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MG MGF Technical - intermittant non starting mgf'96

i have a '96 mgf (not vvc) been at caffyns for almost a month now and has had - new leads & plugs, new coil, new crank shaft sensor been on their computer many many times with spiralling costs they still cannot find a fault, the car seems to be flooding the new spark plugs everytime after every few days - does anyone have any ideas ?? many thanks

Presumably they're now confident that it's not an ignition problem - by an expensive process of elimination 8-/ By deduction, it must be over-fuelling, possibly due to a faulty sensor on the throttle? If the fuel injectors are pumping in too much fuel, that means the ECU is instructing them to do so; either the fault lies with the ECU or the sensors that it takes its information from.
Mike Hankin

many thanks mike, i have heard today that the ecu is still not showing any fault, and it is still over-fueling, they are going to replace the coolant sensor - so ill have to wait again and see....ugh !!
j westbrook

Another prime suspect is the fuel pressure regulator. Checkout the vacuum connection to the regulator, if there is no vacuum applied that can cause over fueling at startup and tickover. The regulator can accumalate gummy deposit and stick, raising the fuel pressure and causing same over fueling at startup. A good dose of Redex balsted through with compressed air helps. REMOVE THE FILLER CAP FIRST. A quick test when it won't start is disconnect the fuel pump electrics then wind the starter, it should start.

Good luck.
Ken Waring

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Hi Jo
Sorry it,s taken so long to answer but I,ve been stuggling with the same problem myself.

Believe it or not I put 10 ltrs. of petrol in and the car started at the third attempt. this is the third time the same thing has happened, in fact the reason I bought the MGF in the first place was because it refused to start for the previous owner so I got it cheap. I don,t know why this should be the case, the car had plenty petrol in before I added the new stuff, perhaps it had become contaminated with water from condensation. Please try this and let me know the outcome unless of course something else worked.

hi gerry, thanks for your comments, i have finally got the car back,(after 2months at the garage)it had a new coolent sensor put in it after the crank shaft sensor and that seems to of done the trick. i'm still not 100% sure and confident with it as yet but so far so good, i don't think it was anything to do with how much petrol was in it tho. kind regards,jo.
j westbrook

car was starting fine for over a week, now gone back to over fuelling and not starting, i have bought a spark plug remover tool and have learnt to dry spark plugs - replace - and to restart...does anyone have any ideas why it is over fuelling, as in previous notes caffyns(main dealer) have no idea !! obviously i am very reluctant to return the car the caffyns for another 2months!! many thanks jo
j westbrook


Sorry to hear of your tale of woe.

I assume that you actually can get the car started. As you say get plugs out dry and then put back in ?

So do I assume from that it eventually starts and then runs normally, or can't you tell as you say it was fine for a week and then acted up again ?

I was just wondering if was related to cold engine versus hot.

If you are able to get the car started and it runs will it then re-start again without problems, ie its now a warm/hot engine and it starts without problems then ?

Will it sometimes start ?



Try the Fuel Pressure Regulator. See my previous post. You could get a used part quite cheaply, any halfway competent mechanic can change it.
Ken Waring

hi brian, it dosent appear to be a hot or cold problem, when it was at the garage we had all weathers even snow one day and they had left it out, and it is always garaged when i have it - it works for about a week or so perfectly then stops for no reason. yes they checked the fuel pressure regulator.
j westbrook

Have you tried Distributor cap & Rotor arm? I couldn't see anything wrong with mine but after I changed it the car started first time and ran like it was intended to.

yes both are brand new.
j westbrook

Have Caffyns ever considered that the ECU may be the root of the problem? Not sure if it can be effectively tested (swapping it seems to be the normal 'diagnostic' method), but perhaps worth eliminating?
Mike Hankin

What are the test results from an exhaust gas analyser? You mention that the car appears to be flooding the cylinders with excess fuel: is this a persistant thing, or is it only related to cold starts?

If only related to cold starts, the finger of blame starts to point at the IACV.

If the Lambda on the exhaust gas analyser shows an over-rich mixture (and the exhaust will be sootier than normal), consider the possibility that the exhaust system lambda sensor is malfunctioning (although this shouldn't cause flooding on start up, it could result in caked up spark plugs...)
Rob Bell

Way back in late '96 I had problems with starting/running of our '96 MPi - the problem was resolved by the dealer fitting a new ECU - still under warranty then so free of charge - not had a problem since!
Ted Newman

thanks all but all sensors is definately not related to cold/hot/damp starts, as it happens any weather. caffyns couldnt find an ecu to be swopped to see if that was the problem, the spark plugs arent really caked up they are more dripping wet with fuel.
j westbrook

This thread was discussed between 13/01/2007 and 29/03/2007

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