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MGF non starter

6K views 27 replies 8 participants last post by  dert 
#1 ·
Hi All,

After 6 months of surprisingly trouble free motoring from our 2001 MGF, I have an interesting non starting issue.

After driving a couple of miles down the road to the petrol station, filled up, got back in, car was cranking, but wouldn't start.

AA came out and after trying (And failing) to get their diagnostic to connect, came to the conclusion that he wasn't going to fix it and towed me home.

Car is cranking fine, has randomly started and run fine a few times, but more often than not, there's no life.

Have looked around the internet, and can't find anything that seems to match the exact symptoms. all seem to be no spark and no fuel or no spark and fuel.

So here;s what i've done/found so far...


  • No Blown fuses
  • It kicks over on a sniff of easy start.
  • Checked there's a good strong spark to all cylinders
  • pulled the spark plugs - fine, but completely dry... which lead me to the fuel system.
  • Checked (and completely bypassed just to be sure) the cut off button
  • Fuel pump is priming and running on crank
  • Plenty of fuel flow and what seems like reasonable pressure from the outset side of the fuel filter (but replaced the fuel filter anyway)
  • Back probed the injector wiring with a noid light - noting at all, until one of he rare occasions it runs, when you get a good steady pulse as expected.

So, i'm thinking we have an issue that is causing no electronic pulse to the injectors rather than any mechanical/injector issue and thinking crank and cam sensors are ok as reliable spark?

I'm thinking ECU / immobiliser issue possibly? But immobilisaer light goes out fine and surely the immobiliser would cut the fuel pump rather than injector pulse.

Any suggestions very gratefully received!

Thanks
Matt
 
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#2 ·
First and foremost you need to scan for codes via the OBD port.
 
#5 ·
Thanks, hadn't thought of that.

I'll pull a jar full from the fuel line and check for water.

my only doubt would be the electrical side of things - there's no pulse to the injectors, surely if if was a fuel quality issue, there'd be a pulse but no/wrong fuel.

Worth a try though!
M
 
#6 ·
Get a can of easy start and spray directly into inlet manifold throttle body (remove flexy pipe between air box and throttle body) while you have someone cranking the engine over. If it doesn't fire, its not a fuel issue and is more likely to be electrical
 
#8 · (Edited)
It can't be polluted fuel, as there would have been still good fuel in the system when you tried to start at the gas station. Also others would be suffering the same problem.
It sounds like some thing is shorting to ground, or you immobilizer isn't seeing the key.
Not sure from memory, but does the MGF have a immobilizer symbol that goes out when you turn the key.

Try bump starting the car, a dodgy starter motor can pull the system voltage low causing various not start issues. Also so could a weak battery.

Be careful of easy start, a car can sometimes run on it even without a spark, just compressing it can set it off. So you can get caught using it.

Measure the voltage during crank at the battery
 
#10 ·
Thanks for the warning, its only been used the once just to diagnose so it should be well out of he system by now.

Battery seems ok, passes a drop test no issues.

The turn over seems as fast as normal, just tried it now and voltage stayed above 10v on crank. Then it decided to start for no particular reason - had it running for 20 minutes now with no issues, smooth idle normal rpm. I'll let it run up to temperature and see if it will re-start.
 
#11 ·
Thanks, will try all of those in the morning.

I've only currently checked the pulse at the multi plug near the throttle housing, so trying at the ECU would be a good idea.

I've replaced the crank sensor today (as my local parts place had one in stock) which didn't help.

Crank sensor seems to be working fine, but hadn't thought to check at ECU - my electrical fault finding experience has mainly been on an old Midget 1500, so not that many computers to worry about ;-) (Just rust... lots of rust)
 
#12 ·
Well, ran up to temperature, start, idle then off 10 times in a row, no problem.

Then turned off, locked the car, waited until the alarm light stopped flashing (which i assume means alarm and immobiliser are armed?).

Opened up and tried to start again, not starting again!

Hopefully checking at the ECU will show something tomorrow

Thanks for all the suggestions everybody
 
#14 ·
Random suggestion - have you tried changing the battery in the remote fob(s) and then synchronising again? (pressing each button alternately several times).
 
