Lambda issue on LPG ?

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haynes_tm · #1 Post by **haynes_tm** » Thu Aug 03, 2006 11:59 am

I've just had my 2001 Volvo v70 converted to lpg (OMVL dream piro). The installer tells me (and showed on the laptop) that the lambda probe (pre cat) is constantly reading 1V (ie too rich?) and as such he cannot setup the mappings until a new one is installed and it is currently running with the default mappings. Now I've only had the car just over a month, and in that time I haven't observed any issues with it running on petrol and having just driven back from the installers on LPG (about 20 miles) the car felt absolutely fine - in fact slightly better/smoother than on petrol and no fault lights came on at all. Could this be a faulty lambda probe, or is it possible that something else is causing the issue? He plugged a voltmeter into the connector and showed it reading something like 3.8v - but I'd have assumed that if the lambda probe was always giving the wrong reading it would have driven very badly and a fault light would have shown ? If I do need a new lambda probe, where is best to get one from and how much roughly for one ?

richy_boy · #2 Post by **richy_boy** » Thu Aug 03, 2006 1:39 pm

Hi Tim; I can't help with the LPG side of things, but many car will run fine with the lambda probe disconnected due to their good mapping. The lambda probe is only really used to 'fine tune' on the move and comes into play most when on a long steady run. With Nissan 200s if the lambda starts playing up it's often better to unplug the thing to improve economy and drivability. You can get the probes from all over the place, but it might be best to head to Euro Car Parts seeing you have a Volvo. (Unless of course anyone knows they supply poor quality units) Rich Rich

desauld · #3 Post by **desauld** » Thu Aug 03, 2006 1:39 pm

Some new cars have a wideband lambda probe(EG vw audi turbo units.). Not sure about yours. But they are 0-10 volt output not 0-1 volt. Not sure how the gas ecu would handel that?

haynes_tm · #4 Post by **haynes_tm** » Thu Aug 03, 2006 1:54 pm

Thanks guys. I've posted on a volvo forum and it was suggested it is a wideband lambda probe, which may be why the voltage is higher. Personally I dont believe the probe is at fault, as the car drove on petrol fine and appears fine on the gas also. I called volvo for a lambda price (£180 + vat!!!), but they did say it was unlikely to be faulty as it would have produced an error code - which obviously it hasnt. Eurocarparts and gsf dont stock the lambda probes for the phase 2 v70's - so this also suggests they are a different part.

classicswede · #5 Post by **classicswede** » Thu Aug 03, 2006 6:46 pm

The Volvo V70's are on a 0-5 volt probe. I would first disconnect the LPG lambda wire from the lambda and measure the voltage. Why did your installer let you have the car back with this problem? VW and Audi use resistive probe that has five wires volvo do not use this probe.

murdo · #6 Post by **murdo** » Fri Aug 04, 2006 12:26 am

Some volvos do have resistive lambda sensors. Your installer should look at the live data on a scan tool.It will look like a normal lambda sensor on there,If your emissions were reading ok and your engine fault light stayed off it should be ok.

haynes_tm · #7 Post by **haynes_tm** » Fri Aug 04, 2006 12:55 pm

I'm taking the car back on Saturday to resolve (had to have use of the car even if on petrol so couldn't leave it with him any longer). I will pass on the advice from here as it appears this is the first of this type of car the installer has dealt with and the lambda probe isn't a standard 0-1V as he had configured it. Searching the web suggests it is a UEGO Bosch type? (0-5v) - which I believe there is a setting for in the laptop config. The car is driving fine on gas (not sure about fuel consumption yet) and still no warning lights - so fundamentally everything seems ok. Thanks for everyones input on the issue.

classicswede · #8 Post by **classicswede** » Fri Aug 04, 2006 7:52 pm

You are very lucky that you installer let you have the car back before completing the install - we do not let a car go out untill the conversion is completed and all running well. We have learnt from mistakes of alowing cars to go out and come back when things ahave not been finished. Customers do not seem to apeciate the installers efforts quite often. The easy way to tell if the probe is the UEGO Bosch as they are a 5 wire probe, not a 4 wire. As this conversion has been done by a Piro installer then I'm sure they will be able to resolve the problem as all piro installer receive comprehensive training. Best of luck and I wish you many happy miles of LPG motoring.

haynes_tm · #9 Post by **haynes_tm** » Fri Aug 04, 2006 11:44 pm

C S Autogas - It is only a 4 wire probe so is that still 0-5v or 5-0V(inverted) or 0-1V ? I'm going back tomorrow morning to hopefully resolve this issue and a few other rather annoying things - like broken plastic clips on the fuse box and air filter where they removed them, broken trim in the rear etc (mind you not sure how these can be fixed apart from new plastic parts). One other concern I have is that the gas pipe and wires have been run into the engine bay via the front left wheel arch. I have noticed that I am now getting a rubbing noise when on full right lock and having taken a look this evening it appears the gas pipe has been run behind the liner causing it to stick out further than it otherwise should causing the tyre to make contact. This does concern me as the pipe will be having the tyre stressing it at least once a day as the entrance to my drive is a very tight right hander. Although not actually touching any suspension parts it also runs fairly close to the suspension strut - is this an acceptable install route ? Hopefully the installer can iron out these issues tomorrow.

