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PostPosted: Thu Jun 28, 2018 10:37 am 
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Just had a phone call from someone at DVSA (took his name but won't mention it here)...

He asked my advice because many owners of LPG converted vehicles have contested MOT failure (due to MIL light being on and since the stricter MOT rules were introduced) because they believe it is normal for LPG converted vehicles for the MIL light to be on. He said he/DVSA had been searching the internet for info on whether this was correct but couldn't find much info, then found my website and it seemed I would be able to answer his question(s).

I told him that the MIL light should not be on on an LPG converted vehicle.
I also told him I was probably shooting myself in the foot telling him the truth, because if DVSA believed it was normal for the MIL to be on it could be a further advantage for owners of LPG converted vehicles at MOT time!

Simon

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PostPosted: Thu Jun 28, 2018 1:59 pm 
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It doesn't exactly fill me with confidence that the dvsa are searching the internet for info they are supposed to be expert in !


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PostPosted: Thu Jun 28, 2018 3:54 pm 
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Not necessarily. If they are finding lots of people querying a fail because the MIL is on and it has always been on since the car was converted, then they are actually doing the right thing by checking. They could simply say that the rules say a lit MIL is a fail so tough but they aren't, they are checking to see if they can allow a bit of leniency.

Not sure exactly what you told them Simon but I would have said that strictly speaking it shouldn't be on but there are a number of cars that can be very finicky and will bring the MIL on for the slightest reason. That way they can advise testers that if the MIL is on, the car is running on LPG and the emissions and everything else seems OK, then they can treat the MIL as a Minor rather than a Major (what used to be an advisory and fail).

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PostPosted: Thu Jun 28, 2018 9:38 pm 
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@4eyes, same thought occurred to me but not sure if they have any experts on LPG converted vehicles.
@Gilbertd, we only briefly touched on aspects such as mixer systems on fuel injected vehicles could bring on the MIL even though mixture etc is fine on LPG. I think the problem from his point of view with this is that MOT testers would need a list of X vehicles fitted with Y LPG system. Similar goes for 'finicky' really and tbh even on finicky vehicles the MIL shouldn't be on if the system is appropriate, installed, setup and calibrated properly. When the MIL is on it might still pass an emissions test if the mixture is lean rather than rich but this gives no pointers as to whether mixture will go too rich under e.g. medium/moderate load. I was put on the spot and gave an honest answer that if had any bias at all favoured LPG vehicles at MOT time.. Managed to keep a bit of wit on the spot but in hindsight was still maybe a bit too honest. In mind at the time were the number of LPG converted vehicles I see with the MIL on precisely because someone had made a bodge of the conversion with emissions that really are well out and tbh on 99.5% of converted vehicles I see with the MIL on either this is the case (usual) or case is that the MIL didn't used to come on but now comes on because a component is worn/broken. We didn't go much further into it than that the early points above but other aspects he would have had issue with are that on some vehicles MIL illumination can also invoke loss of none emissions related functions e.g. on Ford engine'd Jags the red-line becomes 3000rpm, on some vehicles it can lead to the loss of traction control, such aspects would mean more lists.

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PostPosted: Thu Jun 28, 2018 9:55 pm 
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Surely the MOT is about safety critical issues and not minor running issues if emmisions are within limits, everything being acceptable.
Without any form of criticism of Simon whos knowledge and methods of explaining things are nothing short of brilliant, you put many installers to shame, many rightly so. But there are many very good installers and DIY guys like myself who sometimes find minor running issues a way of life and learning, the MIL often displaying itself despite great efforts in sorting things out.
Please dont throw a spanner in the works, let testers use that old fashioned thing called common sense.


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PostPosted: Thu Jun 28, 2018 10:18 pm 
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@redvanman, thanks for the thumbs up. I know I'd probably get more repairs customers if MOT man failed more LPG vehicles but I can at least say I had the industry at forefront of mind during discussion, without an LPG conversion industry I'd be left twiddling thumbs anyway but even if I was no longer involved I wouldn't want to spoil things for other LPG users. Absolutely no intention of throwing a spanner in the works, the thing is that MIL illumination is a fail on petrol and it would be difficult to present a case for things to be different for vehicles running on LPG, and if I'm totally honest especially since I have already learned to sort running issues. The only real get-out would be along the lines of what Gilbert said and only if we factor in the usual emissions benefits that running on LPG generally brings.

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PostPosted: Thu Jun 28, 2018 10:23 pm 
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Unfortunately they can't use common sense. The testers manual gives lists of faults and they are graded as Minor (what was an advisory), Major (a fail) and Dangerous (you ain't driving that home mate). It would be fairly simple to issue an amendment that says that as it is known that certain vehicles light the MIL when running on LPG, if a vehicle is presented running on LPG and the emissions are within limits, then the MIL being lit becomes a Minor rather than a Major. Otherwise it is going to add to the old wives tales about LPG being a waste of time so it won't only be smokey diesels that are failing but a huge proportion of LPG covered vehicles too. I know that the MIL shouldn't be on but an awful lot of people have been convinced it is normal and live with it.

