Jaguar V12 Fuel Pump
When I first got my Daimler Double-Six, I had been using the drivers side petrol tank only. The one on the passengers side looked a bit gungy when I opened up the filler cap and looked inside. The drivers side tank looked nice and clean. Each tank is 45 liters and is mostly independent.
Jaguar went to the dual fuel tank system with the S-Type of 1963. It then flowed into most of the subsequent models, with the exception of the XJS, until the introduction of the XJ40 in the mid 80s.
Just before Christmas, I had the tank on the passengers side removed and cleaned out. It was pretty nasty inside, the lines were full of gunk and the screen on the pickup was all blocked. When it was all put back together, I as advised that the fuel pump for this tank was not able to provide enough volume and it needed to be replaced.
At least on the cars with the quad carburettors like mine, they used a pair of SU AZX1400 series double ended fuel pumps. The original pumps were points type, but the new ones are normally solid state. Each tank has its own pump, and there are valves to make sure the return fuel goes to the correct tank. These same pumps were also used on some Rolls Royce models too. The photo below shows the SU pump that was in my car.
They are now very expensive, at around $1,000 per pump landed in Australia. The pump that I had been using on the good tank was a FuelFlow 2LM12 pump from New Zealand and seemed to be working well. Given I have the redundancy of dual pumps, I decided not to spend $1,000 on a fuel pump, and went with another FuelFlow pump. At $220 delivered, it was a huge saving. The photo below shows the existing FuelFlow pump on the left and the SU on the right.
The pump arrived the other day and I went about fitting it today. The fuel pumps are located in in the boot, in a cavity to the rear of the spare tyre. At least on my car, each pump was responsible for the opposite fuel tank. That mean I would be changing the drivers side pump.
At first it all looked rather complicated, but slowly tracing all the lines had it starting to make sense.
Each tank has its own output line, and those are connected to the opposite pump. There is one line that goes to the engine, which is on the drivers side of the car. Therefore, there is a fuel line that goes from the left side pump, over to the right side pump, then to main fuel filter. Only one pump runs at a time, so when the left pump is in use, the fuel flows past the right pump but not through it.
There is a single return line from the engine, that is on the passengers side. That connects to both tanks, with a valve that determines where the fuel should go. This is important, as if both tanks are full, its important that the return flow go back to the tank it came from.
The wiring also looks more complicated than it is. Since the pumps are double ended, each end has separate power and ground connections. The power feed for each pump goes to the valve, on each side. I didn’t really examine these carefully.
The fuel lines for the FuelFlow pump were the same as the SU. It was quite simple to get the fuel lines setup. The power feed was a bit different. The SU has a single power line per end, and the body of the pump acts as a ground, with an unshielded ground wire. The FuelFlow has a plastic body, so has power and ground lines at each end. The photo below shows the new FuelFlow pump installed.
I didn’t use the unshielded ground wire, I made up a new ground harness that went into the chassis where the valves screw into the body. The power feed was simpler to adapt. The wiring in my car had a power feed to the inner end of each pump and then a wire that went to the outer end. I used the same setup.
The pumps were not screwed in. Rather they had rubber straps at each end that held them in place. The SU pump also had a back plastic surround, that I assumed was to cut down noise. This was missing on the existing FuelFlow pump, but I re-used it for my new one. When I later tested the pumps, the new one was a fair bit quieter, so I’m glad I kept it.
It started to bucket down with rain as I did the job, so I didn’t end up taking the car on a test drive. I was able to verity that the correct pump ran when I toggled the switch on the dashboard.
