I have a 1985 XJ6 and I am about to make some fuel system changes. My stock fuel pump is dying, so I need to install a new one. This isn't such a bad thing because I needed to replace it anyway. I have a supercharger that I am going to add to my LS1 V8 in a couple months, and it will need a bigger fuel pump to supply lots of fuel at a pretty high pressure... probably peaking at just over 70psi. No problem - I found a much larger Bosch pump that will do the job. I plan on still utilizing all of the Jaguar fuel system, including the fuel tank switching and return lines.

Here's the problem: I have this mystery part in the way. It's located in the front right corner of my spare tire well. It looks like it has small fittings on it - maybe 5/16" or so. This is a problem, because I really want to run 3/8" tube or hose from the pump all the way to the engine bay. Having a little 5/16" (maybe even 1/4") section in the way is no good.

So - what is this part, what does it do, and can I get by without it? Do I need to make changes to other parts of the fuel system if I eliminate it?

 

Obviously the canister item is the fuel filter and the little valve behind it is called an air bleed valve. It comes into use when you are switching tanks and it allows the lines to bleed off air to prevent a slug of air travelling up to the fuel rail and causing the engine to stumble. It also serves the purpose of a one way valve holding pressure in the supply line.

I believe you will also have to change the pressure regulator valve in the engine compartment as the original engine set up is to maintain a running pressure of around 38PSI fuel pressure.

Worth noting that the original pump is also capable of a max of 100PSI when in good working condition and should be good enough to give you more than enough flow rate for whatever you are doing.

Hope this helps.

Just an after thought. The same pump you have in your car is also used in the 5.3 ltr V-12 Jaguars. When really pushing that car it will drink gas at an alarming rate. Should be good enough for you.

 

Thanks for the info!

Hmm, so putting in a check valve should be easy to do - there are plenty available aftermarket.

Any thoughts on the air-bleed function of the valve? I am a little surprised air gets into the system in the first place. How necessary is it? Do older XJs have it or is it just something that came out in the later stages of design?

I need a lot of flow at a very high pressure. Essentially I'm doubling the pressure the V12 requires and doubling the flow the V12 requires. I know that pump is a good pump, but it's just not made to deliver that much fuel at such a high pressure. The pump I plan on buying and installing in the next couple weeks is the Bosch "044" pump. It's a little noisy but performs very well at high pressures and has a great reputation for reliability.

 

You should study the return system to make sure you know what goes where.

2nd If your going twice pressure you should replace the rubber sections of the line. Alot of the return goes through the inner cabin in rubber. Something to consider.

Also remember that when you double the diameter of a hose you * 4 the flow capability.

 

and a pic

 

Thanks for all the info guys. I think I am going to hook the new pump up and keep the 5/16" tubing for now, just to keep the car going. Also, I replaced all of the hose on the pressure side about a year ago with fuel injection hose. It's rated really high - I think 100psi working pressure but I am not sure. I haven't done anything on the return side yet, but the pressure shouldn't change much, if at all, on the return side.

And.... my new pump came! It's the Bosch "044" pump, used by racers everywhere. It's also good for everyday use and was original equipment on many Porsche 911 cars. It's conservatively rated at 300lph free flow (which doesn't say a lot) and 200lph at 72.5psi, which is very impressive! It also comes with a one-way valve preinstalled.