Having just done a lighting conversion on a Ford Excursion imported from the States, I've read the manual from cover to cover over the last few days to make sure I've covered everything that it could have failed on.

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PostPosted: Fri Jun 29, 2018 12:00 am 
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Applying Gilbert's points to what you've said @redvanman, MIL light illumination means the emissions system has noted a fault which could at least potentially effect emissions, emissions is another aspect (besides safety) that vehicles are tested on, this is in the light of DVSA having intention of clamping down on emissions related aspects hence the changes to emissions tests in the recent MOT update. I've also mentioned how MIL-on can on some vehicles effect aspects of drive-ability that could have repercussions on safety besides emissions aspects (not mentioned to DVSA but this would surely come up in a lengthy discussion with DVSA).
I don't think I could have done much better for LPG converted vehicle owners without resorting to multiple blatant lies. You don't even need to know much about vehicles to follow a line of basic reasoning - Q1 might be 'What conditions does illumination of the MIL imply, Q2 might then be 'why can't running on LPG avoid breaking such conditions'. If I'd tried it on and told a few porkies to such early lines of reasoning from someone reasonably clued up they could have taken a harsher view of LPG conversions which could have then made for stricter MOT conditions for LPG vehicles. Q3 might be 'why should it be accepted that an LPG conversion will not be able to match a vehicle's on board emissions systems expectations'. If I had to answer Q3 I'd be thinking I'd dropped a bolx, especially in the light of having sorted maybe 50 vehicles this year that came in with the MIL light on due to LPG problems which I then sorted and now the MIL doesn't come on with their being very few vehicles I wouldn't be confident of being able to do the same with. Tell one porky and you've got to keep telling more porkies until you're in a world of porkies and easy to see through. The bloke wasn't that clues up but he seemed clever, was on the case and had the ability to reason, I didn't get the impression he'd easily have fallen for any bs.

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PostPosted: Fri Jun 29, 2018 12:30 am 
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LPG is not the fuel the engine was designed to fuel, mine feels better at lower revs with a small drop of power and torque at higher revs so accept that a differing fuel is a compromise. In my eyes is the ECU not playing ball in accepting a new set of parameters, in not being those its original program could accept and triggering the MIL. Compromise being the word again.


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PostPosted: Fri Jun 29, 2018 3:54 pm 
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redvanman wrote:
LPG is not the fuel the engine was designed to fuel, mine feels better at lower revs with a small drop of power and torque at higher revs so accept that a differing fuel is a compromise. In my eyes is the ECU not playing ball in accepting a new set of parameters, in not being those its original program could accept and triggering the MIL. Compromise being the word again.

Your petrol ECU has no way of knowing how much torque/bhp your engine is making, it takes a few inputs such as amount of incoming air and looks up (from it's database table) how long to pulse petrol injectors for, it then checks exhaust gases to make sure fuelling was right and can compensate for moderately incorrect fuelling by adding it's own fiddle factors by means of the fuel trims it learns. The only thing the LPG system has to do is ensure that whatever mass of petrol would be injected per injection pulse (if the engine were running on petrol instead of LPG) is multiplied by 0.955 (this is 14.7 / 15.4 which are the stochiometric ratios of petrol / LPG) and this result/mass of LPG enters the engine (at the same time, in the same place and squirting in the same direction as the petrol from the petrol injector would have) instead of the petrol. As long as those conditions are met the petrol ECU won't see any difference between running on petrol and running on LPG.
Obviously the LPG ECU cannot directly measure weight of petrol (impossible anyway since petrol isn't even used when running on LPG) and it cannot directly meter mass of LPG it supplies to the engine... Instead it just monitors length of petrol injection pulses, applies fiddle factors (including the LPG map entered by the installer) which compensate for the different response of the LPG injectors fed with vapour compared to response of petrol injectors fed with liquid and pulse the LPG injector for the time it has calculated. The devil is in the detail and any of the above points plus many others can mean a mass different to 0.955 enters the engine, or at the wrong time, or in the wrong place, or in the wrong direction. If any of those points are far enough wrong under some working condition that working condition is likely when the MIL will be triggered, simple as that. The problem for most is the 'devil in the detail' bit if they don't thoroughly understand the theory / concepts, if they don't know particular aspects of a certain vehicle's petrol system, or the difference between that and how an LPG system is supposed (or can be forced) to work, if they buy into hype and supposed specs of components when real world spec can be very different (and not just talking injectors and reducers but also ECUs).

