Go LPG! Research

Jaguar XJS 3.6 and 4.0 litre - Seriously cheap cars to run!

The XJS range may be a little dated now, but good, usable examples can be bought for a couple of thousand pounds, going right on up to 10,000 or more for a later 'Celebration' 4.0. Spares are relatively cheap and it is feasible to run one on supplies from the breaker's yard. Good roadholding and comfort can be found in all models along with good performance. The very 'top end' of the market brings you a fully optioned car with low mileage and full service history. The eariler Cabriolet and later Convertible models have more headroom.....93,000,000 miles with the top down!

Later XJS 6 cylinder models (roughly 1992 onward) are catalysed, demanding a closed loop LPG conversion, but there is little (if anything) to be gained from fitting multi point gas injection. Closed loop single point systems do a perfect job on this car so the much higher price of multi point conversions are avoided.

We developed our own and quite unique gas mixer for this car, which bought huge benefits in reliability and performance. Go LPG have converted 99 examples to date, (mostly in XJ40 and X300 saloons) some having done mileages in excess of 30,000 on LPG with no problems at all.

Our conversion customers vary enormously in the ways they use their cars and the mileages they cover, but all agree on one thing - Performance of the XJS 6 cylinder on LPG is every bit as good as it is on petrol, whilst they save half of their fuel costs.

Safety first -

We include all of the latest safety features in every job, one of the reasons we are rarely the cheapest when quoting a conversion price. We don't mind that. We'd rather not do a conversion than send one out with less than the full safety measures.



Conversion of the XJS 3.6 ( AJ6 engine )
and XJS 4.0 ( AJ16 engine )

We have a lot of experience converting both of these Jaguar models. We are often asked to rectify faults with LPG conversions or Petrol faults caused by incorrect conversion.

The AJ6 / 16 engines are not the easiest to convert properly, although many profess to get perfect results. We beg to differ, judging by some of the cars we are asked to put right. I have to say that we have not seen one single properly converted XJ 40 to date, although there must be some good ones out there somewhere.

In fairness, the convertor is often let down by sub standard equipment or simple inavailability. He or She may then be pushed into using inappropriate equipment, and Backfiring is often the result. When it happens, backfiring not only disables the car on LPG, but often on Petrol too, making it impossible for the driver to limp home on Petrol. This is totally unacceptable to us.

Incorrect mixers cause blowbacks 
and this sort of damage. The car will
also not run on Petrol if this happens. Incorrect conversions often result in
blowback (backfiring), damaging the inlet
'Bellows' and allowing unmetered air
into the system. This leaves the engine
unable to run on either Gas or Petrol.
Go LPG! customers do not have to
worry about this. We eradicated the
problem and no one gets stranded.

To address the problem we spent 3 months dealing with the main culprit, the 'one size fits anything' mixer which often proves to be of no use at all. The result of that research and development, (our own specially produced mixer unit) removes all of that compromise, bringing optimum performance, economy and RELIABILITY to these cars whilst running on gas. AJ6 or AJ16 conversion owners can now drive their cars confident that they will not backfire when pulling away etc. The risk of damage to the Bellows, Airflow Meter or other inlet tract components has been completely removed by our unique mixer design. None of our owners have ever been stranded as a result.

We don't sell any of the conversion refinements we have developed to any other company, and hope you will understand why we don't show or describe them here. We do, however, use them on every Go LPG! XJ40 ( AJ6 ) or X 300 ( AJ16 ) conversion and assure you that backfiring will not be something you are familiar with when we have converted your car.

As specialists in our field, we are indeed a little more expensive than the many ordinary Garage businesses who pick up LPG conversion as an 'add on', but you just don't get Champagne at Lemonade money, it really is as simple as that.


Here are a few pictures of the XJS conversion -

Celebration 4.0 litre, a nice package. The improved AJ 16 engine was shared with the X 300 model and gave good performance. This engine converts to LPG very well.
The fuel choice switch fits neatly into the ashtray. Nice and easy to reach but does not interfere with your night vision. If you don't want to see it at all, shut the lid!
By far the most popular tank option, the 80 litre cylinder. Good, usable boot space remains. Notice the spare has been moved from its original vertical position and lain down on the boot floor.

It is possible to fit a spare wheel tank flat on the boot floor (horizontally) although to do this, the battery must still be moved. The spare wheel must then be stoed horizontally on top of the tank, leaving less remaining (useable) boot space than the cylinder tank option.

The battery was sited in several positions as the model progressed. In the case of the Celebration model it occupies space needed for the tank, and has to be moved into otherwise wasted space inside the rear wing. The exhaust has to be removed to bolt the battery cradle into its new position, then be refitted. There is more to a properly effected LPG conversion than you may first imagine......
The filler is placed in the face of the rear bumper, seen here as the black square next to the rear fog lamp. This is just about the only position that is available without cutting into bodywork. For those who have not seen this type of filler before, a brass adapter screws in for filling, the small black flap closes over the threaded hole to hide it and keep it clean.

A coil is put in the filler pipe to prevent breakage during a rear - end shunt, but even if this pipe where completely severed the multi valve would stop any significant leakage. All that can escape is the gas content of the pipe since the last fill.

Go LPG! XJS Conversion


Early 3.6 (uncatalysed) models require an Open Loop conversion.


Later 3.6 or 4.0 models (catalysed) require a Closed Loop conversion.


All AJ 16 engined conversions benefit from our own specially developed mixer unit which is not available anywhere else in the world. To date ( 1/ 8/ 03) we have converted 38 examples and not one of them has had a single backfiring occurrence. This will continue throughout the life of the car as long as it is kept properly serviced and maintained. Peformance on LPG is practically identical to that of petrol. 12 months parts and labour warranty is given with every job, along with a nationally recognised insurance certificate.

N.B! Catalysed cars require a closed loop system to protect the cat.

Contact us to arrange
conversion of your XJS

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LP Gas burns cleanly.....

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