Misfire?

[dreamin']

6 pot land rover engine

New plugs and leads

Experimenting with mixture - probably richer than needs to be

5 plugs black and sooty, #6 grey and clean

Does this mean no ignition in this cylinder, therefore electrical problem?

What else to check?

[chazza]

Need a bit more info.

Are the plugs sooty when the engine is hot?

Sooty plugs happen on a cold engine, or if the mixture is too rich, or if the spark is not doing its job properly.

Have you checked the valve clearances and the ignition-timing before adjusting the carburettor? Always tune an engine in the order of: valves; ignition system; carburettor. Tuning an ignition system can take some time if you are using points and you really need an instruction book to help you get everything done properly,

Cheers Charlie

[Chris72]

Just a thought but how old is the fuel in your tank ?

Cheers Chris

[dreamin']

Thanks for the quock replies.

In aswer to your questions|

Fuel is definitely fresh

Drove for an hour earlier today - highway speed, so definitely operating temp

Will check tappet clearances and points, then carb - thanks Chazza

Will also test compression in each cylinder, while plugs are out

If fuel, spark and timing OK, could it be valves?

Thanks again

Roger

[JDNSW]

Thanks for the quock replies.

In aswer to your questions|

Fuel is definitely fresh

Drove for an hour earlier today - highway speed, so definitely operating temp

Will check tappet clearances and points, then carb - thanks Chazza

Will also test compression in each cylinder, while plugs are out

If fuel, spark and timing OK, could it be valves?

Thanks again

Roger

If valves, it will show in the compression test. And yes, this is a possibility. Make sure that there is not a track on the distributor cap shorting one cylinder.

John

[wrinklearthur]

If valves, it will show in the compression test. And yes, this is a possibility. Make sure that there is not a track on the distributor cap shorting one cylinder. John

Stick your head under the bonnet when it's dark, with the engine running you can see straight away where the sparks are jumping.

Like all engines that have alloy head's, you could have a blown head gasket.
But the 2.6 does have a tendency to burn numbers five and six exhaust valves.
It helps heaps if you are both ambidextrous and a contortionist to work on those valves
.

[chazza]

Experimenting with mixture - probably richer than needs to be

5 plugs black and sooty, #6 grey and clean

Does this mean no ignition in this cylinder, therefore electrical problem?



Seeing that you have taken it for a good run, then it is probably sooty due to the mixture being fiddled with; however; stick with the plan and start with the valves and compression test. Remember to have the throttle wide open when you do the compression test; the engine hot and record the results wet and dry - good luck!

Incidentally - how did it run on the road? What made you decide it was mixture being the problem?

Cheers Charlie

[dreamin']

OK

Compression test (dry) as follows:

1. 130
2. 125
3. 130
4. 140
5. 130
6. 120

Throttle was open (pedal to the floor), plugs out, battery charger attached for even turning, but engine probably cold and no wet test - I figured if there was a problem that could be rings or valves I will have to get the head off anyway. Also, my compression tester is a bit old and unknown accuracy.

Taking all that into account, can these results tell us anything? I was expecting higher figures generally but also looking out for one or two cylinders dramatically lower than the others. Low readings overall could be wear, but
maybe just my guage? #6 (the one with the non-sooty plug) is definitely lowest but only by about 10 psi.

I also adjusted inlet tappets, fitted and set new points and condenser, and cleaned the distributor cap - both looking a bit old and worn. I have new ones on order.

Started and idled fine but still a bit rough, 'lumpy'. Turned all the lights off and no visible sparks, so maybe they're staying where they should be, Arthur?

This all started when she suddenly started running very rough a couple of weeks ago. I think I fixed the main problem by replacing the carb diaphragm
(Zenith Stromberg) and then went through the manual procedure for setting idle speed and mixture. The engine seems to be very sensitive to these settings, but the adjustments seem very coarse and I just can't get it to run smoothly. Maybe the o-rings on the throttle adjuster?

Tomorrow I'll clean the carb and fit new gaskets and seals - I still think this is
where I'm having trouble getting the air/fuel mix right. She drives well enough - sits happily on about 105 kmh on the hwy - but 'pops' and runs rough at idle and overrun, with strong petrol fumes and I would like to know if I am actually using all cylinders!

Thanks again for your help and advice

Roger

[wrinklearthur]

Compression test (dry) as follows:
1. 130
2. 125
3. 130
4. 140
5. 130
6. 120

Taking all that into account, can these results tell us anything? I was expecting higher figures generally but also looking out for one or two cylinders dramatically lower than the others. Low readings overall could be wear, but
maybe just my guage? #6 (the one with the non-sooty plug) is definitely lowest but only by about 10 psi.

I do think that the spread of those readings is borderline with that lowest reading of number six cylinder being 20 PSI below the highest reading of 140 PSI, the difference is 14.29%, but that's not enough of a problem to pull the whole engine down unless it is also breathing oil fumes heavily, the most likely problem that has been shown by that test is that the exhaust valves now need some attention.

According to my workshop manual for a 7:1 compression ratio engine the test should show 140 lbs / sq in, see if you can catch the attention of Blknight.aus for his opinion, as Dave would have worked on a lot more of those engines and more recently than I have.


Started and idled fine but still a bit rough, 'lumpy'. Turned all the lights off and no visible sparks, so maybe they're staying where they should be, good
.

[chazza]

Seeing that the engine was cold, I think the compression test indicates nothing to be too alarmed about, but I agree with Arthur that the valves probably need attention some time in the future. A wet-test will confirm if that is the problem, or not, on no.6.; as would introducing compressed air into the cylinder with the valves closed and feeling for air at the tail-pipe.

