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The digital life of Jörgen Larsson

Oil-pressure sender dissection

Okay today I had a few hours to spare and since my oil pressure sender was shot and I just got a new one from FieroStore I thought it might be a good idea to put in the new one.
My old one was kind of working but all of a sudden it was showing way lower readings than it used to. ~20 psi cold and 0 psi hot. When hot the red light was on.
I checked with an analog glycerine filled gauge and it showed 75 psi cold and 60 psi hot at 900 rpm idle which is normal.

My new sending unit is made in USA while the old one (2 years old bought at a local GM dealer) was made in Taiwan.

Curious as I am I could not resist to take a peek inside the old sender.

First here’s the bad one.
01_sender

Made in Taiwan!
02_sender

I used pliers to bend out the edge around the bottom of the sender.
03_sender

The bottom part slid right out and the whole thing is pretty rusty although it’s only 2 years old and the car never sees any rain. I thought the unit would be full of oil but it never get further up than half way into the threaded socket.
04_sender

The oil pressure moves a small arm that pushes an electrode on a coil just like a variable resistor. This part was working pretty good, everything was moving easily.
05_sender

Another shot of the bottom part with the arm.
06_sender

In the “lid” there’s three screws and in the middle a small metal axle that is spring loaded, you can push it in. This axle is the oil pressure counterweight.
07_sender

After removing the three screws the last part slid right out and showed the culprint with my sender. The spring has rusted through and snapped making the counterweight all off.
08_sender

The water must have been introduced from the top of the unit by the connector or it might be from getting hot and cold all the time creating condensation inside of it.
When I installed the new one I put a large dab of dielecric grease in the connector making it sealed from the elements.

3 Responses to Oil-pressure sender dissection

  1. Mike says:

    Very informative. I think this is what is going on with my 84 Pontiac 2000..prob smoked the relay right?

  2. todd says:

    You nailed it man , to the T . Thanks for the help.

  3. Tony Jorgensen says:

    Thanks a lot. My 86 gt started just going nuts. I checked the oil level wires all good. I will get a new sending unit from the Fiero store. Thanks again. TJ.

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