This is my first post, so please be kind. My XK140 FHC fuel gauge has started showing about 1/8 full and the reserve light on even when the tank is full. I was thinking of pulling the sending unit, but I see it is about 2/3 of the way up the side of the tank. Does the tank need to have fuel below the level of the sender before I remove it? I don’t want to start a petrol flood. Thanks, Chris.
best be careful there as you will open a hole in tank. you will need the two little gaskets at least to get back on the road once you remove it.
Yes you need to lower the fuel level before asking out the sender unit. If there is a locking ring make sure you use a brass drift not steel to release it.
Hi Chris,
The low level warning light and the gauge itself are on separate circuits and the fact that they are both on indicates that the sender arm is not riding up and down with the fuel level. Probably a problem with the float but it might be that the arm is just be stuck.
The sender is fixed with six 3BA cheesehead screws and as others have said you will need to lower the fuel level and have a new gasket to hand. The replacement gaskets that I have are made of cork.
Eric
Shropshire, UK
You can raise the left side of the car, if you are near half full. And I suggest that you remove the rear, left wheel:
And get some sealant, like Holymar(I think itś called), when you put the sender back, with those 6 screws.
There are adjustmnent screwson the back of the gauge, to calibrate the needle. I have one XK whereI had to unplug the red light, as it was always on.
The incorrect fuel level reading in my xk150 was found to be caused by the sender arm blocked by a baffle in the tank. Sender arm must be adjusted to avoid hitting the baffle.
Chris,
Same problem here as William already mentioned: my 1955 XK 140 FHC had the same problem. The new replacement sender touched the internal flange (that connects the upper and lower part of the reservoir) at the right side of the float. I had to bend the float arm a little (about half an inch or 1 cm) to the left (if you hold the sender assembly in front of you with the corrtect side up, marked TOP).
The new sender works perfect now, although the “warning signal” comes on (far) too early: when the pointer is just below 1/2. Will have to address that.
Bob K.
Use the right thickness gaskets when refitting or else the screws will bottom and the brass threads will strip.
I have the same problem too 14 years since we restored my XK 140 OTS sender been nothing but trouble with leaks around the sender flange dripping onto the exhaust not the best piece of design Jaguar ever did. Also same problem races over to full and red light always on, i have just ordered a replacment sender and based on whats above will check to make sure its not fouling, i will also get the wiring checked as i was convinced it was shorting somewhere sending straight over to full.
It won’t be a short on the wiring that’s causing the gauge to flick to full. It will be a break in the wiring or a poor contact of the wiper on the resistance winding. Open circuit makes the gauge read full.
The low fuel warning light is a completely separate circuit. The bulb is held at 12 volts and lights when a pair of contacts in the sender grounds that line. The contacts are meant to close at a pre-determined fuel level and can be adjusted by bending them. Quality it isn’t but it was a pretty good cost effective arrangement 60 odd years ago.
Eric
Shropshire, UK
Thank you Eric i will look at the new sender and go from there i have to say good for its day it may have been but surprised no one has developed something better, especially with the outer chamber also full of fuel and the positioning half way up the tank over the exhaust is something else.
For what its worth, application of Loctite 518 sealant under the screw heads attaching the sender to the tank, sealed up the leaks on my 140 sender.
Thank you Gary did you also put small fibre washers under the screw heads also.
Hi Rubyflo,
I seem to recall that the small washers were metal washers, and yes, I did use them, putting a small drop if the Loctite 518 under each washer and under each screw head.
Hope this helps.
You will find quite often the flange on sender unit warped from over tightening so a matter of straightening
then use good cork gasket with the original copper washers and a good petrol proof gasket goo on both sides allowing it to go off slightly. importantly tighten in the old wheel nut fashion ie missing one going to next and don’t over tighten. maybe a slight tweak the next day
But most important is to use a Locktite tread sealer on the actual threads as these go through straight into the tank and the fuel will work its way up the thread.
Thankyou Terry and Gary will use Loctite in threads. In your opinion do you think this is going to be more of a problem with modern fuels The guy who has always done my fuel tanks has stopped doing such work since tin plate is no longer available whatever replacement he has tried has been eaten away by the fuels maybe be the dreaded liquid fuel tank liner will have to be used.
Regards
Brian Sewell.
Well have fitted the new sender but not put fuel up to its level the new sender only works fro half full down dosn’t get above half so i suppose this is a step in the right direction.