Purge valve

[dlewis]

Just tried my new fault code reader and have a code 88!

This is either self test or purge valve presumably open.

The carbon canister and valve are assumed to be in the driver side wing having traced the breather from o/s wing to n/s chassis.

Can someone clarify where the pipe connection to the plenum is?

This is a 450 with cats.

I shall block the pipe temporarily and retest.

There does not appear to be any other lower priority fault codes.

Any other comments?

[spend]

The pipe is the one that goes from the plenum to the inside wing near the brake res.

Clamping it will cure 'air leak' symptoms if the pipework near the CC/valve has a fault, but nothing to with ECU. The ECU is seeing that the solenoid of the purge valve is non-operational - which gives the fault. You need to get inside the undertray and check the wiring. The positive to the purge valve comes from the fuel relay and the ecu grounds the other connection to open the valve. That is enough info for you to test the wiring & the valve itself

Dave

[Pupp]

spend said:

The pipe is the one that goes from the plenum to the inside wing near the brake res.

Clamping it will cure 'air leak' symptoms if the pipework near the CC/valve has a fault, but nothing to with ECU. The ECU is seeing that the solenoid of the purge valve is non-operational - which gives the fault. You need to get inside the undertray and check the wiring. The positive to the purge valve comes from the fuel relay and the ecu grounds the other connection to open the valve. That is enough info for you to test the wiring & the valve itself

Dave

Dave do you know when the ECU opens the valve? ie what conditions have to be met... need to try and get the Emerald set up to emulate if poss

[Pupp]

I have had the same 'fault' show once or twice after some pretty spirited use... always seemed to clear itself and I just wondered if it was the valve sticking due to lower than atmoshpheric pressure in the tank at that point

[spend]

This has been asked recently by one of you emerald fitters? Its something like warmed up, 3/4 throttle @3500rpm... MA did say once what the common settings were, they varied a bit depending on the mapping IIRC. Really bugs me that the search engine only goes back 2 years...

Dave

[Pupp]

spend said:

This has been asked recently by one of you emerald fitters? Its something like warmed up, 3/4 throttle @3500rpm... MA did say once what the common settings were, they varied a bit depending on the mapping IIRC. Really bugs me that the search engine only goes back 2 years...

Dave

I thought it had too but couldn't see it... maybe we need an FAQ bit for the aftermarket ECU brigade?

[thenick]

Thats a good plan actually... When we've got them all in and going maybe we should pool ideas on how to best go about the task and stick in on the chimaerapages or something? The next one i'm thinking is a supercharger group buy... After the dust settles from this one though of course!

[Uncle Fester]

As we can read our maps on our laptops, presumably we can print them.

Why not create an on-line library of maps?

That way people could see what was being done.

[spend]

I think thats fair enough as long as you have created the map yourself, and others are aware that it is customized to your particular engine etc. People may be using different sensors, coil packs... not forgetting that cams, induction are not standard on most TVR's. It can be a recipe for disaster if folks just think they can copy someone elses map??? There is a great difference between looking at another installation for inspiration and simply 'cribbing' anothers work (which I sadly believe is far too common).

I also have misgivings with publication of any data which I consider somebody else's intellectual property, some of these people may rely on that info to keep paying the bills! In principle I agree whole heartedly with your suggestion, unfortunately there is quite a gap in these things being completely 'open' systems..

Maybe I am being too pessimistic, but it does concern me that a lot of folks are going off half cocked.. I mean look at this thread ~ having opted for a product and part way thru installing it questions arise about how to work the purge valve? Surely these things should have been considered when evaluating which ECU to buy, but no I fear its a case of 'so&so's made it work' so it should be OK..

[/grumpyramble]
Dave

[thenick]

I do agree with you, we would have to be careful about who's maps were uploaded but as has been seen before, Emerald only have a very limited supply of base maps for RV8's. For the 4.5 engine, the only one available is for a fairly wildly tuned engine which can pose problems when getting it to run ok enough to get it to the RR shop so something a little more standard would be nice.

I though I think the maps are less important as most people will opt for having it professionally set up unless they already know what they're doing in which case they're likely to not need one other than a bog standard base map to go off. What would be more useful is small tips and things to consider such as what to do with the purge valve! I for example had no idea what it was let alone how it was controlled before asking on here! It would have been nice to have considered it first but I did a lot of research before buying the ECU and I still had never heard of its use until I found the wiring myself.

Edited by thenick on Sunday 6th January 16:46

[Pupp]

spend said:

Maybe I am being too pessimistic, but it does concern me that a lot of folks are going off half cocked.. I mean look at this thread ~ having opted for a product and part way thru installing it questions arise about how to work the purge valve? Surely these things should have been considered when evaluating which ECU to buy, but no I fear its a case of 'so&so's made it work' so it should be OK..

