High fuel consumption?

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Freebird
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Re: High fuel consumption?

#61 Post by Freebird » Tue Aug 30, 2016 4:54 pm

Brian_H wrote: Certainly sounds that way
Right then, two on order from Jag specialist SNG Barrett. £111.60 the pair which I thought was pretty good.

Glen.

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Re: High fuel consumption?

#62 Post by LPGC » Tue Aug 30, 2016 8:53 pm

Pretty sure one needs changing, very likely two needed but depending on how lean the engine is running (and size of blow torch) the blow torch might not flow enough gas to make the engine run rich. It's a fair sized engine, how long would blow torch run on the small quantity of gas (if canister type) compared to quantity of fuel/gas the engine would use idling over the same length of time and what percentage of mixture change for this size engine would that flow represent.. The engine could potentially idle with mixture lean enough to still be lean with the blowtorch on. That said, playing devil's advocate a bit because I would expect the blowtorch method to work, just that it might not be quite as conclusive a test as a method capable of getting more gas into the engine. Air enters the engine/filter somewhere, gas pipe could be held further from that entrance.. more fiddly than blow torch but lambda only has to be seen to go rich for a short time to pretty much rule out fault with that part.

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Re: High fuel consumption?

#63 Post by Freebird » Wed Aug 31, 2016 1:28 pm

Maybe, but they are on their way now so I shall replace both.

I drove the car with 123 sensor output on the dashboard again and struggled to get it to read as low as 2V second time round no matter how hard I floored the throttle, so I don't think it's responding like it should.

Thanks for everyone's help, this has been a learning exercise for me. I will let you know how I get on when the parts arrive and I find time to fit them - hopefully this weekend.

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Re: High fuel consumption?

#64 Post by LPGC » Wed Aug 31, 2016 2:26 pm

One more point on measuring lambda voltage - best to use earth reference that is same as petrol ECU earth reference, i.e. to use earth reference that ECU provides to the lambda probe. Depending on how good engine earths are (would presume good since starter motor manages to start the car but some other aspect could also effect this), engine voltage (for example) when alternator is charging can be above battery earth voltage, dunno where ECU etc gets earth but best to rule such aspects out. I have seen issues with closed loop mixer systems on Jags/Daimlers due to lambda earth reference being at different potential to LPG ECU earth reference, better to measure lambda the same way as the petrol ECU does. That said, 2v would be a hell of a difference really.

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Re: High fuel consumption?

#65 Post by Freebird » Thu Sep 01, 2016 9:57 am

LPGC wrote:One more point on measuring lambda voltage - best to use earth reference that is same as petrol ECU earth reference, i.e. to use earth reference that ECU provides to the lambda probe.
Simon
Hi Simon

I'm not sure where to look for that mate.

New probes arrived yesterday, so I will fit them Tomorrow afternoon or Saturday hopefully.

Glen

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Re: High fuel consumption?

#66 Post by LPGC » Thu Sep 01, 2016 10:33 am

Usually on a 4 wire probe there are two heater circuit wires, the lambda signal wire and the earth reference for the probe signal, it would be the latter you'd want to use as earth reference for the multimeter. The most common wiring for a 0-1v probe is 2 whites for the heater circuit, black for the signal, grey for the signal earth but that's not very helpful for you because yours is a 5-0v and has different coloured wires! Nevertheless you can rule two wires out (the 12v feed for lambda heater and the signal wire) leaving you with two earths to try.

But anyway, you'll just be fitting the new probes now so not much point at this stage.

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Re: High fuel consumption?

#67 Post by Gilbertd » Thu Sep 01, 2016 8:55 pm

Titania sensors work differently to Zirconia sensors in that they give a varying resistance rather than generating a voltage. So where a 0-1V Zirconia will have two heater wires, one with 12V and one with ground (the white wires) and a signal out (Black wire) and signal ground (Grey wire), Titania have two heater wires (Red positive and White negative), they then have a signal reference (Yellow wire) which is fed with a 5V reference signal and an output which is on the Black wire and is the reference minus the internal resistance. The output can be measured with a meter with respect to ground but with the difference in potential between battery ground, body ground and ECU ground being only a few millivolts and the range being 0-5V, any difference will be negligible.
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Re: High fuel consumption?

#68 Post by LPGC » Fri Sep 02, 2016 10:52 am

Gilbertd wrote:Titania sensors work differently to Zirconia sensors in that they give a varying resistance rather than generating a voltage. So where a 0-1V Zirconia will have two heater wires, one with 12V and one with ground (the white wires) and a signal out (Black wire) and signal ground (Grey wire), Titania have two heater wires (Red positive and White negative), they then have a signal reference (Yellow wire) which is fed with a 5V reference signal and an output which is on the Black wire and is the reference minus the internal resistance. The output can be measured with a meter with respect to ground but with the difference in potential between battery ground, body ground and ECU ground being only a few millivolts and the range being 0-5V, any difference will be negligible.
Ahh! Thanks Gilbert. That makes sense, wouldn't expect what is effectively a cell to produce near 5v, should have remembered they worked differently.

