FUEL SYSTEMS
PETROL INJECTION - NOTES ON
FAULT DIAGNOSIS

SI/FS/18
(SEPTEMBER 1970)

These notes have been compiled by our petrol injection engineers
as a result of experience gained in the service field.

1. DRAIN-'A' PIPE BLOCKAGE
Complaints of heavy fuel consumption, 'sticky' throttle action, 'lack
of response' and rough idling, occasionally arise with Triumph 2.5
Mk.2 'PI' equipped saloons. These symptoms disappear when a new
metering unit is fitted, but then subsequently re-appear.

The symptoms have been caused by a blocked or restricted drain-'A'
pipe and some Triumph production cars have a return pipe 0.125"
(3.175mm) diameter bore. In certain instances this will not accommodate
the return-to-tank flow, and results in a build-up of back pressure in the
drive cavity.