firing on 3 cylinders, got shock......

[andylekker]

hi all, van has been running badly so i took off the spark plug leads in turn - and found that it was running on 3. also i got a shock from the lead that is running to the non-running cylinder when i'd taken it off with the engine running (didnt get a shock off any of the others)

so i guess i may need to replace that lead? or what else could it be?

thanks in advance,

Andy

[BOXY]

Cracked insulation on the lead and a bit of damp will always let the wigglies get out and bite you. Try swapping the leads around and see if the fault moves to another cylinder.

[andylekker]

thanks, i'll do that in the morning.

if it turns out to be a faulty lead, where is the best place to buy a new one?

or do i have to buy a whole new set?

also, is it ok to drive on 3 or will it damage the engine?

thanks again,

andy

[BOXY]

I wouldn't drive the van on three unless you really have to. The lack of power might make hills a challenge. And having a cylinder of un-burnt petrol is going to reduce the lubrication on that cylinder.

If the mis-fire follows the lead around you could just change one but getting a set would be easier. The usual suspects, GSF, Just Kampers, Brickwerks should all do new sets. My HT leads actually came out of my old Fiat X19 before I got rid of it. You might find cleaning and re-gapping the plugs cures the problem anyway without needing to replace the lead anyway.

[Hacksawbob]

You can check Ohms resistance across the lead 800/900 from memory. Not a bad idea to check them before fitting (or even leaving the shop!) even brand new they can be faulty.

[California Dreamin]

Had this on mine recently....made mine using high quality Lucas hypalon HT lead, straight NGK 500ohm red plug caps. I was just fed up of the poor quality after market leads at £35 posted.

However...I will add...have you removed the metal shrowds from the plug caps. Official non official VW fix. You will need side cutting pliers or tin snips.

With anything between 12 & 25 thousand volts trying to find the easiest way to ground, it isn't suprising that this high voltage finds the metal shrowds an easier route than going through the resistor cap to jump the 0.7mm electrode gap.

Martin

[California Dreamin]

Oh! and getting a shock....if you have pulled the plug cap and lead off then getting a shock is perfectly normal as the high voltage uses YOU to find the easiest route to ground lol.


Martin

[andylekker]

thanks for the responses.

the van didnt really want to start at all after swapping the right hand leads round.

and i only get a shock from the plug cap with the lead that runs to the cylinder that origially wasnt firing.
took the spark plug out of both. bit black and dirty on the 'bad' cylinder, other one looked grey ok.

lead looks alright but there may be a bit of damage in the plug cap so have ordered a single replacement plug cap for now.

having said that, i run the van mostly on LPG and it has been backfiring when cold on gas (not petrol) for a while, especially in damp weather, so i think that might be connected to this as well. id be quite happy to buy a 35 quid new set if they were going to solve the problem.

[ghost123uk]

Getting a shock from the electronic ignition systems used on our vans (and most modern cars) can be dangerous. People have even died.

Easy tip = get a totally dry T towel out of the airing cupboard and use a couple of layers of that between your fingers and the HT lead. Dry cotton is a very poor conductor of electricity.

I have to say, even bearing that precaution in mind, I never touch HT leads when the ignition is on

[California Dreamin]

Did you remove the metal showds from the spark plug caps? just from the offending lead if you don't fancy doing them all.

Martin

[andylekker]

hi, yeah i was going to do that if the new cap doesnt arrive by tuesday which is when i'll have time to look at it.

[edoh]

if you can get past the put you to sleep voice
http://www.youtube.com/watch?v=vzOSHcsY518

[andylekker]

Did you remove the metal showds from the spark plug caps? just from the offending lead if you don't fancy doing them all.

Martin

i had a spare 5 minutes this morning and tried this - it worked! van is running much better too without so many backfires

many thanks for the top tip. new cap should arrive tomorrow so hopefully that will sort the problem for good.

A

[California Dreamin]

I hope the new ones aren't metal showded as well.....

I used these mate..top quality, correctly impeded & no metal shrowds.

http://www.ebay.co.uk/itm/NGK-SB05F-SPA ... 5650351d9a


Martin

[andylekker]

the new one is shrouded but i only bought 1 so i dont mind if it matches the rest, ive fitted it and the van is running great - better than it has for a while and the backfiring when cold on gas is all but gone too. not often you get such a result for less than a tenner

thanks for the link though - if i feel it needs a whole new set i'll go for those ones.

A