LT Leads Shorting at Coil
Discussion
Does anyone have any advice about the LT leads at the coil shorting? eg. Is this evidence of the coil being about to die?
To sort out my lumpy running/ rough riding, I replaced the HT Leads some months back. Recently I had a non-starter due to "broken ignition lead". Today I get the car back (after having new manifolds fitted) and notice there is a short across the LT leads where the HT lead from the distributor enters the coil. The connections are correct and there are no breaks in the leads.
Will replacing the coil sort this out? Or should I take the advice posted earlier (20th Aug) concerning rough running and go to a Ford dealer with a rolling road? It seems from these earlier postings even the specialist TVR garages don't necessarily have the answers.
To sort out my lumpy running/ rough riding, I replaced the HT Leads some months back. Recently I had a non-starter due to "broken ignition lead". Today I get the car back (after having new manifolds fitted) and notice there is a short across the LT leads where the HT lead from the distributor enters the coil. The connections are correct and there are no breaks in the leads.
Will replacing the coil sort this out? Or should I take the advice posted earlier (20th Aug) concerning rough running and go to a Ford dealer with a rolling road? It seems from these earlier postings even the specialist TVR garages don't necessarily have the answers.
When you say there's a short across the LT circuit do you mean there's a lead across them or is it what you've measured with a multimeter?
If it's what you've measured then I'd be a little bit careful in diagnosing a defective coil as the primary windings (LT circuit) will have quite a low ohmic valve 0.1 ohms I think (anyone measured their's care to comment on that value?), because it's an inductive (XL)circuit so the value should be measured in inductance, not readily available on my multimeter. If it's a short between the HT and LT circuits then yes it's possibily at fault.
Obviously AIMHO, personally I'd get someone with the same set up as your's to do like for like comparason's(sp?), i.e. values of LT windings, HT windings and insulation between the two, before I considered anything to be duff.
Even then I'd consider an auto electrician who will be cheaper in the long run than changes the bits that appear to wrong.
Then again this info may already be in the bible, which is in the garage and it's raining
.
Anyone else care to comment?
Harry
>> Edited by HarryW on Wednesday 2nd October 00:34
If it's what you've measured then I'd be a little bit careful in diagnosing a defective coil as the primary windings (LT circuit) will have quite a low ohmic valve 0.1 ohms I think (anyone measured their's care to comment on that value?), because it's an inductive (XL)circuit so the value should be measured in inductance, not readily available on my multimeter. If it's a short between the HT and LT circuits then yes it's possibily at fault.
Obviously AIMHO, personally I'd get someone with the same set up as your's to do like for like comparason's(sp?), i.e. values of LT windings, HT windings and insulation between the two, before I considered anything to be duff.
Even then I'd consider an auto electrician who will be cheaper in the long run than changes the bits that appear to wrong.
Then again this info may already be in the bible, which is in the garage and it's raining. Anyone else care to comment?
Harry
>> Edited by HarryW on Wednesday 2nd October 00:34
"When you say there's a short across the LT circuit do you mean there's a lead across them or is it what you've measured with a multimeter?"
I haven't measured it as I have no meter and probably wouldn't know what to do with one(!) - [Guilty]. What I can see is a pair of short blue sparks from the LT connections on the coil to the HT lead there.
Auto electrician seems like a good suggestion. Thanks.
I haven't measured it as I have no meter and probably wouldn't know what to do with one(!) - [Guilty]. What I can see is a pair of short blue sparks from the LT connections on the coil to the HT lead there.
Auto electrician seems like a good suggestion. Thanks.
quote:
What I can see is a pair of short blue sparks from the LT connections on the coil to the HT lead there.
Had this a couple of times in the past on different cars, fist time ti was simply that the outside of the coil was dirty, thus creating a conductor for the currect to arc along, solved by cleaning with WD40 and a rag.
Second time there wqas a hairlne crack in the plastic part of the coil resulting in the arc forming in the crack, solved with new coil.
