Oil pressure switch or sending unit?

[rumblephish]

I'm confused and I need some help!!



What's the difference in the oil pressure SWITCH and the oil pressure SENDING UNIT?


I replaced my oil pressure gauge with a new AutoMeter gauge and replaced the original oil pressure SENDING unit with the one that came with the gauge (similar to the OE unit). This is the large bell shaped unit where the sending wire snaps onto a post/nipple on the end of the unit.

Just before the sending unit there is a switch with a 3 prong plug attached to it. There are two wires coming off of it, one red and one green. The red goes up and plugs in the choke solonoid on the passenger side of the carb. The green wire loops back and plugs into itself.

What is this switch for and why does it plug into the carb? From what I can gather online it is an oil pressure switch for an idiot light on the dash (newer CJ's). My CJ is a 78 and did not have an oil light on the dash. Just an oil pressure gauge.

If this is correct do I even need to have this switch plugged in? And why does it go to the carb?


HELP!!!

 

[mylittlecj5]

Just a hypothesis on my part, but from your description I'd guess this:
The switch controls the operation of the choke when the key is turned on, but the engine is not running. With no oil pressure (engine not running), you wouldn't want the choke to open, so it waits for the oil pressure to build before completing the circuit.
So, yes I'd leave it plugged in to keep normal operation of the choke.
does that make sense?

 

[rumblephish]

Just a hypothesis on my part, but from your description I'd guess this:
The switch controls the operation of the choke when the key is turned on, but the engine is not running. With no oil pressure (engine not running), you wouldn't want the choke to open, so it waits for the oil pressure to build before completing the circuit.
So, yes I'd leave it plugged in to keep normal operation of the choke.
does that make sense?

Yeah, that does make sense. Thanks.


Anyone else have a different explination? Also, when the Howell kit goes on do you think I can toss the connection? I know I can't pull the swith, but I'd like to remove the plug harness. I'm thinking that since I wont have to worry about the choke on the TBI the plug is pretty useless. Also, just out of curiosity, why does the green wire just loop back and plug into itself? Anyone?

 

[dslywalker]

I took everything out.I have a mechanical oil pressure gauge now.
Mike

 

[54cj3b]

Ones electrical and Ones mechanical

 

[rumblephish]

Ones electrical and Ones mechanical

No, they're both electrical. A mechanical oil pressure gauge would have an actual oil line full of oil running to the gauge. One is a "sending unit" and the other is a "switch". I think mylittlecj5 nailed the answer.

 

[CJ]

Sending unit = signal to drive a gauge. Usually a ground signal that varies.

Switch = On or Off.

 

[Bulto]

I took everything out, because the sending units and the gauges are in not working condition. I have a autometer mechanical oil pressure, mechanical water temp, fuel level & voltimeter. See the picture.

 

[dslywalker]

I think your doing the Howell system.When you do you won't need the sending unit if you have the mechanical or the switch.
Mike