I fitted a brand new 150psi VDO gauge and sender on the weekend but it is reading very low pressure. On idle, the needle hardly moving off the ZERO mark, maybe readin 5psi and the warning light will come on steady. If I rev the engine to 3000+ RPM, the pressure goes to 25psi which is still too low. The engine has good oil pressure and I never had an oil pressure issue. When I had the standard oil pressure switch fitted, the warning light never came on when the engine is running
When I was fitting the new sender, I noticed the pick up hole is really tiny like a pin hole and I wondered if this will ever pick enough pressure. Do I have a dodgy sender? Its brand new. Should I drill the hole slightly larger?
Here is a picture at ide


And here at 3,000 RPM


Thanks

The VDO sender's do have a pretty small hole... but from memory closer to tooth pick size than pin size. I wouldn't be trying to drill it any larger.

Assume you've got some sort of tee set up to have both the pressure sender and the original pressure switch still connected... can you maybe give details of that ??? I've seen it before where the first sender was screwed so far into the T piece that it blocked flow off completely both to itself and the other sender.

The light coming on solid means you definitely have low pressure at the switch, so I wouldn't be running that engine until you figure out EXACTLY what's going on.

TRY SCREWING IT IN BY ITSELF.. see what happens...

unscrew the pressure relief valve and make sure it can slide Up & down easily...
a VW engine has around 300++ PSI from the pump..
the pressure relief valve puts it down to below 50psi
[from memory]

no chance of a leak???
losing oil pressure due to a leaking oil sender?

Lee

PS: drilling the sender hole out won't change anything
Lee

Thanks both, I DO NOT have an issue with the engine oil pressue. As I mentioned above, when I put the original pressue switch back on, the warning lights is NEVER on when the engine is running
The new sender is a combined one with two terminals for the gauge as well as the warning light so no T piece

Here is the sender
http://cgi.ebay.com/ebaymotors/VDO-Sender-150-PSI-Oil-Pressure-Gauge-w-Idiot-...

So if there's no T piece, only 2 things can think of are possibly wiring around the wrong way (connecting to the wrong terminals on the sender I mean), or the sender itself is bad.

Other things like dodgy wiring, bad earth's or even if a cactus or wrong voltage gauge or something really out there crazy like that... well I just don't get how they could affect the warning light.

Weird...

Hi

That's a pretty high pressure gauge for a VW motor, I have a 5 bar one in my sons bug, about 70 psi, my WRX motor in my car uses a 10 bar sender and gauge.

I have a similar sender on my sons motor, the wiring can be confusing. G goes to the gauge, W goes sto the oil light.

That sender would also have much higher threshold for turning on the oil light than a stock VW pressure switch.

Steve

I am pretty sure the wiring is correct, I checked
My engine is an 1880cc. Maybe I should've gone for the 80psi gauge/sender. But again, that won't change the reading. Just the scale will be different

Steve is right that 150PSI is higher than you need, but if the gauge and sender are matched then yeah - it wouldn't change the reading. Unless of course a 150PSI sender and gauge is out by a loooong way at lower pressures ?

The 360-023D part number for that one comes up 150PSI W@7, so the warning light should go out when above 7 PSI.

Pretty sure the stock VW switch puts the light out at about 4 PSI... so it's a bit higher threshold, but not crazily so...

Oh - just had a thought... maybe graspin at straws, but you haven't thread taped or gasket gooped the sender have you ???

These senders all work by going to ground, so you don't want anything between the sender thread and the case that might affect the earth...

No, no gasket
Your explanation above about the cut off pressure for the switchs explains why at idle the light is coming on. From reading the gauge, looks like the sender is say the pressure is 5psi. So it is not reaching the 7psi cut off
Gotta be a f*&^ed up sender
I didn't remove the dizzy when fitting it (can't be bothered timing the engine again) so maybe I didn't tighten it all the way. Will have a look again tonight or tomorrow but unlikely it will make that much difference.
What's a typical pressure at idle speed?

You probably won't be too far out if you figure on 10 PSI per 1,000 RPM.

I'd swap out the gauge for one more suited to the oil pressure band of the engine if I were you.

This morning I hooked up the temp gauge. Its reading 120F/50c even when the engine has been running for half hour in city traffic driving. obviously wrong. I reckon I might have used the wrong gauge wire to wire both of them up. I used 16 gauge as recommended on the instruction sheet. Might go down to 14 and see what happens

Where have you got the sensor for the temp gauge mounted.
If it's in the sump plate it's not reading wrong, they always read dramatically low there.


On the plus side, your generator is charging well.

Yep, sump plate
I will replace the wiring with a lower gauge wire on the weekend and see
Cheers

having an oil temp sender in the sump plate is next to useless !
the guage of wire won't make any difference at all.

They're fine to use to just monitor trends in the sump plate which is fine as long as you're aware its along way off accurate.

Replacing the wiring with lower gauge wire made no difference. I am thinking I might have a bad earth to the whole car. Keep in mind this is a replica not a steel body. Apart from clean the terminals and earthing bolt, how do I check for a bad earth? If I measure the volt between the positive terminal and lets say engine block, will this tell me?

Measure the voltage between the earth term of the gauge to earth term of battery, if zero, no V drop, if anything more, you have a bad earth. My 2c is if it is not an earth or voltage supply issue, your engine has low oil pressure. It has now come to your attention because of the different warning light pressure. VW and Porsche didn't fit gauges because of this reason, they run a low pressure system and the yanks ran high pressure systems and they didn't want the new owners worrying about the visually low oil pressure. I also have lots of issues with the correct fitment of most aftermarket oil pumps, most are loose in the case and seem to suck air on the intake side and loose pressure on the pressure side, to remidy this an O-ring needs to be fitted to seal the pump body to the case. To test your system, put on a tempory mechanical gauge, any good mechanic should be able to do this.

Here is a link to a customer's engine where the oil light was coming on at idle. I fitted a mechanical gauge for testing purposes. The engine is only 200km old and has been removed for repair.
http://www.youtube.com/watch?v=vSY0RbviWRs 

I replaced the gauge and sender with an 80PSI ones. Seem to be much better now. First thing in the morning, the pressure is sitting on 40PSI then dropped to around 25. Sitting on 10PSI at idle after being stuck in traffic for a while