SU Carb...... Help !?!?!?

Hi all,

First of all I need to apologise if this has been covered in a previous post, however I'm hoping if someone knows of several companies that can help, maybe I have a decent chance of getting a good price...

So the story goes my '87 V8 90 is having a bit of a grumble and is deciding to ... "Leak" out of what I can only describe as the overflow from the offside carb.

Land Rover Owner • View topic - SU carb connections - I think it's number 3 on is picture..

Now I have spoken to a chap local to me who said on his 101 this pipe returns to his fuel tank...? Whereby on my 90 it joins with the near side tube and runs down the front of the near side front outrigger, therefore leaks fuel when driving and so the lovely MOT guy first failed it... When I Looked later it didn't leak and passed the mot 2nd time round ? I guessed it was intermittent but hoped it was sorted. Anyway I have removed the carb, checked the float having removed the baseplate, which moves fine, not yet looked at the diaphragm in the top dome part of the carb.. My question is - has anyone come across this before ? And where can I get rebuild kits / o ring kits for my carb? Many thanks

Jack

On the old Rover SD1 3.5 V8's I had with SU HIF6 carbs, the overflow just ran down the front of the engine and exited on the floor, no fuel ever came out of mine. The float should shut off the in coming fuel before this happens.

Also if your carb has a diaphragm at the top it's not an SU it will be a Solex or the like.

Things to check are the float height as this is adjustable, and wear around the float bearing and inlet port. Also be sure that your fuel pump is not over pressurising the fuel line and forcing fuel in. Usually however if the float is set wrong the engine runs rich due to incorrect fuel level at the base of the jet.

For SU carbs you can't do any better than Berlen Fuel Systems in Salisbury for anything from a new carb to all the parts.

The Worlds Sole Manufacturer of Genuine SU Parts - SU Carburetters

Ok, I am mistaken thinking the SU has a diaphragm similar to a solex.... I have twin hif44 carbs. I thought the tube routing would go down there for a reason but I couldn't understand why - due to the fuel leaking/overflow...

How would the float stop the flow? Does it - should it plug the fuel inlet once it's reached the level in the fuel chamber? Could it be possible the float has deteriorated? How do you measure the float for correct adjustment? And when you say check inlet wear, can I confirm this is the head inlet and not the fuel inlet?
Thanks

Jack

I had a similar problem on my 1986 90 v8 from cold start whereby the car was taking a while to start and fuel was spitting out the overflows due to carbs being flooded, when it eventually fired the leak would stop after a minute or two which I put down to residual fuel in the line, mine was due to an intermittent ignition fault though, since thats been sorted fuel no longer leaks out.

J.A.P-LR said:

Ok, I am mistaken thinking the SU has a diaphragm similar to a solex.... I have twin hif44 carbs. I thought the tube routing would go down there for a reason but I couldn't understand why - due to the fuel leaking/overflow...

How would the float stop the flow? Does it - should it plug the fuel inlet once it's reached the level in the fuel chamber? Could it be possible the float has deteriorated? How do you measure the float for correct adjustment? And when you say check inlet wear, can I confirm this is the head inlet and not the fuel inlet?
Thanks

Jack

Click to expand...

Best plan is to call Berlen Fuel systems, they will be able to answer your questions with far more accuracy than me.

SU carburetors rely on engineering tolerance rather than a rubber diaphragm that deteriorates over time, For me I believe SU is about the best carb you can get.

However, from rebuilding a few:
How would the float stop the flow? It stops the incoming fuel flow by operating an inlet needle into the inlet orifice, and set's the fuel level. Float adjustment is critical.

Could it be possible the float has deteriorated? Yes this is possible, but the leak would probably be constant and the engine would probably be too rich to run at idle.

How do you measure the float for correct adjustment? This data is included in the manual you get with their rebuild kit's, I've no idea what I done with my manual, but I would think a quick google would get you answers.

As for inlet wear, I was referring to the inlet jet the float controls on the carb.

If the float is holed it wont seal the needle to orrifice and will leak fuel.
Same if the needle or orrifice are worn.