My factory oil gauge quit at some point this fall and I haven't got around to fixing it. I'm guessing it's a loose plug that slips on the sending unit, I really should get a nut for that thread and attach it using a ring terminal. Anyone know what thread is on the sending unit? For what it's worth I reached behind the turbo and jiggled the factory gauge wire on the sending unit last night, which made no difference on the factory gauge.

Beyond that my Westach oil pressure gauge has been on the fritz as of yesterday. It works fine on a cold start but sometime after being up to temperature it reads zero at anything below 1200 RPM, and above 1200 RPM is jump right up to 35+ psi. No abnormal engine noise or indication of lack of oil pressure. Granted my oil pressure sending units are both in the turbo oil feed line, so it's conceivable there may be some obstruction or issue there before the gauges limiting oil flow to the turbo at low RPM.

Could the sending unit be fouled with a small piece of debris or gunk? What can I use to clean them safely? I was thinking possibly contact cleaner since it is safe for plastic and rubber? Maybe pull the sending units and clean them with contact cleaner in the oil pressure side would help? Or should I just replace them both? Can electronic senders fail in a way that they read zero only below a certain pressure? Should I flush the turbo feed line? It's freakin' cold outside so I'm not looking forward to any of this, but the alternative to getting a solid oil pressure reading is to ride a motorcycle to work which would also be cold.

 

maybe oil Pressure regulator is stuck open ???

 

lonewolf's suggestion seems to match the symptoms.

This web page might make you happy. You can cheat and scroll down to the last photo and read the two paragraphs under it. Fortunately he only had to remove the oil filter to free up the the stuck pressure regulator valve, but reading the whole article explains very well how it works and how to repair one.
diezelcrazeesidipage-oilregulatingvalve

If it's due for an oil change I would definitely (highly) recommend this. The Synthetic version. READ THE FAQs
https://www.motormedic.com/motorflush

I used this when I changed over to all synthetic base synthetic oil, 15W40. Upon first start up, engine RPM at idle had gone UP by 125-150 RPM. and I think that was largely due to the coating from the Motor Medic engine flush.
I drove it 400 miles that way expecting the idle RPM to eventually drop back but it didn't. I had to substantially drop the idle at the linkage adjustment screw at the injection pump and the fast idle solenoid. I don't think it can adjust down any further and it's still idling slightly fast, that was about 2-3 years ago and about 2,000 miles since.

I did this out on the street at about 40 deg F (4.4 deg. C) ambient temperature and I put a quilt blanket over the grill to assist in warm up. Follow the directions. I let the engine run a little bit longer than 5 minutes but NOTE: I do NOT recommend doing that.

 

PS: The higher idle RPM is obviously due to less friction. That also helps cold starts, faster starting.

 

Thanks, this is plausible, though I think a bit odd that at 1200 RPM it goes from zero to about 35 psi, and back just below that. Cold oil pressure reads normal as oil when cold and warming up until it has been at temp for 20-30 minutes. I hadn't thought of that valve though, being fixated on the gauges. Granted the engine is fairly new, about 28k miles on it (https://www.ford-trucks.com/forums/1...hat-to-do.html). I did rebuild the oil cooler with new o-rings and I paid attention to work that pressure regulating valve back and forth to see it was clean and moving. I did not remove the valve from the oil cooler header though.

I'm also coming up on a 5,000 mile oil change... About 300 miles from it. I'll work that valve with a pick to see if it's stuck. This engine has got only Rotella T6 5w40 synthetic since the start and oil changes at ~5k miles aside from the first after a few hundred miles and second after a few thousand. It should be pretty clean. ~28k miles and this should be the 7th oil change.

I jiggled the wire to the factory gauge this morning and that started working, but failed after hitting a pothole and the aftermarket gauge started going to zero below 1200 RPM shortly after that but I was only a minute or two from work by then. I'll try to get the factory gauge working for the drive home tonight and see if it lasts enough to corroborate and conflict with the aftermarket gauge. I may have a mechanical gauge I can plug into the port on the block attached to the turbo, that would be a quick way to determine what's actually going on before changing anything.

 

I've had issues with the PS60 senders on my 93 in the past... mostly what I have seen with the sender is that the OP gets erratic and bounces all over the place.

BUT I agree the best method is to use a Teas gauge to see what is really going on.

I love my BAR.................

 

On the drive home it gave normal oil pressure readings for about 15 mins then dropped to 0 at idle on the Westach gauge, right up to 35-40 psi at 1000 RPM. I was mistaken about 1200 RPM in my previous post, I was just ballparking it. Factory gauge was intermittent reading on the lower end of the gauge or nothing at all and conflicting the with Westach gauge at times. At one point cruising just under 1000 RPM the Westach read 0 and the factory gauge was about the middle of the range, but later returned to lower end of the range then no reading. No abnormal sounds at any time.

When I got home I was able to pull the wire off the factory sender and crimped it a little tighter, reinstalled. Now the factory gauge is more consistent but still reads toward lower end of the range. I wonder if I may have a wiring issue or ground issue to the gauges. I don't recall where I ground the Westach gauge but it may be the same as the factory gauge somewhere in the dash. The aftermarket gauges get +12v off a fuse tap, I know it's hokey but it's a solid 14.6 volts regardless of gauge reading, measured using under dash light as a ground.

