Fuel and braking systems
BOSCH COMPLETE PUMP KITS TR5-6
TR5-6 Mechanical Petrol Injection with a Bosch pump.
Over the years we have seen innumerable variations on the theme of a 'Bosch pump' installation, some good, some OK and some positively dangerous. At the onset it should be remembered that the fuel pressure is over 7bar (100psi) which will seriously spoil your day if there is a leak. Often we find that the fuel delivery system contains a cheap Bosch pump (there are over 300 to choose from) cobbled in with as many original parts as can be used. This is far from ideal as the Bosch pump works in a completely different way to the original Lucas pump.
The first part of the petrol's journey is the tank and this must have a swirl pot to work correctly. Many tanks don't; if it looks original it is over 40 years old and made of steel. There is likely to be corrosion inside it which even at a minimum will create particles which the filters will need to deal with. No fuel system should be expected to deal with dirty fuel but an injection system is particularly sensitive as the fuel is flowing around the system all the time rather than delivering just the fuel that is being consumed, which is the case with a carburettor system. Part number 312359XALK is a suitable aluminium replacement petrol tank.
The pump kit itself needs to be a 7 bar pump; almost all Bosch pumps are intended for fuel systems working in the 3.0 to 4.0bar range and as these are plentiful, they are cheap. No surprise therefore that we come across these very often. There are other knock on effects too. The wiring should be modified with a relay as the original pump drew 3.5 amps and the Bosch pump takes 13 amps. Kit RTR4017K provides all the necessary parts.
The Pressure Relief Valve (PRV) will work but can only run with rubber hose otherwise it screams if the pressure is set correctly (with a low pressure pump the pressure is usually set below limits to stop this; not good for the engines performance). A much longer hose will in most cased stop this but with the pressure set correctly the fuel can permeate through the rubber hose and cause petrol smells in the boot.
If the PRV is changed to a diaphragm type (RTR4456K) and a Teflon lined feed hose used (RTR4048-1), there will be no screaming (resonance actually) and the petrol smell can be greatly minimised and at best eradicated.
After 1972 Triumph introduced an inertia switch to cut the fuel pump electrical feed in the event of a hard collision. This may have been retro fitted; worth checking and if there isn't one- fit one. RTR8346K is the part number of the modern reliable part. If you have an existing inertia switch it is worth checking that it actually works. Many have been fitted in the feed to the Bosch pump, can't take the load and have melted inside and are therefore useless.
A shield part number RTR7259 in front of the pump set under the boot floor is a good idea to minimise the amount of mud that can collect around the pump accelerating corrosion, reducing the life of the parts and making servicing more difficult. Also to make fitting the wiring easier and a good idea for all future electrical needs is an auxiliary fuse box kit RTR8270K that couples directly to the alternator and makes adding additional equipment (in this case the pump and inertia switch ) easy.
1: Bosch pumps must have a good electrical supply capable of passing 13 amps. The original car wiring is not adequate, as the Lucas pump only requires 3.5 amps. We supply a relay kit part number RTR4017K. See below.
2: TR5 and early TR6 cars did not have an anti-surge reservoir in the petrol tank. Cars fitted with this type of tank will experience fuel starvation on tight left hand corners with less than a quarter of a tank of fuel. Our replacement tanks fitted with the correct anti surge reservoir, part number 312359XALK should be fitted to remove this annoying symptom. See Fuel Tank Section where other tanks are listed including an alternative economy tank.
4: We have found that stainless braided hose cannot be used between the pump and the original PRV as the hard nature of the outer sheath gives rise to intolerable resonance. Unfortunately modern fuel will permeate through rubber hose, however fitting Pressure Relief Valve kit RTR4456K is a complete solution which will remove resonance and allow a fuel tight Teflon lined feed hose to be used. See the section titled 'FUEL FILTERS, REGULATORS, VALVES AND TAPS' where kit RTR4456K can be found and is fully explained along with other relevant kits..