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Zenith single carb problems

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Thanks,
But half the fun of having the MG is fixing it myself. Ron come out to the Independant Cruise night in Mililani on the 11th. As long as she is running at all I'm going and I'm bringing the MG. It's always fun to meet others with similar interests.

Status Update:
Okay I fabricated a heat shield for the carb out of some sheet metal and the repair manual said to measure the distance from the gasket on the carb to the float bottom at 16-17mm. I changed it to 20-21mm instead. I then put everything back together and started her up. I could get the idle down to normal but she is still running quite rich. I drove it around the block and it ran alright. Definetly better than before but still way to rich as it bogs a bit when I try to apply power to the wheels. Getting closer to it running right.
 
Ofcalipka said:
Also since I now have the manual I found out that the prior owner did some modifications of his own to the intake. The EGR it connected directly to the intake manifold with a peice of rubber vaccum line and the vent on the valve cover goes strait to the carb. No T connector or lines running elswhere and the place where a line is supposed to run to the primary adsorption canister, which is missing from the car, there is nothing just an open fitting. It seems to me that this carb was only meant to run one way and now I've found some of these items missing so can it function correctly in it's current configuration or do I have to start tracking down some obscure parts?
Click to expand...

I had a similar situation on MY Midget - I took out the pollution stuff and modified similar to what you describe. Basically I have the vent hose running to the carb and that's it. I was having huge flooding issues and it turned out to be that I had blocked the line that was supposed to run to the canister - it is a vent to the float chamber - as soon as I opened it, it stopped gulping fuel into the carb

RE: richness, ZS carbs tend to run rich - are you running the original air filter? I have a longflo filter and corrected my richness by blocking off 1/2 the filter. I just covered the outside with painters tape and tore off strips till it was running right.

Notwithstanding the previous conversation, I don't believe there is a lot of richness adjustment room on a ZS - they seem to have been set up from the factory
 
Did you replace the diagphram when you rebuilt the carb?
I am not sure of how the starter box works but are you sure that when the choke is all the way in (off) the throttle plate is completely closing?
Seems you have the C3754 number carb, the only one with that starter box setup. Check the manifold to make sure it's evenly tight. Those manifold nuts are a royal pain to get a wrench on and I have seen those fat football washers missing.
 
Float chamber vent!!! It ~looks~ like a vacuum take-off but if blocked, it'll do the flooding thing... I hadn't considered it may have been blocked. Thanks JP!! Good call.
 
Wouldn't restricting the airflow on the filter with tape cause it to run richer as your reducing the air getting in and not the fuel? Manifold nuts are all tight. I think I might try adjusting the float even more after the new diaphram for the bypass valve comes in and I have the carb put back together right. I was reading up on how the Zenith carbs function and I might try replacing the metering needle if I can't get it to lean out enough after all that. I don't think it will help but it can't hurt either. Oh, and yes the float chamber vent is open to atmosphere. I'm thinking of tracking down the adsorption cannister and running the lines as maybe it needs a slight restriction there but I'm not sure about that yet.
 
Here you all go here is a video of her current running condition for you all. You can't see it very well in the video but the exhaust is smoking a bit still yet. The audio seemed to come though okay however. Let me know what you all think here.


MG Midget start up and running.
 
Ofcalipka said:
Wouldn't restricting the airflow on the filter with tape cause it to run richer as your reducing the air getting in and not the fuel?
Click to expand...

you would think - and I tried to find the extensive thread in the Spridget forum but I'm search engine challenged. At any rate, without understanding the physics, apparently, you lower air, you lower fuel. All I know is that it appeared to work on mine to the point that the last time I drove it, it backfired under load - too lean, pulled on the (manual) choke it evened out, took it home, tore a strip of tape off the airfilter and it was good to go

then I bought an SU :smile:
 
Say, just a thought. If the auto choke is removed, is the vacuum port for the choke pull off blocked? I still have my auto choke, and it occurred to me there's the piston that pulls the choke off slightly once the engine starts. If the manual choke doesn't block it, it could be a problem.
 
I don't know which port that would be. But I'll look into that this afternoon. I tried driving her in to work this morning and she was fine until I hit the freeway. As soon as I put her into 3rd she started to bog down and tried to die out so I shifted to 4th and it was even worse. But when I step on the clutch and gas it she'll go full rev. 1st and 2nd seem fine even climbing hills. I didn't have time to look it it just yet and the throttle cable frayed and started to stick as well now too. Anyone experianced this before that could help pointing me in the right direction here?
 
