Beginner guide - Jag XJ8 - please help!

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v8vroom
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Beginner guide - Jag XJ8 - please help!

#1 Post by v8vroom »

Hi all,

I have seen a Jag XJ8 V8 that has been converted to LPG for the last 4 years *edit* last 15 years.
I know what to look for in the Jag, having owned one, but I have no clue what to look for in the LPG kit.

Common sense tells me to find out about the brand and to see if there is an LPG certificate. *edit* it has a certificate by an Approved Installer from 2007.

What else do I need to look for? Will the conversion tax any components on the car?
Last edited by v8vroom on Sat May 14, 2022 10:34 pm, edited 2 times in total.

Brian_H
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Re: Beginner guide - Jag XJ8 - please help!

#2 Post by Brian_H »

There should be a tank certificate - tanks are certified for 10 years, typically this would be stamped onto the tank as well, but you might not be able to see that when its installed.

Certificates for the install went digital a few years ago - https://www.drivelpg.co.uk/ has details on the UKLPG scheme and you can check for their certification there, not that it counts for a lot, but your insurance company might want it to be on there.

Have a look how it runs, does the engine management light come on, how well is it installed (does it look neat or a messy jumble of cable ties and loose parts?).

if your intending DIY then some brands are more difficult than others, anything AEB or KME based is fairly easy to deal with, Prins on the other hand really isn't. Not sure on BRC anymore, but worth checking what ecu it is, also this can effect how easily you can get spare parts.

If the tank is exernally mounted, worth having a look at it to see if its rusty where its exposed.

Tanks also come in different types and sizes. Depending what you want to use the car for, it may be better with a torroidal for space reasons, but a cylinder in the boot will give you better range but less boot space.

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Re: Beginner guide - Jag XJ8 - please help!

#3 Post by Gilbertd »

As Brian says, see how it drives. You shouldn't notice any real difference between running on LPG or petrol. On a drag strip you may notice it is fractionally down on power on LPG but not so much you'll notice under normal driving, not even when flooring it to overtake. Is this the Jaguar/Ford AJ-V8 engine? If so it should have a valve saver system fitted to prevent valve seat recession which these engines are known for if one isn't fitted. Make sure the reservoir has some fluid in it.
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Re: Beginner guide - Jag XJ8 - please help!

#4 Post by LPGC »

v8vroom wrote: Wed May 11, 2022 2:27 pm What else do I need to look for? Will the conversion tax any components on the car?
On the Jag/Ford engine it will tax the valves unless a valve lube system is fitted.

One other thing to check for is that DVSA's records (and the V5) have been updated to reflect the current fuel types (LPG and petrol dual fuel)...

When the V5 / DVSA records show LPG as a fuel type few insurance companies raise eyebrows. But if you tell an insurance company that you want to insure a vehicle that is converted to LPG but DVSA records/V5 reflects only petrol as a fuel type it may raise their concerns. Private trade body records are not official records, insurance company's check official records first... then if your mention of LPG conversion doesn't match the official records then some of them (read those that have been persuaded by the trade body/s) may be a bit more inclined to check to see if a private database contains records of LPG conversion. If you mention LPG conversion and the V5 confirms LPG as a fuel type most insurance company's will accept the LPG conversion has been properly done (after all, DVSA accepted the change of fuel type) and not even bother checking unofficial private databases (that very handily happen to be made viewable to the general public, available to view by anyone especially including by busy-body's who work at insurance co's whom really probably should only check official records).

To officially change the fuel type on the V5 you probably need a copy of the receipt for LPG conversion from an LPG conversion pro. The LPG conversion pro needs to be a competent person, they don't need to be a member of any trade body. In my book trade body members and competent person does not necessarily imply the same people.

No factory LPG converted vehicle is entered on the private trade body database and no insurance company questions why they are not entered on a private trade body database, mostly because they all have LPG as official fuel type with DVSA/V5 records. DVSA/V5 records for aftermarket LPG converted vehicles look much the same to insurance companies as factory LPG converted vehicles.
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v8vroom
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Re: Beginner guide - Jag XJ8 - please help!

#5 Post by v8vroom »

Brian_H wrote: Wed May 11, 2022 7:52 pm There should be a tank certificate - tanks are certified for 10 years, typically this would be stamped onto the tank as well, but you might not be able to see that when its installed.

