Photos of Oil Pressure Sender Internals (old type: from a 1987 V6) (Page 1/2)
Brian A JUN 09, 11:51 AM
If photos have been posted before, I couldn't find them. Thought somebody might be interested.

I replace my oil pressure sender because it was exhibiting the common jiggly needle thing.

I replaced the sender (next time I'll upgrade to the 1988 connector & sender) and all is well.

Out of curiosity, I cut open the old sender before I pitched it in the trash. Below are a couple of photos.

Interestingly, I saw no evidence of water infiltration. The mechanism looks quite delicate. It is a mechanical system: a diaphragm is pushed upward by oil pressure and moves a C-shaped brass connector which, in turn, rotates a contact against a wound-wire variable resistor (rheostat type). Interesting.

Presumably the 1988 sender is a modern piezoelectric type.
IMSA GT JUN 09, 12:26 PM
Now I'm going to buy one, cut it open, and display it on my desk
That's an interesting design.

[This message has been edited by IMSA GT (edited 06-09-2024).]

donuteater306 JUN 09, 01:16 PM
That is some serious engineering, thanks for sharing. Wonder what breaks that makes them peg at full psi.
IMSA GT JUN 09, 02:37 PM
I never really thought about it until this thread but is the sender before or after the oil filter? If it's before, debris could get lodged in the sender opening causing these to fail.
theogre JUN 09, 06:25 PM
⚠️ Warning: While the plastic case is Hex shaped & GM maybe used that to install them... Is Safer to use a 9/16" SAE wrench on the nut on the fitting. More so if your removing a good sender for other service work.

Above Pic's are good... I have one taken apart a way more years ago only some pic have posted until now. (like 1 showing base "Nut" posted several times) To get apart I had to cut the metal shell w/ Dremel cut off wheel.
Lower section in order... Note: 3 small spots crimp over the resistor assembly. Larger punch-out is location for the Black Top.


Diaphragm and others as assembled... Note: The "piston" just spreads the load over the Diaphragm. The Pusher is next then the spring. Only a small section of the Diaphragm is free to move.


Resistor assembly showing the arm that the pusher moves/slides up...


Black Top section & Upper shell w/ the resistor arm as Pusher hits...


Diaphragm Failure that causes a Major Oil Leak. 2 lines are ends of the Tear.


------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 06-09-2024).]

richard in nc JUN 09, 06:59 PM
i just replaced mine two days ago because it was pouring oil.guage still doesn't work.time to replace the circuit board on the back of the cluster.i have it already.
theogre JUN 09, 07:58 PM
The top section...
Side Note: This sender was taken apart 10+ years ago but the switch screws not until today & the switch section was still covered w/ oil inside.

The rod pushes the Fuel Pump Switch


How Sender Out Contacts works...


Base Removed you see this...


Base & other parts... Strong spring Opens the contacts. Weak spring just keeps all parts together. Rod & base plastics are "keyed" to keep the Switch Contact in alignment. Then the weaker spring holds the contact in place after that closes as the rod can/will move more as the piston moves more.


Base & parts assembled. ignore the shell as is just holding parts to take the pic here. But the rod is in the shell & hidden.

[This message has been edited by theogre (edited 06-09-2024).]

theogre JUN 09, 08:22 PM

quote
Originally posted by IMSA GT:
I never really thought about it until this thread but is the sender before or after the oil filter? If it's before, debris could get lodged in the sender opening causing these to fail.

The Sender is before the filter on many engines or others after. Is likely just where they had space to mount them on a given engine.

Even mounted after the filter, Low/no Pressure is Not a filter problem for nearly all setups.

Failure cause oil leak is because Diaphragm rip like above. The "rubber" likely fails just because so little moves as the "piston" raises.
theogre JUN 09, 08:29 PM

quote
Originally posted by richard in nc:
i just replaced mine two days ago because it was pouring oil.guage still doesn't work.time to replace the circuit board on the back of the cluster.i have it already.

Check the base to block w/ Ω meter. More so if you use Teflon tape to seal. Many claim that won't matter but often does block the ground enough to cause problems.

Or check Sender out pin to see has 0Ω to block because new senders can be bad.
theogre JUN 09, 08:55 PM

quote
Originally posted by Brian A:
Presumably the 1988 sender is a modern piezoelectric type.

Nope. I'm told the "long" oil sender are mechanical like old type because uses 0-90Ω & very dumb 12v gauge setup but made different so won't dump the oil on the road until the pan is dry or get luck & see it leaking.

88 sender can fail for oil pressure, F-pump switch or both but not leaking problem. I & very many others have upgraded to 88 type years ago & still working so never had a dead one to dissect.
I've only seen 1 leak but because the base failed from Rust. Can't find that thread & even then many pics are lost for many reason so not looking hard to find 1 post.

Other newer models have PCM/BCM to run the dash & can use piezoelectric etc as shown in How it's Made TV Show years ago & maybe still on YT or other streaming. ⚠️ Most Senders/Sensors to them have 5v. O2 sensors is 0-1v.

Some V6 & others oil sender are mounted way low where road crap can hit them. Or has AC & sender mounted high but near the Fiero Engine Vents can have same problem. That can cause rust, electrical or both problems w/ a sender or wires to it.

[This message has been edited by theogre (edited 06-09-2024).]