The V8 Owners Forum -

Lets discuss what you call a misfire!

How would you describe the misfire. Just running lumpy or is there a backfire when you try to rev the engine?

Does the engine start and idle?

If it will idle but its running rough then let it idle and pull a plug lead one at a time to see which plug lead (or leads) does not make a difference to the idle.

If you pull one or more leads that dont make a difference then this or these are the cylinders we need to look into.

that would be excellent, my names mark mills, cheers for the offer im at hr9 7pe ross on wye herefordshire,


id be fine if i knew for definite what the issue was i could get my mind sorted on what to do to fix it,

was a bit soul destroying to have the engine purring yesterday and running awful today after hydraulic lock

mgbv8 wrote:Lets discuss what you call a misfire!

How would you describe the misfire. Just running lumpy or is there a backfire when you try to rev the engine?

Does the engine start and idle?

If it will idle but its running rough then let it idle and pull a plug lead one at a time to see which plug lead (or leads) does not make a difference to the idle.

If you pull one or more leads that dont make a difference then this or these are the cylinders we need to look into.

lumpy tickover with the odd misfire, if i rev it and hold the revs up it almost runs ok bt tickover and low revs runs crap with the odd misfire,,

engine will start fine and idle but is'nt running right

i guess i need to start if up and pull one lead at a time and see what happens but when i started it and went to the exhaust it felt like both banks were missing

nokia_aid wrote:that would be excellent, my names mark mills, cheers for the offer im at hr9 7pe ross on wye herefordshire,


id be fine if i knew for definite what the issue was i could get my mind sorted on what to do to fix it,

was a bit soul destroying to have the engine purring yesterday and running awful today after hydraulic lock

HMM!!
A bit far from Milton Keynes sadly Mark

mgbv8 wrote:

nokia_aid wrote:that would be excellent, my names mark mills, cheers for the offer im at hr9 7pe ross on wye herefordshire,


id be fine if i knew for definite what the issue was i could get my mind sorted on what to do to fix it,

was a bit soul destroying to have the engine purring yesterday and running awful today after hydraulic lock

HMM!!
A bit far from Milton Keynes sadly Mark

no worries buddy, im sure il get to the root of the problem eventually. il be happy once i know the problem and how to fix it,

nokia_aid wrote:

mgbv8 wrote:Lets discuss what you call a misfire!

How would you describe the misfire. Just running lumpy or is there a backfire when you try to rev the engine?

Does the engine start and idle?

If it will idle but its running rough then let it idle and pull a plug lead one at a time to see which plug lead (or leads) does not make a difference to the idle.

If you pull one or more leads that dont make a difference then this or these are the cylinders we need to look into.

lumpy tickover with the odd misfire, if i rev it and hold the revs up it almost runs ok bt tickover and low revs runs crap with the odd misfire,,

engine will start fine and idle but is'nt running right

i guess i need to start if up and pull one lead at a time and see what happens but when i started it and went to the exhaust it felt like both banks were missing

So you have a proper twin exhaust system then, ie one exhaust per bank with no crossover pipe fitted to join each bank of the engine together?

yes one exhaust per bank, have a wideband lambda in the one bank

what else could be damaged with a hydro lock?

nokia_aid wrote:what else could be damaged with a hydro lock?

Hi
this is why I suggested finding out what is actually wrong and fix that, not frighten yourself with speculation! I have seen a 17.5 liter Perkins Diesel set that hydro locked, pushed 2 rods through the side of the block, snapped the crank into 3 parts (the main bearings were over 4 inches in diameter) and needless to say split the block in two. On the top of the building I worked in in 1998 they had two V12 cylinder Rolls Royce generator sets, these were hydro locked, one split the block down the middle the other spat it's crank out the sump pan snapping at the flywheel end for good measure. The generator set at the old TV AM building ingested a few gallons water, this one just snapped all the head bolts lifting the heads off the block and splitting a few pistons. I have seen a Petta two cylinder boat diesel engine that regularly filled with water from a leaky head gasket, all this one did was spit the water out over the first few revolutions after starting, I've seen seagull outboard engines that have sat on the bottom of the solent for 12 hours and start when the water/sand is pumped out with pull start. It varies very much what damage happens, as a guide the more worn out loose tolerance/crude the engine the less damage but that is not a hard and fast rule. Pull the sump and heads off have a look it will save a lot of time/money/anguish in the long run.
Best regards
Mike

As Mike says!

If your concern is bent rods you need to pull the heads off. This will allow you to measure the distance of piston top to the deck and also give you the opportunity to inspect the heads and valves as well as checking push rods for any bending.

if that much fuel got in to a cylinder or two, could there be some fuel left puddled in the inlet manifold still? i'm not sure if there is even anywhere for the fuel to sit

well it might be ok, i figured before i take it apart i would change the oil n filter, redo the timing, change the plugs again, etc etc and now i have it started and its not missing at all the only issue now is that there is a lot of smoke out the exhaust when i rev it


i know iv been told im best of stripping it to find the problem but i was kind of hoping that this smoke is just too much fuel from the carb

click on the pic to see the video

Hi
it looks like white smoke to me, not grey/black which is rich mixture, not blue which is oil, so looks like you haven't cracked any pistons, probably just lifted a head a bit and now you have a bit of a leaky gasket. . . out with the torque wrench then!
best regards
Mike

Have a sniff of the smoke. Does it smell of oil? Is it smoke or is it steam?

If the oil pressure is ok and it drives ok give it a few miles of driving once you have made sure oil and water is topped up. Keep your eye on the temp gauge and make sure its ok. When you have done a few miles at normal operating temp park it up and let it go cold for an hour or so. Check water level and see if there is any signs of water in the oil or mayo in the filler cap?

As Mike said, you could run the torque wrench around the head while stone cold before the test drive.

I would give her a good run and see what happens.

I accidentally filled my exhaust system with water recently. The amount of smoke this generated (after the water had turned to steam) made me seriously doubt the health of my engine. The action of steam must have dislodged all the deposits on the inside of the silencers.

Maybe you have run a load of petrol into the exhaust system. Mind you, this might go bang, so perhaps I am just talking rubbish...

Chris.