Ford Scorpio Fuel Rail
The Scorpio fuel rail for petrol models follows an established practise. A light alloy rail filled with petrol is kept under constant pressure by a regulator valve receiving fuel under pressure from the fuel pump, which is mounted inside the fuel tank. Excess fuel is returned to the tank using a second pipe.
It is when the regulator valve is faulty that starting difficulties can begin. The valve seat jamming or sticking can result in excessive pressure, meaning too much fuel is injected by the timed Injector pulses, the engine is flooded and starting is difficult when the engine has been recently run, often accompanied by the smell of petrol. During idle periods the Long Term Fuel Trims (LTFT(s)) will slide fully into the negative, and DTCs may be generated. After a few hours the fuel rail pressure falls sufficiently to allow the engine to start again.
When the valve fails to open sufficiently to maintain a satisfactory pressure in the fuel rail cold starting will be most affected. The engine needs a rich mixture to start from cold but the Injectors have insufficient pressure to spray enough fuel. During idle or under high loads excessive positive LTFT(s) may be found.
24V Cosworth Fuel Rail
The Cosworth fuel rail is mounted directly on top of the inlet ports. The Injectors are surrounded by fuel and this keep them cool and metering more accurate. The regulator is mounted on the end of one rail and controls the amount of fuel returned to the tank.
1. Fuel Rail 7 334 851
2. Injector 7 334 932
4. Fuel Pressure Regulator 7 334 684
9. Securing bolts 6 555 536
13 Injector seal 7 334 695
DOHC 8V Fuel Rail
The DOHC engines also use Injectors surrounded by fuel.
22 Fuel Rail 7 045 226
23 Injector 7 045 229
43 Injector seal 7 251 926
25 Fuel Pressure Regulator 7 045 224
DOHC 16V 2.0 and 2.3L Fuel Rail
Essentially the same as the 8v, but with the addition of a test valve:
1 Fuel Rail 7 050 652
2 Injector 1 000 312
35 Injector seal
3 Fuel Pressure Regulator 1 075 157
31 Fuel pressure test valve 6 172 229
32 Test valve cap 6 591 031
Fuel Rail V6 Cologne 12v
The Cologne engine is an older design and uses a side feed fuel rail sandwiched between two gaskets. Although this engine is not equipped with OBDII, difficult starting will often be for the same reasons, as I found with my 2.9L Granada.
1. Fuel rail 6 177 895
3 Pressure Test valve 6 172 229
4 Valve cap 6 591 039
15 Gaskets 1 659 956
16 Gasket 6 789 195
5 Injectors 6 175 664
6. Retainer 6 173 459
7 Fuel Regulator 6 154 156
8 Regulator cap 6 454 874
Copyright © 2004 www.fordscorpio.co.uk