Oil Pressure Sensor Sensor

[jon batson]

Where is the oil to the Pressure Sensor fed from?

I think I'm gradually answering my own questions - but in case someone out there knows I'll ask anyway.

The background goes back a few weeks from the time I changed the head on my 2.4TD. The usual problem - the old head cracked etc etc.

Anyway, did all the work, about 3 days in all, mostly because I really wanted to make sure everything went back as it should. Engine runs perfectly - no water loss - power and fuel economy as I remember it - so what's the problem?

First off the Oil Pressure Sensor lead had come off accidentally during all the work and I replaced it on the most obvious (and visible) point. This turned out to be an unused Oil Pressure Switch which gave me a maximum reading with the engine stalled and zero when running.

Took me a while to find the location of the sender which is tucked away very conveniently (and out of sight) under the exhaust about level with No. 4 cylinder about level with the Oil Filter. Attached plug and hey presto – nothing!!

To stress again, engine runs fine, sounds fine - but no oil pressure reading.

My thinking at the moment - and I would really like someone to confirm this one way or the other - is that the oilway to the sensor is from the head. What I think I have done is to fit the head gasket without removing all the alternative holes and that while the oil is being fed to the bottom end bearings (first), and then to the head and hence camshaft / rockers etc (second) that I have blocked access to the sensor (third).

Seems to me that it doesn't make any mechanical sense to feed the oil from the pump to the bottom end via the head as it's the bottom end that needs the oil most! But there is a sort of sense in taking the final feed to the sensor from the lowest pressure point in the system ie the back of the head after the camshaft etc.

Does anyone out there actually know how the oil gets fed around the engine. We all know where it’s got to go – but in what order and what general direction??

It would be nice to know the answer without having to take the head off again???!!!!!

One last question - if I do have to take the head off to replace / refit a new gasket - can I do it without having to remove the exhaust manifold and (especially) the inlet manifold and attendant pipework as they are a real ****??

War and Peace over.

Many thanks if you've got this far.

jon

[TonyN]

The pressure sender is where you said, under No4 exhaust.

You shouldn't need to mess with the head gasket, how you get it is how you fit it.

I don't have a schematic for the 2.4, but the 3.0 goes from the sump-oil pump-oil cooler (where the sender is)-filter-off to the engine. Generally most engine work the same.

[jon batson]

Tony - Many Thanks For Your Reply

Tony,

Your comments make perfect sence - and makes me feel a good deal happier than before I must say!

My thinking about the head gasket comes from the fact that the sensor was working before I changed the head - and now it doesn't. The only other option is that the sensor has suddenly decided to fail at exactly this point in time. Prof Sodd's Law being one reason for this or, (very maybe) some internal overpressure or excessive heat brought about during the last few miles of driving while the head really brewed up the internal temporature?

Next step is to remove the sensor and test it.

I'll do this over the weekend and see where we are after.

Once again Tony - many thanks.

[jon batson]

Good News!

I took out the sensor this afternoon to test it. 14mm open ended spanner slightly bent to clear the block - you'll know what I mean if you have to try it.

After thinking about how to test for a few minutes I decided to cut a few corners and simply turn the engine over and see if oil escapes.

Well, the oil literally ****** out of the sensor hole so I now know that the sensor is definately stuffed!. Which is very very good news indeed.

Then it's call Toyota and try to get hold of one - guy was very friendly and helpful - seems that there is a Denso and / or a Yakasaki for my Surf. He's ordered both and I get a chance to choose when they turn up.

I'll keep you posted - but I do seem to be finally getting to the bottom of this.

Only thing that bugs me is why it chose this time to fail - temperature / heat, or simply Prof Sodd???? I guess I'll never know.

jon

[jon batson]

It wasn't the Sensor - Bugrit!

Replaced the sensor - got the engine running - expected to see the oil pressure gauge register - bugrit! - not a flicker.

Decided to do what I should have done in the first place and test the old sensor. Hooked it up to my compressor and it showed 130 ohms @80psi, 86 ohms @ 50psi, 59 @ 30 and 54 @ 20. Obviously the psi readings are from the compressor guage and not precise - but the overall meaning is clear - the sensor was working.

Then took the meter to the car and at medium revs was getting a reading of about 70 ohms which tells me that the new sensor was also working. £47 up me shirt because I couldn't be bothered to do the compressor test - bugrit!
Anyway - next test the wiring and the gauge again - wiring ok and gauge reads full scale when shorted to earth - but not a flicker when connected to the sensor with the engine running.

After a lot of messing about with variable resistors I finally come to the conclusion that the simple act of shorting the gauge to ground to test it has screwed the internals of the gauge sufficiently to cause it to read lower. Remember back at day one I had trouble figuring out where the sensor was on the engine and had inadvertantly connected it to an oil pressure switch.


