There is a 'manifold' on the L/H side, top of the engine - a fuel line supplying fuel that surrounds the A/C line coming off the rear of the A/C Compressor??
My assumption - to cool the fuel?? Doesn't make any sense to be doing the reverse....and how? But one side of my brain lets me, that although the A/C compresses the freon, it has not been allowed to expand at that point and therefore be cool...in fact it should be warm/hot from the compression cycle??
Curious minds what to know??
Thanks,

Tony

 

Quote from Kirby Palm's book;

"The stock Jaguar fuel pump moves far more fuel than the engine normally needs with the excess returned to the tank.
Since this heats the fuel somewhat, a fuel cooler is included in the return line, using the A/C freon circuit to provide cooling."

and;

"The fuel cooler in the Jag is in the return line going back to the tank.
The pump moves much more fuel than is normally needed and most of it recirculates. The fuel being heated while
passing through the engine compartment as well as the pumping energy itself would eventually heat up the fuel in the
tank significantly, possibly causing vapor lock problems and problems passing EPA emission requirements -- heated fuel
gives off more vapor. The cooler is to counteract the heating effect. This may help explain why the ventilation system
has the A/C running during most conditions."



.

 

Forgive me, you post is written a bit weird. Is your main question that you think the AC is hot and that heating the fuel is bad? I assure you that is the low side line and it is cold, the freon has cooled in the condenser and been pumped through the compressor. Right after that cooler the hose leads to the TX valve and the evaporator.

If you are aware it is cool and you think that cooling the fuel is bad, im not sure what to say. You don't want hot fuel continuously cycling to the tank and causing an increase and pressure, possibly ending in vapor lock.

 

Sidescrollin-
Sorry didn't mean to make it sound confusing, guess I was writing as I was jumbling it around in my head.
I fully ubderstand the benifits of cooling the fuel. As a retired, degreed engineer (ME), the increase in volumetric efficiency is a big plus.
I guess what was tangling my thoughts was the fact that the freon traveling thru this high pressure line coming off the a/c compressor, has not been thru the orifice/restriction before reaching the evap....so it's not COLD, in fact might be a bit warm from the compressor. But I guess on the scheme of things, with the recycling of the fuel continuosly, being heated by the pump, heat under the hood, etc., that cooling from the a/c line is beneficial!
Interesting way the Brit engineers do things!
Thanks for the comments!

 

You have the lines muddled up. The high pressure line from the pump goes to the condenser and dryer and from there to the evaporator. This high pressure fluid goes through a solid line from the US passenger side of the condenser/dryer though a gap on the rad top side and along the US passenger side lower chassis rail, and across the firewall top to the evaporator valve.

The rubber line you are thinking of, IS the return, cold, line from the evaporator. It is this line that goes though the fuel cooler. IF your aircon is working, you will see cold drops of condensation on the metal fittings on this line

The British Engineers are blameless !
Greg

 

Yeah I can't believe I said that. That line is totally the return line from the tx valve to the compressor, you can even just look at it and see it's the line going to the compressor first and not the condenser.

I was still thinking of the right line, but forgot the order of things lol. If you run your AC, just look and feel, that line will be cold and have condensate on it.

 

Safari -
Need your help. You quoted from a book by Kirby Palm. What is the full name of the book and dobyou have ny idea where I might be blevto purchase it??
You can never have enough reference material!
Thanks....

Tony

 

Experience in a Book: Help for the Jaguar XJ-S Owner

by Kirby Palm

Fortunately the book is free. You can download it here;

http://www.jag-lovers.org/xj-s/book/XJS_help.pdf

Mark