MG TF cut out and unable to restart

Right, firstly apologies if my search technique has been poor but been looking for a few days and can't locate the same symptoms as I am experiencing with my 2005 TF 1.6.

Driving home from a shopping trip last Thursday and slowing down approaching a set of lights car just cut out and hazard lights were activated. Car would not restart. No loud bangs when it went and AA guy said it sounded ok when cranking, Cam Belt and Water Pump done about 20k miles and just over 4 years ago along with HG certificate from Trophy Cars on that.

AA recovered after being unable to get it going but found Fuse 2, one of the 30A engine management ones under the bonnet had blown. Tried replacing and its blowing as soon as ignition is switched on, even tried a 40 amp one and same happened.

Weather has been pants so haven't been able to get the hard top off and start removing the t bar to get at the engine and fuel pumps but wondered if anyone had encountered anything similar with the hazard lights being activated with the ignition and not from the switch. Could a fault in the fuel pump cause the fuse to blow?

I am going to get access and remove connections to Inertia Switch and Fuel Pump when I get the chance but thought I would ask here as the hazard activation is perplexing.

Cheers,
AJ

That sounds really weird . Well I would start looking at obvious areas like the boot wiring by hinge on the nearside . I have heard of loads of problems caused by wires that chaff and rub together but not heard anything like this .
I have no doubt that the good folk on here will come up with something that will point you in the right direction.

John

Fuse number 2 of 30 Amps operate inertia switch and Fuel Pump Relay. I would first check Fuel Pump Relay if it is melted or broken andmremove it completely to see if then fuse will blow. If not relay might be problem. If yes, you might have problem in wiring to relay.

So all relays in the boot were fine, removed the fuel pump relay and the fuse didn't pop, swapped relay with the starter relay next to it as they are identical part numbers and same, fuse blew again. Looking at the wiring diagram the only items down line from that relay are fuel pump and ECM. Check of voltage across the battery it 11.6 so its now charging. Hoping the hazard activation is some sort of low battery voltage warning.

When I get a dry evening I will get the hard top off, remove the t-bar and speakers to be able to get access to the fuel pump and try disconnecting that and see if the fuse still blows. Reading that the fuel pump is only energised at when key is turned to position 2 is making me hopeful this could be the issue but its the hazards thats confusing me, can't find anything similar in any forums of information online.

**Edited to add found green wire at boot loom has broken which should hopefully fix 3rd brake light when I get round to fixing that**

So I tested the relays using this guide http://www.autoshop101.com/forms/hweb2.pdf (page 14 on) and went through things and could find no issues. Cleaned up the battery terminals and connections, replaced fuse 23 in the footwell, even though it was not blown there was some discolouration to the legs. Battery was showing 80% on charger and wanted to get safe before rain started so decided to do one final test by adding the 3 relays in the boot one by one, testing the ignition between adding, to see if the fuse under the bonnet blew and it didn't. Gave the key a turn and vrooom fired into life. :woohoo:

Battery connections were showing 13.99v with engine running and dropped to 12.92 once engine was off. Will check what the battery is showing in the morning and may take it to the local motor factors for a load test. hopefully looks like a potential combination of low battery and dirty/poor connections.

Had to post back as one of the most annoying thing I find with forums is the vast majority of OPs never respond with a final resolution once they are sorted.

Thanks @Roverlike and @sworkscoooper for the pointers and helping find some other items for me to fix

Your comment in the last paragraph is gratifying, it really ticks me off when the guys on here use all their combined experience to help some poor soul & then nothing. Did what was recommended work, was it not worth the bother trying, did it end up in a sheet of flames & a large insurance claim. Some of us have spent a lifetime buggering about with cars, some for fun,other for fiscal expediency & some to feed themselves, along the way we've accrued a wealth of knowledge, then someone hops on takes what's free & doesn't say thanks.
So thank you aj76, even though I didn't contribute I'll sneak a bit your politeness to make up for the times we've been pissed on.
Welcome aboard

+1 good to see a new forum member providing useful feedback on a resolved problem.

Just one Q did you repair the green wire in the boot prior to it springing into life?

The poor old boot hinge does get some stick (most of it justified I think) but if ones gone??? I hate to be a merchant of doom but maybe all that opening and closing of the boot has remade a dodgy connection albeit temporary. Your opening thread thread mentioned shopping did this go in the boot just before the breakdown?

To echo what was said thanks for closing this thread or have I just reopened it!

I didn't repair the green wire, confirmed from the wiring diagram that its the third brake light and not circuit that was blowing the fuse, its going to an auto spark to have that repaired and the garage I bought it from is covering that luckily enough. Its just too close to the main loom for me to feel confident making the repair without causing other damage.

I had dropped the shopping off and driven approx 3 miles since boot was last opened when the car cut out.

I had wiggled the wires in the boot loom area and was still having issues with the fuse blowing.

Battery voltage checked and was less than 12V so put on charge

Chain of events in last session before getting it running.

Whilst battery was finishing charge removed all 3 relays from the boot near side.
Using the guide mentioned in previous post, tested the relays using multimeter, test light and one of my motorbike batterys.
new 30A fuse in bonet Fuse 2
Identified Fuse 23 in passenger compartment was also part of this circuit so due to discolouration on the legs opted to change this for a new 15A fuse
Fitted now 80% charged battery (as it was charging on outdoor socket and rain was due) using a green scotchbrite to clean the battery terminals and connections
Refitted the relays in the boot one at a time, after fitting each one turned ignition firstly to pos 2 to check for hazards before trying ignition. Fitted fuel pump relay last of the 3
With car running wiggled boot loom just to be doubly sure.

After leaving the battery overnight with my isolator switch turned off it had dropped to 12.3V, the start was laboured a little but it did start but from my understanding that would indicate a failing battery of about 70% health

I went through the paperwork for the car and found the battery reciept, was new beginning of Feb 2022 and had 3 year warranty checking on the suppliers website. Called their local branch and they agreed to replace under warranty. It was a cheap own brand battery i had never heard of so opted to pay a little extra for a brand I have more confidence in.

Used some cheap wire drill brushes I had to really clean the battery connection and also the earth strap connection and fitted the new battery and used dielectric grease which was not used previously.

can a short in the boot hinge loom affect the engine management loom?

I've just posted this issue with mine
https://www.the-t-bar.com/forum/9-mgf-tf-pitstop/98465-map-sensor-reading#202353https://www.the-t-bar.com/forum/9-mgf-tf-pitstop/98465-map-sensor-reading#202353

but I've also noticed the alarm has become temperamental in the past month too, and that can be a symptom of a break in the boot hinge loom, I've read

So the MG died again the other day, exactly the same just cut out and would not restart with 30 amp fuse 2 blowing.

Tested all the relays in the boot again and found that fuse 2 blew only when ECM relay was put in. So am I looking at the ECU thats in the boot or is there another unit I should be looking for?

Edited to add, having removed the ecu the fuse only blows when the small connector at the top is connected so guessing it is that unit. Will be looking for someone local to test it and hopefully it is the fault and can be repaired

The immediate blowing of 30 amp fuses indicates a dead short somewhere…… 30 amps is a fair bit of current.
If the problem resides within in the ECU, it will be buggered!