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 Post subject: High fuel consumption?
PostPosted: Tue Jul 26, 2016 12:02 pm 
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Hi All

I have recently bought my third LPG car after a brief fling with a smelly old diesel. This time it's a Jaguar XJ6 X300 with the 3.2 litre straight 6 AJ16 engine. It's fitted with a Stefanelli system which has been regularly serviced. It has done 76000 miles since it was fitted so well "established" - 147000 total.

When I bought the car it was running rough and I found that the inlet valves had recessed to the point where it was loosing compression on no1 and no6. I fitted a replacement head and now it runs well but the fuel consumption is noticeably worse than the previous LPG Jag I had and that was an X308 with a 4 litre V8.

Last weekend I took it on an easy cruise down the M3 and back and it gave 18MPG over 200 miles, normal driving is more like 15 where the V8 gave 22 ish. There are no leaks that I can see or smell. I was going to get a software package so I could read the settings in the ECU, but don't really know what I am looking for.

Any advise most welcome.

Cheers

Glen.


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PostPosted: Tue Jul 26, 2016 4:06 pm 
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It is likely that the valve seat recession and poor economy are related - X300 Jag engines don't usually suffer from valve seat recession so maybe the recession was caused by running a lean mixture. A lean mixture could be caused on individual cylinders due to individual LPG injector problems or could be engine wide due to a lambda probe problem.

A test you might be able to do without buying further equipment (to check lambda probe and some aspects of the LPG setup) would be to connect a multimeter to the signal wire of the pre-cat lambda probes, on either fuel you should see the voltage flick between 0 and 1 volt constantly. Of course, if there's a flick on petrol but not on LPG this would point to an LPG system problem (injectors, sensors, calibration etc). Bare in mind it is possible to get a flick with some cylinders running rich and some lean. No flick even on petrol might point to a lambda probe or other engine/sensor problem.

Wouldn't be too surprised with Stefaneli if there's a reducer, pressure sensor or injector issue considering the age of the system. Fixed quite a few over the years.

Simon

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PostPosted: Wed Jul 27, 2016 9:58 am 
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LPGC wrote:
Connect a multimeter to the signal wire of the pre-cat lambda probes, on either fuel you should see the voltage flick between 0 and 1 volt constantly.
Simon


Hi Simon

Thanks for your valuable advice, how do I get to these signal wires? I know there are two pre-cat lambda probes - one on each downpipe. do I just disconnect the wires to them for this check?

Cheers

Glen.


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PostPosted: Wed Jul 27, 2016 10:25 am 
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Must leave the probes connected but connect the multimeter by baring the signal wire, the other multimeter wire goes to earth, battery earth will do. Must use a digital meter.
What colour wires do your pre-cat probes have? Very often probes have black, grey and 2 whites with the black wire being the signal wire.

Simon

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PostPosted: Wed Jul 27, 2016 4:13 pm 
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LPGC wrote:
Must leave the probes connected but connect the multimeter by baring the signal wire, the other multimeter wire goes to earth, battery earth will do. Must use a digital meter.
What colour wires do your pre-cat probes have? Very often probes have black, grey and 2 whites with the black wire being the signal wire.

Simon


OK, understood, though the battery is in the boot so I will find a good earth somewhere closer.

I will look at the wire colours when I get home this evening.

Glen.


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PostPosted: Sat Jul 30, 2016 1:22 pm 
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Hi

The wires on my lambda sensors are white, red, yellow and black. Predictably access isn't great but I managed to spear the black wire of one of them and got a steady reading of 4.7 volts with the engine running on petrol.

The wires disappear behind the engine and connect to miltipin connectors where the wires the other side are different colours. ! sensor = 2 x blue, 1 x white and 1 x red while the other = 3 x blue and 1 x white.

Unfortunately I can't see which colour connects to which, but here I get White = 14.4v, red 4.7v, Blue 14.4V, other Blue 0.01v Same on petrol as LPG. The other sensor reads the same so the 3rd blue = 4.7v.

The other thing I need to fix it that it changes over to LPG too early and the engine will stall if at idle or low speeds.

Does that help at all?

Glen.


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PostPosted: Sat Aug 06, 2016 5:20 pm 
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The other symptom it has is that is momentarily hesitates when accelerating from idle, worse the longer it has been idling for. Fine on petrol though.

I thought perhaps one or more injectors might be leaking into the inlet manifold, so I took them all apart today and they look absolutely fine to me. An unusual (for me) design with diaphragms. There was pressure in the gas line when I disconnected it, so they can't have been leaking.

Still keen to hear suggestions.


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PostPosted: Sat Aug 06, 2016 7:44 pm 
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It look to me that you have a wideband sensor in which case the red one sounds like your signal wire, but I don't think you will be able to read a wideband sensor with a meter IF one is fitted, Don't know your car well enough to tell you myself but a quick goggle comes up with http://lambdapower.co.uk/partsearch/az2.asp?manu=Jaguar&model_grouping=XJ&model=XJ6%20(X300%2095-%3E98)&litre=3.2 which suggests a Titania Sensor which appears to be wideband).

