Sensor Trivia!! - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 02-15-2002, 08:28 PM
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Sensor Trivia!!

First person to figure out what this sensor is gets a... big "thank you"!



I know that's the oil pressure sender...but what is that other sensor to the left attached to the same mounting point? I'm doing the painless conversion and didn't have any connections listed to go to this thing. It had 1 lead cut and the other lead going to the electric heating plate directly under the carb (is that really a heating plate?)....then over to the fuse box where i suppose it gets power...hmmm

NOTE: when i pulled the sensor off...it has 3 prongs going into whatever it's going into..

1980 CJ7 Laredo 258-stock


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post #2 of (permalink) Old 02-15-2002, 08:34 PM
 
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Re: Sensor Trivia!!

looks like a oil pressure sensor with a knock sensor on the same port

jeep the first 4 wheel drive the only 4 wheel drive
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post #3 of (permalink) Old 02-15-2002, 08:51 PM
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Re: Sensor Trivia!!

a pic of the old beast


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post #4 of (permalink) Old 02-15-2002, 09:01 PM
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Re: Sensor Trivia!!

I don't think that's it.....here's the knock sensor (from offroad.com's website)



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post #5 of (permalink) Old 02-15-2002, 09:07 PM
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Re: Sensor Trivia!!

No Tex...that sensor (in the first picture) is for the choke and those wires go to the heat plate. It sends an electrical current to heat up a bimetal spring to speed up the choke opening.

I am a bomb technician, if you see me running, try to keep up [img]/wwwthreads_images/icons/shocked.gif[/img]
'85 Cj7,360,TH400,D300,Pro-jection,D44's,M/T's 35's,8274
post #6 of (permalink) Old 02-15-2002, 09:28 PM
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Re: Sensor Trivia!!

Interesting. Why two wires? Is one ignition power and the other the hookup to the heat plate? Does the sensor say "ok, it's cold....so transfer ignition power to heat plate now!" ?

then stops transfer of ignition power to heat plate when it warms up?

I guess it uses oil temp as the meter and that's why it hooks up where it does. How much trouble should I go through to hook this up when I drive in Texas climate? Seems like Jeep has always started nicely even in the cold. I'm thinking the ole' regular choke can do the job. Whataya think?

post #7 of (permalink) Old 02-15-2002, 09:38 PM
 
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Re: Sensor Trivia!!

That's a run of the mill 'Hobbs' pressure switch, nothing remarkable about that.
(meaning it's not a sending unit, just a pressure activated On/Off switch...)

That meas it's hooked to a device that either tells if the vehicle is running or not running...
(oil pressure or no oil pressure)

Where do the wires come from/ go to?
<hr>
Idiot light pressure switch? Do you have a 'Oil' light that comes on when you turn the key to 'Run' but not started?
If so, that light will have it's own switch.

If you have an electronic fuel pump, that may be the '2 second' switch sender.
If you have an electronic fuel pump, there is supposed to be a circuit that will kill the fuel pump if the engine dies.
It's usually a oil pressure switch to determine if the engine is running or not.
<hr>
Some anti-thieft systems use a 30 second or 1 minute switch and then kill the engine.
Lets what might be a dangerous person get away from your house before killing the vehicle in traffic.
If you leave the vehicle in a place where he can work on it for a while, he will figure out how to defeat your security system, but if you let him steal the vehicle and it gets into city traffic and dies, he has NO shelter or time to look for the kill switch...

I've seen some alternator systems that used that kind of switch to activate the alternator so there is no engine loading until the thing is started and the oil pressure comes up.
I can't imagine anyone doing that in a jeep...

Just guessing here...

So many cats, so few recipes...
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post #8 of (permalink) Old 02-15-2002, 09:54 PM
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Re: Sensor Trivia!!

Yes....you tha man...i figured as such, especially after reading this somewhere:

"Oil Pressure Sender

This sender is on the engine block and looks like a small 2 X 3 inch filter with one terminal. The other sender with the two connectors is an oil pressure switch. It is supposed to close above 4 psi and goes to a dash warning light in some speedometer clusters and in other models it sends the signal to the engine's computer."

Still no good reason for me on why it's hooked up to the heater plate under the carb (maybe previous owner kept his tradition of f-ing up every electrical system on the jeep..woohoo) or maybe the plate is supposed to be on when engine is on only...oh well, whatever....this little guy will remain unhooked up like the rest of my sensors (no emissions in TX yet) until I can find a cool use for it...hmmm...i'm sure i can find a star trek type of mod to add to the jeep to take advantage of the ole' Hobb's switch.

thanks!

post #9 of (permalink) Old 02-15-2002, 10:25 PM
 
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Re: Sensor Trivia!!

Well, TexasCJ-
You quoted that from my "CJ Gauge & Sender Diagnostics" article.
http://www.monsterslayer.com/jeep/Gauges.htm
Give credit where credit is due ...





JAF
http://www.monsterslayer.com/jeep
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post #10 of (permalink) Old 02-15-2002, 10:31 PM
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Re: Sensor Trivia!!

yes! great article...I printed it out earlier today...it really cleared up the gauge wiring as painless mentions nothing about jumping terminals and all that jazz....thank god for the jeep guru's. I think I'll be one too after all my time in the garage


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