volvo940 · #10 Post by **volvo940** » Sat Aug 05, 2006 12:25 am

I, and I'm sure others, would like to know if the installer is LPGA registered

classicswede · #11 Post by **classicswede** » Sat Aug 05, 2006 4:42 pm

It is as a first though a 0-5 volt probe. I would not like to comment on the way a pipe has been run without seeing it.

simon_egas_uk · #12 Post by **simon_egas_uk** » Mon Aug 07, 2006 10:59 pm

Hi Tim Just a question that no-one has asked yet. What colours are the four wires comming from the front Oxygen sensor? This may give away your problem a little easier or not as the case may be ! Simon

haynes_tm · #13 Post by **haynes_tm** » Mon Aug 07, 2006 11:54 pm

I took some photos this evening to try and read a part number off the sensor - but unable to. I think the 4th wire you can see in the attached image is black.<img src="http://www.my90.co.uk/lpgforum/messages/898/3358.jpg" alt="lambda pic">

haynes_tm · #14 Post by **haynes_tm** » Tue Aug 08, 2006 12:19 am

I forgot to add that the tyre rubbing has now been resolved by re-routing the pipe slightly and I'm much happier with that aspect now. The only outstanding issue is resolving the lambda reading (or not as the case may be) - which will be done at the 1000 mile checkup. The car is driving perfectly on gas (better than petrol) no fault lights, so I'm happy. First fill up showed I managed 23mpg - a bit lower than I had hoped, but I imagine this is partly due to my spirited driving to try the car out on gas and that it is only running with the default map at the moment. In answer to an earlier question - the installer is not an lpga member, but offered the right kit at a good price and provided references (including FES the kit distributor) and so far (bar a few niggles like some broken trim) I couldn't really have asked for a better level of service.

lpg_auto_conversions · Fri Aug 11, 2006 8:23 pm

Hi to every one who has an interest The lambda probe on this vehicle is a standard 0-1 volt The probe has failed and is giving a near constant reading of 3.8 volts (checked with the lpg system disconected) The lpg system fitted to this vehicle is the latest Piro as it is a fully slave system it does not rely on the lambda signal to operate (as many cheaper systems do) it uses pulses from the petrol injectors to fire the lpg injectors and is therefore controlled by the vehicles own ecu Tim seems to have forgotten to mention that we obtained a probe and attemped to fit it but his old one is siezed in the manifold he did not have time to leave the vehicle with us nor did he want me to force it out and risk pulling the treads in the manifold As for the broken clips we advised him we would obtain new ones which would be fitted on the 1000 mile service We worked late on this vehicle trying to resolve the lamdba problem, keeping Tim waiting As a jesture of goodwill we filled the lpg tank free of charge

haynes_tm · #16 Post by **haynes_tm** » Fri Aug 11, 2006 11:08 pm

Hi Steve, I've done some digging around since we spoke last on Saturday and am almost 100% certain I dont have a standard 0-1v probe, rather a WRAF sensor (Wide Range A/F) which is a 4 wire type rather than the more typcial 5 wire ones. This will read a fixed voltage as we see (well above 1v), and the important signal relating to the a/f ratio is actually the tiny current generated by the probe which is measured by the ECU. Here are the links I've found that best descibe this 4 wire device (these are actually for Toyota's but appears to match exactly what we see): <a href="http://www.babcox.com/editorial/us/us10226.htm" target=_top>http://www.babcox.com/editorial/us/us10226.htm</a>(talks about how to test these types of sensors) <a href="http://www.aa1car.com/library/wraf.htm" target=_top>http://www.aa1car.com/library/wraf.htm</a> Also the Vadis s/w details the probe as a 'current' signalling device (which I showed you on Saturday) and ties up with our observations and those articles. With regards to the replacement 0-1v probe, I hadnt mentioned that as we never got round to trying it and therefore couldnt add anything factual to the thread. If you can have a look at those articles I'll give you a call to discuss early next week and how best to move forward, but I strongly believe my probe is operating properly based on that information. Best Regards, Tim.

gasspark · #17 Post by **gasspark** » Mon Aug 14, 2006 9:55 am

steve, of course it relies on the lambda as this is one of the oem inputs that controls the petrol pulse. if this was faulty wouldnt the MIL be illuminated? Iam inclined to agree with Tim in that this is not a 0-1v Lambda and the problem lies elswhere

lpg_auto_conversions · Mon Aug 14, 2006 1:24 pm

we all know that the vehicle needs a lambda signal to run what i said was that the piro system is directly comtrolled by the petrol injector pulses and not by the lambda its self all probes should show a flutuating voltage not a constant reading if the vehicles ecu sees this condition it will put in its own value to enable the car to run this i agree shoud put on the mil acording to several supplies of lambda sensors it should be a 0-1 volt according to the wiring inn the old one it is a 0.1 volt volvo dont know so may be the best thing is if the vehicle goes into volvo for a diagnostic check and new probe if needed

gasspark · #19 Post by **gasspark** » Mon Aug 14, 2006 4:55 pm

not all lambdas show a varying voltage!

classicswede · #20 Post by **classicswede** » Mon Aug 14, 2006 9:48 pm

Steve is spot on the piro when in slave mode does not need to see the lambda readings. As to voltages - some lambda's output is a variable voltage as where some other rarer ones use variable resistance.