faulty oil pressure guage/wiring?

[petegangies]

Hi all, drove the truck earlier this week for the first time in a few weeks. Normally my oil pressure guage will sit near the H mark while driving, insead however, it is now sitting at the L mark. I'm not sure why the sudden change in behaviour, but it obviously has me slightly concerned. I know these guages aren't the most accurate, but this is dramatically different behaviour that I find hard to ignore. I have no other symptoms, car drives perfectly fine, and there is no ticking/knocking from the engine.

I found the testing instructions from the FSM, but want to check I've conducted the test properly. How I did my test:

1. disconnect black connector from centre of pressure guage below exhaust manifold
2. connect my alligator clip of test light cord to ground on side guard.
3. place probe into black connector on harness side.
4. get wife to turn ignition to on. Red light in test light lights up, but gauge does not move to high mark.

Is that correct?

Interestingly enough, I then reconnected the black connector to the sender, started the car, and hit the top of the dash, and the needle came up to just over half way. So I turned the engine off, disconnected the black connector and tried grounding it again.. but the needle stayed at L.

I've attached a video of me driving it around the block where you can see needle behaviour.

 

[petegangies]

unless the issue is that my LED test light is the wrong wattage? There's no published wattage, but being LED, it's probably too low to effectively use for this test. I may have to rig something up with an incadescent globe and some alligator clips or just go directly to earth for a short period.

 

[John McVicker]

That test light is fine for what you’re doing.

 

[petegangies]

That test light is fine for what you’re doing.

you think the LED has the required wattage for this test? A friend of mine who was an auto elec 20 years ago, says it's not appropriate. He said just ground it with a wire directly for a split second, and see if the needle flicks to the top, then disconnect.

 

[John McVicker]

^^^
Sorry, I didn’t catch that your test light was LED.

I actually don’t know if that would affect your testing. I don’t think it would but I don’t really know.

 

[robnicko]

remove the sender and clean its internals by spraying carb cleaner in its port and see if any difference, youd be surprised how much dirt / crap comes out if original sender. I did this to mine a couple of years back when it showed abnormal reading compared to normal. I did run a mechanical gauge in to be sure it wasnt anything else and cleaning of the sender restored it back to normal operation

 

[petegangies]

remove the sender and clean its internals by spraying carb cleaner in its port and see if any difference, youd be surprised how much dirt / crap comes out if original sender. I did this to mine a couple of years back when it showed abnormal reading compared to normal. I did run a mechanical gauge in to be sure it wasnt anything else and cleaning of the sender restored it back to normal operation

Thank you.. I read you should put some Loctite 242 or equiavlent on 2 or 3 threads when reinstalling. Did you do that or just screw it back in?

p.s did much oil come out when you removed it? just wondering how messy of a job it might be.

 

[robnicko]

Thank you.. I read you should put some Loctite 242 or equiavlent on 2 or 3 threads when reinstalling. Did you do that or just screw it back in?

p.s did much oil come out when you removed it? just wondering how messy of a job it might be.

just unscrew it and put back in, i used a tiny bit of teflon tape but not much & do not overtighten. It will dribble a little oil when removed but not much. Also, do it with a cold engine as its a steel thread going into aluminium

 

[petegangies]

just unscrew it and put back in, i used a tiny bit of teflon tape but not much & do not overtighten. It will dribble a little oil when removed but not much. Also, do it with a cold engine as its a steel thread going into aluminium

thanks Rob.. much appreciated!

 

[petegangies]

I rigged up a 5w lightbulb and grounded the harness plug again, and confirmed that the needle does go from L to H, which means the gauge itself is operational, and therefore it's likely the sender? I'll try cleaning it first as @robnicko suggested, and if it still doesnt work, then I'll put a new sender in.

 

[Mat Jadamec]

Lessons learned on my 1994....Pegging the gauge can bend the internal heated spring in it, which can lead to low readings under normal load later. The fsm clip above shows a 3.4W bulb which most of the indicator bulbs in the gauge cluster are. The gauge internal spring can be bent back if you are careful. I'd check the wire harness directly attached to the sender as the wires corrode at the terminals at the sender end, and the wire insulation near the engine gets brittle and can crack leading to shorts and pegging. If you rework the harness make sure you use the OEM style terminals and connectors shown on your photo. And make sure in any case you check the actual pressure at the port with a mechanical gauge so you can believe your gauge later.

 

[petegangies]

Lessons learned on my 1994....Pegging the gauge can bend the internal heated spring in it, which can lead to low readings under normal load later. The fsm clip above shows a 3.4W bulb which most of the indicator bulbs in the gauge cluster are. The gauge internal spring can be bent back if you are careful. I'd check the wire harness directly attached to the sender as the wires corrode at the terminals at the sender end, and the wire insulation near the engine gets brittle and can crack leading to shorts and pegging. If you rework the harness make sure you use the OEM style terminals and connectors shown on your photo. And make sure in any case you check the actual pressure at the port with a mechanical gauge so you can believe your gauge later.

