Hi guys
I have an Autotune Aristocat (XK150 replica) which I believe is based on S1 XJ6 that has a 4.2 litre engine with twin Strombergs (I think?). I've never had the car running although the engine turns freely. I’ve have replaced most of the ignition system and now have a good spark. I have fitted a new fuel pump - however whilst the fuel pumps as far as the carburettors it doesn't seem to get into the carbs (maybe?) because after cranking the engine for some period of time, when I take a plug out there's no smell of petrol. I'm only a hobby mechanic with rudimentary knowledge so any help you could provide me in sorting out this particular issue would be appreciated

Cheers

Craig

 

Is the carb a CD175, should be printed on the top, if so read on...

CD175 are famous for float problems. See if you have fuel pressure at the carbs. See if the car will run on Brake Clean. BTW there are 2 type of brake clean. You want the highly flammable "non-chlorinated" which is... highly flammable by wont explode like starting fluid. You are inexperienced so you MUST HAVE a fire extinguisher rated for fuel near by and a fire suit may be beneficial too.

Problem with the CD175 is the rebuild kits suck and the replacement needle isn't any good in many cases. Good luck. You'll need to get experience with a CD175 or find someone that has experience with a CD175. It's an emissions carb and a bit more complex than earlier carbs.

 

You can try gently tapping the bottom of the carburettors with a screwdriver handle, which may cause the float to move.

 

That could work but if the needle is stuck closed, then it could stick open and that can lead to over fueling and a fire. The needle and seat have to work right. It's not a TV set from the 70's that just needs a good wack now and then. You're dealing with gasoline and if not working right can set your car a blaze. Sometimes internet advise is worth what you pay for it.

 

I've not worked on a Jag with carbs yet but have done the light tap trick to release a hung float on small engines. It works ( sometimes ) but you can also see and smell if it starts to overflow. Unless you are my Dad ! He was working on a small tractor with the breather off while fighting carb issues and kept trying to crank it AFTER overflowing the fuel bowl. It backfired and caught all the spilled gas on fire. Luckily I was visiting / talking to Mom inside where I could see it happen. While he stood there looking around trying to decide what to do ( he can't move so fast anymore ) I grabbed the house extinguisher and put it out before it damaged anything other than his pride.
So PLEASE follow the above advice to get a fire extinguisher for your shop and be careful working on the fuel system, I also keep one in my trunk just in case for good measure.

Cheers,
Brian

 

Internet advice aside, if the concern is about 'over fueling', the best approach is to remove the carburettors and disassemble the float chambers to find the reason for the needle/seat not functioning correctly.

Whilst the carburettors are removed, check the fuel pressure with a gauge to see if the pressure is within specifications.

 

Thank you for the prompt response.
Where precisely should I be looking on the carbs for the 'CD175' - all I can see is '7 704' ?
Also how can I see if I 'have fuel pressure at the carbs'?

 

Take a pict of the carbs and post it. Since the car is a bit of a project it may be best to see what we are dealing with.

For a novice, my advice to "see" fuel pressure is to install a see through or clear fuel filter on the fuel line. This way so you can see if the fuel is clear or moving or not in a safer manner.

What I would do as an experienced mechanic is get a long piece of fuel line and extend the fuel supply from the carb all the back to the tank fill door and watch the flow rate over a few min. The pump would have to be strong enough to push fuel all that distance with a brisk flow rate. Then I'd pinch off the hose a bit and observe the pumps ability to generate some pressure.

ANYTIME you're playing with fuel a fire extinguisher rated for fuel must be at hand. Nothing between you and the extinguisher. Stuff happens.

 

When the fuel line is taken off the carbs the petrol runs our at a fare (?) rate. When I nip up the tube the the pump ticks away for 5 or 6 seconds?

 

Those are not CD175's and I dont have any experience with those carbs. They appear to be older carbs with a manual choke converted AED. Someone else will have to chime in about those carbs but I suspect a float issue all the same.