Fuel System
Behind every well-running Aceca is a fuel system quietly doing its job, drawing clean petrol from the tank and delivering it, at the right pressure, to the carburettors. When it falters, even a perfectly tuned engine will stumble, so it pays to understand it.
From tank to carburettor
Fuel is drawn from the rear-mounted tank, along the fuel lines beneath the car, through a filter and a fuel pump, to the float chambers of the carburettors. Depending on the engine and specification your Aceca may use a mechanical pump driven off the engine or an electric pump, and the carburettors themselves may be SU or Solex, but the delivery principle is the same, and it is the delivery side that this article covers. For setting up the carburettors, see the Solex carburettor guide and the tuning article, which covers triple-carb balancing.
The common faults
Most fuel-delivery problems come down to age and contamination:
- Dirt and rust in an old tank, which blocks filters and jets and starves the engine, a symptom that comes and goes, and worsens as the tank empties and stirs up sediment.
- A tired fuel pump: a worn diaphragm on a mechanical pump, or worn points on an electric one, giving weak or fluctuating delivery and fuel starvation under load.
- A sticking float needle valve, which either floods the carburettor (fuel leaks, rich running) or starves it.
- Perished rubber hoses and cracked lines, which weep, let in air, or (worse) drip onto a hot engine.
Fuel starvation and vapour lock
If the engine dies or stumbles under sustained load or when hot, suspect the fuel supply before the ignition. Vapour lock, where fuel vaporises in a hot pipe or pump and interrupts the flow, is a known classic-car nuisance in traffic on hot days; routing lines away from heat and insulating where needed helps.
Modern petrol and ethanol
Today's ethanol-blended petrol is harder on old fuel systems: it attacks certain older rubber hoses, seals and gaskets, absorbs moisture, and can corrode some materials. Renewing perished hoses with ethanol-tolerant modern equivalents, keeping the system clean, and not leaving the car standing with stale fuel for long periods all help. Check what fuel and additives suit your car with a marque specialist, and see the fuel, oil and additives guide for the longer discussion of ethanol and lead replacement.
Keeping it healthy
Clean fuel, a sound pump, fresh flexible hoses, a clean filter and a rust-free tank, get those right and the carburettors can do their job. If the engine is starving, hunting or flooding, work through the delivery system methodically before touching the carburettor settings. For the pre-drive checks that catch a failing fuel system before it leaves you stranded, the before a long run checklist is a good companion.
About the author
A lifelong classic-car enthusiast in North Yorkshire, near Thornton-le-Dale, who owns and maintains an AC Aceca, writing the single-model reference he always wished existed. Read the full bio.