Certificates for the install went digital a few years ago - https://www.drivelpg.co.uk/ has details on the UKLPG scheme and you can check for their certification there, not that it counts for a lot, but your insurance company might want it to be on there.

Have a look how it runs, does the engine management light come on, how well is it installed (does it look neat or a messy jumble of cable ties and loose parts?).

if your intending DIY then some brands are more difficult than others, anything AEB or KME based is fairly easy to deal with, Prins on the other hand really isn't. Not sure on BRC anymore, but worth checking what ecu it is, also this can effect how easily you can get spare parts.

If the tank is exernally mounted, worth having a look at it to see if its rusty where its exposed.

Tanks also come in different types and sizes. Depending what you want to use the car for, it may be better with a torroidal for space reasons, but a cylinder in the boot will give you better range but less boot space.
Sorry for the late reply! I did not get any email notification of a response.

The car is some distance from me so I cannot check it, so I have been meticulously asking multiple questions to the current owner.
The car was converted by a UKLPG Approved Autogas Installer (which dissolved after 30 years) in 2007; at 59k miles. This begs me to ask the next question - has the technology advanced over time? Would I be better off buying another car and converting it with the latest technology?

I do not know which ECU is used, or what type of system. I do know that it has a 58L Stako Torodial tank. Am I able to upgrade the tank to a larger capacity?

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Re: Beginner guide - Jag XJ8 - please help!

#6 Post by Brian_H »

You can stick whatever tank you can fit into the car - this will be a combination of the available space and what your willing to sacrafice in way of load space, obviously this differs with the vehicle. Torrioal types fit into the space for a spare wheel, Full torriadals you get now (with the centre of the doughnut filled in) will give some more capacity than the traditional doughnut type ones.

You should get email notifications for replies to your own posts, you might need to check the forum settings for that though?

ECUs now are generally better than the ones availale 15 years ago, but that could always be swapped later if you wanted to. Really depends what system its got, what price its at and the overall condition of the rest of the car as well as the price its at?

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Re: Beginner guide - Jag XJ8 - please help!

#7 Post by LPGC »

ECU's and injectors tech has moved on in 15 years but good results were possible on this engine with the tech back then. Probably regardless of the components fitted 15 years ago improvements (at least in terms of tech/theory even if not noticeable in terms of driver experience/seat of the pants) could be made today but if the old system seems to be working nicely you'd probably rather invest in a bigger tank rather than engine bay changes...

Jag XJ's are a bit unusual in terms of their spare wheel well design which slopes upwards towards the rear. 'Back in the day' some installers like myself used to 'massage' the shape of the spare wheel well on these (using a big hammer!) to knock the rearward part of the spare wheel well down lower thus allowing more headroom toward the rear which in turn allowed both a deeper LPG tank (read greater LPG capacity) tank and for the tank to sit more parallel with the ground. I remember my dad seeming a bit bemused that I was knocking the hell out of a very nice car with a big hammer lol, he died 14 years ago.

I have just checked my records... seems I have fitted 680x270mm 30 degree (internal toroidal) tanks (76 litres rating) on most of the XJ8's I have converted over the last decade or so. Before checking my records I had it in my head that I'd fitted 79 litre tanks on them. I reckon the 79 litre tanks I seemed to remember were probably 0degree Stako brand tanks of similar dimensions. For a given set of dimensions Stako tanks tended to give a bit better capacity than most other make tanks (or at least according to their own ratings) but Stako kind of did themselves out of most markets many years ago and zero degree tanks are a lot more hassle to fit internally (especially on some model vehicles, not least on Jags) than purpose designed internal 30 degree tanks...

Your choice of replacement tank should probably boil down to either 680x250mm or 680x270mm tank. If I remember correctly the 270mm height tanks would mean the centre of the boot floor (the boot floor flap) would be raised by around 10mm with the floor hammered down, the 250mm tank would allow the flap to sit normally/flat as standard with the floor hammered down.

It always seemed a bit brutal taking a big hammer to a nice car but we're only talking about bending some pressed steel that forms the wheel well... and by doing so you gain much better LPG capacity, as attested by the difference between the 76 litres I mentioned compared to the (I forget the exact figure but lower by around 20L?) tank that you mentioned, If it were my own car I'd fit a 680x300 tank for even better capacity, it seems my customers have been more concerned about loss of luggage area than I would have been.