So I wonder if the 4.7V Glen read was actually the 5v reference... because I don't remember Glen saying he'd seen near 5v on more than one wire (on the same probe). This could also mean probes not reflecting lean mixture... and you and I have noticed these probes often read 5v lean mixture when they fail..

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Re: High fuel consumption?

#69 Post by Freebird » Fri Sep 02, 2016 12:52 pm

Gilbertd wrote: they then have a signal reference (Yellow wire) which is fed with a 5V reference signal
The plot thickens then.

I'm sure I was getting battery voltage to both the red heater wire and the yellow ref (in) wire. I now need to double check. If this is the case, why might it be?

I have definitely been seeing the 4.7V on the black ref (out) wires though. I pierced them with my multimeter probe.

Glen.

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Re: High fuel consumption?

#70 Post by LPGC » Fri Sep 02, 2016 3:23 pm

Freebird wrote:
Gilbertd wrote: they then have a signal reference (Yellow wire) which is fed with a 5V reference signal
The plot thickens then.

I'm sure I was getting battery voltage to both the red heater wire and the yellow ref (in) wire. I now need to double check. If this is the case, why might it be?

I have definitely been seeing the 4.7V on the black ref (out) wires though. I pierced them with my multimeter probe.

Glen.
If other points are correct (and they will be) then could guess that either the yellow reference wire was supposed to be 12v / or 5v reference voltage regulator has failed, sending 12v ref instead of 5v / or under certain conditions the reference voltage is supposed to be 12v instead of 5v (nah!) / or you've seen 12v on 2 wires because one of those wires was supposed to be the earth but isn't connected to earth (so 12v seen on that wire via probe heater). Gilbert?

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Re: High fuel consumption?

#71 Post by Freebird » Fri Sep 02, 2016 5:05 pm

Mmm, well I have double checked and I am getting:

Black = 4.7v
Yellow = 12v engine off, cycles between 7 and 14v at idle
Red = 12v
White = 0v

I shall see what the X300 forum have to say too.

Glen.

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Re: High fuel consumption?

#72 Post by Brian_H » Fri Sep 02, 2016 5:06 pm

LPGC wrote:
Freebird wrote:
Gilbertd wrote: they then have a signal reference (Yellow wire) which is fed with a 5V reference signal
The plot thickens then.

I'm sure I was getting battery voltage to both the red heater wire and the yellow ref (in) wire. I now need to double check. If this is the case, why might it be?

I have definitely been seeing the 4.7V on the black ref (out) wires though. I pierced them with my multimeter probe.

Glen.
If other points are correct (and they will be) then could guess that either the yellow reference wire was supposed to be 12v / or 5v reference voltage regulator has failed, sending 12v ref instead of 5v / or under certain conditions the reference voltage is supposed to be 12v instead of 5v (nah!) / or you've seen 12v on 2 wires because one of those wires was supposed to be the earth but isn't connected to earth (so 12v seen on that wire via probe heater). Gilbert?

Simon
I'd have a probe about with the meter once you've disconnected the sensor if I was seeing that.

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Re: High fuel consumption?

#73 Post by LPGC » Fri Sep 02, 2016 5:54 pm

Recap of main points that don't seem to have already been disproved...
Gilbertd wrote:Titania have two heater wires (Red positive and White negative), they then have a signal reference (Yellow wire) which is fed with a 5V reference signal and an output which is on the Black wire and is the reference minus the internal resistance. The output can be measured with a meter with respect to ground but with the difference in potential between battery ground, body ground and ECU ground being only a few millivolts and the range being 0-5V, any difference will be negligible.
Freebird wrote:Mmm, well I have double checked and I am getting:

Black = 4.7v
Yellow = 12v engine off, cycles between 7 and 14v at idle
Red = 12v
White = 0v

I shall see what the X300 forum have to say too.

Glen.
Possible problem with the 5v reference on the yellow wires then? But could yellow wire reference reach 7v/12v if there were no electrical load at all, such as maybe in case of broken probes? Would think ref voltage would stay the same anyway? And in any case even if ref voltage could reach higher voltage with disconnected or broken probes, the probes are still outputting 4.7v (not same as yellow wire voltage), so probably implies probe is at least putting some load on yellow wires. But this assumes probe uses same earth wire as the heater circuit to pull yellow wire ref voltage down to output signal voltage. Or what else could be going on? If yellow wires should be 5v (so if ref voltage is incorrect) could they be disconnected from the petrol ECU and another 5v regulator used to hold yellows at 5v?
Brian_H wrote:I'd have a probe about with the meter once you've disconnected the sensor if I was seeing that.
Me too Bri. Might run the meter past the old and new probes too, see if there is much difference between old and new probes in terms of readings between all of the pinouts (2 pins at a time of course, a few combinations there...). If that doesn't reveal anything it might not be best idea to just plug in new probes at this point? Thinking that could damage new probes if something really is amiss with yellow voltage.

