Oil pressure sending unit

Sometimes they will give you a right angle adapter so you can get a straight spin on the hose and gauge. Otherwise, it just flops around....

You should hook up the tach to get the proper baseline reading. 'Usually' engines are listed as X psi for every 1000 rpm. I normally see something like 10 psi per thousand rpm depending on the engine as the lower 'safe' wear limit. 56 psi at 3000 would be for a new engine with a fresh oil change likely.

I do notice my oil psi drops when the oil gets old.

My Jeep runs a mechanical pressure gauge and it swings from about 15 psi at idle to 50 or so on the highway. This fluctuation is perfectly normal with a mechanical gauge.

Your new test gauge should be a sealed unit so oil can't get where it isn't supposed to be.

Grounding the wire to the gauge should make it pin out either high or low depending on the system. Opposite of unplugged anyway.... If it moves smoothly across the range it might be ok, if it is jerky across the range, you likely have found a/the problem. I think I would do this step first.

Also check the plug itself. If dirty or loose it can give shaky readings.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Ah, that's it! I didn't even think of that! I first tried screwing off the gauge and adapter connected to the hose, but that didn't work (wrench just kept spinning repeatedly with no progress). Hope I didn't damage any teflon sealing tape by doing so.

Well, I just did do the oil change last week, but the car has 190,000 miles on it!

Mine drops when mine gets hot.

My gauge starts out pretty high, but it continually drops, so after about

10-15 minutes of driving, the gauge reads at 0 or near 0 when idling and the warning light comes on. Pressing the accelerator makes the needle go higher, as does travelling at any speed. And if you stop the engine for a half an hour then restart, the oil pressure goes back up. A regular poster here by the name of "sdlomi" has an ingenious solution to this problem that doesn't involve expensive repairs to fix low pressure, and I am trying to contact him. He hinted at this solution in 2003 on this newsgroup. (I'll make another post about that).

Ok, good, assuming I didn't ruin that my trying to unscrew the adapter at the end of the hose.

Thanks. Would connecting the positive and ground prongs of the connector do the same thing (so I would be completing the curcuit then)? Also, for some reason, the connector has three prongs! I know the tan wire is supposed to be positive though. The problem is I have been having trouble with jumper wires. Not sure what the problem is. I need to find a way to securely attach a jumper wire terminal to the pins of the electrical connector, so I can crawl out from under the car and then watch the in-dash oil gauge. But then that may be too late to see any needle movement!

The other day I bought 100' of 14-gauge thin stranded wire (black), as well as 100- and 30-watt soldering guns/irons, 1/2 pound of rosin core solder, alligator clamps of various sizes, and various terminals, including 2 banana plugs (useless, since most alligator clips and terminals won't fit over them). I still need to learn to solder though. I also bought 8 jumper wires with alligator clips on each end already, each 40 in. long at Radio Shack. So I might be able to make one long jumper wire by clipping alligator clip to alligator clip to alligator clip.

Otherwise, my plan is to make the following

3 ft, 8 ft, and 10 ft jumper wires with alligator clips on each end, to be able to connect the battery to flat type electrical prongs.

Then I will open the clips and insert a paper clip in between the jaws to be able to test pin type electrical connectors. But I still don't know how to make the paper clip stay securely in place while I go to start the car or whatever.

Yep, oil is everywhere! UI should have use Teflon tape when I originally installed the sending unit. Or maybe a better quality one (AC Delco).

thanks Mike,

Julie

I googled this group to find an answer to my oil pressure problem, and this is what I found: here is sdlomi's post from 2003:

