Oil change now no pressure


PaulZ

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Sheit! I changed my oil today while I was mucking around installing a kill switch. Didn't change the filter. Got all done, fired it up, gauge showing no pressure! Dipstick shows full. I've run it about 15 seconds so far.

All other gauges working properly. When I turn the key on the oil pressure gauge actually drops some to the dead bottom of the gauge, then back to zero where it was when off once started. I did splice in a toggle switch to the power wire of the coil pack, that shouldn't have caused this. The oil gauge was working in the normal range, although I probably hadn't looked at it in the last few days.

I'm sure it's electrical but want to make damn sure. Anyone know where the sending unit is? '99 4.0 OHV.
 


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Take your splice out and see if that affects your readings.

If you have a change then you caused it, if no change then progress to something else.

Ray
 

PaulZ

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Thanks. I've just been reading that many others have the same oil gauge problem, usually caused by the sending unit.
 

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And just so you are aware... it's just an oil pressure switch. Also... the gauge is a fake.
 

PaulZ

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Yeah I read that, weird. To be honest it may have quit a week ago, I don't make a habit of checking anything but the gas gauge. Guess I'm an idiot light guy at heart. Speaking of which, I let it get real low on gas a couple weeks ago and the 'check gauges' light came on. Went off when I got gas. Wonder why the check gauges light doesn't come on when the oil gauge is at zero?

Anyway I'm relieved to know it's likely not an engine problem. I was really second guessing myself: did I drain the wrong thing? Did I pour the oil in the wrong hole, lol.

Thanks.
 

4.0blue98

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My check gauges light comes on when my oil pressure gauge freaks out. I have a spare sender in my garage but the old one won't completely die. Location of yours and mine should be the same and I believe you have to come in from the driver side (?) wheel well to get to it. Not positive on this. I wanted to put a real gauge in but the location of the sender makes it difficult. I've been contemplating using one of those oil filter sandwich plates with a few connection points for thing like that.
 

PaulZ

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Argh! Went to change my temp sensor. It's on the front of the engine, drivers side, behind the front A frame bolt right? Green wire? The new switch I bought has a hex fitting, my old one takes one of those larger goofy special sockets...and it has just a straight push on connector, the new switch has a rectangular plastic plug connector with lock tab. Am I dealing with the right sensor?

I tested the new one, apparently they are open circuit until they see pressure, then ground? So I took a jumper and grounded my wire. Started it up, still no gauge reading. Maybe it's not the sensor?

Yesterday I installed a kill switch under the dash. I spliced into the red power wire going to the coil pack. Works great. The only other thing I did was disconnect another red wire that has a connector in the same harness just an inch or two from the coil pack, thinking that may kill the engine. It didn't, so I plugged it back together. No idea what that is for.

Dang, I need to drive it!
 

4.0blue98

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Are you sure your Ranger is a 99? My 98 has a simple looking sensor but the 99 has the plastic shrouded connector.

Check out this:1999 and this 1998
 

PaulZ

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Says 10/98 manufacture on the door sticker, 99 n the op manual and title. The sensor that is in there looks like the 98 example, the one they sold me has a plug like the 99 example but a smaller regular hex head.

What's got me bugged is why the gauge wouldn't show normal with the sensor wire grounded.

got one locking hub on while trying to figure this out..
 

PaulZ

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In a rare stroke of brilliance, I connected an ohm meter to the old sensor, still in the truck and ground. Fired it up, went to dead short so I know the sensor is working and I have oil pressure. At least I can drive it around knowing I have oil pressure until I figure this out. Thanks for the help blue
 

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Flip the "kill" switch and see if your guage starts working...
 


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