Loss of engine revs/power and 'pop'py running

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As per title my engine sounds and runs terribly suddenly.

It was fine all day then pulled into the woods to let my friend have a go and had some fun myself so the engine was used a very little bit harder than normal but hardly much and only for 10 minutes.

Driving back it begun okay then trying to pull away from the lights it coughed slightly and revs seemed to drop so I dipped the clutch and pressed the throttle to see if the revs picked up and if the engine would run smoother again but nothing - it just kept popping, juddering, hesitating and producing no power . I limped round the corner at my max speed of about 2mph (no joke - almost zero power) ..and I really did limp round, if the apex of the corner didn't run downhill I wouldn't have made it.

I left it in the drive for 4 hours then just went out to film it and after it first started it seemed okay again. Then as soon as it got revved a bit it spluttered then stalled. Then second time it starts (on the video) it stays running a bit long but sounds really bad and has this constant popping note.

Can anyone shed any light on this?

Sorry the video is not great quality and the fan seemed to have shagged the mic but I hope it is clear enough to help a diagnosis. I think towards the end of the second time it starts is when you can see/hear it at its worse.

The video is here: [nomedia="http://www.youtube.com/watch?v=SIew2zyWPxk"]VID 00000-20110815-1748.3GP - YouTube[/nomedia]


P.S. You might notice that the engine will also only start once I RELEASE the ignition key. If you have any input on that problem I have it open on another thread here: http://www.landyzone.co.uk/lz/f6/engine-only-starts-when-ignition-key-released-160628.html
 
hard to tell on my computer ,but remove rocker box and see if all rockers are going up and down fully ,and let us know and go from there
 
Inlet manifold worked loose? Manifold gasket gone? Hole in inlet manifold? Stuck valve? Timing chain tensioner wheel broken up? Dizzy drive slipped a cog? (I've had both of these last two happen and the symptoms were similar to yours)
 
My vehicle had similar symtoms. Not as acute though.

In the end I discovered the dizzy was rotating on clamping ring which was bent and lost its grip. It was worse when the engine was warm - less grip from expansion?

All fixed now. I'd try the dizzy and ignition first.
 
I agree, it does sound ignition related, maybe even coil breaking down ? Fuel must be ok as it does start to rev

As for the ignition switch, I remember when I was in my teens, the neighbours had a ford transit (v reg 79 ish) and it would only start when the key was held on the starter position and would pop and bang when on normal ignition position. Turned out it had a ballast resistor that cut the voltage to the coil down to 9 volts when running and only 12 volts was kicked to it when cranking. Just check that voltage is getting to the ignition circuit when held on cranking position
 
hard to tell on my computer ,but remove rocker box and see if all rockers are going up and down fully ,and let us know and go from there

I've removed the rocker cover and turned the engine by hand and the rockers do all go up and down though some look as though they are not rising as much as others and some of the pairs look slightly out of sync with each other. I have no idea how they are meant to be/look so does this sound right or not? What other tests can I do and where to next?

As for other suggestions - I loosened the dizzy clamp and rotated it with the engine ticking over and positioned it where the engine seemed to run and start best (though that is the best of a bad bunch of choices!). Clamp retightened.

Inlet manifold seems in tact. It was replaced along with new gaskets a year ago so I'd like to think it won't be that.

Ignition coil seems to perform well on the whole and this issue has happened before and disappeared for a while of its own accord and now come back so my logic is kind of saying the coil is probably good as it performed well all the other time in between.

My multimeter has broken so can't check any voltages right now.
 
there not in sync as you might think ,the some not opening as far as others needs looking at rocker wears on pad touching valve, push rod can wear through brass follower lobes on cam can wear,if exhaust valve doesnt open fully this also shortens time its open as well anany gas not let through will have to go through both closed valves and past rings,if inlet doesnt open enough not enough air will get in for proper combustionmits allways worth checking tappets (rocker to valve clearance ) with number nine method 10 thou,then check thread poking out of adjuster nut they should be all about the same if not find why
 
there not in sync as you might think ,the some not opening as far as others needs looking at rocker wears on pad touching valve, push rod can wear through brass follower lobes on cam can wear,if exhaust valve doesnt open fully this also shortens time its open as well anany gas not let through will have to go through both closed valves and past rings,if inlet doesnt open enough not enough air will get in for proper combustionmits allways worth checking tappets (rocker to valve clearance ) with number nine method 10 thou,then check thread poking out of adjuster nut they should be all about the same if not find why

Thanks James, before I throw myself into this (it's the first time I've ever had a rocker cover off), are the things you're suggesting possible causes of my initial problem with the funny running and engine not revving? In time I'd like to think I'll revisit all work that's needed but right now I just want to get the old girl running again so just want to make sure I'm focussing my efforts in the right place.