Off topic but I like the old Jag XJ's... The design is based on a 60's design and what a revelation they must have been for the time. Things I don't like are the relatively small cabin space and headroom for the size of the car, and even though the handling must have been superb for the time it feels (simply put) unusual compared to modern cars, kind of like 4 wheel drift bump steer. But I'd love to have one! the 8 was the last engine update, I also like the big straight 6's and of course the V12's. Converted them all to LPG.
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v8vroom
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Re: Beginner guide - Jag XJ8 - please help!

#8 Post by v8vroom »

Brian_H wrote: Sat May 14, 2022 10:38 pm You can stick whatever tank you can fit into the car - this will be a combination of the available space and what your willing to sacrafice in way of load space, obviously this differs with the vehicle. Torrioal types fit into the space for a spare wheel, Full torriadals you get now (with the centre of the doughnut filled in) will give some more capacity than the traditional doughnut type ones.

You should get email notifications for replies to your own posts, you might need to check the forum settings for that though?

ECUs now are generally better than the ones availale 15 years ago, but that could always be swapped later if you wanted to. Really depends what system its got, what price its at and the overall condition of the rest of the car as well as the price its at?
Would changing the tank require the fitter to recalibrate anything?

My settings seem fine, which is odd.

My thinking was new technology would mean better fuel efficiency. Perhaps I am wrong. If all is needed is a tank replacement, I am happy. Although, as mentioned below, I need to find out if the valves have a lubing system.

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Re: Beginner guide - Jag XJ8 - please help!

#9 Post by v8vroom »

LPGC wrote: Sat May 14, 2022 11:28 pm ECU's and injectors tech has moved on in 15 years but good results were possible on this engine with the tech back then. Probably regardless of the components fitted 15 years ago improvements (at least in terms of tech/theory even if not noticeable in terms of driver experience/seat of the pants) could be made today but if the old system seems to be working nicely you'd probably rather invest in a bigger tank rather than engine bay changes...

Jag XJ's are a bit unusual in terms of their spare wheel well design which slopes upwards towards the rear. 'Back in the day' some installers like myself used to 'massage' the shape of the spare wheel well on these (using a big hammer!) to knock the rearward part of the spare wheel well down lower thus allowing more headroom toward the rear which in turn allowed both a deeper LPG tank (read greater LPG capacity) tank and for the tank to sit more parallel with the ground. I remember my dad seeming a bit bemused that I was knocking the hell out of a very nice car with a big hammer lol, he died 14 years ago.

I have just checked my records... seems I have fitted 680x270mm 30 degree (internal toroidal) tanks (76 litres rating) on most of the XJ8's I have converted over the last decade or so. Before checking my records I had it in my head that I'd fitted 79 litre tanks on them. I reckon the 79 litre tanks I seemed to remember were probably 0degree Stako brand tanks of similar dimensions. For a given set of dimensions Stako tanks tended to give a bit better capacity than most other make tanks (or at least according to their own ratings) but Stako kind of did themselves out of most markets many years ago and zero degree tanks are a lot more hassle to fit internally (especially on some model vehicles, not least on Jags) than purpose designed internal 30 degree tanks...

Your choice of replacement tank should probably boil down to either 680x250mm or 680x270mm tank. If I remember correctly the 270mm height tanks would mean the centre of the boot floor (the boot floor flap) would be raised by around 10mm with the floor hammered down, the 250mm tank would allow the flap to sit normally/flat as standard with the floor hammered down.

It always seemed a bit brutal taking a big hammer to a nice car but we're only talking about bending some pressed steel that forms the wheel well... and by doing so you gain much better LPG capacity, as attested by the difference between the 76 litres I mentioned compared to the (I forget the exact figure but lower by around 20L?) tank that you mentioned, If it were my own car I'd fit a 680x300 tank for even better capacity, it seems my customers have been more concerned about loss of luggage area than I would have been.

Off topic but I like the old Jag XJ's... The design is based on a 60's design and what a revelation they must have been for the time. Things I don't like are the relatively small cabin space and headroom for the size of the car, and even though the handling must have been superb for the time it feels (simply put) unusual compared to modern cars, kind of like 4 wheel drift bump steer. But I'd love to have one! the 8 was the last engine update, I also like the big straight 6's and of course the V12's. Converted them all to LPG.
First of all, thank you for such a detailed response. I hate being in the grey on a new topic to discuss with a mechanic, so this information is crucial to me.

