My car has been running really well since the tune up but, yesterday the car stalled when pulling up to a set of lights and then only spluttered back to life before running normally again.

This morning the car didn't want to start, it wouldn't fire, like there was no spark? I popped the bonnet and the coil was loose but, all electrical connections were intact. I secured the coil and tried to start it again but without the choke this time and it fired.

With the engine now running smoothly I took a look under the bonnet and there was a strong smell of fuel, probably indicating that I flooded it in the first start attempt. I then noticed that the rear carb Float Bowl Overflow has fuel pouring out of it!

Sounds similar to this thread:

https://www.jaguarforums.com/forum/x...-petrol-68530/

But I have HS8 SU Carbs with the Float Bowls to the side.

I think I need to get a couple of rebuild kits (may as well do both while I'm there).

 

YEP.

HS8, awesome carby.

Needle and seat not sealing, COMMON.

Float sinking to the bottom of the bowl, COMMON.

Talk to the guys at Midel, in Sydney somewhere (9759 5598) They are the SU agents and have all the goodies, and the books if you need them.

 

Thanks Grant,

I'll get on the blower first thing Monday morning.

 

thought I'd close this one out (am I speaking too soon?). I spoke to Midel this morning and they got the parts to me mid afternoon the same day! I stayed on the safe side and got the Float Bowl Needle Valve, Gasket and a new Float too.

Apart from the sticking pin, its a pretty simple job. The new Needle Valve was a slightly different design but works in the same manner, and when the Float was fitted, all the angles and clearances looked right.

The first test was just to turn the ignition on to conduct a static leak check for a minute or so, then with a little bit of choke she fired up first time. A quick drive to test the engine under load and all was well.

Job's a good'un.

 

SWEET.

Jags are sooooooo reliable, aint they.

 

I did speak too soon!

The fuel isn't coming out during initial priming when the ignition comes on and the car drives fine, however, when parking up after a drive with the engine running at idle the fuel is coming out of the overflow again.

Therefore until my Workshop Manual arrives, I'm after some information please.

1. What is the fuel pressure for a Series 1 XJ6?

2. If not the Fuel Pump Assy, what sets the fuel pressure?

Thanks in advance.

 

Mmmmm, Bugga.

Pressure is about 3 psi, maybe 4psi. Needle and seat simply shut off supply when the bowl is full.

If the fuel level is getting high enough to run out of the overflow spigot there must be heaps of raw fuel flowing out of the jet into the inlet manifold. I say this coz the fuel level in that jet is visible if you look down from the top with the piston removed.

I would remove both pistons, and prime the system, and look down at the fuel inside the jets. It should be ABOUT 2-3mm below the top rim with the jet in the raised position, as in NO choke. Any higher than that and the fuel level is too high.

Not sure of any fuel line restrictors on these, but that was a LOOOOONG time ago.

Thinking as I am typing.

1) The needle and seat may NOT be sealed 100% to the lid. Did you do a vac test (suck and tongue over the inlet) just to ensure it is sealing as it should. Our 4.2 had issues with the front carby doing that, and sealing that n/seat to the lid was not as simple as it should be.

2) What fuel level height did you set it at????.

 

It would appear that the fault might be pressure related as when I switched to the LH Fuel Tank, and thus pump, the problem went away? I need to do a proper test run to confirm as I've only done the 10 min drive to and from work.

Limited info on the pumps in the Workshop Manual.

 

On the way into work this Morning the front carb decided to do the same and dump fuel out of the overflow.

 

Look at/ listen to the fuel pumps; in the boot, spare wheel well. They should be SU type pumps, if not, they will probably be producing too much pressure.
I agree with Grant, check your fuel levels in the carbs, and set your float levels.
Try the info on this link.
Gower & Lee Helpfull Tips page

 

Look at/ listen to the fuel pumps; in the boot, spare wheel well. They should be SU type pumps, if not, they will probably be producing too much pressure.
I agree with Grant, check your fuel levels in the carbs, and set your float levels.
Try the info on this link.
Gower & Lee Helpfull Tips page

 

They are definitely not SU Fuel Pumps but they do look new.

I'll have a go at this procedure and see how I get on.

 

I've replaced the Front Carb Float Bowl Needle Valve and all fuel overflow has stopped but I will go through the other checks over the weekend.

 

OK.

Weekend here also, sooooooo get me the numbers/brand/whatever that is on any ID plate on those pumps.

I will more than likely have the specs for them somewhere in my library. They may be too high on the pressure spec. I have had some that were at 8+psi. which the needle/seat should handle, but it is getting at the top end of the chart.

Most SU for carby are "low pressure/high flow" style.

 

Right, I've had a good look at the Fuel Pumps and pulled the following info from them:

Make: Ingrams
Model: 871960
Pressure: 0.3 kg/cm2 (4 psi) - a more accurate conversion is 4.2 psi

I also pulled the top of the Carbs off and primed the system to check the fuel level and the fuel was slowly filling the carb up!

I also noticed that the Choke Cable was not seated properly and therefore it was always on a little bit?

I'm going to re-adjust the Choke and do the fuel prime check again later today.

 

That pump is just fine.

The filling whilst watching via the jet opening is classic needle and seat NOT sealing. More than likely the seat portion to the cap of the bowl is not sealed 100%, and is common as it gets. Sometimes the "thin" washer simply splits and allows leakage.

The choke ON a bit will see that jet slightly "down" the tube, and that can be enough for the fuel to overflow. Those 2 choke levers MUST be down as far as they will go, and the jet sitting flush with the top of the carby bridge. This is the "base setting", and then mixture is usually base set 2 turns down on each screw. That will get it started, and fine tuning is simple after it warms up.

I have had fun with these over the years, and they will test your patience a tad. Once right, never touch them again for a long time.

Maybe you are getting a small amount of silt?? from the tanks, so a fuel filter somwhere under the bonnet would be good, if it does not have one??.

 

Thanks Grant, that gives me a bit more to work with, and good to know that the pumps are fit for purpose.

 

Grant,
It's a very long time ago but isn't there a horseshoe shaped lever which rides on the float to actuate the valve?
I had problems with overflow and it was this lever worn/sticking.

 

Steve,

You are correct, sort of. The HD series had the "horseshoe" lever attached to the lid, with a seperate float over a centre pin. The HS series is a flimsy tin affair actually attached to the float, and it wears at the ears and the brass pin.

HD had a brass float. HS had a "nitrile" (plastic) float with arm attached.

That did wake up a few more brain cells, mmm.

The HS floats can jam in the bowl. Quite rare, but the wear of the ears and pin, and then add the rough attitude some "mechanics" apply to bending that lever when setting the fuel level reeks havoc.

I have seen that arm with the little tab to limit the floats drop travel missing totally, so the float drops too far, the needle slides too far out, and the then jams when fuel tries to lift the float to shut flow off.

Both series floats do fill with fuel over the years, and that also causes its own issues.

 

I have the non-adjustable plastic type Float with no metal lever attached. Obviously there is a modicum of adjustment available by changing the thickness of the Crush Washer under the Needle Valve.

Actually, the new Needle Valves didn't come with new Crush Washers which means they might not be sealing properly?

Also, I was going to adjust the mixture but when looking at the procedure for HS8 SU carbs, it says not to adjust the mixture screw as it is pre-set during manufacture? I'm guessing that I can adjust it anyway?