guages not working properly question?

I own an 85 wagoneer with the 2.5 inline four cylinder. I am replacing my engine right now and want all guages to work. My volt meter works properly but my oil and temp guages don't work properly. When you turn the key to access the temp. guage when the engine is warm will go to half way and stop there. when I start the truck it goes all the way to the right and burries itself and stays there until truck is not running then will go back to half when access is on but not running. With key off it goes flat to the left. The oil pressure guage as soon as you turn the key on to access it pegs itself out all the way to the right. Only goes down when truck is turned off. What could be causing this and what could be the possible fix? Am I able to get these guages working properly again or do I put in a new set? I bought the truck two years ago and volt meter has always worked but the oil and temp. guages have always never given a proper reading. They register when you turn on the truck but when engine is running they just peg themselves to the far right. Any help will be greatly appreciated. I hope I explained it good enough. If not let me know what your questions are.

Thank you in advance for the input.

that sounds like a symptom of having the wrong sending units. The gauge type sending units are a potentiometer output (or a variable resistor) someone may have replaced them at aome point and not specified that the vehicle has guages and not dummy lights, which is not as common on a 4 cylinder as the 6.
The sending units are meerely on/off switches now, hence the needles "pegging" instead of a variable voltage input(probably 1-5v) its getting a solid 5v or 12v, whichever the supply voltage to that circuit is.

If the sending units were replaced with what you say as dummy lights then why in access would the temperature guage read the proper temp. untill I started the engine and then would peg itself and stay there until I shut the motor off then it would read the proper temp. The oil pressure guage does almost the same thing. I don't know much about the electrical in most vehicles so I am kind of new to this.

What year vehicle did the new engine come from? In 1991 Chrysler reversed the polarity of the gauges, so a 91 or newer sender in your 85 vehicle would cause the gauge to operate in reverse -- temp would show hot when started, then taper down as the engine warms up. Oil would peg, then steady down when the engine starts, and the pressure would show an increase at idle and then drop as the RPMs increase.

Swap in the sending units from your old engine and see what happens.

I just got the original engine out and will be working on getting the other motor in this weekend. These problems were with the original engine and I wanted to take care of the problem while I put in the other engine. The other engine came from an 84 wagoneer. Both donor truck and my truck have the 2.5 inline four carbed. I bought new guages but I don't think that this will fix my problem. I think it is something else causing this problem. I am not able to ask previous owner if anything was replaced concerning the temp. and oil guages. Any help is needed and appreciated. Thanks for the replies so far.

It sounds like the senders you have are for idiot lights rather than for gauges. You need to try senders that are the correct unit for your year vehicle -- forget what year the engine came out of, the wiring in your vehicle is what determines what sending units to use. The senders for the idiot lights (oil pressure and temp) are simple ON/OFF switches.

The diagnostics for the oil pressure gauge say if you disconnect the wire from the sender, the gauge will go to HIGH (80). That's no different from an idiot light sender not being triggered by a low pressure condition. Pull the wire off the sender and ground it to the engine with the ignition on. The gauge should go to zero.

Coolant temp gauge should read COLD if disconnected. If you ground the wire to the block (ignition on) the needle should go all the way to HOT.

Thanks for the help Eagle. I will try those things this weekend to see if that is the problem. I hope that I am able to use my original guages and just have to spend the money on new sendors. Does anyone know how much they are going to cost me? Where are the sending units on my wagoneer? Any info is great. Thanks again all.

Oil pressure sender is adjacent to the oil filter. Temp sender is in left (driver's side) rear corner of the head, on the top sticking straight up with a single wire to the top of it.

Thanks again Eagle. I will see what I can do this weekend. I can't get to the jeep until then. I live about 35 miles away from where I am working on the jeep. So I will post back with the results and let you know what happened. Again thanks for the replies.

also, the oil pressure gauge will do as described if it goes bad, or the connector comes loose. and a bit of advice: DON'T buy this stuff at Advance Auto Parts- or you will end up buying it all again very soon.

Thanks for the info on the guage. Much appreciated. As for Advanced Auto I only buy certain things from there. I just got my gasket set from there and my front exhaust pipe. I don't trust their electrical parts though. I do most of my parts shopping at carquest.

me too!!!