It does sound painful but hey, if it works, it works!

The current tank has a capacity of 53L, which I am assuming is the total capacity; not the usable.
With the 80% rule, that means I can use 42.4L. Assuming the car gets 14mpg city on LPG (16 on petrol), that is 14x9.3gallons which means the car can hypothetically get 130miles out of a full tank for £33 (0.78p x 42.4L)
This works out the same with my current VW Passat 2.0 TDi.

If I get a 72L tank (60 usable), I can get 182 miles for £46.80. Is an upgrade really worth it? Perhaps so once I hit the motorway.

I do love my Jags. It's not smart of me to sell the Passat that I've had for two weeks only because I miss the XJ8 that I sold 3 weeks ago. An XJ8 will overall cost less than the Passat, but the Passat will have a buyer. Oh well, this XJ8 is meant to be my daily for a longggg while. Check eBay! You can pick an absolute minter that has had ALL preventative maintenance work done, for around £5000!

Another question! Exhausts!
1. Will the exhaust notes sound different than petrol when I do an exhaust mod?
2. Will the gas system need recalibrating if I go ahead with this?

Many thanks,
M.

v8vroom
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Re: Beginner guide - Jag XJ8 - please help!

#10 Post by v8vroom »

LPGC wrote: Wed May 11, 2022 11:45 pm
v8vroom wrote: Wed May 11, 2022 2:27 pm What else do I need to look for? Will the conversion tax any components on the car?
On the Jag/Ford engine it will tax the valves unless a valve lube system is fitted.

One other thing to check for is that DVSA's records (and the V5) have been updated to reflect the current fuel types (LPG and petrol dual fuel)...

When the V5 / DVSA records show LPG as a fuel type few insurance companies raise eyebrows. But if you tell an insurance company that you want to insure a vehicle that is converted to LPG but DVSA records/V5 reflects only petrol as a fuel type it may raise their concerns. Private trade body records are not official records, insurance company's check official records first... then if your mention of LPG conversion doesn't match the official records then some of them (read those that have been persuaded by the trade body/s) may be a bit more inclined to check to see if a private database contains records of LPG conversion. If you mention LPG conversion and the V5 confirms LPG as a fuel type most insurance company's will accept the LPG conversion has been properly done (after all, DVSA accepted the change of fuel type) and not even bother checking unofficial private databases (that very handily happen to be made viewable to the general public, available to view by anyone especially including by busy-body's who work at insurance co's whom really probably should only check official records).

To officially change the fuel type on the V5 you probably need a copy of the receipt for LPG conversion from an LPG conversion pro. The LPG conversion pro needs to be a competent person, they don't need to be a member of any trade body. In my book trade body members and competent person does not necessarily imply the same people.

No factory LPG converted vehicle is entered on the private trade body database and no insurance company questions why they are not entered on a private trade body database, mostly because they all have LPG as official fuel type with DVSA/V5 records. DVSA/V5 records for aftermarket LPG converted vehicles look much the same to insurance companies as factory LPG converted vehicles.
Thank you for the indicator. Would you suggest I walk away if that system is not in place? The car has only done 20k miles since the conversion.

I just checked the V5C and it states the car is a petol. The current owner, however, does have the official conversion certificate!

Another route is obtaining a minted XJ8 for dirt cheap and doing the conversion myself - how much would you charge for an ideal system? I’m willing to have this discussion in the private!
Last edited by v8vroom on Sun May 15, 2022 1:18 pm, edited 2 times in total.

Brian_H
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Re: Beginner guide - Jag XJ8 - please help!

#11 Post by Brian_H »

v8vroom wrote: Sun May 15, 2022 12:53 am
Brian_H wrote: Sat May 14, 2022 10:38 pm You can stick whatever tank you can fit into the car - this will be a combination of the available space and what your willing to sacrafice in way of load space, obviously this differs with the vehicle. Torrioal types fit into the space for a spare wheel, Full torriadals you get now (with the centre of the doughnut filled in) will give some more capacity than the traditional doughnut type ones.

You should get email notifications for replies to your own posts, you might need to check the forum settings for that though?

