What Voltage For The SAD From Ecu?

[pug_ham 244 3 Cars]

I've been trying to solve the high idle issue on Fidod's car today & we have narrowed the cause down to the SAD not closing, ever.

 

Noel has had a brand new one fitted (along with a re-manufactured AFM) & we tested the SAD so we know it will close with 12v's to it, which led into trying to find out why with it plugged in as it should be it doesn't close at all. I measured the voltage at the plug with the engine running & got 0.4v. It is fed along a wire which comes from the injectors & I'm fairly sure they won't use 12v to operate.

 

I thought the heat of the engine would eventually close it so after wiring a 12v feed to it & removing this once it had closed & was idling normally I unplugged it. This didn't work either & without a voltage to it once closed it opens again pretty quickly.

 

We wired the SAD directly to the battery as a temporary fix until we could solve the problem at a later date but I got a call from Noel saying our 'fix' (bodge) had failed within an hour & it was back at a 2k idle speed.

 

Anyone got any ideas on what else might be stopping the SAD from closing or what voltage it should have from the ecu to heat the bi-metallic strip that closes it up?

 

All plugs were checked & there are no pushed back pins or broken wires.

 

Graham.

[Pugnut 9 1 Cars]

the injectors get a constant 12v from the tach relay when it is energised.the injector neg is switched from the ecu . if you didnt get 12v at the plug but finger traced it back to the injectors and the plug etc is good then you should get 12v across one pin to the battery neg . if you get this 12v then the neg to the plug must surely be broken.

[Rob_the_Sparky 9]

AFAIK it uses 12V to close it but TBH this is more of an assumption. However, the bodge should work. A simple switched 12V should close the SAD.

 

As you have found the engine heat soak will not close the SAD.

 

I would agree with Pugnut's comment, it is likely that the neg connection is bust as I doubt the engine would run too well if the 12V feed to the injectors was bust...

 

Rob

[pug_ham 244 3 Cars]

Thats odd then, all the wires belled out fine but I wasn't getting 12v in anyway at the SAD plug. I didn't check the voltage across the injectors though.

 

I was looking at my old Jetronic loom to trace the wries route but even looking at the Haynes diagrams it shows that the feed to the SAD runs on from the injector wires which comes from the tachy relay. (wire #18). Maybe the wire to the SAD has broken down & gone high resistance for some reason & all that power thats getting through is 0.4v which I measured across the plug & directly to battery earth iirc.

 

I'll measure the voltage at t0he injectors on mine & see if the motronic gives 12v at the injectors & SAD plug later.

 

Graham.

[Rob_the_Sparky 9]

Continuity check is a good indicator but it is always better to use a resistance measurement. However, in this case I would have expected a continuity check to be enough. It is only really an issue where the current draw is significant.

 

What I don't get is why your bodge failed, I ponder whether you have a cracked wire. These can check out fine until you bend them a particular way, then they go open circuit.

 

Rob

[fidod 0]

Hi, Everyone...

 

The car in question here is mine... :-(

 

After Graham (and thank you for all your efforts, by the way) wired the SAD directly to the battery terminals as a temporary fix... it all appeared to be OK... and when we tested that configuration it was fine. Even taking it out for a run or two.

 

But like Graham said... a short time I left for home, the car was idling at 2000rpm. I checked the connections on the battery and they were rock solid - and although we had fused the circuit (so that I could disconnect it when the engine was not running), the fuse was OK.

 

On my trip home the car remained the same - EXCEPT when I sat in a slow queue from the M62 to M1 on the slip road. During that time the engine increased in temperature, as you would have expected... and as I sat there the idle speed dropped progressively down to about 1100 rpm (before I joined the M1 and started moving again). Once I'd been running 2 mins... I dipped the clutch and we were back up to 2,000 rpm.

 

So it appeared that the SAD would close based on engine temperature without a current... but it has to be "stop start traffic" heat... not just regular engine bay temperatures.

 

I have not had chance to remove the SAD since I returned home to see if it closes under a 12v supply still... as it seemed as if it was fried when it didn't work... but if it uses 12v normally, that shouldn't be the case. Maybe there a was a dodgy connection in the circuit somewhere...?

 

SO...

 

I am wondering what to try next - although I am not an expert so "be gentle"... ;-)

 

A new engine wiring loom occurred... but struck me as overkill... if it was just down to the wiring from the injectors to the SAD.

 

Should I get an auto-electrician to check and rectify that area of the wiring, do you think... as the car seems to run OK... except for the SAD thing...?

