My Maestro Turbo woes!!!

[Raptor]

Hi, can anyone help me please? My MG Maestro Turbo has been laid up for over 8 weeks now and the fault it is suffering with cannot be diagnosed by myself or 2 local garages. In that time the following new or replacement items have been fitted: carburettor with stepper motor, fuelling ECU, spark plugs, leads, coil, distributor cap and rotor arm. The car is till playing up. What happens is that the car will idle, but not smoothly. It will run in a fashion up to around 3000 rpm, but over this (coinciding with the turbo starting to whistle), the revs drop off as if there is no fuel coming through (though the fuel pump works fine). Diagnosis with an original Rover testing kit suggested there was no signal being received from one of the 2 temperature senders, but this seems to have been rectified. What on earth is happening?

The only other thing noticed is that there is nothing inside the black and red 3-way junction in the breather – this is described as a regulator valve in the original Rover service manual, Fuel System Turbo Charger p.7. Has something fallen out? The 3 outlets go to a. the 1 way valve in the inlet manifold b. the breather on the engine and oil cap and c. back to the air cleaner.

If anyone can shed any light, please respond. I can be reached on 07947 435185 or would be happy to phone you. Cheers.

[steve smith]

i speak to you tomorrow about the problem at the show..

steve

[G Force]

It will run in a fashion up to around 3000 rpm, but over this (coinciding with the turbo starting to whistle), the revs drop off as if there is no fuel coming through (though the fuel pump works fine). Cheers.

There could be more than one problem concerning the idle & rough running, but this particular problem sound like the float chamber vent valve is stuck open.

Locate the vent valve solenoid which is fastened to the bulkhead under the servo area. Follow the rubber pipe to where it connects to the carburettor float chamber. Remove the pipe from the carb, then with some thing suitable block off the brass stub pipe of the carb its self. Drive the car to see if it cures the cutting out at 3000rpm.

There should be a plastic top hat shaped small restrictor in the breather hose where it connects to the 1 way valve in the manifold. If this is missing it will cause rough running at idle and light throttle.

[G51 NAV]

Split balance pipe can also give rise to similar symptoms.

[E_T_V]

As above, or a split in the carburettor balance pipe (between the carb and the inlet manifold). They very commonly split and are a bugger to trace. As soon as the turbo comes on boost it blows the fuel out of the carb and it conks out.

Also check that the pipework on the carb is right as there are lots of cars out there with the wrong pipes in the wrong holes so to speak.

Lastly give the fuel pressure valve a good tap (whack) with a hammer on the top. As very occasionally they can stick if left laid up for an extended period and the shock brings them back to life usually.

[E_T_V]

D'oh my post was too slow!

[mgdavid]

D'oh my post was too slow!
but was more thorough :-)

and also it could be a pinhole or tiny split in the boost pressure hose going to the fuel pressure regulator...