A carburettor kit sounds like a good idea Roger, as does the new ignition parts. Is the spark a nice electric-blue? If not a substitute coil of known quality would be a good check,

Cheers Charlie

[Chris72]

You could to see if the mating surface between carby and manifold is leaking, use some carby/throttle body cleaner (also seen this done using lpg) spaying around the mating surface if the idle changes while doing this it's sucking air, you can do this around the inlet manifold as well but keep a fire extinguisher on hand.

[dreamin']

Thanks Chris

Will get to the carb tonight. On this engine, the inlet manifold is part of the alloy head, so fewer joints to leak. I have an overhaul kits with all the carb gaskets, o-rings etc, so will do them all and see if it makes a difference.

Cheers

Roger

[Chris72]

Roger what are these motor's really like as I have one thats out of my series 2a and don't no a lot about them apart from what I've read and most have been swapped out for something with a bit more power, I'm just waying up if it's worth rebuilding or doing the swap.
How did you get on with the carby rebuild ?

Cheers Chris

[dreamin']

Hi Chris

Didn't get to the carb last night, but I did go for a drive and think that new points, tappet adjustments etc have made a difference. Carb is next to do.

I'm really just learning about these engines, but here's what I think about mine:

First, its's the original engine in an original condition land rover, and both are a bit rare, so I want to keep it that way. As you said, not many left.

Second, as I get the hang of it, I'm finding it great to drive.

Most of the time I take off in 2nd, 3rd is very torquey and 4th will sit happily at 100-110 kph on the highway. I also have an overdrive but only really use it to reduce revs at top speed on flat or downhill runs, and occasionally as a '3 and a half' gear when climbing steep hills.

It took me a while to get used to double-declutching, but now find 3rd is so strong at low revs that I rarely need to change down to 2nd. It is definitely not nippy, but its is lugging 2 tons of Dormobile around.

Also, it makes a beautiful exhaust note when accelerating under load.

The Holden engines are more powerful, less fickle, and easier to get parts for - but they aren't the reasons I drive old land rovers.

Good luck with your decision!

Roger

[gromit]

I'm told that the exhaust valves are a weak point (as on most F-head motors).
PITA to get to to adjust, ended up removing the dipstick tube so that the cover plate can be removed (otherwise the manifold has to come off).

Details here of a 6-cyl overhaul. Done on the cheap....... I ended up hand scraping the wear ridge at the top of the bores.
http://www.aulro.com/afvb/leaf-sprung-military-land-rovers/118730-ffr-refurb.html

I haven't done much with it for a while (lost momentum on this project) but a couple of times it has suddenly run very 'lumpy' and then shut down. I suspect a problem with the carby but not sure yet.

Spares for the 6-cylinder are getting hard to find and/or expensive. Water pumps are expensive/scarce but you can go to a specialist and get the original rebuilt. Exhaust manifolds regularly crack.
4 Wheel Drives in Blackburn have some spares.

Best of luck,


Colin

[dreamin']

Thanks Colin - rebuild thread very helpful. I am lucky mine is in better nick to start with.

I have been putting off doing the exhaust valves - thought I could only do it with the manifold off, which means dealing with rusted studs etc etc. till do 't quite get it - do you put it on ramps and work on it from below?

'lumpiness' sounds like what I have just fixed with new diaphragm, but still not happy with overall tuning yet.

Say hello to Narre for me - I grew up in Rowville.

Cheers

R

[JDNSW]

I have not worked on a six, but perhaps it should be remembered that on all Series Landrovers it is quite easy to remove a front mudguard for access (The first time you may have to twist off and replace a couple of bolts, but if you use antiseize it will be easy in the future.

Hope this helps

John

[dreamin']

Thanks John - good point

[gromit]

Thanks Colin - rebuild thread very helpful. I am lucky mine is in better nick to start with.

I have been putting off doing the exhaust valves - thought I could only do it with the manifold off, which means dealing with rusted studs etc etc. till do 't quite get it - do you put it on ramps and work on it from below?

'lumpiness' sounds like what I have just fixed with new diaphragm, but still not happy with overall tuning yet.

Say hello to Narre for me - I grew up in Rowville.

Cheers

R

I didn't put it up on ramps, just took the dipstick tube off from below, filter had to be removed to do this.
The cover plate would then just squeeze past everything (I don't recall having to take anything else off). Bonnet needs to be removed or opened up against the windscreen.
I'd adjusted the clearances after the rebuild, fitted a new manifold (old one was cracked) then after running it for a while it sounded tappety so I decided to re-check.

There's a picture in my FFR thread (post# 28)that shows me on top of the engine adjusting the exhaust valve clearances......


Colin

[wrinklearthur]

The first time you may have to twist off and replace a couple of bolts, but if you use antiseize it will be easy in the future.

I use a Molykote antiseize paste, but if you get it on your fingers and you have a itch that needs a scratch, the whole world knows! :angel:
.

[dreamin']

Things are getting better

Since my last post, I have fitted new dissy cap and rotor button, so all ignition components except the coil are new.

I took the carb off and cleaned it inside and out, fitted new gaskets and o-rings throughout and put it all back together. Some of the o-rings were a bit gummed up, one or two gaskets looked damaged.

I also got a timing light and found ignition was way advanced, so reset at 2 ATDC as per the manual.

Engine certainly seems smoother now, and far less 'popping' at idle. Drives well too, but power seems to come in at higher revs than before. Still not sure I am getting the best out of it.

Will try a longer drive, get it properly hot and reset inlet tappets and mixture. Then the exhaust valves will be all that's left and I will HAVE to deal with them.

R