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Alarm/ Immobiliser problem that isn't caused by the spider


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I have a 1997 300tdi defender 110, and recently I've been having issues with it starting. This was tracked down to the immobiliser/spider as it starts just fine with a 12V wire straight to the starter solenoid, however, after having bypassed a second hand immobiliser (as is recommended in "the definitive alarm spider post" - pins 4 to 8, and 6 to 10 are connected) it's still hesitant to start. Sometimes it starts right away, sometimes I have to hold the key in the start position for 10-20 seconds before it finally kicks in. Is there likely to be some more dodgy solder joints in the alarm ECU or does the problem lie elsewhere?

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When you tried the 12V straight to the starter, was that directly from the battery or from the ignition switch? If it wasn't from the switch, I'd suspect that. The contacts can burn to the point they wont even power the starter relay reliably.

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Might be wrong here, and sorry if this is a bum steer, but a mate of mine had a similar issue, starting sometimes and other times taking forever, immobiliser would work then wouldn't, it seemed to have a mind of its own, but up behind the dashboard or wherever they maybe on your wagon, but on his there's a line of relays, on a disco 1 they are behind the plastic panel to the right of your drivers foot, one of them was corroded,  i dont know how it came around but by luck he was messing around with something else, basically shaking stuff about in his dash, for want of a better description, went to start it and it fired straight away, when it stopped on him the next time and wouldn't start, he said he just,  and in frustration pulled and wiggled it all about a bit again and it fired again, after a proper investigation it turned out to be the relay, he spent hours and hundreds of pounds on bits and bobs to get it going and it was a 5 quid relay and terminal that had corroded,  I don't know the relevance of the  colour of the relays but he had 3 or 4 yellow ones, one of them being the issue, close to others green, black and what ever other colour was there, I know this sounds a bit vague to say the least but he's never had a problem since, give it a go, nothing ventured as they say,

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Yeah the 12V to the starter was from the battery, the starter relay (the yellow one under the fuse box) is clicking consistently when I try to start it, so I think that rules out that and the ignition switch. 

 

The next thing I think I'll check is this connector below, it's located just behind the engine and I reckon it's gummed up with oil and diesel which could be stopping me getting a full 12V at the starter.

image.thumb.png.7c11e68ebae706cafc276550e42017de.png

Edited by AStarMustDie
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Even if the relay clicks, doesn't mean it's getting enough current to the starter. As in the reply above. So definitely worth substituting for another one. It can't hurt to look at the connectors either of course.

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On 10/9/2023 at 7:11 PM, AStarMustDie said:

it's still hesitant to start. Sometimes it starts right away, sometimes I have to hold the key in the start position for 10-20 seconds before it finally kicks in

Just checking: are you waiting for the starter motor to turn? Is that the hesitancy? If so, carry on.

Otherwise there’s the immobiliser feed to the fuel solenoid to consider too although that always needs to operate once started so I doubt it is relevant really. 

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That's correct, turn the key to start and it doesn't crank at all.

I've now checked the connector - it's fine, totally clean inside - I've measured the voltage at the starter solenoid: it goes down to about 8.8V while cranking, and voltage at the battery itself is about 9.5 while cranking, so there is a bit of drop between the battery and the solenoid. I haven't been able to take the measurements while it's having the issue though as it's cranking fine at the moment, when it's having trouble again I will try to measure to see if there's a difference somewhere.

I've swapped the starter relay with the one on the end (the heater rear window one) and we'll see if it trouble again in the future.

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I have had trouble at those relays. The third one is for the headlamps and on a couple of occasions they have died as I was driving. I think my intermittent fault was the connections at the relay base rather than the relay itself.

I have tried to clean and spray with contact cleaner and all seems OK but I’ll find out during the winter darkness I’m sure.

The only way to properly fix would then be to strip out the fuse box assembly and re-crimp new spade sockets.

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