Sounds you want to know 'what' and 'why' and then desire to fix it yourself. If so:::::You may find that your oil pump or pump pickup strainer is clogged up, with 160,000 miles of grime. This would be manifested by the engine running relatively quietly 1st time started in the mornings; then after driving it a short distance, the oil press. lite comes on and the lifters start clacking (metal tapping metal due to lack of oil pressure); a noticeable loss of power as the hydraulic lifters quit functioning & hence dis-allow the valves to open and close efficiently; and then the only way to quieten it back down is to let it sit and cool completely down. These exact symptoms, in the order stated, could indicate decent oil pressure at first, when cold; lower/lost oil pressure after it runs a little and picks up grime from the lower part of the oil pan, and lost circulation thru whatever openings were clogged up as the grime 'tried' to flow; and then as it cools, it 'lets go' of the suction (& grime) it had developed on the non-flowing oil, and allows the grime to fall back down into the bottom of the pan. Now, some of those few openings are open once again, just enough to allow oil to flow for a short while until the cycle begins again. But the key is quiet at first with no oil press. lite burning; noisy and oil press. lite on after driving it a short distance(maybe even several miles); after cooling down(maybe a few minutes, maybe a couple of hours) it again runs quietly with the light no longer burning; probably starts same cycle before you get right back home. If this is the scenario, email me, and I'll give you a simple enough cure that has saved me $thousands--I'm retired from the automobile business where I enjoyed applying both engineering principles AND common sense to operate more effectively and efficiently. Hope I can help & good luck. sdlomi

*If you wish to email, you may have to remove an obvious 4-letter word (NOT a dirty one, mind you!). [end quote]

My problem is similar to the one sdlomi describes above: my oil pressure is decent when first starting up, but then slowly declines after driving for 15 minutes or so, sometimes to the point where the warning light comes on for no oil pressure. The longer I idle in traffic, the worse it gets. Letting the car sit with the engine off for a while temporarily solves this. And when I accelerate, or drive at a continuous speed, this also increases the oil pressure. Idling decreases the pressure.

So I emailed sdlomi a few days ago, but no response yet. I hope he still posts here! He gives good advice!

Julie

Ya got teflon tape on the sending unit???

On some sending units, this can mess up the ground signal so the gauge reads 0 or jumps all over creation.... So if the pressure is ok on the mechanical gauge then that could be the problem....

On the wiring, I hook jumpers together or usually use booster cables to get power close then short alligator clip jumpers from them. A second person comes in handy when doing this so you can probe with a pin into the wire or plug and have them see the gauge....

On the plug, 'usually' only one wire goes to the gauge, the other two are for a no oil pressure safety switch so the vehicle shouldn't start with 0 oil pressure. One would be power in, one would be power out with the switch in the sender unit or it could be a ground tag using the sending unit as a switch.

So normally it is only the one wire to the gauge that needs to be grounded. I would make sure there is no power in the wire first before grounding anything.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 (More Off Road album links at bottom of the view page)

No, no tape, but I read somewhere you are supposed to use tape when installing the sending unit. But now I know better. :) (Except there is oil everywhere. Would help if my shop manual had the porper torque!)

I tried your advice re the right-angle adaptor. No luck. The problem is the bore for the adapter is so recessed (it's above the tranny, under and to the left of the intake manifold) that the hose is going to have to bend anyway, even with the right-angle adapter installed. And this is with the 2 inch extension adapter I used--it's still too recessed. It is just too difficult to connect the hose, given I am working on my back in limited space.

I could try angling the right-angle adapter upwards diagonally, and shoot the hose in from the top of the engine, but I still would have to actually screw it in from below, which would then require someone on top turning the hose and gauge in unison with my turns of the adapter.

They really need to make a oil pressure tester where the hose can disconnect from the adaptors without needing to screw the hose and attached adapter on. Maybe a quick connect system??

So right now I have no way of checking my oil pressure! I'm stuck with testing the gauge and sender unit only and hoping that works. If not, then I must assume I have bad oil pressure and go from there. This sucks!

Maybe I can cut the hose of the tester, and then use a larger diameter hose to connect the two pieces, thereby making my own quick-connect system???

Ok, I did check, and the problem is the wires have so much oil on them, you can no longer easily tell the colors. One is pinkish red, and the other two are tannish yellow. Maybe I will need to try each one?

And an idea that comes to mind so I don't need an extra person, is to ground the wire from inside the car, while I am watching the in-dash gauge. I need to find a ground somewhere though.

Why?

Thanks again Mike!

Julie

When you turn the key to "on" in my car, the gauge smoothly goes from 0 to

1. This is without the connector connected to the sending unit, and not jumping anything.

So do I still need to test the gauge with jumper wires? I am sorry to ask so many questions. Anyone can answer if they wish.

