THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

Just a query, while my son was looking under the bonnet he remarked that the fuel level in the glass bowl was almost empty. As the car has not been run for several weeks would this be expected or should I be looking for a leak.


Regards John


1B 1257BW

Sorry John I have never looked but I know that when ever I turn the ignition on the fuel pump ticks away filling something so one would assume it is filling the float bowls and glass bowl. I will now look at mine before I start the car and report back.

John, if it any help this is my filter after the car has sat three weeks while I was away.

Mine is completely empty after four days! Damn, another problem to add to the list.

I will check mine and let you know I have never noticed empty.
Dave J.

I will blame my son for being observant!!!


John 1B1257BW

A certain amount of evaporation is inevitable. The starting carburettor is open to atmosphere after all. That might explain why Nigel still has some fuel left in his after three weeks, because (I think I'm correct in saying) his car no longer has the starting carburettor.

John

I do not think you have any cause to worry; this fuel drop is quite natural on all the Jaguars and Daimlers up to the DS420.

You will find the drop in level is mainly the result of fuel creep through the fuel pump exhaust valves. As these valves do not seal perfectly, usually with minute dirt particles on the seats, you will be spending countless wasted hours if you are trying to prevent the fuel level drop. It has already been mentioned that the evaporation through the choke system will cause some drop in the bowl level.

There is a slight variation between fuel levels on cars depending upon the efficiency of the pump valves.

At one point I had 15 Daimler 420 cars on fleet, all with carburettors (The last model in Europe with SU Carbs) and it was possible to see different fuel levels in the bowls. This was used to some extent to judge the condition of the pump valves as we serviced and swapped pumps on a time line. The pumps on these models were submerged in the tank and unnecessary pump changing was not on our welcome list.

So, Norman, do you think (some of) the fuel drains (or is sucked) back into the tank(s)?

I still have the starting carburetor on my car, it was on my XJ that I removed the AED and changed to manual chokes. If you are concerned about fuel flowing back into the pumps/tanks then fit an XJ fuel filter with a shut off tap on top like in the previous photo I posted, it's also useful for working on the carbs and changing the filter not to mention an effective anti theft device.