ECUs now are generally better than the ones availale 15 years ago, but that could always be swapped later if you wanted to. Really depends what system its got, what price its at and the overall condition of the rest of the car as well as the price its at?
Would changing the tank require the fitter to recalibrate anything?

My settings seem fine, which is odd.

My thinking was new technology would mean better fuel efficiency. Perhaps I am wrong. If all is needed is a tank replacement, I am happy. Although, as mentioned below, I need to find out if the valves have a lubing system.
No swapping the tank would just involve swapping parts, though you might need to work out what will fit easily. As to if its worth it or not, depends how often you want to fill it up. For Me if I could gain extra capacity I would, though I've had to fill the tank more than once in a day and go all over the place, some of which is going into the areas with few filling stations left etc.

Only thing that may need attention in the software is the gauge settings on the tank if its swapped.

I'll have a look on the settings. Only other thing I can suggest is if its ended ip in your spam or junk folder, or been blocked. Email notifications working fine for me.

Re valve saver, depends if you want to be pulling cylinder heads off to sort valve issues, Ford engines are known for eating valves on gas without valve saver fitted. Or with non working valve saver

v8vroom
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Re: Beginner guide - Jag XJ8 - please help!

#12 Post by v8vroom »

Brian_H wrote: Sun May 15, 2022 1:23 am
v8vroom wrote: Sun May 15, 2022 12:53 am
Brian_H wrote: Sat May 14, 2022 10:38 pm You can stick whatever tank you can fit into the car - this will be a combination of the available space and what your willing to sacrafice in way of load space, obviously this differs with the vehicle. Torrioal types fit into the space for a spare wheel, Full torriadals you get now (with the centre of the doughnut filled in) will give some more capacity than the traditional doughnut type ones.

You should get email notifications for replies to your own posts, you might need to check the forum settings for that though?

ECUs now are generally better than the ones availale 15 years ago, but that could always be swapped later if you wanted to. Really depends what system its got, what price its at and the overall condition of the rest of the car as well as the price its at?
Would changing the tank require the fitter to recalibrate anything?

My settings seem fine, which is odd.

My thinking was new technology would mean better fuel efficiency. Perhaps I am wrong. If all is needed is a tank replacement, I am happy. Although, as mentioned below, I need to find out if the valves have a lubing system.
No swapping the tank would just involve swapping parts, though you might need to work out what will fit easily. As to if its worth it or not, depends how often you want to fill it up. For Me if I could gain extra capacity I would, though I've had to fill the tank more than once in a day and go all over the place, some of which is going into the areas with few filling stations left etc.

Only thing that may need attention in the software is the gauge settings on the tank if its swapped.

I'll have a look on the settings. Only other thing I can suggest is if its ended ip in your spam or junk folder, or been blocked. Email notifications working fine for me.

Re valve saver, depends if you want to be pulling cylinder heads off to sort valve issues, Ford engines are known for eating valves on gas without valve saver fitted. Or with non working valve saver

As LPGC mentioned above, fitting a new tank may be a viable option.

I am now getting notifications, which is great. Thank you.

The owner got back to me and said they're pretty sure it has the valve lube system in place.
They have also mentioned it being regularly serviced, too.
The car has been sat for a short while - will this be an issue?
What other questions should I be asking?

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Re: Beginner guide - Jag XJ8 - please help!

#13 Post by Brian_H »

Didn't change anything on the settings, it may have to do with your post count as you've now dropped out of the newly registered users group. As long as its working now thats great!

Being stood shouldn't be too much of an issue as far as the lpg side is concerned, though I've known odd bits to play up when its left sat for a while (solenoid coils particually) they aren't major to sort, and you'd probabbly change the one on there with a new tank anyway as you'd need a matching valve.

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Re: Beginner guide - Jag XJ8 - please help!

#14 Post by v8vroom »

Brian_H wrote: Mon May 16, 2022 6:07 pm Didn't change anything on the settings, it may have to do with your post count as you've now dropped out of the newly registered users group. As long as its working now thats great!

Being stood shouldn't be too much of an issue as far as the lpg side is concerned, though I've known odd bits to play up when its left sat for a while (solenoid coils particually) they aren't major to sort, and you'd probabbly change the one on there with a new tank anyway as you'd need a matching valve.
so, I bought the car!