If so, where is a good place to ground the wire from within the car? On a side window regulator? Or somewhere under the dash on an unpainted metal surface?

Also, I was able to securely stick a paper clip into one of the pin terminals in the connector, and I set up a string of jumper wires with alligator clips.

Julie

Quick question.

Was there oil all over when you started this?

If yes, the sending unit has failed.

Mike

"Julie P." wrote:

Yes!

But even when I installed a new sending unit in 2003 (a cheap Sorensen brand), the oil pressure started out at around 60 psi, then gradually dropped to around 10 psi after a half hour to 45 minutes of driving, but only when idling. Now it drops to 5 psi or even 0 psi when idling after

15-20 minutes of driving. So I must have low oil pressure. So I am hoping sdlomi posts here with his solution he mentioned. Otherwise, I will have remove the flywheel cover, starter, oil filter arm, oil pan and exhaust pipe just to check the oil screen for clogging. And I am not sure even if I can pull the flywheel cover without first removing the engine.

Julie

Well, when lots of them fail they leak oil out the end.

They fail with your exact symptoms.

You also have to think of the mileage. Lower pressure is to be expected when the engines get worn. It is normally worn main bearings that allow the oil to flow too easy. Folks sometimes go to a thicker grade of oil, say 20W40 instead of 10W30 to keep the pressure up a bit. 10 at idle is still within the drivable range. My engine only has about 50K on it and when hot at idle runs about 15, sometimes when really hot down lower.

I would change the sender before messing with the oil pickup screen. I have even filled engines with mineral spirits to flush out filter screens on the hope of raising the psi back up, but a worn engine is a worn engine....

Are you starting to get any spits of oil into the air filter yet?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 (More Off Road album links at bottom of the view page)

Ok, I will try what you recommend first then Mike! I really don't want to get into the engine now, especially with winter coming. I am using 5W-30 now, for winter, which is what my manual recommends. But maybe I will go to a thicker grade.

Well, I just checked. Had to pry the cover off with a screwdriver since the rubber gasket was melted/stuck the housing. The filter is disgusting. I thought I had changed it a few years ago. It was dirtier than I had ever seen it before when it came time for a change. Also, on the inside of the filter, there appear to be either oil stains or burn marks all the way around. Same with the butterfly choke plate/TBI injectors or whatever you call the stuff in the center :) It's a dark brown/black from oil or burn marks.

A strange thing happened though after I got done reinstalling the old sender unit: the car would not start. The starter was turning and the battery was fine. It reminded me of years ago when I used to pull my fuel pump fuse when I parked in the city, as a security measure, to thwart car thieves. Sometimes I forgot to reinstall the fuse, and the car would not start, just like it was not starting now. So this time, for the heck of it, I checked the fuel pump fuse, and it was blown!! What in the world could have caused this??? It was fine before I pulled the sender unit.

The only things I can think of is before I had tried to start the car, since I already had my new jumper wires out to test the oil gauge, I decided to see if the jumper wires really worked by testing my radiator fan and also blower motor, which still don't work even though I just put new ones in. Both motors worked fine when jumpered to the battery. I did accidentally connect the two paper clips I was using for test leads together, while the other ends were connected to my battery. This caused some sparks. I also previously had connected a jumper wire to the oil gauge electrical terminal (while the oil sender was disconnected), and the other end to the my side window guide frame (it's unpainted--I have my door panel off), and then turned the ignition to "on" and watched the oil gauge rise to full (80 psi). Oh, and I also attempted to connect the coolant temperature sensor electrical connector terminals to my battery, and to each other. And also the coolant temperature sensor terminal on the sensor itself to the battery and to each other. (I was trying to test if my coolant temperature sensor was bad).

So did doing any of the above cause my fuel pump fuse to blow? It seems weird! I finally was able to start the car three times in a row after I put a new fuse in, so it seems ok now.

Julie

I know now I am going to Harbor Freight Tools and buy one of those mega packs of like 150 spare fuses they have for $8.99, and carry it with me in my car at all times. I do carry emergency fuses with me now, but there is only one of each type in that kit. I need to have multiples available in case of an emergency.

