Series 2 Zenith woes

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Brasletti

New Member
Posts
7
Location
Newbury
My neighbour bought a series 2a that has had a nut and bolt restoration to original spec. about 2 1/2 years ago by Hobson Industries in Lincolnshire the vehicle has then sat in a barn unused and unstarted since. Apparently they run all restorations for 500miles before sending them out to their new owners. He was having trouble getting it started so I offered to have a look.

It was belching out black smoke, would not idle and then cuts out after a few seconds of running but more worryingly was leaking fuel heavily from the carb onto the exhaust manifold. All the electrics looked as new and appeared to be working so I have removed the carb and stripped it down. It obviously has been ultrasonically cleaned and had a rebulid kit recently and all jets seemed clear and the needle valve worked fine when blowing through it. So I put it back together and set the float height to 32mm since it was at 28mm thinking that this should solve the leak at least. The mixture screw was out at 2 1/4 so I reset it to 1 1/2. It ran for a 20 secs slightly less rich than before but still rough, worryingly it was still leaking fuel so I have increased the float height to 38mm. When I use the lift pump to fill the bowl it still seems to leak out of the throttle linkage rod. It is clearly getting fuel up to the carb but the engine dies almost as if it has emptied the carb bowl. Should I feel a stop when using the lift pump when the needle valve closes? This is the first petrol landrover I have looked at and the carb seems pretty straightforward but something is clearly wrong there. Hobson Industries only warranty their work for 12 months so we are clearly beyond that besides they are 4 hours away so I thought I would turn to this hive of information for advice! Oh and I started with and empty fuel tank to which we added 2 gallons of unleaded with the appropriate additive.
 
First check to make sure float isn't leaking. The restorers may have used a copy Zenith and these are known to have problems with the two halves not seating together properly. The face of each may need gently lapping to ensure they are perfectly flat. As far as I know, the lift pump manual lever does not stop when the float bowl is full. Have you taken the spark plugs out and given them a clean and regap? I would also check the point gaps and the timing. When they are left idle for a long time, they do tend to smoke on start up but that should clear when the engine gets warm. Black smoke sounds like oil burning off.

Col
 
The other thing to consider is that if it's been left for 2 and a half years, the valve guides may have dried out and be causing oil to get into the combustion chamber. A compression test can give a clue to this.

Col
 
Hi Col, thanks for your help. I checked the points gap and cleaned up the plugs and re gapped to 0.9mm but cannot get it running long enough to check the timing. The restorers seemed to have done such an amazing job on everything else that I didn't want to meddle too much at first. The carb has Zenith 361v in the casting so I assume it is original, before I put a new float bowl gasket on I went over the 2 halves of the float bowl with a steel rule looking for gaps after I had cleaned the old gasket off. I just cannot see why it leaks when clearly the needle valve seats well if you invert the empty carb and blow down the fuel supply line. Is there a limit to how high you can set the float level or should I just keep raising it until it no longer leaks through the butterfly spindle?
 
It's possible that when they ultrasonically cleaned the carb, a speck of debris has found it way into a jet or its seat. If all else fails you may have to strip the carb and give it a good clean with carb cleaner. You can get a tool to clean jets, it's a series of fine needles that you poke into the jet very carefully. All carb refurb instructions I have read say you shouldn't poke bits of wire into jets but I have, with some success. A compressed air line is also useful for cleaning out carbs. If the carb had petrol in it when the landy was parked up, that would have evaporated leaving behind a tar like substance which plays havoc with tiny appetures.

Col
 
Thanks Col. I can see that it was ultrasonically cleaned by the amount of tiny aluminium particle residue there was in the bottom of the float bowl when I first stripped the carb and how little shellac like residue there was. I removed and went through all the jets with varying sizes of of nylon fishing line, carb cleaner and an air line, all seemed clear and the valves all worked as they should. very little wear on the butterfly spindles, so all good there. I then found online a rebuild guide from AutoExpress where I got the float height to be 32mm. so I put it back together with new gaskets and oring from Bearmach, they only thing I couldn't assess was the accelerator pump diaphragm but again it looked new like the jets, needle valve and seat. It clearly needs to come off again, I will see how well the floats float or just put new one in.
 
Have you taken the air mixture screw out and looked at the tip? I had loads of problems setting mine, when I took it out, I found the end was slightly bent. I put a new one in and it made a good improvement. Generally, these Zenith carbs aren't much trouble, they may not be the best for performance or fuel economy but they work in all conditions for years and years. I bought a container with a plastic tube and tap that I can hang on the raised bonnet. I was having some fuelling problems, so to eliminate the pump and full lines I wanted to bypass them. The container is filled with petrol had hung above the carb, the tube is connected to the carb and the flow can be controlled with the tap. I bought it off eBay. This might useful for trying to get the engine to run with out fuel leaking all over the place cos you can shut the fuel off for a couple of seconds when it starts leaking. It's more than possible that the problem may resolve itself if you can get the engine running long enough to get it up to temperature.

