XJ6R – Fuel System

Fuel System

I have been trying to decide on the requirements for the fuel system needed for the Super Charged engine. It had two fuel pumps in the tank, the second one came on around 4000RPM. On top of that, there is a vapour control system with a carbon canister and various valves. There is also a small pump and a release valve in the engine bay. I have read that there is a test carried out by the ECU after about 5 minutes of running where the vales are closed/opened to monitor the pressure changes in the fuel tank. This could be a problem unless I manage to include all the components somehow. I don’t know what the end result of this test failing will have of the engine running. Will it just generate an error code and carry on or cause other issues?

The fuel lines required for the XJR setup consisted of 3 separate 10mm fuel pipes and a smaller vacuum pipe that ran from a valve next to the Carbon canister all the way to the engine bay. I did remove the old pipes from the XJR however being steel and obviously not designed to fit in the S2 XJ6 they would need major re-bending and after a couple of attempts to adjust them I decided to purchase new copper based pipes all round. These will also match the new brake lines I have run too. I have also ordered some rubber covered stainless P-Clips to support the pipes along the underside of the car.

OK, so we will have new fuel lines and I have found a suitable location to fit the rectangular Carbon canister which is under the car roughly below the rear passenger seat area. That then leaves me with the issue of the two existing XJ6 fuel tanks, changeover valves and the need for a high pressure fuel feed.

  • My initial thoughts were to do away with the internal pumps in the two fuel tanks, feed the fuel lines via the change over valves to the new high pressure pump and then onto the engine.
  • I did try putting the XJR tank into the boot of the XJ6 but the boot hinges are in the way so it would need a lot of work to get the fuel filler pipe to one of the original filler caps.
  • I read on the Jaguar forum, a post by Larry Lowden, who suggested a smaller “surge” tank in the boot fed by the original pumps and still using the twin fuel tanks. The surge tank would be connected to a high pressure pump to feed the higher requirements of the engine. I doubt that with today’s level of traffic,  I could sustain high revs long enough to empty the surge tank faster than the standard pumps can refill it if it was say over a gallon or so in size.
    • This means I need to have find a specially made up tank or maybe I could do something with the XJR one.
  • I thought about getting the XJR tank cut down to size?  I took the round access panel off of the tank and looked inside. The two pumps sit inside a circular anti swirl assembly and there are two baffles either side of them about a foot apart. I could therefore get the tank reduced in size either side of the baffles or even just remove the side that has the filler pipe/cap assembly. That would reduce the overall capacity of the tank to around two thirds of its original size whilst resolving the sealing off of the filler pipe and retaining all of the original functionality of the pressure testing, dual fuel pumps and so on.
  • There is a local company I have used in the past to make up one off metal work items I could ask if they would be prepared to work on the tank. There is a real threat of explosion as the tank has had fuel in it, in fact it still has a small amount of fuel in it right now so a major safety issue. My welding is not good enough to make a fuel proof seal anyway so I have to get some one to do it for me.
  • The alternative to modifying the XJR tank is to look into the racing type fuel tanks that are available.

Looks like some research is in order, where would we be without the internet 🙂

Decision made!

2 Responses

Leave a Reply