Oil Sender question

[j-monty]

Hello, So it's a friend's 2000 Ranger, 3.0 flex fuel...

She keeps complaining about the oil pressure gauge. new sender installed around December, and already crapped out...

Instead of wasting more money, mechanical gauge is going in...

Here is my confusion... I've read many threads about this and searched a lot of other forums, but have not gotten a 100% definite thread size for the oil pressure switch. I've heard 1/4NPT, 1/2NPT, and i think someone even said 3/8 NPT, which I know is way off...

I know many people battle this problem and many get a brass 'T' fitting to run the switch and a mechanical gauge. Anyone know exact size of the switch threads? Or would it be best to pull the switch and bring it into NAPA when I go to get the 'T' fitting anyway?

Thanks

 

[RonD]

Just as a heads up on engine sensors, most are 1 wire sensors, so use the threads/engine as the ground.

Some use teflon tape as a sealer, which is not what it was made for, and they use too much, more is not better in this case, lol.
The tape prevents a good ground, causing no sensor or intermittent sensor issues.
A dab of high temp sealant on threads is enough to prevent leaks and won't interfere with the grounding.

My '94 ranger had odd readings on oil and temp gauges at the same time but not all the time, turned out to be a loose ground strap from head to firewall.
They are both resistance sensors, so short and long path grounds effect their readings on the gauge.

Anyone who has ever troubleshooted trailer wiring will have stories, lots of stories, about grounds and the odd issues they cause, lol.

 

[j-monty]

When I replaced the first sensor (went with motorcraft because I have a dealer connection and figured I can't go wrong there...), the new one had the RTV threadlocker (stuff that comes on it from factory) in the threads and I cleaned the hole, I'll check the grounds, and make sure that the sensor wire is good, but I doubt the grounding strap is toasted because everything else works great, and it's the irratic jumping needle on the gauge...

I also know the joys of trailer wiring, so I'll make sure to check those grounds...

But regardless of condition of the grounding straps, a mechanical gauge is going in...

 

[Earl43P]

Clean the IAC and then reset the computer so it'll relearn its idle.
Low idle will make the oil pressure gage flicker (sender is just a switch).

 

[j-monty]

The idle holds smoothly at 1k RPM, and since it's a switch, it makes the needle go up to mid range on the gauge once it's above 6 or 7 psi so RPM shouldnt affect the needle.

My '97 Grand Cherokee with a 4.0 has a normal, sweeping gauge, and even difference between WOT and idle isnt that much jumping on the gauge.

Even if it were a sweeping gauge, if it jumps that much at idle, theres a serious problem. Oil is full, no smokes, ticks, or knocks.

So I take it that nobody knows the switch thread size?

 

[RonD]

Sorry, don't know the thread size.

Long shot....disconnect coil and EFI, remove oil sensor, turn engine over;
could be something in the oil senders passage, not likely but not impossible either.

 

[j-monty]

I also thought of a blockage, especially since she has been going to walmart, Sears, Valvoline .... for oil changes for the past year. I changed her oil yesterday and added a quart of rislone with the new oil, figured we'd see if that does anything ...

If problems still exsist, when I start mechanical gauge install, I'll try that to blow out the oil passages.

 

[Explorin94]

1/4 NPT is what you will need. Like Earl said all the sender and gage are is a mere switch. I think you are doing the right thing by putting an actual gage in it.

 

[j-monty]

IMO it's the only thing to do. If it were my truck, I woulda done that the first time around and not worried about the switch....

Does the engine computer in these trucks read oil pressure off of that switch at all?
I know if I completely remove the sender for the mechanical gauge, it will always have a check gauges light. I'm wondering if when I install the 'T' fitting, should I do a new switch along with the mechanical gauge for the factory systems?

I know some vehicles will throw a fit if it doesn't think there is oil pressure...

I guess I could just ground out the wire, and then it would always read the half...

Probably best for resale and other mechanics if i either replace, or leave that switch, instead of gettin rid of it...

 

[Explorin94]

No you will be fine without the factory sensor. GM's are the worst for doing the oil pressure sense before starting. Now if you want you can do a "T" and still use the factory sender and gage, with no light bugging you.