Mfru problem?

[JonT]

1.6 k series. Just arrived donington for a track day and the car won't restart. Mfru just clicking away madly whenever i engage the stater.

 

Already has an external relay bypass. Any ideas?

 

Was slightly reluctant to restart after getting petrol on the way here but otherwise has been fine.

[SM25T]

Battery failing ? Small wire down to solenoid from relay failed inside insulation near primaries, loose connection on any of the fat black or red cables from battery to starter or alternator, or earths to engine and chassis

[Jonathan Kay]

Private Message sent.

[JonT]

Thanks Jonathan. Now seems like complete electrical failure. Almost certainly something trivial given it drove here this morning, but don't think I'm going to fix it in the pit garage :(

[SM25T]

How old is the battery. Mine experienced sudden death syndrome last time out.

[SM25T]

See if you can jump start or push start it. If it runs ok on alternator, possibly dead battery.

[JonT]

Battery is newish. I've just limped home. We got it bump started but I wasn't prepared to go out on track. Seems to run OK although idling at 2000rpm. Driving home seemed the better option than recovery. Nothing even clicks now when i turn the ignition on. Will double check battery voltage but i think it's OK. Wondering if it might be the fia isolator switch or ballast resistor.

[SM25T]

Those FIA switches are a known potential source of trouble. Try bypassing it by connecting inlet cable to outlet stud. If all ok, replace the switch.

[JonT]

So I've been checking my records - battery was new Nov 2017, however during early 2019 the car was off the road for a while at 7workshop, so maybe that didn't do it any favours? It's usually left on a CTEK at home, so that might have hidden a brewing problem? Having said that, it started fine this morning first thing.

But having stuck a voltmeter on the battery a couple of hours after getting home it's on 10.5V. I checked on getting home and it was seeing 14.5V ish, (and it got me home!) so alternator is good.

Going to start with a battery and see how things go from there. Then I just have to sort out all the other bits of electricals I was fiddling with trying to get it working at donny 

[SM25T]

What does it drop to when you turn on the ignition, and then when you press the starter ?

[JonT]

So the plot thickens. New battery fitted, and I started sorting out the other bits of wiring I'd been fiddling with. I've got a fan override switch and lights on buzzer fitted behind the drivers knee panel, and I was suspicious something there might not be right. Some of the grounds are connected one of the mounting bolts on the battery isolator (ie so definitely connected to the scuttle/chassis and should be ground). Wierdly I measured 10V on that pin when the ignition was on. So I pulled off my additions, and it's still doing it - so now I think it might be the isolator. In any case, I've ordered a new one.

I also stuck the ammeter on the battery - it was showing ~100mA off (which seems high). Turning the ignition on, it pulsed to 5A while the fuel pump primes, then back down to ~1A. Wasn't going to try starting as the multimeter is only rated to 10A. However turning the ignition off, it was still showing 0.5A, which disappeared when I turned the isolator off. So I suspect the reason I couldn't see a short is because it's the isolator and it's shorting directly to the chassis, which is a pretty big ground and has a fat supply cable.

Anyway, I'll get the new isolator fitted and see what happens. Meanwhile I've disconnected the new battery to save that! 

[revilla]

Quite normal to see a high drain for a few minutes after turning off the ignition. The ECU remains powered up. It does a few little housekeeping jobs like recycling IACV but more importantly ... in a Rover (where it thinks it is!) it would continue to monitor the temperatures and run the fans for a while of required. After a while it switched itself off by turning off the Main Relay and the drain will drop off.

[JonT]

Ah, thanks, that's useful to know. Yes, I head the IACV recycle but it had finished by the point I was still seeing 0.5A.

[john milner]

As nothing clicks (#7) it sounds like the starter button has failed.

Also relay replacements can fail in the same way as MFRU relays.

[JonT]

With the new battery it starts and runs fine now (sorry, should have updated that bit). But my concern now is that the new battery will get killed in short order if there's a short somewhere causing undue drain. The fact that a mounting bolt on the isolator appears to be at 12V when the ignition is on definitely isn't right.

[john milner]

I would expect a mounting bolt to either be totally isolated from the electrical system or more likely connected to the battery via earth. Anything else and there is probably a short circuit somewhere. A voltage of any type sounds wrong if controlled by the ignition. Could there be a poorly wired FIA switch? FIA switches should have a resistor to dump alternator current to ground when turned to off so perhaps something is wrong in that area.

[JonT]

Exactly - new FIA switch is on order...

 

[Wrightpayne]

Have you had a good look at the connections on the inside to see if anything wrong?

[JonT]

New isolator arrived yesterday and fitted. Car ran fine, but playing with the voltmeter I was still seeing 10.5V on the isolator mounting bolt in certain conditions. I got fed up and left it overnight, but carried on thinking. 10.5V suggests some sort of potential divider, or some resistive connection. So instead of measuring voltage, I changed the meter to resistance. Sure enough, the "earth" bolt wasn't actually a good ground, it was showing resistance to elsewhere on the chassis. I think that when the car got resprayed last year, Tony did such a good job the mounting bolt isn't actually making good contact with the chassis. So I've stuck on an extra earthing wire from that bolt to the another bolt (aeroscreen/windscreen bracket)

Now seeing 0 volts on the FIA mounting bolt (and of course 0 ohm from it to earth), and everything else seems ok. 

Not sure why it's only just shown itself as a problem <shrug>. Or maybe it's always been like that, and it's only because the battery died I started digging. Guess it would have been interesting if the FIA key had been needed in anger as it wouldn't have earthed the alternator properly on disconnection.