Oil pressure gauge type anyone?

[KKson]

Hi, can anyone confirm the type of oil pressure gauge on my 350i? The gauge works intermittently so assumed it was a VDO unit and bought a new sender - but it doesn't work. Therefore assumed it was a duff sender so bought a second and likewise it doesn't work with this gauge so now thinking it's not a VDO one. It's the same gauge type as my mate has on his S2. Of course it could be the gauge that's knackered? I've plugged in a manual oil pressure gauge and all is good so I know that there is good pressure.

When I got the car pressure was always a healthy 50psi when running. Then one day without warning it dropped to less than 20psi and as I'm driving along it now varies between 0 to 20psi. I did have a run out with a manual gauge plugged in and pressure at tickover is around 25psi going up to 50psi at 3000rpm.

I have taken the oil pump housing apart and cleaned all the oil ways and taken the sender unit out and cleaned that also, but no difference.

Any clues?

[ElvisWedgely]

Have you tested your existing oil gauge by earthing it to see if it shoots up to maximum? When you say new sender not working, is it not working at all? Even if you have the correct sender, these gauges normally require calibrating, just like I did when I fitted a new water temperature sender recently. These gauges all work in a similar way.

Tony. TCB.

[KKson]

Hi Tony, yes if I earth the gauge sender then gauge does do a full lap of honour. Of the two new senders the first one (from David Gerald) produced a gauge pressure of around 5psi despite 50psi being applied to the sender and the second one (flea - yes I know I shouldn't have!) produced a full scale "off the clock" movement.

Maybe I should try re-calibrating the first one but I can't see any resistors in line unless they are internal in the actual gauge? Thanks.

[ElvisWedgely]

KKson said:

Hi Tony, yes if I earth the gauge sender then gauge does do a full lap of honour. Of the two new senders the first one (from David Gerald) produced a gauge pressure of around 5psi despite 50psi being applied to the sender and the second one (flea - yes I know I shouldn't have!) produced a full scale "off the clock" movement.

Maybe I should try re-calibrating the first one but I can't see any resistors in line unless they are internal in the actual gauge? Thanks.

Ok. Seeing as they work I can tell you a way to calibrate them by paying a visit to Maplins and the use of some resistors. You need to use the one that goes off the scale and use a risitor to bring it down to the right level. It's easy to do and takes only about 30 minutes. I did it on my temperature sender and now it's spot on. I can let you know how if you want to proceed.

Tony. TCB

[mrzigazaga]

Hi Keith...I might have an oil pressure gauge...Not promising anything but I'm having a look through my box of bits....Ziga

Right i have found this VDO oil pressure gauge...Unfortunately no TVR logo on it...You are welcome to try it and have it if it works...

Edited by mrzigazaga on Thursday 2nd June 13:00

[KKson]

Thanks gents for the replies. My mate with his S2 has a spare identical gauge so he's posted it over so I'll see if there's a difference. My view is that it's the sender unit.

Last year I did borrow a spare sender off Ade from his 400SE but the gauge went backwards so engine not running gauge showed 100psi and with engine running pressure was zero!

My other thought is that most VDO gauges/senders are to 10 bar not 100psi (7 bar approx) so for the David Gerald supplied sender, which only went to 5psi instead of 50psi, could it be that signal the gauge is seeing is bks as the sender is the wrong range?

I'll swap the gauge first and if no luck then I'll have a play with resistors. Tony - would be keen to know how you went about it.

Cheers.

[hrepo]

Stewart-Warner gauges have sender resistance range 33 Ohm -240 Ohm with 100 being the middle point. This applies, it appears, to all their gauges - fuel, temp, voltage, oil pressure.

So having 3 resistors (33, 100 and 240 Ohm) would allow quite accurate testing of S-W gauges. 100 should set needle to half-way mark, and the others should be the extreme values. (better than 0 ohm / open circuit...)

That's how I tested my gauges. Mine were identical to ones in picture and were S-W made.

[ElvisWedgely]

Even if you change the gauge, there is no knowing how accurate the gauge reading will be. The only way I know is to calibrate the two together to get a fairly accurate reading. I will explain how I did mine, but poinless if you don't need it as it's a long winded explanation, but easy to do. If all else fails let me know and I'll pm you how I did mine.

Tony. TCB.

[TVRleigh_BBWR]

Make sure when installing you don't use PTFE tape, as the gauge need to earth on the block.

unless it's a 2 wire sender then I think you need to earth one of the posts.

[mrzigazaga]

Could also be that the gauge is faulty and in need of a rebuild and re-calibration...I did the same thing with the Smiths temperature gauge on Delilah....I bought the wrong sender and when normal operating temperature was reached it would say 280F...However my rad fan was set to kick in at 92 degree C so didn't have to worry...I soon got used to it...It was quite funny when i was contacted by the new owner who thought she was going to blow up...

Sounds like the oil pressure is right judging by the pressure test....My monies on the gauge...Resistors work but i read its a lot of faffing about...If you go this route then obviously put it sender side....

[Number 7]

Keith, I have the same gauge in my 400, although without taking it out, I couldn't tell you what make it is. I replaced the sender unit 3 years ago - its a Lucas SOB505, which I got from here (£39!):

http://www.ignitioncarparts.co.uk/

It works fine, although I do have a capiliary type gauge as well, which is better laid out.

[KKson]

Number 7 said:

Keith, I have the same gauge in my 400, although without taking it out, I couldn't tell you what make it is. I replaced the sender unit 3 years ago - its a Lucas SOB505, which I got from here (£39!):

http://www.ignitioncarparts.co.uk/

It works fine, although I do have a capiliary type gauge as well, which is better laid out.

Brilliant - thanks for that. If the replacement gauge makes no difference then I'll order one of these sender units. Thanks for all your replies gents. Cheers.

[KKson]

Ah, SOB505 has a M10 thread whereas mine has a 1/8th NPT thread so I'll need to source a suitable adaptor if one exists.

[mrzigazaga]

KKson said:

Your veneer looks nice Keith....

[KKson]

mrzigazaga said:

Your veneer looks nice Keith....

Hi Mark the main dash and gauges veneer is good but the glove box is going milky and is cracked so will need to sort it out as it annoys me! Issue is the glove box lid on mine is padded and not your usual solid wood panel as on the 390SE. Here's a photo of when I bought her - the glove box lid is now not looking quite so pretty!

[mrzigazaga]

My glove box lid is padded too....Although i have a bit of plastic veneer...The panel is bolted on, There is a cover on the inside that conceals them...The lacquer might need removing carefully and a re-laquer...A lot of the time its the lacquer thats cracked and not the wood.