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Head Scratching Time 9 months 2 weeks ago #202140

97 MGF Non-VVC
Daily runner for last 2 years, no issues at all
Non-starter after 2 days not used (garaged). Turns over but doesn't fire.

Has:
Strong spark, compression, correct timing, fuel (smells like it might be getting too much?) but still won't fire

Replaced:
Battery, ignition coil lead, plugs, coolant sensor, crank sensor, fuel & air filter
Had the HG and water pump replaced before I bought it.

Checked:
Fuses, earthing points, relays, inertia cutoff switch, timing belt and timing etc

Alarm/immobiliser all working as should. Fuel pump primes as normal.
Has never lost coolant or dropped oil etc, has started first time everytime in last 2 years
Just won't fire - head scratching time now - any advice before I cut my losses and sell as a non-runner

Cheers

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Re:Head Scratching Time 9 months 2 weeks ago #202142

Have you got or can get hold of an OBD Scanner or pscan they is the best way to start diagnosis

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Head Scratching Time 9 months 2 weeks ago #202143

Ok let’s go through things in a logical order, we maybe covering ground that you’ve already covered but by doing it in an order it sets shit to bed in my mind.
Have you done an OBD diagnostic check with a Testbook T4 or a PScan? If not you might save a shitload of time and money doing so.

You said that you’ve changed the spark plugs, I assume you checked the gaps before installation.

When you say you have a strong spark, where did you take this from…..the coil lead or the plug leads?
If you took it from the coil lead, please check the spark from the plug leads.
If your spark isn’t a nice fat juicy zap you should check the dizzy cap and rotor, may as well check the plug leads too while your at it.

When you say that you checked the timing, I gather you used a timing light, had you at anytime adjusted the timing in recent history? If the answer to these two questions is yes, check the harmonic balancer isn’t failing…has the outer pulley rotated on the centre? If yes replace the harmonic balancer and reset the timing.

So now we should’ve established that we are throwing a big healthy spark an the appropriate time and place.

Let’s now check that all sensor plug connections are properly fitted and going to the correct sensors, whilst doing this we need to make sure all the terminals are clean and free from corrosion. Test all sensors with a multimeter to see that they’re within specs.

Now we hope we have established that the ECU is getting all the correct information to make the car run.

Next is check the fuel system a pump pressure and flow rate test. Failure here and you should try a new filter and retest. Further failure, replace the pump.
Then the injectors, should be tested for flow rate and spray pattern. Failure here and you should ultrasonically clean the injectors and replace the nozzle tips then retest, further failure, replace injectors.
Test signal is getting through to the injectors by plugging in noid lights into the injector harness, if the lights don’t light up when you turn over the engine, then you need to find a wiring harness problem.

Now we have established that there is nothing likely to impede fuel getting in.

When we had the spark plugs out did we do a read of them, did they have deposits, black fluffy carbon or oil shit on them? Was one or more too clean as like steam cleaned?
Do a compression test, and whilst you at it a cooling system pressure test, let’s establish that the head gasket that was new when you got the car is still good now.

Another thing to check is the exhaust, in particular the cat converter isn’t falling to bits and those bits haven’t clogged up the muffler , en exhaust pressure test is the easiest way of doing this it shouldn’t read over 2 psi but I’m the only person I know that has the gauge for this, so I don’t like your chances of finding someone who can do this test, you may have to resort to pulling the exhaust apart and see if it rattles when shook.

I know that you’ve replaced a lot of items, so you need to check that they’re within specs, never trust a new part without checking it, sometimes they’re worse that the ones you replaced, especially if they’re rubbish from China!

Once you’ve ticked all these things off the list and you still can’t get the bastard to go, get back to me and we’ll seriously get all forensic on it’s arse!
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"
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Last edit: Post by Cobber.

Head Scratching Time 9 months 2 weeks ago #202144

Let’s work back on this one. You’ve had it for a couple of years & I guess enjoyed the experience, once it went adrift you were sufficiently inspired to work through your list & it’s pretty comprehensive, however the think that’s causing your problem isn’t on your list; find that & you’re off for another few years of happy motoring.
As a runner it has a value, probably in excess of 1k as a non runner you could be unfortunate to have to pay to have it taken away, like a chap in our village. Although this is unlikely.
If you spend a couple of hundred quid you could buy a pscan sort the job out & still have the pscan which there would be any number of folk on here jumping up & down on here wanting to buy a slightly used unit, providing you hadn’t become besotted with it in the interim.
Now this is just a thought & I have a bit of a reputation for looking at things in oblique way, as many of my friends & family will attest; it has served me well & has helped a number of folk around their road blocks.
And what would you replace your MG with that is so affordable & would you enjoy its dynamism on the road.
As I say just a thought.
Mike.
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Head Scratching Time 9 months 2 weeks ago #202145

I notice you’ve got Cobber sniffing around your exhaust, he’ll tease out the problem with wise words, sarcasm & well placed swearing. Even from the other side of the world he will diagnose almost by telepathy.
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Head Scratching Time 9 months 2 weeks ago #202146

Thanks all - one of the reasons I love this forum, never a shortage of solutions, advice and experience!

ODB Test only showed a faulty coolant sensor, which has now been replaced and ODB not showing any fault codes (annoyingly)
Forgot to add its had a new ignition coil too.

Cobber - Thanks, fuel pressure check tomorrow and get the muti-meter into the sensors. Couple of the old plugs when pulled did look fairly 'washed' - but then it had been cranking a fair amount and not starting - other 2 were blackened and had carbon build ups. In terms of exhaust, it had a new flexipipe last Nov - but will have a look at the rest while its on the jacks.

Airportable - love this little motor and would begrudgingly replace with another. This one is a Japanese spec, bodywork and paintwork are very straight, no rot, no major dings and only just gone through 30k miles. Got it for pennies so it owes me nothing, but as is the norm with older motors - repairs and maintenance have hugely outstripped the original purchase price!

Cheers

SAT

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Head Scratching Time 9 months 4 days ago #202342

Good news is that this particular MGF lives once again.

Retraced a few steps on the back of great advice from Cobber - fuel pressure/flow rate test which threw up a few issues. Replaced the fuel filter as advised (despite fuel filter being new) - and started first time - go figure.

Pulls as it should, idles at right speed, seems a little lumpy when pulling away in 1st at junctions after running for 10-15 mins, but maybe just needs some miles in it.

Thanks to Cobber for the advice matey

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Head Scratching Time 9 months 4 days ago #202343

My pleasure.

You might’ve got some dirty fuel, possibly you filled up just after the petrol station got a load of fuel delivered, stirring up all the shit in the servo’s tanks and pumped straight into you poor unsuspecting car.
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

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