Dave

Not pessimistic but a bit harsh and verging on being rather dismissive of people's efforts IMO. Maybe you would have had the time, inclination and knowledge all on tap together to have ruthlessly researched all possible permutations and eliminated all save the very optimum product. Others are a bit more constrained by their circumstances perhaps, and the Emerald is a great product made available to us through the efforts of someone who worked bloody hard to pull it together at a great price. Given the idiosyncracies of the car the thing is being applied to, and the variances in OEM equipment over the years do you really think a fit all plug and play solution was ever going to be found in a group buy scenario?

Sure the purge valve issue is one to think about for those affected but it's far from a show-stopper and I certainly don't think it's a sign of anything going off half-cocked, more an indicator of knowledge being gained (and hopefully shared if folk don't get too precious about it). I for one will happily share any knowledge I come about, including map settings, in the interest of assisting someone enjoy their Tiv at its potential best. Problem?

Edited to add

Edited by Pupp on Sunday 6th January 18:53

[IainG]

I had code 88 appeared when I first connected my fault code reader. It disappeared after driving the car. I assumed that the code appeared because the purge valve does not operate when the car is stationary. I thought I was going to have to find the carbon canister in the wing and was delighted to leave it in peace.

[Cider Andy]

dlewis said:

Just tried my new fault code reader and have a code 88!

I think the '88' code relating to the purge valve is a red herring. I think '88' is a display test for the fault code reader to show that each of the seven segments in each digit in the display is working. I think '89' is a purge valve problem. I think your car's ok!

[rev-erend]

Perhaps it's time we had a dedicated forum on PH for Engine Management Systems - with a FAQ wiki..

What do you think..

I often trawl all the forums for EMS 'knowledge'..

I started from zero knowledge, read Dave Walkers book, read every ems website and no mention of this purge valve is mentioned anywhere ..

But the std ecu does this function..

We need a wiki.

[spend]

Theoretically you can use one of the aux outputs to ground the purge valve, different ecus have different capabilities for this (product selection issue). All cars (of every make) since early 90's have Carbon Cannisters & purge valves fitted, it is not a TVR special! If you don't purge the cannister, you will run the risk of it becoming saturated (blocked) much faster than its normal duty cycle, and needing replacement. Some ecu installers just rip it out & stick a filter on the pipe. This impacts on you if you want to put the car back to std in the future. I'm not sure if it will leave smelly vapours in the undertray (air vents in to the car through this area) which also concerns me as liquid fuel is safe but fuel vapour is quite dangerous - but I am more yellow than green? If, like Rev, you attempt to research how DIY alt-ecu installers have attempted to replicate std ecus purge valve control it will only confirm my concerns about 'cribbing' past experiences. I'm sorry if you consider that as dismissive, but it is actually just trying to move things forward. The power of the internet can be a negative influence in some ways, we should be very careful to avoid poor 'common practises' where possible IMHO.

Dave

[rev-erend]

I like the way Nick has approached this ..

When you get an Emerald (and probaly others..) they tell you what their ECU needs..

But Nick has also approached it from the other angle..

What does my existing ECU do .. and then matched that to the new ECU..

Hence all his very sensible list of questions..

[dlewis]

OK back to the OP.

Dave

Pleased to report that I have continuity from pin 87 of fuel pump relay to valve and continuity from pin 17 of ECU to valve.

Have not yet found a way of testing valve since it is so awkward to access and it's valve connector block is small. I could either take out the canister which looks a pain or put a 12 supply on to the valve using the male connector block. Any comment?

Could you also clarify when the ECU triggers the valve? I did a test at the valve connector with ignition on (not running engine) and there was no feed.

Thanks in anticipation.
Dave

[spend]

If you've got the connector off the valve and checked continuity to the relay, check connectivity of the other one back to the ecu (ecu grounds the valve to operate).

You should be able to hear the valve click by sticking 12v across it, but its not very loud! I replaced mine with a different version so had to this to work out how to wire it up before I installed it, didn't seem to do any harm.

There have been 2 versions fitted BTW. The early ones have a separate valve from the cannister which is reasonably easy to remove (make sure you note the pipe connections for re-assembly ((in either case!))), the later ones have the valve clipped to the cannister which doesn't like being separated.

Dave

[dlewis]

Yes, I have continuity in both wires grey earth to pin 17 and purple feed from relay pin 87, to my relief.

I have the later version canister and did wonder if the valve could be removed insitu.

Putting 12V on is then my next move, I did wonder how loud its functioning would be.This may save a tricky canisterectomy.

I have also taken the car for a spin and checked code reader to see if it clears.

Does the ECU purge during starting or when, as I have not seen a trigger yet during test with ignition on?

Edited by dlewis on Wednesday 9th January 00:49

[spend]

dlewis said:

Does the ECU purge during starting or when, as I have not seen a trigger yet during test with ignition on?

Answered in 5th post of this thread, best of what I remember MA saying, but sure it was a combination of up to temp, reasonable revs & Throttle open wide(ish). I'll stick a test led on the LR one day out of interest, but it isn't high on my priorities

If you can scab a look under the bonnet of a Disco, its nice & handy for you to study, right on the wing

Dave