Dvderlm, any ideas? I'm figuring this out as I go along (as you can probably see) so I'm now qite comfortable with how the relay switch works and how to wire it up (I'm proud) but I'm now stumped..?

I work with electronic engineers but they're all digital or radio frequency.

What's the coil resistance of your relay?

Perhaps a complementary latch circuit could be used to trigger the relay switch-on.

Or a T mount for two oil low-pressure switches, one for the dash. One for your relay so there's no voltage drop due to the J114.

eg

http://cgi.ebay.co.uk/OIL-PRESSURE-GAUGE-F...0-/300558621254

Sorry, working it out as I go along aswell.

Gulp, did the page just flash

DON'T GIVE OUT DUFF ADVICE. IF YOU DON'T KNOW THE ANSWER THEN DON'T ANSWER - SIMPLE!!!

No, I think I'm falling asleep.

Edited 2 June, 201115 yr by dvderlm

That sounds like a solution that would work. I spoke to my dad yesterday and he seems to know a lot about electronics and he explained that it won't work in its current state partly due to the fact that the Loil pressure light in the dash is what is bringing the output down to 11v as opposed to vehicle voltage of 12.5 etc.

I do like the idea of your t piece and fitting another switch. I think that will work. I'll ask my dad and see if he thinks that will work. You're suggesting for that on the high pressure switch? Then I'd need another high pressure switch yeah? (Would it have the right thread for the side of the t piece?)(is there actually any difference between the high and low pressure switches? eBay only lists one and doesn't refer to high of low?)

Once we've got a solution that I've proved works I'll be sure to do a write up and we can put this is the faq :)

m10x1 thread for all oil pressure senders (vw ones anyway)

That sounds like a solution that would work.

So does everything until you try it...

I do like the idea of your t piece and fitting another switch. I think that will work. I'll ask my dad and see if he thinks that will work. You're suggesting for that on the high pressure switch? Then I'd need another high pressure switch yeah? (Would it have the right thread for the side of the t piece?)(is there actually any difference between the high and low pressure switches? eBay only lists one and doesn't refer to high of low?)

No, another low pressure switch, a high pressure will be off at low-ish revs say 1000 to 1700rpm.

Low switches at 0.3 bar (black body specced 0.2 to 0.4 bar) so just cranking without firing should achieve that with sufficient oil in the system.

High switches at 1.8 bar (white body specced 1.4-1.9 bar). The J114 monitors the revs and checks only the high switch is on when over 2000rpm. Otherwise checks the low pressure just like every other make of car on the planet.

So you'd want another low pressure switch in the T piece. You only need signal that the engine is turning.

I think the low pressure sender connects the contact to the block when pressure reached.

But the wiring diagram appears to show the high pressure switch as normally-open and low as normally-closed

so that needs checking.

Checked a white pressure switch (high) - it was open circuit.

Checked a black pressure switch (low) - it was closed circuit.

If neither are broken .. I'm wrong.

The VW low pressure would need a logic invertor to energise the relay when pressure rises above 0.3 bar

and contact switches from closed to open (no longer connected to block).

So you need low pressure normally open M10x1 sensor as well as T-piece.

Personally I'm not sure I would buy a eBay rubbish pressure sensor, I'd take one off a scrap car and test it or, use a motor-factors or GSF or eurocarparts or even VW dealer.

I will speak to my dad again soon to clarify, but I think when I spoke to him earlier he suggested that instead of taking pin 85 from the existing low oil pressure switch circuit, I could take a switched live from the ignition and run it in parallel to the oil pressure circuit with the lamp in, so it would give me a live straight from the ignition, bypass any relays in that circuit altogether, and only ground when the low oil pressure switch let it whilst the engine was running.

Although now you've said that about the low pressure being normally closed (which of course grounds the oil light and illuminates it when there is no oil pressure, and opens when there is oil pressure to turn the light off) I think the solution is a combination of the two suggestions. Get a T-Piece, find a normally open low oil pressure switch, and run the circuit as my dad suggests to once again bypass the oil pressure light circuit altogether.

I guess there's nothing I can do to utilise the high pressure switch is there? That's normally open and will only close if the pressure gets too high etc.

On second thoughts, it's actually looking pretty tricky to find a low pressure switch that's normally open. So maybe I'm trying to solve a problem with parts that don't exist..

edit - would this be the answer to my problems?

site http://www.wellsve.com/custom_searches/ds_...php?showall=yes

PS121 has the right thread to go straight in (M10x1), it has three terminals instead of 1 like the vw standard one.

1 terminal is normally closed to ground - opens at 2-5psi (0.13-0.34bar)

and the other two (although 1 would be redundant) is normally open - closes at 2.5-9psi (0.17-0.62bar)

That would do what I want quite elegantly without the t-piece or a second sensor, would it not?

Edited 3 June, 201115 yr by runforrestrun

PS121 has the right thread to go straight in (M10x1), it has three terminals instead of 1 like the vw standard one.

1 terminal is normally closed to ground - opens at 2-5psi (0.13-0.34bar)

and the other two (although 1 would be redundant) is normally open - closes at 2.5-9psi (0.17-0.62bar)

That would do what I want quite elegantly without the t-piece or a second sensor, would it not?

PS121 sounds perfect.

Looking possible now and your dad's wiring suggestion makes sense to me.

You reckon those pressures are close enough for what I need? Thanks for your help, on your word I'll get on and order it, and when I know it's all working I'll collate it all into a sticky for the FAQ. :)

You reckon those pressures are close enough for what I need? Thanks for your help, on your word I'll get on and order it, and when I know it's all working I'll collate it all into a sticky for the FAQ. :)

I can see way more than 0.6 bar on my oil pressure gauge cranking with no spark plug king lead.

It reached nearly 3 bar. That is with cold oil and cold engine which is always higher though.

Should be okay.

I like those odds, I'll get one ordered

I owe you a beer

Small update for you. My oil pressure switch finally arrived so I've fitted it tonight.

I've connected the original wire to the normally closed switch, and taken a new wire from the black switched live on the ignition barrel, through pins 85 and 86, to the normally open terminal on the new switch. So far so good. Testing with my meter I get voltage now on pin 30 (which I always did as it comes straight from the battery) and pin 85 (which comes from switched ignition) if I ground it. However I still can't get the relay to energise when 85 and 86 are connected (although I can when 85 goes to battery and 86 goes straight to ground)

So I think the answer is, as the normally closed works fine (it opens at a lower pressure than the normally open) but I can't get the normally open side to close, after checking the oil and realising it's just below min, it's gonna be as simple as topping up my oil to bring up the pressure. So tomorrow I'll buy some more oil and top her up, and hopefully I'll have solved it and I can finally get my facet on and working EXACTLY like I want it to!

I've topped up the oil and after realising that the two pins on the oil pressure switch need their own ground, i.e normally closed grounds to the block and normally open needs it's own ground (hence requiring two pins) we've got the voltage that we need coming at the right time. Woohoo!

However, it appears that the facet pump I've been sold is leaky. However tight I do the top thread, it still seeps through the thread area. I'm thinking that using the original pierburg swirl pot is building too much pressure and hence the leak (it's only a seep) so I'm gonna remove the swirl pot and put a t-piece in with the pierburg (before I fit my bike carbs) in the hope that solves the problem. Hopefully I'll still get enough fuel without the swirl pot. Should do.. right? If you can run bike carbs without a swirl pot you should be able to run a pierburg?

All sorted.

Bought some thread seal (petrol resistant)

job done. I was making it into a bigger problem than it actually was.

Next job, collate this into a guide for the FAQ

good job chap il look farward to reading it