[Mk2] [Turbo] MR2 rev1 intermittent power to starter

[archangel]

Hi all. Have a strange problem. Car cut out the other day as i was driving off a ramp after oil and filter change. Turn key and dash lights up, hear fuel pump running as long as i've disabled immobilizer, but nothing when i turn key to start. No turning, cranking or anything. Can't hear any clicks from efi relay. Pulled some fuses and all seemed fine and then it started up and i drove home. Now again it is having the same issue. No power to starter (tested using multimeter between big cable to starter and the little brown connector then tried turning key). While checking around in the engine bay and trying this and that it then started after i secured some loose cables, but now again same straight after. Does anyone have any ideas on things to check? Could the efi relay gone bad? Or is it more likely something loose somewhere?

[archangel]

So very strange. Gave up yesterday. Just wouldn't turn. Tried this morning and it starts. Don't get it. Haven't touched a thing. Have ordered a replacement starter relay already but just don't quite understand the behaviour.

[abovetherim]

Could be a failing immobilizer!
Also could be starter relay or wiring to it in boot.

I would first check ignition switch and wiring to it tho

[archangel]

So swapped the starter relay but doesn't seem to be that. It started up but after looking at some other issues (testing temp gauge by earthing the connector that's normally comnected to the water temp sender) it now isn't starting again. And hasn't sprung into life by itself like it has sometimes previously. Again the same thing where i turn key and nothing, press button to disable immobilizer which it does and then the hear the fuel pump and rest of dash light up but still no turn over or starter relay click when i turn key all the way. It does sound like it could still be the immobilizer that may not be activating the starter relay circuit but not quite sure how this works. Electrics are such a pain. So many wires all over the place.

[abovetherim]

Again check the outputs on the ignition switch with a meter. If that checks out then move on to the immobiliser.

Trace all the immobiliser wires and label where they join the loom and remove and reconnect the original wires.

[archangel]

Thx for your help and advice. So i think there were a few potentially related issues. First off i cleaned up the main ground and noticed that my transmission ground had a melted connector and parts of the cable had also melted. Must have been run with a dodgy/discommected main ground or something in the past. Anyway replaced that. Made no difference but glad i've done it for safety. Looked at some other connections and i think the 2 things that were happening was that i believe the immobilizer has some kind of circuit protection that when tripped it stays disabled for a while before reactivating. This was being triggered when i was testing some sensors and grounding them to check their max readings etc. Then after all the on/off testing running fuel pump etc. I eventually ran the battery flat so either the ecu or immobiliser was preventing it from starting. Anyways jump started the car again and took it for a drive for an hour and it was fine. Haven't tried starting it again since but i'm pretty sure it will start again ok. I'll just need to remember if i'm testing sensors again in future. The behaviour may be coincidental but i'll monitor it for a while

[abovetherim]

Glad to see you think you have got to the bottom of this.

The engine and gearbox earths are essential to be in good shape. Especially for starting as the starter motor can draw some ampage especially if it is old and worn.

Further to this there is an essential earth under the inlet manifold that needs to be good.

[archangel]

Thanks for all the help guys. Refreshing all the major grounds in both engine bay and battery did help and so did cleaning up terminals on starter motor but would still get some intermittent issues. Think i've finally got hopefully the last piece of the puzzle. The wire that has the brown comnector to the starter seems to have been cut and recrimped at some point in the past and the insualtion left some wire exposed at either end. When i removed insulation it looked ok but cut it out and resoldered and reinsulated and now it's starting fine when it wouldn't even crank just before. Really surprising how much impact a little oxidation/corrosion in wires can have. Fingers crossed this is the last thing to fix for this issue.