Crown Oil pressure gauge help

Ok long story short replaced the dash and everything in it on my 75cj5 the PO had a sunpro manual pressure gauge inplace and i went with crown gauges. installed the new sending unit and gauge and didnt work is there a way to test the sending unit and just to make sure that i hooked it up right
S= sending unit wire
G= ground
I= ignition
is this correct?

 

with key on, check for weak voltage/pulsation at sender end of wire.
If present, ground the wire and watch oil gauge needle move across gauge.
If not, sender bad.
If no voltage at wire, check connections and power to the gauge.

 

I had the same problem. I did alot of research and it seems there are 2 different senders. If you have the wrong sender, the gauge wont work. I ending up going with a mechanical gauge, which everyone says is more accurate. If you do a search about the oil sender you should find the info I am talking about. Hope this helps. Good luck

 

The sending unit is new as well but that dont matter i guess, how does it get its power to send voltage and how much voltage should i be looking for and. I see why people go to manual oil pressure alot less issues.

 

If I might ask is the oil gauge a stock unit or aftermarket stand alone type deal? Voltage to the sending unit for stock gauges is 5-7V and as mentioned it's a pulsing voltage as it goes through a small voltage regulator. Also on the stock setup the wire going to the sending unit is the ground.
If it's an aftermarket gauge, not a clue what the voltage is.

 

It’s a new crown oil pressure gauge and a new crown sending unit that’s for a 72-86 cj5 232-258, the sending unit only has one threaded terminal post which the purple wire mounts to and runs directly to the S terminal on the gauge. Thats why i asked how the sending unit gets its power it makes no since how it would supply voltage if there is no power going to it unless its battery operated internally.

 

On an electric gauge system, a voltage source is sent to the gauge which passes through a coil which interfaces with a needle arrangement that moves according to the current flowing through the coil. That current is controlled by the sending unit which is screwed into an oil galley in the engine block. There are different sensing arrangements but the most common is a variable resistor which allows a calibrated amount of current to go to ground, this is calibrated to the gauge face and thus you get your numbers.

 

Yup, what he ^^ said.
When you think about it "sending unit" is kind of misleading as what they really are is a variable resistance ground source that doesn't really "send" anything .

 

Ok so how do i test the sending unit i dont guess im understanding and do i have it hooked up correctly
S= sending unit wire
G= ground
I= ignition

 

You can test the sending unit with an ohm meter. One test lead on the terminal the other to a good ground. Check the reading not running then recheck running, If there's now change in ohm'age then it's a crap sending unit. Basically as stated above though, key on, touch the wire that goes to the unit to ground. if the gauge moves you have a complete circuit between there and the dash gauge.

 

As the conversation is going, I believe it is thought that your sender has one terminal on it for a single wire connection. Is this the sender that you have or does it have two?

 

Yes I have the single pole sending unit
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After spending an hour and half on the web this morning, I cannot find any electrical information on crown oil gauge/sender J5750279. If you had no install instructions, then I suggest you contact crown to get the information. Crown gauge systems wiring is not always the same as Stewart Warner and other typical system wiring so I will not try to guess. Sorry I am unable to help.

 

That's ok thanks for trying I'm gonna try and work on it this afternoon and see what happens worse case I put the old sun pro manual gauge back in
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Ok so with key on 12v at ignition post and 3 volts and 11.5 ohmson sending unit post I start it I have 14 volts on ignition post and 1.9v and 2 ohmson sending unit. When I ground out the sending unit side the needle don't move so bad gauge is this correct

Ok thanks for everyones help the manual gauge is back in and working great
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