Thread: Zenith alternatives

Originally Posted by the big fist

Quick update:
Pulled the carby and stripped it down. The bowl is full of orange crystals plus they all around the block under the top side of the carb. Looks like crystalised fuel from lack of use ? I recieved a kit today so will put that through it.

Sounds as if you have found your carburetter problems! Make sure that all foreign material is removed everywhere in it.

I also found that the floats look to have small cracks in it. What affect would this have if they werent cutting the fuel flow off ?

Would cause rich running and probably hard starting. Try the traditional test for a leaky float - submerge the float in hot water - if there is a hole, the heat causes the air inside to expand and there will be a trail of bubbles from the leak. No bubbles, no leak, and it only "looks" to have small cracks.

On another topic, I found that the mark I am using to set my timing is not where the 3 strips are with the number 6 at each end. So could my dizzy be out of phase or my timing light not connected to number 1 ? I am taking number one as the cylinder closest to the radiator.

Interesting....

Timing may well be out. But if it runs at all, it is not all that far out. The factory setting for timing is done using static timing, with the points just opening at 4 degrees for unleaded. This will give correct timing, provided that the distibutor vacuum and centrifugal advance devices are working correctly. However, for best results, having set this, adjust carburetter idling speed and mixture for best idle, then make slight adjustments to the distributor timing while the engine is idling for highest idling speed. If there is a big increase in idling speed, readjust the carburetter and repeat.

Then take it for a drive, and check for preignition under load. If this is encountered, retard the ignition timing a couple of degrees at a time until you no longer have the problem. If there is a big change here (unlikely unless there is a problem with the vacuum advance), you may need to readjust the carburetter.

No. 1 is the front cylinder.

John

The saga continues !

Very hard to start unless almost full choke. When it idles it chugs badly. Increase revs and it chugs and the whole motor shakes around.

Idle mixture screw all the way in, all the way out, no difference.
Looking down the throat there is fuel coming out from that main u shaped nozzle in the middle of the carb ?

I run electronic ignition (Petronix) and have their coil. It has a 12V supply. It gets quite hot as well. Off before running I have approx 3 Ohms across the terminals. After running about 4.1 Ohms.

Spark plugs are sooty but I don't want to replace until carb is sorted. They look to be sparking decently.

Sucking on vac tube moves the internals of the dizzy. Reconnected at idle and viewing timing I give a small rev but the timing doesnt move. ???

What do you guys think. Is the root of all this that the carby is still not 100% ? I reset the floats to 33mm. They are these foamy sort of things, not brass ones.

Help !

Cheers,

Peter

p.s
the O-ring in mine is in the bottom half of the carby around the throat. In the drawings I've seen it looks to be sitting in the neck on the emulsion block !?

If the plugs are sooty, then the mixture is too rich - problem is carburetter. From your description, I would say there is a leak somewhere in the carburetter. The most likely is the O-ring. This may be damaged, or incorrect. It seals between the emulsion block and the venturi, and may have been dispaced aaand pinched during assembly. Alternatively, it may not be being clamped. This is normally due to a warped top cover, but can be due to the screws holding the emulsion block stopping the cover from going fully home (because they are the wrong screws, burred, or wrong washers. Fit the top without the O-ring - it should sit flat all round. Then fit the O-ring aand refit - should sit up about a millimetre, but pull down easily with the two screws each side of the throat.

The other possible cause for the rich mixture is the float and needle valve are not cutting off fuel -this may be due to either faulty valve or floats sinking - check that they do float in petrol.

John

Thanks John.
I checked while running and there is a fair bit of petrol droplets coming from that emulsion tube. I couldnt see any coming from around the join in the venturi. I put a new O ring in and it sat a tad high which pulled down with the screws. Before it was flat with the old O ring.
I put the float in water and it floated. It's like a solid foam float. I left it for ages and it still floated. If I put it in hot water and submerged it bubbles would come out. With the landy off if I prime the pump manually it gets to a point where it wont prime anymore, I thought that might mean the needle and seat are ok ?
I am really lost now. How could excess fuel get into that tube ?

Any help greatly appreciated. I took a video if that helps !

Cheers,

Peter

Originally Posted by the big fist

Thanks John.
I checked while running and there is a fair bit of petrol droplets coming from that emulsion tube. I couldnt see any coming from around the join in the venturi. I put a new O ring in and it sat a tad high which pulled down with the screws. Before it was flat with the old O ring.
I put the float in water and it floated. It's like a solid foam float. I left it for ages and it still floated. If I put it in hot water and submerged it bubbles would come out. With the landy off if I prime the pump manually it gets to a point where it wont prime anymore, I thought that might mean the needle and seat are ok ?
I am really lost now. How could excess fuel get into that tube ?