I think your best bet is to get a look at diagnostics if you can - either for the Stefanelli side of things (which will tell you if the pressure sensor is reading something sensible or otherwise plus give an idea whats going on, not sure if you'd be able to do much otherwise unless you can turn individual cylinders to petrol to see if you can isolate anything that way - this would for example show up any miswired injector cuts) or the Jaguar side if your able to do so (might be very tricky as its pre OBD). Otherwise you may be into blindly swapping exhaust sensors without being able to confirm they are even the fault. Not so much of a gamble when you've got only one to deal with, but an expensive option to chance without knowing for sure.

Does it start up ok once its been running on LPG? or does it crank for longer before starting?


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PostPosted: Sat Aug 06, 2016 8:57 pm 
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Might be right Bri.. But I'm not sure if I've seen a straight 6 engine'd Jag with a wideband sensor. I seem to remember some with unusual coloured wiring and maybe 0-5v / 5-0v sensors.

Possible to confirm proper closed loop operation on pre OBD2 vehicles (without the proper OBD1 interface) by adjusting LPG calibration at idle. Assuming the vehicle has idle speed control, if LPG system calibration (at idle) is adjusted a little, manifold pressure at idle will remain the same while pinj changes and ginj doesn't change. If manifold pressure and/or ginj changes during the test, this means the fuel system hasn't compensated the mixture so the engine has to draw more air (in the case of lean mixture or sometimes less in the case of slightly rich mixture) to compensate idle speed with a none stoch mixture.

Also, some Stefanelli systems don't have the usual compliment of pressure sensors..

Simon

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PostPosted: Sat Aug 06, 2016 9:59 pm 
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LPGC wrote:
Might be right Bri.. But I'm not sure if I've seen a straight 6 engine'd Jag with a wideband sensor. I seem to remember some with unusual coloured wiring and maybe 0-5v / 5-0v sensors.

Possible to confirm proper closed loop operation on pre OBD2 vehicles (without the proper OBD1 interface) by adjusting LPG calibration at idle. Assuming the vehicle has idle speed control, if LPG system calibration (at idle) is adjusted a little, manifold pressure at idle will remain the same while pinj changes and ginj doesn't change. If manifold pressure and/or ginj changes during the test, this means the fuel system hasn't compensated the mixture so the engine has to draw more air (in the case of lean mixture or sometimes less in the case of slightly rich mixture) to compensate idle speed with a none stoch mixture.

Also, some Stefanelli systems don't have the usual compliment of pressure sensors..

Simon


Figures that the pressure sensors might be a little odd/different from what you'd said above. Given the 4.7V would this appear to be the signal wire to you (which doesn't appear to flick on either bank from what the OP has said?) I'd mistaken the reference the op made to AJ16 to say AJ6 earlier, I realised that now!

Sounds like he will need access to the Stefanelli software either way and thats probabbly easier to achieve than access to the Jaguar side of things. Leads available from http://www.lpg-kits.com/interfaces.htm (check that it is one of the mentioned systems first) and other places I'm sure, but given the prices of the bits I've seen I'd be inclined to swap the front end to something more accessible rather than sink further money into it if its getting old, especially given the prices of the few bits I've seen for those systems. Or run it past an installer who can give an opinion on it/May have bits around that would sort it.

First thing to do is get a look at the ECU and see which one it actually is though?


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PostPosted: Sun Aug 07, 2016 9:22 am 
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Agreed on all points Bri

Simon

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PostPosted: Sun Aug 07, 2016 10:20 am 
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Hi Guys

Thanks for all the advise, some of which I actually understood. :D

My Jag does have OBD2 though it must be an early version obviously. The only code was P1621 which seems to be a spurious immobiliser fault.

The company in Brian's link also list it on eBay, but this one is half the price - I wonder if it's any good though....http://www.ebay.co.uk/itm/152192626909?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Glen.


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PostPosted: Sun Aug 07, 2016 10:51 am 
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The eBay one is listed as being suitable for Stefanelli as well as Romano. Romano is usually AEB but I don't thing Stefanelli is so it may not work. The LPG kits one will and if it doesn't you'll be talking to a man in Norfolk not being ignored by someone in a different country.

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PostPosted: Sun Aug 07, 2016 1:41 pm 
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Gilbertd wrote:
The eBay one is listed as being suitable for Stefanelli as well as Romano. Romano is usually AEB but I don't thing Stefanelli is so it may not work. The LPG kits one will and if it doesn't you'll be talking to a man in Norfolk not being ignored by someone in a different country.


Good points both.......


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PostPosted: Sun Aug 07, 2016 5:13 pm 
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Freebird wrote:
Gilbertd wrote:
The eBay one is listed as being suitable for Stefanelli as well as Romano. Romano is usually AEB but I don't thing Stefanelli is so it may not work. The LPG kits one will and if it doesn't you'll be talking to a man in Norfolk not being ignored by someone in a different country.


Good points both.......


The Stefanelli one he lists is plug 13 - Not one of the ones in his universal kit so its probably a peculiar one (wiring could be different to anything else). So I'd suspect that the lead will only work with Stefanelli and nothing else. You need a laptop to use it on though, If you have a serial port on the laptop get that type of lead for preference, otherwise it will have to be the usb type.

