Need help identifying a sensor

Wave34

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Oct 17, 2017
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321
I'm learning my engine, and identified all the sensors except this one.
Someone knows? (VP 5.7Gi-D)

1SENSOR.jpg
 

Bt Doctur

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Aug 29, 2004
Messages
19,092
Might be either but I will go with a temp sender for the gauge. With key on short it to ground. You will get an audible alarm or the temp gauge will peg
 

Thalasso

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Jan 18, 2011
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2,876
Doesn't look like a sensor to me. Looks to be more like a rounding stud
 

Wave34

Petty Officer 1st Class
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Oct 17, 2017
Messages
321
I have a two wire sensor in the thermostat housing for the ECU.

I think the dash temperature indicator is on the starboard side of the engine at the brass drain plug, it looks like a 2 inch diameter canister.

So, it's may be like Bondo said, an over temperature alarm switch.
It's not a ground stud because I can see a layer on insulator.

Won't be able to test it before spring though. Boat is still winterized.
 

Fun Times

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8,776
That wire on the top of the intake manifold is going to be for the temperature gauge sender unit.

https://www.volvopentashop.com/epc/e...%2F7744330_046 ,
3852029 Item # 20 Sensor, coolant water temp, Volvo Penta 3852029 engine temperature sending unit sends signal to temperature gauge. https://www.marinepartssource.com/te...-penta-3852029
http://boatinfo.no/lib/volvo/manuals/5057a-f.html#/66

The 2 wire switch (yellow/black) item # 19 3850397 is the sender unit for the ECM and would help sound the EFI warning horn for an over temp of around 200 degrees.

The sensor down by the brass drain plug is called a knock sensor to help retard ignition timing if needed. Item number 21 3850357.

Audible Alarm:
EFI Engines - When the ignition switch is turned to

RUN (key on, engine off), the alarm emits two short

beeps to indicate that the ECM is performing a check

of the sensors. If there are any problems detected by

the ECM, the alarm will sound; otherwise, it will re- main off.
https://www.manualslib.com/manual/91...page=26#manual
 

Wave34

Petty Officer 1st Class
Joined
Oct 17, 2017
Messages
321
Thanks Fun Times for the drawings.
So it is a coolant sensor for the gauge.
For the ECU sensor, it is weird that they call it a 'switch' when in realty it is a thermistor that varies resistance with temperature. Mine is working well, I tested it in hot water, warm, and room temperature vs the chart.

So, the canister I see at the brass drain plug is a knock sensor. It is a bizarre place to mount it. On cars, that sensor is always mounted directly to the block.
 
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