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ZENITH CARB.

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had a couple of hours tinkering with my friends mk2 zodiac convertable today. i built the engine for him 10yrs ago. its been run for the last 10yrs and always been tempremental. mechanically new, reground crank, rebored, head fully rebuilt and unleaded conversion. now it seems everytime he go's out it conks out and wont start til its cold. i had a look over it today, re set timing to 10 deg btdc, found a loose ht cap and a plug lead that wasnt working. sorted them then had a play with the carb which is a single zenith. when reved from idle it splutters but once passed that it will rev right up, over n over again no problem. ive never played with this type of carb as ive always had webers.  but it seems the accelerator pump is throwing too much juice in. there is 3 holes to adjust how much the pump lever pushes and put petrol in. tryed all 3 and still the same. any ideas or is there anywhere else to adjust that ive missed?

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When it stops what does it lose, fuel or spark? Taking its a six pot, you will have a fair old quirt of fuel on accel pump. If it's still on points set the gap on dwell rather than gap. Advance and retard on dizzy ? Check diaphragm  by sucking it or vac pump and check stator plate for movement. Failure when hot on lecy side could be King HT lead LT lead from dizzy to coil insulation on points breaking down, condenser or coil. Fuel side weak pump of tank not venting ( run with fuel cap off ) fuel filter in line blocked.

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12 minutes ago, colr6 said:

When it stops what does it lose, fuel or spark? Taking its a six pot, you will have a fair old quirt of fuel on accel pump. If it's still on points set the gap on dwell rather than gap. Advance and retard on dizzy ? Check diaphragm  by sucking it or vac pump and check stator plate for movement. Failure when hot on lecy side could be King HT lead LT lead from dizzy to coil insulation on points breaking down, condenser or coil. Fuel side weak pump of tank not venting ( run with fuel cap off ) fuel filter in line blocked.

yeah 6 pot. also forgot, it has elec ign. not sure what type as he fitted that a while ago. yeah it squirts a fair bit of fuel in from the accel pump. and the vac advance on the carb i blanked with a hose and bolt. glass bowl filter, full. could try with cap off though. thats an option. seems to me like when its dying it has fuel and i kept the strobe on so i could see it flashing with the spark. i have suggested stripping and rebuilding the carb. he also has 3 other carbs, all old and unused for a few years so i wouldnt count on them!

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You could always eliminate ign feed see to coil, hot wire it direct from battery to ign pack. Could the ign pack be faulty when hot?

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8 minutes ago, colr6 said:

You could always eliminate ign feed see to coil, hot wire it direct from battery to ign pack. Could the ign pack be faulty when hot?

again a possibility. i will try and get a couple of hours next week to look at it. my other mate whos a mechanic, came to pickering with us, rang me earlier. he also has a zodiac to have a look at, although i think that one runs, just a service on that. i'll keep you posted on it.

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On 31/07/2018 at 22:57, colr6 said:

You could always eliminate ign feed see to coil, hot wire it direct from battery to ign pack. Could the ign pack be faulty when hot?

well we had a few hours on the Zody today. put another carb on thats just come from a running car. put another voltage regulator on, went through all the wiring to the coil and elec ign. found a few loose terminals and wires wrapped round. pulled the dash clocks out to check the wiring behind there as he thought the ignition switch could be dodgy. there was a wire that at some point has shorted out and melted all the plastic outer. taped that up. and a terminal on the rear of the switch had a connection loose! took the car round the block for a spin and run the best it has in ages. he's gonna take it for a longer drive to see how it goes and if it conks out. but so far so good!

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On 31/07/2018 at 22:57, colr6 said:

You could always eliminate ign feed see to coil, hot wire it direct from battery to ign pack. Could the ign pack be faulty when hot?

update. well it seems all the things i found and did on the car have sorted it out. he's been out 4 times over the last couple of week with a tow on stand by, and its run fine. i went over this morning and we took the zody out for an hour. best it ever run! i cant believe how comfy and how smooth it is on the road! could just do with an extra gear.

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