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Fuel System Q&As


Fuel tank supply pipe corroded. 


The petrol supply from the tank draws only the top 4 gallons or thereabouts, then I top up with another 4 gallons to fill the tank, so the driving range is about 110 miles. Books say that this is a corroded supply pipe issue, but no solution is given!!  Do you know the best way to overcome ?



The cure, alas, is to cut open the fuel tank, once removed from the car, and braze in a new pipe as its probably corroded below the 4 gallon level (tank takes 8) and is sucking air. There should be a bit of rubber pipe at the very bottom of the feed pipe but this has often completely vapourised by now, but its loss is only about an unusable 1.5 gallons.










Air silencer/filter

Is there any way to remove the wire wool in the air filter housing. Other than using a scribe to hook it out. Or should I leave it and just wash it out in paraffin?

Its a ‘silencer’ not and air-filter. The mesh is permanent. I wash mine in petrol (cheaper than paraffin), dry it, then put oil on the mesh to stop it rusting. The only ‘air-filter’ on Y Types is the export version Oil-Bath type.


Petrol Filler Cap 

I am about to remove the filler neck from my YB (0279) to fit a new seal where it goes through the inner rear wing and a new filler cap (from MGOCC). Can you tell me which way up the cap should be fitted – ie hinged at the top so that you have to hold it open to fill the tank, or hinge down so that the cap falls open if the catch is knocked?


Filler neck can be at any angle, I’ve seen many at odd ones. In the photos of the time the cap opens towards the rear door, but slightly downwards so it will stay open.


Fuel Starvation
I have just been out in my YT and a mile down the road I lost power as if only firing on 2 cylinders. I turned round and just about limped home with a couple of stops on the hills when with relief I arrived on my drive, I pulled the plug leads off one by one they all had a good spark (electronic ignition) and the erratic firing continued unchanged. I then got her back in the workshop where she fire up on full power again making further investigation difficult. Before I venture out again could you confirm my thinking or suggest another possible reason. Could it be one of the float chamber must have stuck closed causing petrol starvation in two cylinders. I have recently had my petrol pump pack up on a busy roundabout and I had to fix a new spare pump I was carrying, one float chamber was disturbed whilst investigating the petrol starvation.



Was it damp and cold? You might have suffered carburetter-icing! The water (in all petrol) would have frozen up in the jet, starving the engine. It could also be another fuel-starvation as you say, poor pump delivery. The cure for carburetter-icing is a hot-spot in the inlet manifold, something the YT does not have! Other causes might be blocked filter in the petrol-pump, muck in the bottom of the jet-tube, but I would go for the first two.


I have had the YT running in the garage at full temp she started well and after a short while returned to the loss of power.  As the only major change recently I am suspecting the new petrol pump being erratic. When the weather dries up a bit I will venture out


The new pump was not new it had a blockage on the intake which eventually caused it to pack up. The points on the old pump have been cleaned and it has been re-fitted all is running well now.


Heat shield

Any suggestions to cure hot starting problems on the twin carb engine? Difficult to fit insulating blocks.



Alas, you need to insulate the carbs, try a few thick gaskets, about an eighth of an inch-worth. A heat sheild is also vital.


Fuel gauge readings
Any suggestions as to how I can get my fuel gauge to stop telling lies?

The guage is just a voltmeter, it reads the signal from the variable resistor mounted in the tank woked by a float. The tank-mounted ‘float switch’ can wear through the copper wire windings and give odd readings; the EARTH at the float switch needs to be a good one, it often is NOT causing high resistances and false readings. Remove the switch from the (empty) tank, connect it up and operate it by hand whilst watching the guage. New ones can be had from NTG of Ipswich. Hopefully the car has been re-wired with modern plastic insulated wires; if not the wiring may also be very suspect, especially those behind the dash that become brittle (old cotton covered rubber wires are dangerous now). When re-fitting or fitting a new float switch, make sure the float has a free -arc’ to move in and does not hit any of the baffles (just bend the floats wire arm to suit). Also use a sealant that is resistant to petrol (Hylotyte) on BOTH sides of the gasket (beware using old cork ones as the ethanol in the fuel disolves the glue holding the tiny bits of cork together….also beware shearing off the six set-screws holding in the float switch, un-do;do-up;un-do;do-up until you’ve freed it up.)