Col
 
Yes, the mixture screw looks fine and new like the rest of the brassware, it has not been screwed in too far since I realise that this can be a problem - damaging the seat. It seems happiest set at just below 1 turn out. Good idea about the feed bottle, I have one so will try that since if we can get it running for a few minutes then I am sure we will make some progress. My experience is more with motorcycle and small bore engines where the carbs have always been more cooperative todate!
 
Sometimes, it is possible to clear an obstruction by removing the air filter and placing a hand over the throat of the carb whilst the engine is running, the increased vacuum inside the carb sucks any crap into the combustion chamber. Did you set the air mixture screw with the filter on or off?

Col
 
I set it with the filter on, I will try the above but just need to get it to run long enough to get it up to operating temp first, so hopefully using the fuel bottle will get me there. I will have a go this weekend. Not knowing the vehicle it would be nice to know how it was running when it was delivered, it has been restored to such a high standard a true last nut and bolt job. Looking at the tyres I would like to know where it is supposed to have done the 500 miles that it apparently has done, since that should have delt with some of the teething problems.
 
It could be that a rubber o ring has perished/dried out/split causing the carb not to function. It's a bit weired that you say petrol seems to leaking out of the butterfly spindle. For that to happen the float cannot be working. Is the choke mechanism working ok?

Col
 
Choke working fine, I put in the new O ring that came with the £8 eBay Bearmach seal kit, I will see how well the float floats in a pot of fuel when I pull it apart at the weekend, since when the engine was cut it continued leaking fuel out of the spindle for a minute or so !
 
Welcome to the Zenith Warp zone.
I have had exactly the same problem. I eneded up "lapping" the two halves several times to get my 2.25 to run without belching black smoke. In fact today I am back on landy zone becuase I need a new carb and want to buy a new zenith remake not from that lot. So basicly you need to lap the two halves on flat surface with sand paper and oil. Then your engine will warp the carb some more on a hot day, back to lapping again. Maybe 3 to 4 times before it stops warping but by then the zenith may be out of spec. sigh its gotta be zenith warp, becuase black smoke, 2 1/2 years ago restoration?, my zenith is maybe 7-8 years old. Also watch out on the float, ethenol weakend a float I had and it wasnt floating. Went back to striaght unleaded gasoline. The remake zenith with the warp problems is a tuff one to make work.
 
Sounds like the float is either sticking or has a leak and petrol has entered the float. I can’t see that a warped top or bottom casting would allow the car to overfill.
 
Yesterday we finally got this Series II running - yeah! I have not posted recently since had no updates until now. Thank you Col for the suggestion of using a seperate fuel supply and thank you everyone else for your inputs. I used the seperate supply on the work bench to work out how sensitive it was to float height but more importantly found that the fuel leak was coming from the throttle spindle, which when the vehicle was sloping backwards even slightly and the throttle touched, the accelerator pump sprayed fuel onto the spindle which then let it leak onto the linkage. When we got it running properly this went away since the excess fuel was sucked into the engine. As suggested I lapped both sides of the cases but these had clearly been done before and were flat enough.
So after going through all the jets again and reassembling the carb for the third time, we got it running perfectly on the gravity feed aux bottle in the engine with no leaks. Going through the fuel feed from the tank the lift pump worked fine but non reinforced pipe had been used to supply from the tank to the pump. This was still nice and supple but had been zip tied to the brake lines with really thin ties compressing the tube and I presume pinching it in a couple of places. Anyway when these were replaced with fatter, looser ties and the carb connected to the correct supply the old girl ran beautifully and pulled well going uphill in fourth so hopefully we cured the cutting out problem as well. I left her with a note to be used and not to be left for 2 years again!
 
Brasletti said:
Yesterday we finally got this Series II running - yeah! I have not posted recently since had no updates until now. Thank you Col for the suggestion of using a seperate fuel supply and thank you everyone else for your inputs. I used the seperate supply on the work bench to work out how sensitive it was to float height but more importantly found that the fuel leak was coming from the throttle spindle, which when the vehicle was sloping backwards even slightly and the throttle touched, the accelerator pump sprayed fuel onto the spindle which then let it leak onto the linkage. When we got it running properly this went away since the excess fuel was sucked into the engine. As suggested I lapped both sides of the cases but these had clearly been done before and were flat enough.
So after going through all the jets again and reassembling the carb for the third time, we got it running perfectly on the gravity feed aux bottle in the engine with no leaks. Going through the fuel feed from the tank the lift pump worked fine but non reinforced pipe had been used to supply from the tank to the pump. This was still nice and supple but had been zip tied to the brake lines with really thin ties compressing the tube and I presume pinching it in a couple of places. Anyway when these were replaced with fatter, looser ties and the carb connected to the correct supply the old girl ran beautifully and pulled well going uphill in fourth so hopefully we cured the cutting out problem as well. I left her with a note to be used and not to be left for 2 years again!
Click to expand...
Excellent, well done.

Col
 
Yes, good job well done. When I found the butterfly spindle and its hole in the body of the carb was worn I filled the hole with chemical metal then re drilled
The correct size for the new spindle. Worked fine for years. Never had a warping problem with original carbs.
 
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