Zenith 361v Mixture screw and vacuum

Hi All, Just bought our first Land rover, 1982 ex Military, 109 12v Full tilt.
It had been standing for 3 years but run up and down the drive regularly.
Can't quite get it to run right, It will not run well without choke.
With choke /half choke when warm it runs ok .
No choke it just splutters and bogs down.

I have emptied the tank and fresh fuel,
Cleaned out filter bowl
Rebuilt carb with a overhaul kit.
Static timing as best I can
Fitted electronic ignition module to replace the points and condenser.


The carb kit did not have a mixture screw in it, the original mixture screw had a groove running the length of it, this was full of muck so I cleaned this all out is that correct thing to do ?

Turning the mixture screw right in doesn't seem to make much difference,
turn it out 1 1/2 to 2 turns makes no real difference. 3-4-5 turns not much change ?

On The carb there are 3 tubes protruding,
Top one for fuel
One on the bottom of the carb which the vacuum pipe to dizzy is attached to.
And then there is a smaller brass tube nearly next to the mixture screw which isn't attached to anything, should this be attached to something ?

I have borrowed this image from the web of a Britpart carb


My next job will probably be carb off again and Mate all the surfaces as I found a good link on here on how to do this.

Any thoughts or ideas would be great

Thanks
Russell

It sounds to me like your idle jet or one of the passages is blocked as the mixture screw isn't doing anything.

Here's a set of diagrams for the 36 which should help trace it. https://dl.dropboxusercontent.com/u/78197607/Z36IVWS.pdf

A few tins of carb cleaner spray (wear goggles its fierce stuff) and chase the problem back through the channels and you should be good...

D

I don't remember there being a groove on the mixture screw

Thanks for that Dom,
The muck in the mixture screw was very difficult to remove, almost as if it had been purposely put in there.
Thanks for the schematic , I was quite sure I had cleaned the carb well, used a whole can of carb cleaner, every hole was sprayed well.
I hadn't checked the gauze filter on the fuel bowl, took that out today and it was as clean as a whistle.
I took a couple of photos of my carb today, Mine is a lot later design, I had some kind of solenoid which goes straight to the + on the coil.
Also my vacuum pipe goes to the pipe at the bottom of the carb, your diagram clearly shows this further up the carb. This was how I bought it, bar the tape round it , I put that round the join between the 2 pipes in case air was leaking.
When I pull the bottom hose off, there is a lot of suction if I put my finger over the hole.
there is no suction at all from the upper tube on tick over.
http://i1382.photobucket.com/albums/ah279/russfrancis/IMAG0209_zps82318ae1.jpg

A few more photos of the plumbing layout.
http://i1382.photobucket.com/albums/ah279/russfrancis/XX-72A0DD75-1369807-1280-100_zps63ad8b32.jpg

http://i1382.photobucket.com/albums/ah279/russfrancis/IMAG0214_zps722fac21.jpg

Certainly not the vacuum advance arrangement that I've got. I have a small rubber connector on the upper brass connector. I think there's a blanking plug where your advance is connected - and my advance pipe is a lot thinner, connecting to a similar connector on the dizzy. Have you got a copy of the manual?

There are two options for vacuum advance ported (i.e. above the throttle) and non-ported below the throttle.

All the Landy diagrams I've seen have used ported vaccum which means that the ignition is _not_ advanced at tickover but advances quickly as you open the throttle. I suspect you should be on the upper pipe.

I believe that solenoid is an anti run-on valve which cuts the idle circuit when you turn the engine off. If that is broken or the supply off then you will get the symptoms you're describing.

With the engine off and the ignition on if you pull the wire on and off the solenoid you should be able to click. If not that may be shot (or more likely the wiring is broken). If it sounds like its working then a strip down and check might be in order if the plunger is sticking it will starve the idle circuit.

Another thought - should there be an o ring seal on the idle screw?

You haven't mentioned the throttle stop adjuster screw. If you give the engine a whiff of throttle, will it idle with no choke?

(From the wing side, have a look at the throttle linkage - you'll see a small screw, probably with a similar plastic shroud to the mix screw, which sets the position at which the throttle linkage can't close any more)

That was certainly the score on mine - again, gunked up mix screw preventing that from doing much. Even as you adjust it, the effect at idle is subtle, and easy to miss.

Start with the mix 1.5 turns out. Tighten the throttle stop in a turn or so. Then loosen it until the idle starts to cough and die. Then tighten it a little until it's stable. Rev the engine, and let it drop back to idle. You want to get the speed a LITTLE bit higher than the bare minimum to stop it dying on the way off revs.

Then adjust the mix until it sounds and drives "cleanly". If you've got access to a colourtune or gas analyser, great. If not, hey-ho. Get it running about right, and keep a screwdriver in the dash...

Thanks for all the help and ideas , I shall have a go tomorrow and report back.
Cheers
Russell

Thanks for all the input,
I had I little play today, As suggested I connected the vacuum pipe to the top / upper thin tube and used the hose with a bolt in it to seal off the lower tube.

I then checked the solenoid as instructed and sure enough , no clicking.
I removed and cleaned the solenoid and got it working really well.

I put the solenoid back on but sadly it is still the same ,

I can't find any reference to the mixture screw having any O rings on them yet.

The throttle stop adjustment screw I think is about right, without choke it will idle beautifully, Then if you rev it, it will bog down/hesitate then rev but not cleanly, When I was a Lad it is almost like my off road bikes did when the air filter was blocked.( Air oil filter is good- no change on or off)

As we have only had it a week we have not been far, ( Mainly due to it only doing about 3 Gallons to the mile at the moment as the choke is on)
We took it up to the beach and along the sea defences, Which is a concrete wall of about 30 degrees.
Whilst driving up the sea wall (still on half + choke) I noticed the landy was running out of power as if it was suffering from fuel starvation.

I believe I read somewhere this week that the possible cause for that is incorrect float height ?

I have got the carb off this evening,So my plan of action for the weekend is
to rub down all the mating surfaces on the carb as per instructions on this forum, and clean out again and then check the float heights.
Then go back to the beginning with the set up.

If any one else can think of anything else to check that would be great.

Russell

May seem a bit obvious but have you checked the ignition is set up OK? - it's usually the first thing to eliminate as a potential problem. Those sort of MPGs are definitely excessive - one of the problems of the 36IV is a tendency for the body to warp, allowing fuel to bypass the jets and go straight from the float bowl into the inlet! Worth putting the two halves on a sheet of flat glass to check - lots of threads on here about how to fix this.