 

To be honest... it is heartbreaking not to have nailed this one... as I hate sitting in traffic sounding like a boy-racer revving my engine. And I have a nice new Magnex manifold and system to fit... but can't do that until the idle speed is something sensible...

 

Thank you for all your help with this so far... :-)

[jack biscuit 0]

I want to say first of all i hope you crack this nut as soon as possible, but i have to say ('cos i've had a drink) that is it not the case that our pug's along with many if not all french motors of recent times, have the worst electrical systems out there. TBH as much as i love my car, the electrics are a shower of shizzle, amazing corrosion that has the ability to be a perfect electrical insulator and be bullet hard too.. i like to think i have an open mind but i've work on many cars and it's interesting to see where the money is spent on each.. and isn't it bloody obvious that this car was designed and built just as peugeot was gonna go to the wall! We love the 205, and rightly so.. but if we all sat down, engaged our brian's we could take this flawed beauty and resurect are reliable update. That doesn't leak.

or lock you out.

 

with guages that always work..

 

(sits down and considers creating a whole new loom.. hic)

[Pugnut 9 1 Cars]

and its definately you're SAD? try blocking the pipe to the sad completely , obviously it wont tickover well when cold but once hot you should have a perfect idle (as perfect as it gets on a 205!!).

 

if its still no good then i'de be looking firstly at the cleanliness of the throttle body and the air bleed screw but i assume Graham has done all that allready.

 

Al

[pug_ham 244 3 Cars]

and its definately you're SAD? try blocking the pipe to the sad completely , obviously it wont tickover well when cold but once hot you should have a perfect idle (as perfect as it gets on a 205!!).

 

if its still no good then i'de be looking firstly at the cleanliness of the throttle body and the air bleed screw but i assume Graham has done all that allready.

 

Al

I asked the same thing before seeing the car & it is definately the SAD that is causing this.

Squeezing the SAD hose shut lowers the idle back to a nice even 1k & to check if the SAD was closing at all I made a short hose to run from the SAD to inlet hose so we could get access to the SAD in seconds after switching the engine off. With it all wired in to the current loom & plug we went for a godo 20 minute drive & the idle was high when we got back so we switched the engine off & I quickly removed the hose to look at the SAD aperture. If anything it was now wider open than when we had started.

 

All the intake system was wiped through on Tuesday, none of it was particularly dirty anyway but whilst it was apart figured I might as well.

 

A new loom is excessive (unless you swap to motronic ) but I can check the wiring through again sometime rather than taking it to an Auto electrician.

 

Graham.

[Rob_the_Sparky 9]

Well the wiring in question is only two wires so to replace them completely is possible but you'd have to source a suitable connector or tack in the old one.

 

It does sound like the SAD as stationary traffic will result in heat soak in the engine bay that could help it close.

 

A session with a multimeter really should be able to sort this out though. If a direct connection from the battery won't shut it then the SAD is dead, new or not...although this does sound very unlikely. Shame you guys aren't exactly local...

 

The SAD electrical connection is simply a heater coil, no more complex than a light bulb, so if you feed 12V to it without a high in-line resistance it will close if it works.

 

Rob

 

P.S. I have come across cars with terrible corrosion in the electrics but most of them the electrics are actually quite good (apart from the starter).

[pug_ham 244 3 Cars]

Yeah, now we know that it is the SAD alone that is causing the problem then fixing it shouldn't be that hard & a plug is no problem to find, new or from a breakers yard.

 

I think I've linked Noel up with Super Josh's MP3.1 loom now anyway but we can see if he want to still go that route if this can be fixed easily.

 

Graham.

[Rob_the_Sparky 9]

Graham,

 

Do you know any one who can supply Pug original connectors? That would be quite handy...

 

Rob

[pug_ham 244 3 Cars]

Do you know any one who can supply Pug original connectors? That would be quite handy...

Rob, You can get the same ones or ones with better clips etc from www.vehiclewiringproducts.co.uk

 

 

 

Or there is also www.simtekuk.co.uk who offer a 5% discount to members of this forum as well iirc.

 

Graham.

[fidod 0]

I am hoping to get hold of Super Josh's Motronic setup... as Pugtorque has indicated that this will result in a better end result than fixing the current system... and that sounds like a good thing...

 

If that happens, then I'll have a nice reconditioned AFM available if anyone wants it... only been on the car for about 600 miles... (if that)...

 

Fingers crossed on getting the Motronic... ;-)