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Have you ever wondered what happens when the sending unit on your Fuel Press/Oil Press/Oil Temp/ etc goes bad? On our Dynon unit when the resistance on the unit drops, the reading on the engine monitor goes to the highest reading (and so does your blood pressure). We have had a fuel pressure reading that started to be inconsistent, and then would stay at 99PSI when the boost pump was on or the engine was running.
Trouble shooting the unit, I found the readings to be accurate near the low end, but then as the pressure rose to the normal levels, the indication was high. This was confirmed with an ohm meter at the sending unit. The high pressure reading was basically ?open?, the same as if the ring terminal was removed from the post.
A spare sending unit was installed and it appears all is normal. Have you ever wondered what breaks down as the unit wears? Here is the photo of the sending unit with the cover cut off:
http://i54.tinypic.com/ejc3mb.jpg
Take special note of the small wear mark on the resistive material to the right of the ?pointer?. This is evidently where the fuel pressure normally runs at 25PSI on our injected engine. It also is why once the ?pointer? moves to the left of the wear spot, the resistance goes to zero and the engine monitor displays 99psi.
Hope you find this interesting.
Trouble shooting the unit, I found the readings to be accurate near the low end, but then as the pressure rose to the normal levels, the indication was high. This was confirmed with an ohm meter at the sending unit. The high pressure reading was basically ?open?, the same as if the ring terminal was removed from the post.
A spare sending unit was installed and it appears all is normal. Have you ever wondered what breaks down as the unit wears? Here is the photo of the sending unit with the cover cut off:
http://i54.tinypic.com/ejc3mb.jpg
Take special note of the small wear mark on the resistive material to the right of the ?pointer?. This is evidently where the fuel pressure normally runs at 25PSI on our injected engine. It also is why once the ?pointer? moves to the left of the wear spot, the resistance goes to zero and the engine monitor displays 99psi.
Hope you find this interesting.
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