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Re: High fuel consumption?

#74 Post by Freebird » Fri Sep 02, 2016 6:19 pm

LPGC wrote:Me too Bri. Might run the meter past the old and new probes too, see if there is much difference between old and new probes in terms of readings between all of the pinouts (2 pins at a time of course, a few combinations there...). If that doesn't reveal anything it might not be best idea to just plug in new probes at this point? Thinking that could damage new probes if something really is amiss with yellow voltage.

Simon
OK, tomorrow I will compare old to new across all combinations of 2 pins. I assume I am looking for resistance?

The key point for me is what the yellow wires should be delivering. Where is Gilbert when you need him?

Glen.

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Re: High fuel consumption?

#75 Post by Brian_H » Fri Sep 02, 2016 6:29 pm

I'd have a look whats being fed down in terms of voltage on the car loom with it/them both disconnected (that is what I meant earlier). Another way they can fail is to short the heater voltage to the signal though I'd expect the car to have picked that up really. Resistance probably a good bet with the sensor as it won't have anything else to read when you haven't connected it up anyway.

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Re: High fuel consumption?

#76 Post by Freebird » Sat Sep 03, 2016 11:15 am

Hi all

I must apologise for making an error in my post yesterday and leading everyone up the wrong path. I mixed the yellow and white wire readings up. This is what I have actually got ignition on, engine off. The references in brackets come from here: http://www.lambdasensor.com/main/mcolours1.htm

Black (Ref out) = 4.7v
Yellow (Ref in) = 0v with continuity to earth.
Red (Heater +) = 12v
White (Heater -) = 12v

Interestingly it's exactly the same from the car side connector with the lambda unplugged - both 123 and 456 being identical. Advice from the X300 forum says the yellow wire is the common ground signal between both sensors and I should be looking for a flick on the black one - which is what I have been doing.

I also compared the resistance of a new lambda with both of the old ones. The only pin combination that was not open circuit on the new one was between red and white, the heater. The new one was 9.6 Ohms, 123 was 6.9 and 456 was open circuit.

So 456 is definitely in need of replacement and I would have done that by now if only I could get it out of the exhaust pipe! I am going to have to get inventive with a crows foot or similar.

Yours despairingly.

Glen

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Re: High fuel consumption?

#77 Post by LPGC » Sat Sep 03, 2016 12:41 pm

Freebird wrote:I am going to have to get inventive with a crows foot or similar.
I made a range of tools for removing various probes, e.g. ring spanners cut down and welded to half inch socket extensions, one with a cut out like a pipe spanner so wires will slot through the cutout, one without cutout for tougher jobs needs at least plug cutting off probe but is better for tighter probes.

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Re: High fuel consumption?

#78 Post by Freebird » Sat Sep 03, 2016 1:05 pm

LPGC wrote:
Freebird wrote:I am going to have to get inventive with a crows foot or similar.
I made a range of tools for removing various probes, e.g. ring spanners cut down and welded to half inch socket extensions, one with a cut out like a pipe spanner so wires will slot through the cutout, one without cutout for tougher jobs needs at least plug cutting off probe but is better for tighter probes.
Simon
I cut the side out of a long series 17mm socket with a thin wheel using my angle grinder, leaving the top part intact.

Glen is now a very happy man, new 456 fitted and both now flicking beautifully. A quick drive showed it still changed over to gas quickly, but this time no stalling, no hesitation and no perceptible difference in performance v petrol. The proof will be when I measure the fuel consumption of course, but for now it's looking good.

Many, many thanks to all of you for your valuable advice, I would never have done this without you.

Glen.

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Re: High fuel consumption?

#79 Post by LPGC » Sat Sep 03, 2016 4:53 pm

Cheers Glen.

The turning point was shifting focus away from looking into potential problems with the LPG system and towards looking into lack of lambda flick which occurred the same on petrol as on LPG.

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Re: High fuel consumption?

#80 Post by Gilbertd » Sun Sep 04, 2016 9:20 am

Freebird wrote:Where is Gilbert when you need him?
Currently in Latvia visiting my partners parents with very limited internet access...... Nice drive to get here though and with LPG at 0.48 Euro a litre (and even cheaper in some countries on the way, like 0.385 in Belgium) cost me naff all.

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