Any help greatly appreciated. I took a video if that helps !

Cheers,

Peter

If bubbles come from the float when submerged in hot water, this indicates that it has petrol in it. You said it was a foam float, but if it is absorbing petrol, this mean that while it may not be sinking, it is probably floating lower than it should. This will set the actual level of fuel higher than it should be (despite being set correctly), giving rich mixture, especially when idling.

Your action priming the fuel means the needle and seat are working at least to some extent, but does not necessarily mean that they are not leaking sufficiently to upset idling mixture.

John

Originally Posted by JDNSW

If bubbles come from the float when submerged in hot water, this indicates that it has petrol in it. You said it was a foam float, but if it is absorbing petrol, this mean that while it may not be sinking, it is probably floating lower than it should. This will set the actual level of fuel higher than it should be (despite being set correctly), giving rich mixture, especially when idling.

Your action priming the fuel means the needle and seat are working at least to some extent, but does not necessarily mean that they are not leaking sufficiently to upset idling mixture.

John

Thanks John,
That would make sense. After I rebuilt it I reset the float level as it was at roughly 5mm out of where it should be. I have the original Zenith but it has plastic floats. I may test them. I also noticed under the seat fitting there was 2 quite thick washers shimming it up.

Hopefully I wont sound like too much of an idiot but why would the fuel be coming out from the main jet / emulsion tube at idle ?

Thanks greatly,

Peter


Also,
I found this on the net which was the fix to my problem on someone elses LR.

It turned out to be a plugged jet in the idle system. Since the idle system wasn't providing any fuel, I had the idle rpm screw turned in to make it run and it was activating the main jet circuit and dumping loads of fuel in. This idle jet has a ball valve, so you can't see thru it.
The only way I found out it was plugged was to poke a thin copper wire thru it.

On mine the idle rpm stop is also all the way in otherwise it just doesnt run.
Strange thing is that the carb was like this from new. Damn Indian copy. I wonder if I should check this valve as well !

Far out, this is driving me nuts. Last night Iplayed with the float level. Filled the bowl first from normal idle running then pulled the top of the carb off. Fuel was about level with the O Ring. I lowered the float height by about 5 mm, reinstalled and ran at idle again. Ran the same. Took the top off and fuel level was about lower than the O ring aroudn the base of the casting. So I guess the float works ?

Played around a fair bit and found that my "idle" is infact very very light throttle. Found the dlow idle jet has a ball valve in it which was clogged. I also found that in my wisdom many moons ago I must have plugged the port that runs to the idle mixture port with O ring as per one of the dodgey zenith fixes.
So took it to work today and stripped it again. Lapped it again, new gaskets, new jets, reset floats and reassembled. Only issue is being a copy, the economy device diaphragm wouldn't fit so had to use the old one.

Refit this afternoon and the car starts easier and idles at half choke.

HOWEVER. It is still chugging roughly, all through the rev range, only on deceleration does the engine sound smooth. I checked the leads, all have low resistance. My last guess is the plugs ? Could the old fouled plugs be causing this chugging. It's really driving me nuts !

Any help appreciated.

Thanks.

*edit*
Great, just found this video and that is exactly how it sounds:
[ame="http://www.youtube.com/watch?v=DQIvA2qeEKc"]Land Rover Series IIA driving - YouTube[/ame]

That sounds as if it is missing regularly, in other words, one cylinder is not working. This could be either a spark plug, or a high tension lead, or lost compression on that cylinder, probably due to a stuck valve or a piece of carbon on the valve seat. This last is the easiest to check - just turn it over by hand using the crank - all four compressions should feel about the same.

To confirm that it is a regular miss on one cylinder, with the engine idling, remove plug leads one at a time - if this is the problem, you should find one makes no difference.

When you find the one, try swapping the plug to another cylinder and see if it makes a difference. If it does not, try removing the complete plug lead and swapping it for another cylinder. Obviously, if it is a plug, change them all, and if it is a lead change them all.

There are two other, less likely possibilities for the sound. The first should be easy to find - an exhaust manifold leak - look for loose nuts on the studs holding it to the head, and a leak between it and the head, or a crack in the manifold casting, probably on the leg to either 1 or 4. The other one is that one cylinder is firing, but less well than the others. This will be due to low compression, either because of stuck rings or a burnt valve, and may not show up on the crank test - needs a proper compression check with a gauge.

Hope this helps. My best guess is the high tension leads (been there!).

John