Weak spark

[tvrwolf]

Just had the autotune man out to help with a problem of not starting. He elimated most things and got it down to a weak coil trigger signal leading to a poor spark (he tested front 2 offside plugs). Voltage on HT was 5000v and should be nearer 50000v he recks. He checked coil suply + and seems ok. Other strange thing is that it the 2 times i have got it started in past few weeks it has been when i released the starter button - more surge as releasing strain from starter motor perhaps.
It always starts fine when warm although wouldnt need as much spark so probably explains this. eliminated all usual stuff, temp sensors, battery.
pointing towards a faulty connection - have looked at both coil connectors and no corrosion, plenty of grease in there. anyone know if leads from coil go straight to ecu or if i need to find another connector along the way?
Also have checked ignition box in boot for dry joints and touched any up with solder just in case. its all about elimination i guess! thx

[Luckyone]

Sorry this is a bit obvious but have you tried jumping it?
Ours is a pain to start in this cold weather as the battery is a bit buggered, even when fully charged it won’t start from cold, with a jump it’s fine. Once warm it will start fine of it’s own battery, the battery it’s self is still stone cold, so I put it down to the oil being thinner once it had warmed a little.

[tvrwolf]

not tried jumping it yet. having said this even if it did start this would mean having to do this every time as it has been getting progressively worst. so there is a fault somewhere. Good idea thought if i need to get it to a proper garage rather than towing. thanks

[ridds]

Again I'd start with a good charge in the battery.

Tank it out, check it has plenty of fluid in it and give it a good charge.

Batteries hate cold weather, also the colder it is the tighter your engine so the battery has even more work to do.

[tvrwolf]

Thanks Ridds but battery brand new ie put in at time of service few weeks back and even bought an accumate and left overnight so that box is well and truly ticked. Have got a meter so will put across the terminals - what should i get - 13.2 i think i read somewhere?

[speed8]

I would have said the same, check the charge getting to the battery. When mine was down I could turn over plenty but just not get enough spark to fire. A jump start got it going. Might be worth changing the big fuse as a precaution. If it starts to break down it will affect the charge to the battery.

[Luckyone]

tvrwolf said:

Thanks Ridds but battery brand new ie put in at time of service few weeks back and even bought an accumate and left overnight so that box is well and truly ticked. Have got a meter so will put across the terminals - what should i get - 13.2 i think i read somewhere?

Ah, it is quite possible your new battery is duff, I've had a couple of new ones that were. If you can jump it I'd give it a try then you know it’s the battery.
Did it start ok before it had it’s new battery?
Also did it run ok those times you got it going, if so the coils can’t be too bad…

speed8 said:

I would have said the same, check the charge getting to the battery. When mine was down I could turn over plenty but just not get enough spark to fire. A jump start got it going. Might be worth changing the big fuse as a precaution. If it starts to break down it will affect the charge to the battery.

Our big fuse went for the first time in five years the other day, after fixing it I found the radio worked for the first time ever! It must have been cracked all this time, it still looked fine after it went (till I took it off that is).

[tvrwolf]

thanks, will try a jump. had it on accumate all night and showing 13.15 volts. would it read this if it was a dudder though?

[luckyone]

tvrwolf said:

thanks, will try a jump. had it on accumate all night and showing 13.15 volts. would it read this if it was a dudder though?

I'm no expert, but I think you have to test it under load, there are some threads on here somewhere about what voltages you should get with different things turned on in the car. But I think it's safe to say if it starts with a jump, the battery is duff - just make sure the jump leads are good ones, I spent a day or so trying to work out what was wrong with the car when the jump lead had broken it's connection in side the handle

Make sure you use a big car to jump from, my 535 BM is great (the battery is twice the size of the cerbs & it's got a smaller lower compression engine )
But my little old VW bug can't help...

[tvrwolf]

done it! well sort of. Hooked up my big volvo 80 (no jokes please, its a family car ok!) and started a treat. Battery still showing good volts and feel it more likely that there is a leak to earth somewhere, esp as bettery brand new. if you were to look for rusty earth to chassis where would be the main culprits. I will also check the battery earth has been put on ok while at it. going out now to have a rummage...