Like you, I'd hope for a lot of compromise from DVSA but we'd want the compromise to be long term... we wouldn't want them to realise they are compromising on emissions and then at some point decide they didn't want to compromise any longer. DVSA know that if the MIL is on it's likely on because as far as the petrol ECU is concerned there is a potential problem with emissions. DVSA also know that if there are no problems with mixture a vehicle running on LPG is much cleaner than one running on petrol, this is the main reason why duty is lower on LPG after all. From there it isn't clear if it would be better for LPG users if DVSA believe a lot of converted vehicles have the MIL light on but it's an accepted condition that can't always be avoided / Or if it would be better that DVSA believe there's no reason for the MIL to be on for an LPG converted vehicle because the tech allows the vehicle's original petrol fuelling strategy to be followed very closely, the petrol ECU sees no potential problems with emissions because there are no problems. The former could end up being more of a negative for LPG users in the long term than the latter.

What's your van, LPG components and does your MIL come on?

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Last edited by LPGC on Sat Jun 30, 2018 9:20 pm, edited 1 time in total.

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PostPosted: Fri Jun 29, 2018 6:50 pm 
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Simon as is usual brilliantly and enlighteningly put into words.
My trusty old van is Astra mk 4 formerly a 1.6 8v but since fitted with the C20XE redtop engine.
A factory NECAM system was originaly fitted and the rear end kit is still in place but upfront is an elderly King ecu, Magic jet vaporiser and OMVL fast injectors.
The MIL is sometimes lit and the fault is the lambda sensor getting in a monk and not switching above 0.5 volt, sometimes lasting seconds and another time until the ignition is turned off.
My wife drives a car similarly converted but with a King MP32 ecu just suffers from a constantly variable tickover speed anything between 900 to 1300 with random and short lived fault codes illuminating the MIL
Neither vehicle runs a cat but this could start a new topic!!


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PostPosted: Sat Jun 30, 2018 9:22 pm 
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Cheers Redvanman!

Like you said.... new topic?

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PostPosted: Sun Jul 01, 2018 6:16 am 
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I can't see any reason that the testers should give converted vehicles any more leeway on the MIL than non converted ones.
If the job is done right, the light should be off. If the light is on because the mixture us wrong then the engine will either be creating more pollution than necessary (and negating the reason for lpg attracting less tax than petrol) or potentially damaging itself.
Apart from that, if the light is on all time other problems could be masked because the driver won't receive any further warning.


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PostPosted: Wed Jul 04, 2018 9:51 pm 
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I think that's a common sense way of looking at it Morat.

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PostPosted: Mon Aug 06, 2018 8:36 pm 
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I wish the new mot test could use common sense with the engine light issue. My lpg Outlander converted by someone reputable previously on here with a brc kit had the light on for 8 years. Strangely I am having to scrap my good Seat diesel tomorrow because of the engine light which has been on for 4 years and they will not pass it even though it passed emissions. I am not letting a diesel disaster break the bank. Should I appeal? :twisted:


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PostPosted: Mon Aug 06, 2018 10:11 pm 
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I suppose it depends why the light is on. Have you read the codes and do they tell you what it is offended about? Either that or wire it in parallel with the charge warning light.....

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PostPosted: Mon Aug 06, 2018 10:12 pm 
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Not saying that I condone or agree in any way but a google search for MIL cheater brings some enlightenment and greedbay sells some ready made items.....fair, right, common sense or down right wrong or maybe they dont work, I have no knowledge of these but have used EGR cheaters/deletes and found they worked well.


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PostPosted: Mon Aug 06, 2018 11:32 pm 
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billynoband wrote:
My lpg Outlander converted by someone reputable previously on here with a brc kit had the light on for 8 years

GDI direct injection model converted using LPG mixer components(?)... Or MIL light shouldn't have been on and I could have set it up properly so it wouldn't be on. Can't remember who was reputable on here who fitted BRC...

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PostPosted: Tue Aug 07, 2018 4:56 pm 
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It was the 4g69 engine in my lpg car which was just a normal injection system. Ran well. I dont feel so bad scrapping the diesel now as the brake servo failed on the way to the scrapyard. I have found a 2008 2.0l ford s-max lpg converted, on the register too. I might return to the fight.


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PostPosted: Tue Aug 07, 2018 7:36 pm 
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Engine light shouldn't have been on on that engine, might guess at what problems might have caused it to be on... Points like unusual low emulation resistance could be necessary so might have needed an AEB124, or if the 4 cyl engine is managed for closed loop purposes as 2 cylinder banks some BRC 4 cylinder ECU's of the day couldn't handle that so you'd get one bank causing fuel trim errors. Come back from the dark side anyway! :-)

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