Thanks for the help as always.

Andy.
 
poor spark can give lack of power as you try to rev it and back fires can happen, but if you have a push rod or two that have worn through follower it can give your symptoms i cant tell from vid as sound isnt good enough,but so can blown head gasket if between two cylinders
 
There's anther video showing the problem again with the rocker cover off in case it helps at all:[nomedia="http://www.youtube.com/watch?v=TpbakuIBZcM"]VID 00001-20110829-1201.3GP - YouTube[/nomedia]

As it stalls this time it doesn't give the puff back through the carb as it sometimes does but I think you can hear a bit more how it's struggling. Also, can you tell visually if any of the rockers look problematic?

I appreciate it's probably hard with the low quality videos but I'm just trying to provide as much supporting info as possible.

Cheers,

Andy.
 
Take the dizzy cap off and check to see if there's any damp in there,also check the points to see if there's a good spark,with the cap and rotor arm off and in neutral get someone to spin it over on the key whilst you look to see if it's a good spark at the points,it should be a strong blue arc,also check the gap on the points.
 
I've had no end of ignition problems with this but thought they had gone! I had checked ht leads and dizzy cap for moisture but they were all sound. Anyway, I took your advice to check the spark as hadn't done that this time and there was a spark but only orange as oppose to a strong blue. I got this orange spark from the spark plug AND the HT lead from coil so perhaps my ignition woes are not behind me. Spare coil anyone??

I noticed however when the (6 month old) plug was removed it was very blackened with oily deposits which http://www.aa1car.com/library/reading_spark_plugs.jpg tells me is worn valve guides or piston rings. Do either of those tie in with my symptoms here?

I will start working through the ignition system again to try and get a reliable strong blue arc in the meantime but as I have had those issues for a long time, but the rough running is only recent my gut tells me there is probably another problem beyond the ignition.

Thanks for everyones input so far.
 
This morning I got the ignition behaving a bit better and have a blue spark from the HT lead from the coil. I wouldn't call it a strong blue spark but it is consistent, blue (as oppose to orange) and is quite visible. So I removed a plug again (different from yesterday) and tested that by earthing it on the engine block and it seemed to only get an orange spark. It also only sparked for a few seconds and then stops sparking at all. Although the engine was running and so presumably the other three plugs that were still in were creating some form of spark - at least enough to keep the engine running. Although my problem is that the engine stalls after about 20 seconds so perhaps it is because the plugs are not sparking strongly enough or are stopping sparking all together after the initial startup.

Also, what I thought to be oil on the plugs yesterday smells very strongly of fuel. Is it possible it is the unburned fuel that has blackened my plugs somewhat or is it normal that they smell strongly of fuel especially if they are not igniting properly?

I will check the dizzy again (point gaps etc) and re-gap plugs - although I have done this about 4 times already in the last year so don't think that is going to fix anything. Any other ideas as to what could reduce my blue spark at the coil to an orange spark at the plugs, especially one which seems to stop sparking all together after about 20 seconds?

:confused:
 
if you get good spark on ht lead it means cap ,rotor arm or leads are poor check carbon brush in centre of cap as well new parts can often be poor now i usually ensure i have 2 of each there cheaper enough
 
I have cleaned the plugs up a bit and put them back.

Now I've taken the dizzy out and can see that the red plastic arm that sticks out to touch the cam and open the points is weakened and so the points are not always opening fully. I guess this could be causing all my problems. Think I have a spare dizzy set somewhere - as you say, they were cheap enough so I bought 2 - so I will replace this and see if it helps.

Will report back when done.
 
Take the air intake top off the top of the carb, and check your air filter! Presumably it is a wet one, and may be full of crap in the bottom of the bowl. If it don't get air, it don't run!

Your inlet valve rocker clearance should be 10thou, with 12 thou for the exhaust. Your points shopuld be set at either 25thou or the thickness of a fag packet - whichever is nearest to hand.

You said that you have a black residue on the plugs, which sounds as though it may be a combination of not enough air and not enough spark.

Which spark plugs are you using? They should be Champion N9Y.

I look forward to your comments.

OSD
 
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