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Fiesta 1.1 fuel pressure

Hi, I have a CFi 1.1 thats been running rich and failed emmissions. The exhaust is full of soot.

Have ruled out the IAT, CTS (both measure around 35-40k), Cat and HEGO have been replaced. New sparks, oil and filters.

Wondered if it could be the injector itself so did a fuel pressure test.

On the inlet side it holds pressure at 14PSI, which seems correct. Switch the engine off and see what pressure it drops to after 1 minute. No need - it drops to zero immediately!! It will not hold pressure at all.

I checked the pressure on the fuel return line and it is over 40 PSI. Is this correct? I would of thought the return would dump the petrol right back into the tank and shouldn't have any restriction.

I tried blowing down the return pipe until my cheeks bled, and it spat petrol back out at me.

My guess is the fuel has been trying to get back to the tank but is not able to and is forced back down the injector, hence the running rich, emmissions and soot.

Does this sound right to anyone? Or is the fuel return a closed system and kept at a high pressure?

Any help appreciated.

Reply to
Roger
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Sounds very feasible.

Reply to
Conor

Return blocked, split at coupling between pump and tank sender outlet (inside tank) assuming you have identified the feed and return correctly.

Reply to
Jimmy

Ok, double checked - but this time removed the fuel filler cap.

I can blow down it easily and hear gurgles from the tank so its not blocked after all. Though surely the tank has to vent when the filler cap is on? Or is the tank kept at 40PSI?

Any ideas on what is causing the lack of pressure hold when the engine is switched off? The Haynes manual states it should drop to no less than 0.5 bar (7 PSI) after one minute. Its dropping to 0 immediately.

The injector seals all look good.

Reply to
Roger

Tank venting is one way, ie to allow air into the tank to replace fuel used. If it worked both ways it would increase the risk of fuel spillage in a rollover accident.

Steve

Reply to
shazzbat

Could be the pump. Or a leak somewhere. But if the running pressure is ok I wouldn't worry too much.

Reply to
Dave Plowman (News)

If this is true, then surely the entire EVAP system is redundant?

I'm under the impression that the fuel filler cap lets air in when the tank is under vacuum, and the rollover valve vents vapour out to the EVAP carbon canister when the tank is under pressure.

My guess is the rollover valve is not venting as it should.

Reply to
Roger

Yeah, ok, nothing to worry about.... NOT!. Ok, the car drives perfectly, is structurally next to perfect, is low mileage (50k) The only fail is a minor emissions transgression (ooohh... instead of 0.30% its 0.50%). Totally invisible to conventional carb testers

EVERY other sensor has been checked. The OBD flash code sensor shows '11' - no faults.

However, there is a blatant sooting of the exhaust going on.

My simple blowing down the pipes test seem to indicate a block in the EVAP system, Of course I may be deluding myself and such EVAP systems are kept under 3 bar pressures? I don't know pray tell how the Ford CFi systems work??

Reply to
Roger

OK, the following should be checked for excessive fuel consumption, which is roughly a similar fault:

Timing. Fuel Pressure. Engine Coolant Temp (ECT) Sensor. Throttle Position (TP) Sensor. Manifold Absolute Pressure (MAP) Sensor. Heated Oxygen (HO2S) Sensor. Oxgen Sensor Heater. Idle Air Control Valve. Park/Neutral Switch. ECM Earth. EVAP Canistor Purge Valve. Intake Air Temp (IAT) Sensor.

Reply to
Conor

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