I changed the oil. It was black as night but no signs of metal. No abnormal sounds from the engine. I sprayed the pressure regulator valve with brake cleaner and tried to grab the end of the inner bit with a pick but feel nothing. It seems like it's fully seated. Starting it after the oil change oil pressure came up quickly, Westach gauge reading as expected, factory gauge was very slow to come up and more consistent that previously but still somewhat erratic. After letting it idle for about 10 mins I came back outside and both Westach and factory gauge are reading zero or below. So basically no change from waht I had originally, except the factory gauge is more consistently intermittent after reseating the connection on the sending unit. No change in engine sound from cold idle around 40 psi to hot idle with gauge not reading any pressure. I have to imagine it would have seized by now if there was really no pressure.

Before oil change: After oil change:

 

ur engine is clean, it definitely has low oil pressure

 

I haven't drove the truck the past week and change but this past weekend I checked my dash grounds. I found I had already run a new 12ga ground behind the radio to the metal dash frame and tied off that for the head unit and amp. I removed this and cleaned the rusty dashboard to bare metal and reattached. I also took the A pillar trim off and reseated all gauge connections, all seemed good but all moved a bit to ensure a better connection. After a longer test drive I had the same symptoms on both gauges.

Today I drove the truck to work and when I was about a mile from work it began reading zero oil pressure at idle on the gauge. I made a turn and accelerated quickly, winding it out to nearly 3000 RPM and not worrying too much as it read 40+ psi Oil pressure read steady just over 30 psi at idle the rest of the drive to work. Similar on the way home, though dipped a bit at idle (25-30 psi rapidly, but sometime solid on 30 psi). A few more higher RPM pulls to just over 3000 RPM and it seemed to stay fairly steady around 30 psi at idle.

I usually drive this truck like an old man, rarely revving over 2200 RPM. I'm wondering if it could be some tiny bit of junk between the pressure relief valve and seat that got dislodged at higher RPM when the oil pump is pushing significant volume and could trip the relief valve. Alternatively it could be some tiny bit of junk in the oil feed to the turbo that got stuck in the oil pressure sending unit orifice and was dislodged. The factory gauge is still erratic and intermittent, a replacement sender arrived in the mail that I plan to install soon. I also dug out a mechanical gauge that I was going to use to test after getting home tonight if it was reading zero at idle, but now the oil pressure reads normal.

 

I've never really liked most OP Senders as most of them have a really small orifice (used for pulse dampening) like the PS60 it don't take much to restrict them.

 

Only another reason I prefer mechanical oil pressure and water temp gauges at the very minimum. A standalone volt meter is also nice because you generally catch the alternator when it's weak and don't get stranded.

 

I'm not a fan of Capillary water temp direct mechanical gauges.. I don't mind a Temp transducer to drive the gauge...but even some mechanical direct reading oil gauges have the same small orifice ...BUT with the normally long run of steel or copper line to the gauge it is less likely to see debris to plug that orifice than a sender directly on the Port ... I guess you could solve the issue to the sender by using a length of tubing to it and that way if it is mounted off the engine it will not be destroyed by heat or vibration either... line length and size has it's own issues too. (pressure drops)







Basically, I think anything is better than "Buy New Engine Light" ... you know IF it turns on it's too late

 

The gauge was back to zero at idle when hot yesterday. Factory gauge still inconsistent. I did not drive the truck today, but knocked off work early and took advantage of the warm weather to pull the sending units. Even after sitting for 24 hours a fair amount of oil came out of the line when removing the senders.

I replaced the factory style PS60 sender with a new one. The aftermarket sender had one of the two terminals loose in the sender body, which I tightened up. I gave it a quick spritz of contact cleaner as well though the hole didn't look plugged. I installed both sending units only to realize I should let the them sit at least overnight with the thread sealant before pressurizing, if not 24 hours. I checked the ground from the factory sending unit body to a clean bolt on the intake. It was reading erratic. The bolt holding the bracket and plumbing the sender screws into was somewhat oil from crankcase vent oil dripping form the turbo intake. I loosened this, cleaned the oil, and tightened it. Not getting under under 1 ohm, something like .3x from sending unit body to clean intake bolt. This may have been the problem with the factory gauge. I may add a dedicated ground if that's what it turns out to be.

I will leave the intake elbow and filter off to verify no leaks and test tomorrow. If it still reads low at idle I'll put the mechanical gauge on the third port on the turbo oil feed block to see what pressure that reads. Tough to trust anything if three gauges give three different readings though. There must be oil pressure since the engine isn't making a racket, zero difference in sound at idle when reading 35 psi vs below 0 psi. Turbo turns freely, doesn't feel like much slop in the compressor wheel and can't touch the compressor housing.

 

The factory gauge now reads rock solid around middle of the range after replacing the sender and cleaning the ground. The Westach gauge still drops below zero when hot at idle and immediately jumps to ~35 psi at RPM. Factory gauge readds in normal range when Westach reads below zero. I ordered a replacement sending unit for the Westach gauge. I will add a new ground wire from the intake bolt the sending unit bracket mounts to the firewall, and check my other grounds. I don't believe there is any oil pressure problem, though I've still been lazy and not checked with an analog gauge.