Hey Mat, I used a 5w parking light wedge bulb for my testing, that I rigged up specifically for the test. I didn't leave it on there either, we disconnected it as soon as the needle hit the high mark per my video above, so I don't think I'll have bent anything. The FSM tells you to test it this way, and I while I did use a bulb slightly higher then what was called for, many ground it directly with no issue for short periods of time. All the terminals and plugs look good to me, no corrosion or damage. I will spray the black plug with electrical contact cleaner, but even that looked fine, as does the wiring itself. I'm leaning more towards a faulty sender now, but yes, will definitely check pressure with a mechanical gauge for peace of mind, for sure.

 

[petegangies]

I've just ordered a new sender and will install this weekend. My mechanic said if that doesn't sort it out, to drive it to his place to put a mechanical gauge on it for testing. I thought about doing that first, but honestly didn't want to drive another 45min trip if it genuinely is low oil pressure. The sender only cost me $60 and shouldn't take more then 30mins to remove the old one and install the new one.

 

[petegangies]

We have success people. It was a faulty sender. Replaced and pressure is back.



Part number 83520-60011

 

[robnicko]

cool, did you use an aftermarket sender? i cant imagine OEM for $60 in Aus

 

[petegangies]

cool, did you use an aftermarket sender? i cant imagine OEM for $60 in Aus

Nah, I used OEM, but had a mate who imports parts from UAE/Japan and happened to have one for me at cost

 

[Kernal]

What oil viscosity and which oil filter brand/part # are you using in your 80 and is the oil filter newish or high miles?
What was the ambient air temp when you made the cold start video above with the new sensor installed?

Post up another video showing the gauge positions with a fully warmed up engine ie: at idle (~650rpms) and at say 2000 rpms.

Either way, a direct measurement using a mechanical oil pressure tester will tell you exactly what the pressure is.

Your mechanic likely knows this but FWIW the oil pressure port size/threads are 1/8" x 28 BSPT (British Standard Pipe Taper).

 

[petegangies]

What oil viscosity and which oil filter brand/part # are you using in your 80 and is the oil filter newish or high miles?
What was the ambient air temp when you made the cold start video above with the new sensor installed?

Post up another video showing the gauge positions with a fully warmed up engine ie: at idle (~650rpms) and at say 2000 rpms.

Either way, a direct measurement using a mechanical oil pressure tester will tell you exactly what the pressure is.

Your mechanic likely knows this but FWIW the oil pressure port size/threads are 1/8" x 28 BSPT (British Standard Pipe Taper).

I normally use a Ryco branded large filter, Z something.. this one is the same size but the Syntac version which is their top of the range filter. Yes, it's new, but I had high oil pressure with the previous filter too. It was only this sudden issue of being on L that it became a problem.

I do often wonder why mine reads so high, but as it's done it for years and never been an issue, I haven't been concerned about it.

I can take some more videos, I have older ones, but better to send something current. Ambient temp is about 23 Degrees Celsius.

I use Penrite HPR gas 10w50, the same oil has been used in this vehicle by my dad for as long as I can remember. Recent oil analysis showed the engine to be in good condition with no abnormal wear. It was at the time I changed the oil and took a sample that I fitted a new filter. I'll be lucky to have done 500km since the oil change.

Are you concerned about what you're seeing?

 

[Kernal]

Needle a bit high on a cold start (IME) but then you're using 10W-50 oil and on a cold start the bypass valve of the oil filter
will be wide open so you get more flow/pressure to the engine (but little filtering). So likely normal for your engine/oil/filter assuming the oil pressure gauge reading drops down somewhere in the middle or less at idle once the engine/oil warms up. If it stayed that high (almost pegged to the top) after warm up one possible cause is a defective oil filter bypass valve where the oil is bypassing the filter all the time.

 

[petegangies]

Needle a bit high on a cold start (IME) but then you're using 10W-50 oil and on a cold start the bypass valve of the oil filter
will be wide open so you get more flow/pressure to the engine (but little filtering). So likely normal for your engine/oil/filter assuming the oil pressure gauge reading drops down somewhere in the middle or less at idle once the engine/oil warms up. If it stayed that high (almost pegged to the top) after warm up one possible cause is a defective oil filter bypass valve where the oil is bypassing the filter all the time.

If you watch my video above I pause and come back when its warm. It sits about 3/4 when warm at idle. It had only been moved from one car spot to another. Not a proper drive only about 1min. I'll take some more videos for you this weekend. Link to my oil: HPR GAS 10 10W-50 (Semi Syn.) | Penrite Oil - https://penriteoil.com.au/products/hpr-gas-10-10w-50-semi-syn
and I'm pretty sure this is my filter: https://www.repco.com.au/parts-serv...yco-syntec-spin-on-oil-filter-z9st/p/A9690928

They also do a smaller filter: https://www.repco.com.au/parts-serv...o-syntec-spin-on-oil-filter-z418st/p/A9690917 (not the one I have on my truck)