Fuel hose connects the various components of the petrol-supply system, the petrol tank to the petrol pump, the pump to the carburettor, the carburettor return line where one is fitted, and the various smaller hoses for filter housings and vapour-recovery connections on later cars. Modern UK petrol is meaningfully different in composition from the petrol the cars left the factory drinking, and modern fuel hose needs to be specified to handle the ethanol content of E10 unleaded, which is now the standard UK forecourt fuel.
Ethanol-Resistant Construction
Ethanol-resistant fuel hose uses a nitrile-rubber inner liner that does not swell, soften or degrade when exposed to ethanol-content petrol over extended periods. The original-specification rubber fuel hose fitted to classic MGs during production was specified for the 100% petroleum fuel of the time, and modern E10 ethanol-petrol can cause the inner liner of an old hose to degrade, softening, swelling, or breaking down internally into small particles that block carburettor jets and fuel-filter elements. The headline issue is not a sudden hose failure but the gradual breakdown of the inner liner producing carburettor and pump issues that defy diagnosis until the hose itself is identified as the source. Renewing fuel hose with ethanol-resistant specification eliminates the problem at source.
Sizes and Specifications
Fuel hose is stocked in the internal diameters used across the classic-MG range, typically 5/16-inch (8mm) for most low-pressure fuel-supply applications, and 3/8-inch (10mm) for higher-flow applications such as the tank-to-pump line on V8 cars or modified MGB applications. The hose is rated for the operating pressures the SU and Stromberg pumps produce (typically 1.5 to 3 psi for the original-specification pumps, with the appropriate higher rating for performance pump applications). Wall thickness is matched to the application, with the heavier-wall hose specified where the hose passes through harsh under-bonnet environments and the lighter-wall hose appropriate for shorter runs in cooler areas. Braided fuel hose, covered in the dedicated Stainless Braided Fuel Hose section, is the alternative for owners running performance or competition specifications where the visual appearance and the additional burst-pressure rating of braided construction are valued.
Renewal and Application Notes
Fuel hose is a regular renewal item on any classic, the recommended renewal interval is typically every 5 to 10 years depending on the exposure environment and the type of petrol the car has been drinking. Renewal is straightforward: drain the relevant section of the system (or pinch the hose with appropriate hose pinchers to prevent fuel loss during renewal), cut the new hose to the appropriate length, fit the new hose with the original or renewed hose clips, and check for leaks at the joints once the system is repressurised. The hose clips themselves are covered in the Hose Clips section, Jubilee-pattern clips are typically appropriate, with the option of period-correct slotted-band clips for owners restoring cars to concours specification. The technical team is available to advise on the right specification for a specific car and original-equipment configuration.