I will be getting it serviced but I did have one mechanic take a look at it. They could not service it, but he mentioned I have either the Bi Gas or Romana system installed. He also mentioned it does not have the valve lube system installed.

My plan is to get it installed as soon as.

It has done 20k miles without this system - should I be concerned?

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Re: Beginner guide - Jag XJ8 - please help!

#15 Post by Pinger »

Is there - apart from loss of boot space - any reason why an additional cylindrical tank couldn't be fitted to supplement the existing toroidal?

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Re: Beginner guide - Jag XJ8 - please help!

#16 Post by v8vroom »

Pinger wrote: Fri May 20, 2022 6:24 pm Is there - apart from loss of boot space - any reason why an additional cylindrical tank couldn't be fitted to supplement the existing toroidal?
No reason at all. I believe even with an additional tank, I would have more than enough space if I wanted to go travelling with a few bags in the boot.

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Re: Beginner guide - Jag XJ8 - please help!

#17 Post by Brian_H »

Its possbile to fit several tanks if required - this is often the case on motorhomes where they use LPG for both heating/cooking and as fuel for the engine. Its really just a case of what space you are happy to give to the tanks. Just every tank needs another valve and the associated pipework and electical feed. You might be advised to feed the rear solenoids via a relay to reduce load on the ecu, particaully with older ecus when you have more than one hooked up.

Level gauge readout can be a problem as you can only really read from one electronically.

Valve saver depends on the engine being used - It may help if you post what it is as I can't see it mentioned? Ford engines tend to need it which some Jaguars had as Ford owned them at one point. Its been known for some engines to show issues after 10k, but it can depend on how well tuned the setup is (a lean running setup due to incorrect calibration will acclerate valve wear for example).

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Re: Beginner guide - Jag XJ8 - please help!

#18 Post by LPGC »

Converted loads of XJ8s to LPG when they were relatively new. Converted a couple of them for the same bloke, a 747 pilot who wrote his 4L V8 off then bought a 3.5L V8 because the the 4L had more than enough power and he hoped the 3.5 V8 would be a bit more economical than the 4L. My first thoughts were... What? A 747 pilot crashes his car? Hmm not very confidence inspiring for next time I'm passenger on a plane. My dad gave the pilot/owner a lift to a train station... was a few years ago, my dad died in 2008.

As said you can fit as many LPG tanks as you like really. Compromises are luggage space and to a lesser extent weight. LPG only weighs around 0.5kg per litre but tanks tend to weigh around 0.5kg per litre of gross capacity (depending on type/design etc). Relays etc may be a bit of a moot point, over the years different LPG ECU's have been able to handle different electrical current on the tank solenoid output but in any case we're only talking the cost of a relay to handle an unfeasibly high number of tank solenoid coils (more tanks than could ever be viable/practical). I've fitted 3 tanks to fuel the engine on many vehicles e.g. American RV's... over 100 English gallons net capacity worth in 3 tanks. Handling the electrical current of around 3 Amps not a problem for the AEB ECU's (internal relays in those ECU's) at the time, other ECUs of around the same time had smaller relays, modern ECU's have bigger or smaller relays depending on the make of ECU but we'll be talking a minimum handling capacity of 2 Amps except maybe for Egas and AG.

A bit off topic because we're talking about XJ8's but with RVs if a solenoid coil shorts out then the resistance of the long wire from the ECU to the tank coils (long length of the RV) can mean that instead of the short causing the 10 or 15 Amp main fuse to blow the relay in the ECU has to carry the (still overload) current of maybe (say) 8 Amps constantly with the engine still running on LPG because there might still be 2 tanks with good solenoids still feeding the engine with LPG and 1 tank with a shorted tank solenoid coil (if the wiring were shorter the lower electrical resistance of the shorter solenoid wire would carry more current and cause the main fuse to blow). The make and model of vehicle (or rather number of tanks, gauge of tanks solenoid wiring and length of tank solenoid wires) can dictate whether a separate relay and fuse should be fitted for multiple tank solenoids.

For me the proof would be in the pudding - You're unlikely to be able to compression test a sellers car (or have the inclination to do so) but If it idled OK with warm engine on LPG then that would do me. Then if it didn't have a lube system fitted on the Jag V8, if I bought it I would immediately fit one.
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