I got myself into this situation once, of not knowing if the coil was defective or not, so I ended up hacksawing one apart to see how it was connected, (the oil inside stinks by the way).
Both HT & LT negatives are common. [i.e. the symbol (-) on the top of the coil is the same for HT and LT].
LT.
The (+) terminal on the top of the coil is directly connected to the (-) terminal albeit via a very, very long length of coiled wire with a very low resistance.
HT
The coil output to the distributor, or HT output is also directly connected to the (-) terminal on the top of the coil. This is also just a very, very, very long length of wire with a very low resistance.
Therefore you will get what apears to be a short circuit between all terminals of the coil, as they are all connected to each other, via the (-) terminal.
Without doing inductance checks, (which incidentally are measured in Henry's!!) the best way to see if coil works is to connect a sparkplug to the HT coil output to see if you get a good clean spark. Don't touch it when it's working though, because the voltage is much higher on an electronic ignition and can KILL you!
I hope this clears it up!
Jas.
Both HT & LT negatives are common. [i.e. the symbol (-) on the top of the coil is the same for HT and LT].
LT.
The (+) terminal on the top of the coil is directly connected to the (-) terminal albeit via a very, very long length of coiled wire with a very low resistance.
HT
The coil output to the distributor, or HT output is also directly connected to the (-) terminal on the top of the coil. This is also just a very, very, very long length of wire with a very low resistance.
Therefore you will get what apears to be a short circuit between all terminals of the coil, as they are all connected to each other, via the (-) terminal.
Without doing inductance checks, (which incidentally are measured in Henry's!!) the best way to see if coil works is to connect a sparkplug to the HT coil output to see if you get a good clean spark. Don't touch it when it's working though, because the voltage is much higher on an electronic ignition and can KILL you!
I hope this clears it up!
Jas.
I have now replaced the coil, but I still have shorting from LT leads to the HT at the coil terminals PLUS (interestingly) at certain points along the HT lead back to the distributor.
So... I considered the possibility of a faulty HT lead (even though I put a new set on only months ago), so I put back on the old one... and... I still have the same blue sparks everywhere(!)
Having said that, the car now runs a little more smoothly, but I think this may be down to a "cleaner" spark - if that makes sense. There is still the old hesitation at lower revs and the blue sparks.
Anyone have any ideas here as to the cause and solution? The best idea solution-wise from earlier similar postings was to take it to a Ford rolling road for some diagnostics, or maybe an auto electrician. Incidentally, the car was fine before I decided to have an electric ariel fitted. I have heard that ariels are hard to earth on fibreglass bodied cars. Could this be an issue with earthing the electrics....?
Any Auto electricians out there care to comment? Can anyone help, please?
P.S. Thank God, I didn't kill myself with the test with the spark plug. I agree it's better to spend £20 and fit a new one than risk life and limb. It may be a TVR, but it's still "only" a car!
So... I considered the possibility of a faulty HT lead (even though I put a new set on only months ago), so I put back on the old one... and... I still have the same blue sparks everywhere(!)
Having said that, the car now runs a little more smoothly, but I think this may be down to a "cleaner" spark - if that makes sense. There is still the old hesitation at lower revs and the blue sparks.
Anyone have any ideas here as to the cause and solution? The best idea solution-wise from earlier similar postings was to take it to a Ford rolling road for some diagnostics, or maybe an auto electrician. Incidentally, the car was fine before I decided to have an electric ariel fitted. I have heard that ariels are hard to earth on fibreglass bodied cars. Could this be an issue with earthing the electrics....?
Any Auto electricians out there care to comment? Can anyone help, please?
P.S. Thank God, I didn't kill myself with the test with the spark plug. I agree it's better to spend £20 and fit a new one than risk life and limb. It may be a TVR, but it's still "only" a car!
quote:
........
Without doing inductance checks, (which incidentally are measured in Henry's!!) .............I hope this clears it up!
Jas.
