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post #7 of (permalink) Old 11-18-2002, 07:44 PM
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Re: 2.5L Oil Pressure Problem

Sorry about the following looong read; I have not figured out how to copy an old thread and forward the shortcut so all you have to do is click on the shortcut and go to the thread.

Following is a thread from September on the gauge topic.


Gauge Needle Jumping:

How can I test my sending unit? I think its bad, but I dont want to toss $20 at a new one if not. My guage sometimes works, othertimes it flings over to way beyond the guage lines. Sometimes it will do it when it revs, most of the time it just sits there. And some of the time it will work for a week w/o issue, like now. I've hooked up a manual guage, and the oil pressure is good, no issues. So I know there is no problem with the motor in that respect, just the guage or sending unit. Can I disconnect the guage and measure resistance across the terminals on the sending unit? If so, what are the ranges?


Re: Oil Pressure Sending Unit... [re: pr0ntab]
09/27/02 11:08 AM Edit Reply

Most probably wiring problem, I would say check all the wiring and clean harnesses.

Re: Oil Pressure Sending Unit... [re: alkan]
09/27/02 11:12 AM Edit Reply

The basics have been done. I've cleaned it, removed it reseated it... , continuity tests between the guage and sending unit plug, all good, no shorts. -

Re: Oil Pressure Sending Unit... [re: pr0ntab]
09/27/02 09:49 PM Edit Reply

Mine did the same for about a year. I checked, cleaned and basically did everything you did. Then finally replaced the sending unit. That fixed everything and guage works fine now.

Re: Oil Pressure Sending Unit... [re: kgound]
09/28/02 11:04 AM Edit Reply

Very easy to Test... first things first, is your guage always pinned? the needle to the far right?

1990 xj sport

Re: Oil Pressure Sending Unit... [re: binare]
09/28/02 02:23 PM Edit Reply

It is when its freaking out. It pins over to the right. Right now if I go out and start it, it is working fine. Some days it will be working fine, but when the needed moves because of pressure change, like if you rev it up, it will peg, then come back, peg then come back.. Right now today, its working as designed, tomarrow may be another story -

Re: Oil Pressure Sending Unit... [re: pr0ntab]
09/28/02 02:45 PM Edit Reply

Heres what I would do, Take the one wire and put it to ground (a good ground). This should make your guage read zero pressure al the time, leave it like this a for a day or two. If it stays at zero and doesnt move, replace the sender and put the wire back. If the guage still jumps around, look at the gauge or wiring as your problem. My initial bet is the wiring is your problem, when the sender is faulty or you have a short or cut in the sender wire, your gauge will be pinned to the right. Actually first check the connection, but you've probably already done that. If you get a new gauge specify that you have a guage NOT the dummy light. And do not be worried if the new sender looks different, they changed it over the years but works the same.

Re: Oil Pressure Sending Unit... [re: binare]
09/28/02 08:07 PM Edit Reply

Bin, good troubleshoot idea. The sending unit is basically a current sending unit. By grounding the wire, you are doing a safe check of wiring. This will not hurt the gauge. If in fact, it stays at 0, then it indicates the sending unit is going open. I had a simular problem. In my case, the nut that holds the terminal stud on sending unit was loose. Once I tightened it, it went steady.

If your a technogeek like me, put a current meter in series with the sending unit. If the reading stays steady while the needle bounces, then it is the guage. If the reading bounces around, the use the above step. Steady, and it is the sending unit.

84-CJ7, 89 Cherokee
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