#15 ·
This sounds like an immobiliser problem where it is not releasing correctly. I had exactly the same problem when i reconnected the car battery after winter storage. The red immobiliser light would go out after i used the remote unlock button and i would try to start the car. It would turn over, but not fire, maybe on the odd occasion it would fire for a fraction of a second and then stop.
I would take the suggestion above and change the remote battery and re-sync the fob to the ecu. If you know the EKA code then you could try entering the car by using the EKA as this is another way to turn the immobiliser off.
Good luck and please keep us posted.
Nigel
PS, in your last reply you say you locked the car with the remote and waited for the red led to stop flashing. The red led should always be flashing when the immobiliser is active and should extinguish when you press unlock on the remote or use the EKA.
 
#16 ·
This problem looks like imtermittent problem.
I would suggest to re-check the fuses, and even replace them although they might seem fine. Two things might happen: fuse is holding on tin wire ready to give up, or you have corrosion on fuse terminals which might happen during time.
Corrosion might be removed if you pull and return fuse to,its terminals.
Here I am talking about fuses 1 & 2 in engine compartment fusebox and fuses 14 &19, especialy this 19 from under steering wheel.

Second problem might be in your ignition switch. You might have problem with switch itself on the very bottom part where it makes eletrical contact when turned.
 
#19 ·
On filling up the op said it wouldn't start. The fuel rail and system would still be full of the fuel he arrived in.

Quality control on fuel is a lot better then most give credit. It does go wrong now & then but not often.

I did pick up some crappy diesel once that blocked my Audi's fuel system, so I can happen.

But he has no injector pulse so this is electrical for sure.
 
#20 ·
Hi All,

thanks for the suggestions & sorry for delay in replying, been mad with work and trying things when i get a chance.

So all connections from ecu to injectors (positive and ground) have reliable continuity.

Tried re-syncing the remote after changing the battery.

The talk wasn't empty when filled up (and as mike mentions, there's no electrical pulse and perfect running when it decides its going to pulse)

What i have been able to find is it tends to start after sitting for at least 12 hours. It will reliably re-start as long as the immobiliser doesn't engage (when i said the red light stops flashing i wasn't clear, i meant stops flashing rapidly and return to normal "armed" flashing every few seconds) Every time without fail after letting the immobiliser engage it won't start again (repeated this 5+ times now).

It's not a warm start issue - as I've run up to full temperature, stopped the engine without arming the immobiliser and it starts perfectly every time regardless of engine temperature.

This leads me to think it's an immobiliser issue:

So, does biting the bullet and replacing the ECU and immobiliser unit make sense at this stage????

From what I've read, it's a relatively simple as long as you replace with like for like part numbers and replace the ECU, 5AS unit and fobs at the same time? (Some packages on ebay have the alarm sensor too - i'm assuming that is coded too so will probably go for one with that too as it doesn't seem to make much difference to price) is there any software update required as long as the above parts are replaced with a matching set?

Thanks again,

Matt
 
#21 ·
Matt,
Good to hear you have narrowed it down.
If you know your EKA it would be good to know if using this to open the car after the immobiliser was active allowed the car to start. This would point to the radio side of the immobiliser being defective and mean you only need a replacement 5SAS module. It would also help others with the same problem be able to start their cars.
Do you have access to a PSCAN unit? This would allow you to reprogramme a replacement 5SAS unit to your MEMs ECU.
Where are you located? it may be that someone nearby has a PSCAN and would help with the resync.
Nigel
 
#23 ·
Hi Nigel,

No EKA code unfortunately, could kick myself for not checking it had it knowing what i know now.

It seems to be pure luck whether the immobiliser property disarms or not, but leaving longer seems to increase the chances of it working.

Don't have a pscan, but was debating investing in one, but wondered if they're worth the money, sounds like they are! I'm in south Liverpool if anybody local can help?

(I'm decent with the old mig welder to return the karma)

Thanks
Matt
 
#24 ·
Well, the ECU relay pack came this morning... not that either... i wasn't expecting much, but worth a try eh!

Been debating whether next move should be to invest in a p scan, at least then it looks like i'd be able to get some decent live data out of the ECU or to get a matching ECU set off ebay.

Going to go for the cheapest (but possibly not wisest) option
... off to ebay ECU shopping.

I'll update once it arrives!
 
#27 ·
Hi All,

Well, the replacement ECU set arrived today

Painless installation and success!!!

Car's now starting, every time, even after immobiliser being freshly disarmed (almost immediate start on crank, as opposed to half a second or so before so the issue could have been brewing for a while)

It's still in a state of disassembly so probably won't get it out for a drive until the weekend, but all looks good.

Thanks so much for all of your sound advice - who knows, one day I might be some use in return :)

Thanks again
Matt
 
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