Sticking Diesel Throttle / Injection Pump

[garyd]

I have a 1.9Td AAZ engine fitted. I am now finding that the engine revs do not drop away properly when the throttle pedal is released. I have confirmed that the pump lever is returning directly against the stop but the revs remain high. The only method I have found to bring the revs down is to engage a gear and drag the clutch. Once down the revs stay down until the pedal is pressed again.

An injection repair specialist suggested a possible blockage of the fuel return pipe but this blows through very easily. Likewise the spill pipes on the injectors.

Any ideas, please?

Garyd

[andysimpson]

I have a 1.9Td AAZ engine fitted. I am now finding that the engine revs do not drop away properly when the throttle pedal is released. I have confirmed that the pump lever is returning directly against the stop but the revs remain high. The only method I have found to bring the revs down is to engage a gear and drag the clutch. Once down the revs stay down until the pedal is pressed again.

An injection repair specialist suggested a possible blockage of the fuel return pipe but this blows through very easily. Likewise the spill pipes on the injectors.

Any ideas, please?

Garyd

Turn fuel screw out 1/4 turn.

[caveman]

You can try Mr andysimpson says, but it is possible the bushing for the throttle lever is worn in such a way that it is now binding. Doesn't happen often but can.Also make sure the throttle cable is adjusted properly. Has it started since it's gotten colder? A cable adjusted when it was hot may now be too tight once much colder.

[caveman]

I have also heard of a sticking or plugged injector can cause such a problem. I guess it has to do with the bad injector messing with the internal pressure of the pump.

[Simon Baxter]

Have you been messing with the residual fuel screw?
To me, considering the cold weather, are you sure there is no water in the throttle cable conduit and that it has not frozen?
Happened to me in the past.

[garyd]

Thanks for your suggestions. I obviously didn't make it clear enough that the cable is not part of the issue. The effect can be created by moving the pump lever directly and seeing it return against the stop, leaving the revs elevated.

I will give Andy's suggestion of adjusting the fuel screw a go when I get a chance. (Tied up with decorating in the house at the moment!)

thanks
Garyd

[garyd]

OK, I have eventually tried Andy's suggestion of backing out the fuel screw by a quarter turn. This did the trick in that the sticking throttle symptom was relieved. However, when driving it there was a noticeable reduction in power. After a ten mile trip, which included passing it's MOT test, I wound the screw back in and it has remained OK.

Someone else has suggested that there may have been air collected in the fuel/pump/injectors as a result of it standing for several months. If that was the case, it seems to have cleared now.

Thanks for your help
Garyd