[Sharky1]

My GU TD42 started cranking slower & slower recently until it would no longer turn the motor over. Having done high km & with new batteries I suspected the starter. So I put in a new one & away we went for about a week. Then yesterday it stopped throwing back at all. It has full power to the motor itself but only 7.6V at the ignition wire when key fully turned. If I hotwire it directly to battery it turns over without issue.

I have a proximity immobilizer that is at least 6yrs old. It was in the car when I got it. I have been suspicious of this as part of the cause for some time now as it has been playing up a little recently.

My question is, could this be the issue?

I can't find a starter relay or solenoid anywhere. The starter has an internal earth & my batts/chassis/engine is well earthed. It has to be something like ignition switch, immobilizer, fuse, connection etc I would think.

Coincidentally this did happen the morning after a 4x4 river crossing. It started perfectly in the morning, then half an hr later it won't start at all. It has started once since & also last night something drained my battery & I had to jump start & then hotwire to get it going this morning. I use this car for work so I need to fix it asap. Any help or advice appreciated.

 

[Boundry Rider]

My GQ only supplies 11.6V to the starter solenoid. Wasn't enough to throw the solenoid so I pulled starter solenoid power from the battery isolater instead where I got 12.6V. No more probs.

 

[Sharky1]

Yeah I will have to hook up a separate start button for now but I'd still like to diagnose the issue.

 

[ST391GQ]

This is an easy fix. Just put a relay in start circuit so that when key is turned ...relay activates and a full 12 volts goes from batt, to starter. Any auto sparky worth his salt would know how to do this standing on his ear !!!.

Cheers Keith

 

[Sharky1]

This is an easy fix. Just put a relay in start circuit so that when key is turned ...relay activates and a full 12 volts goes from batt, to starter. Any auto sparky worth his salt would know how to do this standing on his ear !!!.

Cheers Keith

Cheers Keith. I spoke to my Auto sparky mate earlier on who said the same thing. I should have thought of that. With a sick child I haven't slept much the last 2 nights lol.

I can wire a relay. They're easy.

 

[Sharky1]

Hmmmm so it seems the relay didn't fix my issue.

When I had the starter hardwired direct from battery through a button, it cranked fine but with relay it's back to how it's been for the past few weeks, struggling to crank & as a result, barely starting a lot of the time. So it's reasonable to say that the voltage from the ignition wire is & has been continuously dropping for many weeks & given that the immobilizer has been doing other things in that time like rearming whilst cranking & completely shutting my ignition down including dash lights etc, I wonder if it's the immobilizer or one of those blue relays above the fuse box.

 

[Boundry Rider]

Where did you get the power from?
The power supply needs to come direct from the battery to the relay, and go direct to the wire from the key that goes to the small starter plug on the starter solonoid. Then test the voltage at the small starter plug on the solonoid whilst cranking. If still not good voltage recording, 12.6V, then you power the small plug direct from the relay.
The key is reading the voltage at the small plug on the starter solonoid whilst cranking until you see a difference, thus isolating the problem.
Good luck, wiring problems with starters in these old harnesses can be a headache.

 

[Sharky1]

Yeah this is exactly what I did. Like I said, take that wire (from ign barrel) out of the equation & everything works well. I only have 7.6V coming through this wire. I will have to check the voltage coming out of the relay & then again at the solenoid whilst cranking.

I have double checked the relay & I've wired it correctly.

85 is earthed
86 is from ign barrel
30 is from battery
87 goes to starter

so that when the coil is activated it pulls the relay closed.

I'm getting a new immobilizer shortly as I know mine is playing up & I'm pretty sure it's also causing this issue. The thing has started arming itself after I've disarmed it & started cranking the engine

 

[BeNos]

Sounds like maybe your ignition barrel contacts could be us. That power should be heaps to bring in a relay. Then it's direct battery voltage to the starter solenoid.

 

[Leethal]

The obvious thing would have been to spend 30 seconds bypassing the start circuit cut of the immobiliser to confirm or deny the immobiliser as the fault.

I had a faulty immobiliser that intermittently cut everything. I suspected turbo timer as coincidentally I had just fitted it a couple of weeks earlier, but after disconnecting that to no avail I just rejoined the ignition and start cuts of the immobiliser, never played up again so that was obviously the fault in my case.

And 7.6 volts is pretty unlikely to even trigger a relay so that wouldn't have solved it in this case, but assuming that's under load then it would of course be a fair bit higher at the 86 pin since the relay draws no where near the load of the start solenoid, would be interesting to hear what the voltage at the 86 pin was when attempting to crank engine.