air in fuel system

[alicarv96]

so i've been having some spotty performance from the rocco as of late and discovered tonight there is quite a lot of air in the fuel system. There is a bit missing on the sender unit allowing some air into the tank which surely shouldn't be the problem, the fuel pump is another potential cause, i can get a new vapour unit and pump on heritage for 40 quid. are there any other potential causes of the problem? thanks in advance

[gt11rocco]

what engine ?

[alicarv96]

1.8 carb EX

[gt11rocco]

have u changed the fuel filter and swiral pot ?

[alicarv96]

no

[bengould]

Just out of interest, how have you determined that there is air in the system?

If it is because the fuel filter is not full, this is normal, I have owned 3 and have never seen the inline fuel filter full on either of them.

There is a very good chance your running issues are caused by blocked jets due to rust in the tank from the filler neck. The first thing I would do is remove the fuel sender and look into the tank for tiny particles in the fuel. If there is anything at all in there, this is more than likely your problem.

Ben.

[alicarv96]

there is air bubbles in the fuel lines, and have had a look in the tank and that is very clean in side barely anything in there, have had to order a new sender unit as one side was cracked off and missing and causing a huge fuel leak

[bengould]

Ahh, OK.

The return line will have air in. The feed line shouldn't have much although there will be some, the swirl pot / vapour separator should get rid of that before it gets to the carb though.

Good luck though, hope you manage to get to the bottom of it.

Ben.

[GTXTRA]

Went through this last year on my GTL.

Carb mounting gasket been changed recently?
Do the 'spray carb cleaner around base of carb and see if revs drop' trick.

[alicarv96]

never heard that one before GTXTRA

[Nate]

How would a leaky carb flange (snigger) put bubbles into the fuel line?

[the edmundator]

I would have thought there is a broken pipe or poor clamp (rose clamps instead of fuel line clamps can be a problem) allowing a bit of air to be sucked in somewhere, if there is air in the supply line.