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MG MGF Technical - Rover 200 Starting Probs (no F content)

Ok... Diagnostic hats on people please:
Rover 214 Sli (SPi)

Have replaced air filter and plugs- all plugs fireing correctly (fancy tester)
Runs correctly when going and starts up IMEDIATLY after stopping
Refuses to start from cold / slightly warm, after experementing with spraying WD40 directly into (the thing which used to be a carb?) the car starts.
Also the car starts first time if I tightly stuff a rag into the air intake (to the filter).
I am guessing a problem with the Choke?
1) does it have one ?
2) what is the stepper motor for and how can I check it?
3) any other ideas?


Go on, there must be some partialy educated stabs in the dark?


Fuel injected engines come with a cold start fuel injector located at the end of the manifold, which gives shot of fuel at start up. Yours may be faulty. Your WD40 shot seems to provide surogate assistance.

I don't own a MGF, so I don't know where it is. But I'm giving it a stab.
a stabber

Would that make it start OK with the intake (mostly) blocked?


I don't know. Perhaps, by blocking the intake with the engine cold, you create a richer than normal mixture at start-up with the regular injectors and the use of WD40. This may be why the engine starts and continues to run.

You hypothesize that the problem may be traced back to the choke. Well, I think this a reasonable guess. The cold start injector is "the choke." When the engine is warm, your engine restarts because the cold start injector is not needed.
a stabber

There is but one single injector, hence the SPi designations all fuel is controlled by this one injector.

Cold start enrichment is achieved by the system reading the coolant temp and ammending the injector open time accordingly. This allows for the extra fuel that would normally be added via a choke.

I would firstly suspect that there is a duff coolant temp sensor, the one which is easy to get to on the small alloy coolant pipe stub that comes from the right front of the head. Not the one you have to remove from underneath that same stub.

A sensor that is providing less internal resistance will be telling the MEMS control that the engine is apparently hotter than it is and as such will not inject as much fuel.

Another issue can be the injector itself now that these SPi engines are really quite old and will have potentially passed many thousands of gallons of fuel. Each time that the injector passes fuel some aill wet the end and when the ening is switched off this fuel will evaporate and leave deposits. Over time these are built up layer on layer and with heating become quite solid, just like varnish.

Now normal MPi injection systems suffer more from this problem as they have a smaller nozzle, but over time it is quite probable that the injector has become slightly clogged and flow as well as spray pattern is likley to have become interupted. Application of off the shelf injector cleaners can often improve things, but usually only by small amounts for short periods. However if treatment does provide an improvement then it is worth having the professional treatment done which uses a very volatile liquid that 'eats' these deposits. Speak to your local tuning outlets. I favour the 'on the car' treatment rather than off the car as it also does a damn good 'decoke' as it does the injector.

Another thing that can affect these SPi cars is a break in the power to the inner manifold 'porcupine' This is a heated circular spiked addition which fits into the underside of the manifold and which has an internal heating element. These are designed to assist with mixture mixing and deterring fuel from condensing and lying on the manifold base.

I also expect there to perhaps be other minor issues, perhaps with the ignition side of things, rotor arm, cap, leads and plugs especially, which is not giving a strong enough spark to ignite a weakened mixture.

Roger Parker

This thread was discussed between 18/12/2001 and 23/12/2001

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