Air-cooled 2.0L 3 cylinders out of 4 firing ????

[Becsteer]

I just had the van (T25 2L air-cooled CU engine) down on the rolling road to set up the new webbers on it. They have found that there is only 3 cylinders firing. They checked the compression of all 4, good, the leads and the plugs all good timing spot on, they are say to strip the engine down and do a re-build on it or buy re-con. Anybody got any ideas what else to try before I go to these lengths.

Many Thanks

[VWCamperfan]

If the compression is good then that just about coveres any engine problems related to this misfire and should tell them that the engine doesn't need pulling apart and rebuilding!
Do you know which cylinder isn't firing? Either 1,2,3,or 4 or back left, front right etc?
I take it the Webers are new from the description ie. out of the box?
I run webers on mine and have no problem at all with them but they do have to be set up spot on!
Also, did you have this problem before fitting the new carbs?

Ps. A little trick to finding out which cylinder isn't firing is to run engine for about 20 seconds, turn off and see which exhaust leading fron which cylinder is cooler than the others! Don't rev the engine when doing this, just let it idle.

[covdubber]

as said above, if the compression test has shown its ok on all four cylinders then the fault is somewhere else, if it were me, get a friendly vw owner or specialist to compression test the motor again unless you buy a gunsons compression tester & do it yourself, its easy peasy anyway!

if compression is ok then look at swapping all your ingniton ht leads, put a new coil on, dizzy cap/rotor arm, check all the connections, spade ends on the coil, if you have electronic ignition swap the dizzy for a good used spare, either way the moron at the rolling road should have had the skill to sort that problom or at least checked all the above to point you in the right direction of whats at fault,

if copression turns out to be down on one cylinder its probobly a burnt out valve but in the worst case scenario a bust piston ring or two or holed piston but i'd say

re-check compression somewhere else or do it yourself, you can get the gunsons tool in halfrauds if all seems ok
change all igniton wiring for new including what i've said above, also change ya plugs for new ones, at the end of the day all your electrical service items are only £30max at gsf
if that dont sort the situ try a good working 2nd hand distributor, if that dont sort it it may be more serious

also what webers are you using?

you dont want to pay for a rebuilt or good 2nd hand motor if you dont need too

[covdubber]

as said above, if the compression test has shown its ok on all four cylinders then the fault is somewhere else, if it were me, get a friendly vw owner or specialist to compression test the motor again unless you buy a gunsons compression tester & do it yourself, its easy peasy anyway!

if compression is ok then look at swapping all your ingniton ht leads, put a new coil on, dizzy cap/rotor arm, check all the connections, spade ends on the coil, if you have electronic ignition swap the dizzy for a good used spare, either way the moron at the rolling road should have had the skill to sort that problom or at least checked all the above to point you in the right direction of whats at fault,

if copression turns out to be down on one cylinder its probobly a burnt out valve but in the worst case scenario a bust piston ring or two or holed piston but i'd say

re-check compression somewhere else or do it yourself, you can get the gunsons tool in halfrauds if all seems ok
change all igniton wiring for new including what i've said above, also change ya plugs for new ones, at the end of the day all your electrical service items are only £30max at gsf
if that dont sort the situ try a good working 2nd hand distributor, if that dont sort it it may be more serious

also what webers are you using?

you dont want to pay for a rebuilt or good 2nd hand motor if you dont need too

[dugcati]

Ps. A little trick to finding out which cylinder isn't firing is to run engine for about 20 seconds, turn off and see which exhaust leading fron which cylinder is cooler than the others! Don't rev the engine when doing this, just let it idle.

If your feeling daring you can also do the old with the engine idling... remove a HT lead one at a - the duff cylinder will not make any difference to the engine idle sound/speed when it's HT lead is removed

[Becsteer]

I've removed the HT leads while the engine is running and its number 1 or as you look at the engine from the back looking forward it top right, this was also confirmed by removing the plug and finding it with fuel or over it. My next thought was to run an engine flush though it just in case its a block hydrolic tappet and it stuck in one position. I will keep you posted.

[toomanytoys]

If there is good compression on that cyl then it is nowt to do with the tappets.. and in any case the tappet would be very noisey..

Sounds like an ignition related problem... either plug, lead or dizzy cap.. no other components are "cylinder" related..

unless of course the carb is flooding that cyl and it cant ignite it...

If they have done a compression test and seaid its ok, I cant see how any mechanic could say it needs stripping and rebiulding..... thats just daft.. are you sure they said compression test was good?

[dugcati]

adding to that...

it is certainly worth ruling out that the valves are actually opening properly - I would guess that valves not opening properly due to worn cam's,bent/wrong/incorrectly seated pushrods could cause this.

out of interest how old are the plugs? I have seen more than once that old "chemical'ed" up plugs act really strangely what voltage is put through them and under compression - not sparking or sparking across the side walls etc..

[fullsunian]

If there is good compression on that cyl then it is nowt to do with the tappets.. and in any case the tappet would be very noisey..

Sounds like an ignition related problem... either plug, lead or dizzy cap.. no other components are "cylinder" related..

unless of course the carb is flooding that cyl and it cant ignite it...

If they have done a compression test and seaid its ok, I cant see how any mechanic could say it needs stripping and rebiulding..... thats just daft.. are you sure they said compression test was good?

What Si ^^ says.. If compo good has to be ignition side OR them webers
Can't understand why garage would say engine strip..

[dugwiththevwbug]

as all have said above change all cheap parts ie plugs correctly gapped as not always from new,leads, cap and rotor arm. worst case if not firing on that cylinder but you have fuel on the plug the hyraulic lifters may possibly have drained down and the engine needs running for a while to get them properly pumped back up to pressure or the lifters have been set as solid lifters with no preload but be honest sounds like a spark problem as even new parts can be duff good luck
regards doug