If you have access to the obd side can you see any live sensor data? That might help you more than fault codes, as you can get an idea with any luck on what the o2 sensor readings are showing, which can give some insight into whats going on. Its not always possible with an off the shelf reader though, varies greatly by manufacturer and age of vehicle. What are you using to see the fault code you have listed (app on a phone or a handheld reader?)

It may be that the ebay listing is for a few different cables - if you translate this section

Wichtig: Informieren Sie uns nach dem Kauf bitte, welche LPG-Anlage Sie genau haben...danke !
Importante: Fateci sapere dopo l'acquisto si prega di quale sistema GPL...grazie!

Important: See which LPG system you have us exactly after purchase please ... thank you!

I'd be suspicious of a listing that says its located in Germany but gives a Russian web address for tracking though. In the event of any problems you have somewhat better chance of getting it resolved by the other one thats listed.


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PostPosted: Mon Aug 08, 2016 12:05 pm 
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Cheers Brian

I won't go for the cheap one.

I have a hand held OBD2 reader but I can't see live data unfortunately. The readers for that on old Jags are well over £100 and I'm not sure what data will be available anyway being such an early version of OBD.


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PostPosted: Mon Aug 08, 2016 12:13 pm 
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Been a while since I worked on a Stefaneli system, I think a lot of them may have gone well past their use by dates and been replaced with a different system (Bri's point on expensive parts). Reducers seem to fail in a way which leaves them outputting very little pressure but by that point the injectors are usually also pretty worn and it's likely another part will soon fail. I have a specific Stefaneli USB cable and as memory serves (years ago) I bought it because I had problems connecting using generic (interchangeable plug) type interfaces.

Need to get it running right on petrol first (lambda flicks etc), then in Freebird's position I'd: Check now to see if it runs properly on gas - If so then leave things at that, perhaps do a stethoscope (bit of pipe in ear!) check to see if injectors are noisy or any make a different sound compared to the others, change all injectors if any seem on their way out (replace with same type injectors using nozzles from old injectors, new injectors could be left in place and used as part of a new replacement system anyway), check again to see if it runs OK on gas. If at this point it still doesn't run properly on gas, consider whether it's worth buying a specific Stefaneli interface... I'd think probably not worth buying a specific interface (not dear but will only work on Stef) but worth buying a generic interface (which may or may not work with Stef) but could be used to calibrate a different system in the case the old Stef system isn't worth repairing (at this point quite likely). If the generic cable works with Stef, delve into software to see if readings show an inexpensive component is broke (though I don't know what would be worth replacing as some Stef systems don't even use a gas temp sensor, probably the only very cheap component) / use the cable to try to tune the system (but assuming it was calibrated OK before, something has changed, likely to be a duff component). If the generic cable doesn't work, maybe replace the Stef with something newer and better, already got a cable to calibrate it with.

Simon

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PostPosted: Mon Aug 08, 2016 3:17 pm 
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Freebird wrote:
Cheers Brian

I won't go for the cheap one.

I have a hand held OBD2 reader but I can't see live data unfortunately. The readers for that on old Jags are well over £100 and I'm not sure what data will be available anyway being such an early version of OBD.


I suspected that could be the case - as you suggest its unlikely to show live data, though some pre OBD cars do. If you had the equipment to see it was worth a try, but probably not worth buying it on a hunch. I'd be more inclinied to either get an installer to have a look at it (as they should have some way of looking at the live data to calibrate it anyway unless its something really odd - But you can always contact them first to check that anyway) and confirm if there is anything wrong on the petrol side. Or buy the lead and see if you can spot anything wrong in the lpg side (but given the age of it, and the cost of new bits for the front end which won't work with the lead you have brought this might not be the best option anyway - the pressure sensor I saw on Tinleytech was over £100 I think, and there wasn't an awful lot of other bits available on there or elsewhere for them either).

Is there a vacuum line running between the vaporiser and manifold?


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PostPosted: Mon Aug 08, 2016 8:30 pm 
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What year is the Jag? Although the OBD standard didn't become mandatory in the EU until 2000, it was introduced in the US from 1996. So anything that was likely to be sold in the US was OBD compliant even though it didn't need to be. I've got a Launch C Reader V1 (http://www.ebay.co.uk/itm/Launch-Creade ... 1882872565) and that reads and displays live data from my 1998 Range Rover perfectly well.

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'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.


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PostPosted: Mon Aug 08, 2016 8:47 pm 
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Gilbertd wrote:
What year is the Jag? Although the OBD standard didn't become mandatory in the EU until 2000, it was introduced in the US from 1996. So anything that was likely to be sold in the US was OBD compliant even though it didn't need to be. I've got a Launch C Reader V1 (http://www.ebay.co.uk/itm/Launch-Creade ... 1882872565) and that reads and displays live data from my 1998 Range Rover perfectly well.


That looks quite interesting - for the cost its a more sensible buy to me than the Stefaneli lead as at least it should continue to be useful for other vehicles as well.


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