So my problem had nothing to do with the head change - nothing to do with the head gasket - except that the work entailed caused the oil pressure sensor lead to become detached and all my problems started from that point - bugrit!


The fix - quite simple - connect a variable resistor (potentiometer) across the sensor and (in my case) set it to 80 ohms. The gauge now reads correctly and swings quite happily between the upper and lower pressure marks as it did before.

Could it be anything to do with the two different types of pressure sensors?

The answer to that is a maybe? but unlikely as both old and new sensors test the same and the other type had a much smaller feed hole for the oil so again unlikely. Both types of sensor read open cct while unconnected and as I couldn't take both home to try I am afraid the jury is still very slightly out.
Next job is to wite the currently unused oil pressure switch to a warning light and job over - BUGRIT!!!!!!!!!!!!!!!

[chasharman]

oil pressure

Hi Jon, is there any chance you could post pics of the new style sender so as to compare to the style I have got currently fitted. When the mechanics changed my engine last year, the managed to nip the sender wire between the engine mount and the engine. Like you I think there was damage done when it shorted to earth. When I spotted what they had done I made up a new cable and reconnected. The gauge now sits in the middle and never moves, regardless of revs, engine off, under load, hot or cold. Do you know if the gauge has a central default setting if it is u/s or is getting no signal.
Any advice welcome, but not to technical as I hate electrics.

[TonyN]

I can't speak for 2LT/E's but on Robs 1st gen Surf there are 2 tyres of sensor, the wrong one caused his guage to work backwards, ie, engine not running but ignition on so no pressure it read max, and running it showed zero pressure.

[dar_sbb]

i have the same problem...

my oil pressure gauge wasnt working and when i went to check the switch out i found out that the wire was just hanging on the ground...

my problem is i dont know where the wire goes to... it is connected to the switch but from there i have no clue... if someone could plz point me in the right direction

thanks.

[brownpile]

It looks like you already found the problem, but this is a common problem when people try to put an upgraded instrument cluster into a truck that originally had just the oil warning light, and no guage. The sender for the oil light will damage the pressure guage, so the pressure guage should only be connected to a correct pressure sender. Interesting that your truck had both the oil light sender and oil pressure sender on it...

The oil light sender is a small threaded unit, with a little round metal connector on the top of the hex head. The oil pressure sender is a larger rubber-covered cylinder shape, maybe 40 mm in diameter and 30 mm tall, with a pigtail wire and connector coming off of it, and of course a threaded nipple to go into the block.

[Vagrant No2]

Andy
I know of the upgrade you are talking about which is mentioned on another forum . These Surfs/4Runners are Japenese spec in the UK and come with a oil pressure gauge as standard on the 2nd gen and are also diesel engine which I believe was not available in USA . The dash upgrade was usually for the 1st gen SR5 4 gauge to 6 gauge when , as you say , you need to change the sendor .

[brownpile]

Yep, that is correct.

The petrol and diesel guage senders are the same, as far as I know. I had to get an oil pressure sender when I swapped a 2L-TE into my former V6 truck. My 2L-TE came from a Japanese LX-90 and only had the oil light sender, which would have damaged the pressure gauge in my stock dash cluster. (i'm not quite done with my swap yet).

[POPEYE]

Just caught this thread and reading with interest, i've fitted aftermarket oil pressure and temp gauges but have'nt fitted the senders yet, am i right in thinking that if you connect a new gauge to the existing sender you will not get a true reading or will short the gauge out? I've been putting this off as i know the original sender is a sod to get at and i have to fit two "tee's" to take the original sender and the two new ones, the oil pressure sender is a large'ish diafram type thing and the temp is a small hex unit, My question is - are there any other (easier to acess) plugged off oilways that could be used without disturbing the original? Cheers Ian

[ent]

more oil guage questions

i think i'm having the same problem as Jon.
just purchased and installed new oil pressure sensor and nothing is happening on the guage,
could someone please explain to me how the pressure sensor-pressure guage operates..does the guage send current to the sensor or is it vice versa.how come after installing a sensor i get nothing on the guage..could the guage be damaged or does it just need to be reset?
Jon, you reckoned the problem was with your GUAGE after the wires had been shorted, but to fix it you put a potentiometer across the SENSOR..help! i'm lost with electrics.. what does the potentiometer do to the sensor, especially seeing as the sensor is new...and how do you know how much ohms to apply across the sensor, are you in fact calibrating the sensor to a certain extent here?
should I see a change in resistace readings with a multimeter across my sensor as i rev the engine?
are potentiometers readily available/expensive and how would I know many ohms to apply across the sensor?
sorry for all the questions, just can not get me head around electrical guages

ent