Ah good old henry, normally accompanied by his friend milli
Jas, I've done some exploring before but I've never had the urge to cut open a coil, ah the quest for knowledge
. As has already been said looking for the tell tale blue HT halo in the dark on a running engine (or a 910, if you know what a 910 is email me off line
)normally leads to the path of smooth running. Again as has already been said do NOT put your fingers near the blue bits, it bites/can kill. If you do put the plug on the end of the coil HT output to check for sparking, make sure the plug outer is making good contact with a substantual part of engine metal or it won't spark as it'll not have a return path. Also doing this can damage electrics, even the ECU
with surges, if it arcs onto other electrical string . Harry
Thanks, Jas. I will try and get the LT spades away from the HT terminal and if that doesn't work invest in (yet another) HT lead.
By the way, looking at the pic of your S2, when was that taken? This looks very like S Club Heaven last April (I think that's when it was). Probably bumped into you there....
Simon.
By the way, looking at the pic of your S2, when was that taken? This looks very like S Club Heaven last April (I think that's when it was). Probably bumped into you there....
Simon.
I have now sorted this out. Here's how.
I took the car to an auto electrician with a rolling road, but he did not need that. He tested the plug extenders on top of the distributor. One of them was faulty. He declared that that was what was causing the problem of the shorting at the LT Leads.
For good measure, he replaced the Distributor Cap and Distributor. I asked him to order a set of the plug extenders to good measure. Hey, at £2 plus VAT each, why not?
The whole lot, including labour, plus the "dreaded", came to less than £100. And now the car runs as smooth as a baby's. And in the rain too!
My advice, having been through this, is "horses for courses". Even if your beloved is serviced regularly at a recommended TVR garage, if they are no good at electrics, they will just not know. Keep the TVR garage for the servicing, anything electrical, take it to a specialist.
Simon
I took the car to an auto electrician with a rolling road, but he did not need that. He tested the plug extenders on top of the distributor. One of them was faulty. He declared that that was what was causing the problem of the shorting at the LT Leads.
For good measure, he replaced the Distributor Cap and Distributor. I asked him to order a set of the plug extenders to good measure. Hey, at £2 plus VAT each, why not?
The whole lot, including labour, plus the "dreaded", came to less than £100. And now the car runs as smooth as a baby's. And in the rain too!
My advice, having been through this, is "horses for courses". Even if your beloved is serviced regularly at a recommended TVR garage, if they are no good at electrics, they will just not know. Keep the TVR garage for the servicing, anything electrical, take it to a specialist.
Simon
Paceracing said: The picture of my car was taken at Virginia Waters 2 earlier this year. The car looks nothing like that now, with most of the paint rubbed down to bare fibreglass, no dashboard, no bonnet, and within the next 3 weeks - no chassis either!
Oh the joys of restoration!
Jas.
How's the restorating going Jas? When do you expect to be back on the road?
[quote How's the restorating going Jas? When do you expect to be back on the road?
Hi Podie,
Things have stalled a bit. Now the racing season is over I can start to make a bit more effort. I may be shouting for help soon, as I plan to take the body off the chassis in the beginning of December. It's ready to lift off now as it happens, but I have too many commitments with work, etc... to find the time at the moment!
Jas.
P.S. I'm thinking about getting rid of the XR2 and changing it for a MK2 RS2000 which a friend used to use for Autotests. Of course it would need to be converted to race spec, but the advantage is that it is already half way there. What do you lot think?
>> Edited by Paceracing on Friday 8th November 19:47
Hi Podie,
Things have stalled a bit. Now the racing season is over I can start to make a bit more effort. I may be shouting for help soon, as I plan to take the body off the chassis in the beginning of December. It's ready to lift off now as it happens, but I have too many commitments with work, etc... to find the time at the moment!
Jas.
P.S. I'm thinking about getting rid of the XR2 and changing it for a MK2 RS2000 which a friend used to use for Autotests. Of course it would need to be converted to race spec, but the advantage is that it is already half way there. What do you lot think?
>> Edited by Paceracing on Friday 8th November 19:47
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