Also, I have been having bad luck lately:

1) The other week while backing my car off the ramps I use during oil changes, I drove over my wheel chocks, and now the plastic is all warped and white where it was stressed.

2) And now one of my 3-ton floor jacks is leaking oil from the bottom ram cylinder, and won't lift my car all the way up, even though it has only been used minimally. I don't know how this happened, since there is no score marks there where it is leaking from rubbing against anything. The jack cost me $49 on sale at PepBoys. Luckily, I have 4 spare larger-sized jacks (3 to

3.5 ton), and 5 smaller ones (1.5 to 2.25 tons), but I liked the particular one that is leaking, since it is lightweight, yet still full-size, profesional grade.

3) And today, while I had by car jacked up on jack stands, I was going to rotate the tires since I really didn't accomplish much at all today with my oil sender unit, but my impact gun battery was not fully charged, and there wasn't enough torque to break loose the lugnuts, which were set to 100 lb. ft. And I didn't feel like stringing out an extension cord so I could use my electric one. And my 12 volt DC impact gun that plugs into a cigarette lighter outlet is kind of pathetic and embarrassing to use.

Oh well, not really bad luck I suppose, but still... :)

Julie

I just checked the old oil sending unit, the one I pulled out in 2003. It had teflon tape on the upper threads, near the sending unit body. I think it was the original sending unit. So may be it is ok to seal the threads with tape?

Julie

So may be it is ok to seal the threads with

It would be -if- teflon tape were meant to be used to seal threads. It isn't. Teflon tape is used to lubricate tapered pipe threads so that they can be tightened sufficiently to effect a seal.

You want "pipe dope."

It does come in the teflon variety and is well suited to automotive uses. #2 Permatex works well also.

Another idea would be to somehow find two more of the 2" extension adapters that came with the kit, as well as another male-to-male connector. This way the adapters would be long enough, so when I connected the right-angle adapter, I the hose would just hang straight down, and it would be much easier to spin.

Perhaps I can get buy brass tubing and thread the ends with a die, but I would still have trouble with the making male-to-male connector (which has female threads on each end). Maybe a machine shop?? Or, maybe just make one

4" brass extension with male threads on each end using a die. I wonder how hard this would be.

Otherwise, I would have to buy two more oil pressure tester kits at $58 each, just to get the adapters!

Julie

So what if I used teflon tape then to lubricate the threads so I could tighten the sender unit sufficiently tight, to effect a seal?! :)

I did notice that this tape was used on my original radiator's draincock, as well as on the flare nuts which hold the tranny lines to the radiator.

Yep, I have that too (but it may not be Permatex). Thank you! I like the sweet smell of it too.

Julie

I just checked what the tap was called. The package said "pipe sealing thread".

I just searched my supplies, and I have what is called "Loctite PST - Pipe Sealant with Teflon". Hope this is good enough.

Just a guess, but the plug to the oil sender has a safety in it so the engine won't start if there is no oil pressure. That is why I mentioned making sure there was no power in the line you were going to ground... That is likely the source of the blown fuse.

Your air filter has the symptoms of an old engine getting long in the tooth... I would put a fresh filter in and just check it more often. I only get 2 or 3K out of an air filter before I notice a drop in gas mileage.

You also can get a spray can of throttle body cleaner to get all the brown junk off the insides. It is worth doing. Spray out any passages you can see and wear glasses doing it. The spray can blow back at you easy and it stings the eyes bad.

Mike

"Julie P." wrote:

Yes, that is the right stuff.

The tape is fine for lots of applications, but it can sometimes interfere with a clean power signal so it isn't really recommended for sensors. Rad drains, tranny lines, used carefully on brake line fittings, etc. are ok...

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 (More Off Road album links at bottom of the view page)

Given that an oil pressure sending unit is a fairly fragile part, you'd probably assist in its demise.

Oft times you will find it being used where it either shouldn't, where there is a better choice or where it makes no sense. Using it on the tranny cooler lines makes no sense as a sealer, the cooler lines seal at the flare, not at the threads, if it was put there from the factory it was probably intended to lubricate the threads to keep the metals from galling.

Yup, that's the stuff.