gauge setup belongs on display in a museum, not in your car.
This is what is inside the stock sender:
http://pengaru.com/~swivel/cars/rx-7/ops/
The theory of operation is a bit ... retarded. To sum it up, theres a heating element wrapped around a bimetallic strip that bends when heated inside the sender. The oil pressure bends a plate that moves a lever that contacts this bimetallic strip at the end, this closes the circuit when they are touching causing current to flow through the heating element and subsequently moving the gauge needle in the car (which also has a bimetallic strip & heating element inside of it). But when the current flows, the strip gets heated up, making it bend, it bends away from the lever being located by the oil pressure, once it bends enough from the heat it will break the circuit and current will not flow until the strip cools enough to unwind, thus closing the circuit again reheating the element, the process repeats itself, thus creating a crude form pulse width modulation. The frequency will change as pressure increases, because that lever moved by pressure applies a preload on the bimetallic strip, the greater the preload the more it needs to be heated / bend to open the circuit up (causing it to stay closed for longer periods). The longer the circuit is closed, the hotter the strip in the gauge will get, making it bend more and more til it pegs or worse yet exceeds the range and rotates the shaft inside the needle. When you short the wire to ground for a long period, that strip in the gauge is bending like crazy getting very hot screwing up the gauge, this is also why when the circuit is open (wire just hanging there) the gauge won't move.
At least thats how I remember it, has been a while since I had to deal with the stock setup. The aftermarket senders are usually simple variable resistors.
Since it's pegging you either have faulty wiring, a faulty sender (the internal electro-thermo-mechanical PWM b.s. is stuck in the closed state) or ridiculous pressure (unlikely IMO).
I've had the wire short to ground on my old setup and it shot so far up it rotated the shaft inside the needle causing it to be shifted at all times even after fixing the wiring, the gauge had to be disassembled and the needle zero'd.
I wouldnt sweat it, put an aftermarket sender & gauge on the car and see what it says, the stock oil pressure sender & gauge setup belongs on display in a museum, not in your car.
This is what is inside the stock sender:
http://pengaru.com/~swivel/cars/rx-7/ops/
The theory of operation is a bit ... retarded. To sum it up, theres a heating element wrapped around a bimetallic strip that bends when heated inside the sender. The oil pressure bends a plate that moves a lever that contacts this bimetallic strip at the end, this closes the circuit when they are touching causing current to flow through the heating element and subsequently moving the gauge needle in the car (which also has a bimetallic strip & heating element inside of it). But when the current flows, the strip gets heated up, making it bend, it bends away from the lever being located by the oil pressure, once it bends enough from the heat it will break the circuit and current will not flow until the strip cools enough to unwind, thus closing the circuit again reheating the element, the process repeats itself, thus creating a crude form pulse width modulation. The frequency will change as pressure increases, because that lever moved by pressure applies a preload on the bimetallic strip, the greater the preload the more it needs to be heated / bend to open the circuit up (causing it to stay closed for longer periods). The longer the circuit is closed, the hotter the strip in the gauge will get, making it bend more and more til it pegs or worse yet exceeds the range and rotates the shaft inside the needle. When you short the wire to ground for a long period, that strip in the gauge is bending like crazy getting very hot screwing up the gauge, this is also why when the circuit is open (wire just hanging there) the gauge won't move.
At least thats how I remember it, has been a while since I had to deal with the stock setup. The aftermarket senders are usually simple variable resistors.
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03-27-05, 03:01 PM
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i am legendary
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James is my hero. He's always there to help me, but yes he does tell you you're stupid in the process 
You just gotta get past that part and listen to the actual information he spouts out.
You just gotta get past that part and listen to the actual information he spouts out.
03-27-05, 03:35 PM
#12
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Ouch, came back to bite you in da *** eh? Just get a cheap one from an auto parts store or something, but first check the ground and **** for the stock sender. I know the autometer ones are only like 30 something, that's what I ordered when I was having oil pressure problems 
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