Rejecting upgrades
QI’ve fitted a Felicia engine to my Škoda 120 with a rebuilt Weber 28/36 DCD carburettor from a V4 Saab 96. On its first drive it only seemed to run well with the choke out, and it’s refused to start since.
There’s a spark at the plugs, but they seemed wet when I removed them, suggesting too much fuel. I’m using a Facet electric pump. Do you think it might be generating too much pressure and overfilling the float chamber when the ignition’s on but the engine’s not running?
Paul Johns, Totnes
AThe wet plugs may be a red herring. Some other defect may be hampering starting and the wet plugs may be an effect rather than a cause. Examine all possibilities.
Firstly, the servo hose runs from the back to the front of the car and may be drawing in air. Cap off the stub on the manifold and try starting/driving the car again. If you’re using a coil and distributor, try another coil: a weak or variable spark will cause the issues you describe.
The Saab carburettor shouldn’t cause major problems in starting and driving, though it’ll probably need rejetting to perform at its best. Float height should be 5mm from the gasket with the carburettor top held vertically, so the float just touches the sprung ball of the valve but doesn’t compress it.
What model of Facet pump are you using? A carburettor requires around 4psi of pressure, which can be measured by connecting a pressure gauge directly to the pump. Some models produce a higher pressure – so you will need to fit an in-line regulator.