75ZT Community

Just looking for some advice. A friend of mine has an MG ZR with the 1.8 K series in it. And it's having trouble starting. When you turn the key, you can hear the fuel pump priming and everything getting ready, but the starter doesn't turn. If you hold the key round, it will eventually turn the engine over, and the engine starts absolutely fine. I've checked all the connections and there's nothing obvious there. When the car is warm, it starts absolutely fine. I think the problem is either the solenoid or a sticky pinion that's not playing ball. Wiggling the wires by hand while the key is turned seems to have no bearing on whether the starter motor works or not. I don't know whether it's a common problem on the starter motors or not and was just looking for some advice? Seeing as people on here will be more familiar with the engine than me...

It's more common on diesels but I believe all the starter motors can suffer from failed contacts in the starter solenoid. I have heard of it on V6s too so I'd be reasonably confident looking there. It being OK when warm could easily be explained by this, once the components in the starter have warmed up, they expand a little and contact is OK (for the moment).

Sometimes it can be the white/red wire on the starter being loose, or I've seen once where the relay inside the immobiliser was faulty and gave very similar symptoms on very cold days.

If it was the relay inside the immobiliser, would that stop the fuel system priming? Because you can hear the fuel system priming as soon as the key is turned, which is what made me look at the starter motor.

No the immobiliser relay problem only stops the starter motor operating. It's between the starter switch and the starter motor. I repaired one at an early Nano.

Ah I see. I will investigate further.

The car now no longer starts fine when warm, and also if you lock and unlock the doors while holding the key round it starts, but only if you lock and unlock the doors? Once it's started it's fine. I'm guessing something to do with the immobiliser rather than the starter motor. Can anyone give me some guidance as to what the problem with the immobiliser could be and if I need to change a part, whereabouts is it?

Using the lock / unlock is unlikely to be related. The locking / alarm and the immobiliser aren't linked in any way on 75s.

On the immobiliser fault I described, when there was a problem, if the owner held the key in the start position for a few seconds, the car would eventually crank. I reckon you might be seeing similar. Try holding it for a while without pressing the buttons.

The immobiliser is at the bottom of the A pillar. You can check the circuit using a multimeter. With the key turned, check for voltage on the thick white / red as it comes out of the ignition switch. Check it as it goes into the immobiliser, and as it comes out. Finally check the same wire at the starter solenoid. If the voltage is missing somewhere it will tell you where your problem is.

The longest it's taken the car to start so far is 12 minutes. It often takes at least three minutes to start. And the owner needs her car to start on the button as she's starting a new job doing domicilary care as opposed to working in a care home.

Thanks for your advice, I will check it out when I get the chance. I hope it's in the same position on the ZR as it is on the ZT, thought I doubt it is as the 25/ZR is a continuation of the R8 platform, using the same dashboard, same wiring loom, etc.

Doh.

I'd completely missed it being a ZR, I am a plonker!

The immobiliser and alarm system is totally different to a 75 in just about every way! Let me have a look at the workshop manual for the right car and try again.

What age of car is it please? There was a significant change in the body controller / security / immobiliser.

If I remember right it's a 54 plate, one of the very first facelift ones.

OK, I'm fairly sure they don't use the 5AS alarm / immobiliser, but a Pektron one. I used to visit the .org forums for the 45 I had, and I seem to remember that these did give trouble, but I never looked into it as mine was older. So it could be this. As it's so different to the 75, it may help more if you do some digging in the 25/ZR section of .org.

From what I can see the starter relay is in the underbonnet fusebox, so a wiggle or swap of this might be a good start. The relay is switched on by the immobiliser unit, and the supply to the starter comes out on a brown/red wire. Check if this wire is going live.

Thanks fot the advice Duncan, you're a star. I'll grab a voltmeter and test as soon as I can. From what I've been able to gather so far, it's the same system as on the Freelander/ Range Rover P38A. If so that'd make life a lot easier for me!

Probably similar to earlier Freelander, but not the same as 38a. That uses the BeCM for immobilisation, with HuF keys, whereas 25/45 use Lucas 5AS and Lucas keys and then Pektron immobilisers later.