Use some ingenuity and a teflon lined bicycle brake cable for that throttle cable. Save time and money... the "replacement" ones are a disappointment by comparison.
 
Well I get home from work and the parts I ordered last week came in. So I change and get to work on the MG. I get the bypass valve put back together and make a few more adjustments to the carb. I start her up and she runs fairly well. So I take it around the block it is still bogging down a bit when I gas it up or apply some power but it seems to get past it and keep going. So I drive down the road to try a quick drive on the freeway. But just before I hit the on ramp it starts to sputter out again so I pull over to the shoulder pop the hood and start checking things. First thing I notice is that the in line fuel filter I installed barely has any fuel in it at all. So I start thinking maybe I have a blockage in my fuel line somewhere. She is still running so I figure I could start limping home. As I am closing the bonnet some twit in a pathfinder drives past yells "Fag!" at me for what reason I don't know and throws a cup of soda or something at me. I duck and it misses but what the heck? Anyways I get back on task and start making my way home. About a mile or so away. She starts dying out every block or so but starts right back up. I get within about 2 blocks of my house and she dies again and I'm only just able to pull over right at the corner. This time she won't start. So I get out and check under the bonnet again and find the fuel filter completely empty. Now I'm thinking maybe the fuel pickup has gone bad in the tank. So I pop open the petrol cap to add more fuel and hear a loud sudden sucking swish. Apparently the tank wasn't venting. I go check under the bonnet now and there is some fuel in the filter. So I get back in to try and start her up again and the starter motor goes out on it. AHHHHHHHH!!!!!!! So I'm sitting there with the hazards flashing waiting for my brother-in-law to come down with his truck to tow me back home and some fool pulls in behind me on the shoulder and starts laying on his horn. I signal for him to go around and he starts yelling "Get out of the way!". I get out and see from the look on his face that he did not expect a male being 5'11" 210# in this little car at which point he takes off rather quickly leaving me alone again. My brother-in-law shows up finally and I pop the clutch as he tows ma and she starts up and I get her home and find the previous owner had crimped the fuel tank vent line closed. Why?? I remedy this and try and start her and now the starter starts working. I take it around the block near my house about 3-4 times and other than still running rich it seemed okay this time. Well that was todays adventure. Some people were having a bad Monday today I guess. Mine was pretty good as it seems I'm that much closer now to a running MG.
 
Yes I know it's late but I just had to vent. I read the manual some more and noticed that one possible cause of my problems could be a malfuntioning EGR valve. So I try to take it off to inspect and clean it. Instead I snap it in half and destroy any chance of getting the car running again until I buy a new one. I scoured the internet and found nothing. So I got creative and welded it back on. One of my best welds too I think. I try to put the little pipe that goes to the intake manifold on and come to find out that I warped the spot it screws into when I was trying to remove this handy little device. Now I have to find a replacement one. I scour the internet some more with some creative searches and come across the Little British Car Co. who claim to have this part for just under $60. Well their order forms leave a bit to be desired but otherwise the new part will be here in a few days and in the mean time I have to take the exhaust manifold back off and down to the local machinist to have the old EGR I so brilliantly welded back together taken out and have him retap the hole is secures into so that the new one can be fitted on. I will get this car going yet as I have not yet begun to fight! Oh and for those of you who were wondering turns out the EGR valve was completely frozen up anyways so it needed to be replaced regardless of my destructive forces at work here.
 
Boy, what a day! Are you sure you're not in New York?? It sounds like after finding the venting problem with the fuel tank and EGR you are hopefully on your way to a good drive. Your car looks great. Keep up the good work.
Mike
 
Another rambling thought: the pump is high on the firewall... a better location would be low and in the rear. Have it push fuel rather than try to suck it.
 
I disconnected that electric fuel pump and reconnected the stock mechanical one.
 
Did that change anything?
 
sounds like quite an adventure. sorry. re: the vent, Yours would have originally had a canister attached to the vent - I suspect that it might have been removed and the vent blocked then. (which is when I capped my carb vent - I didn't think it was needed. :frown: ) this makes me wonder how much of your pollution stuff is left. My Midget, which also had the EGR valve had it removed long ago. Are you sure you even need it, or can you bypass it?

I plugged the hole to the manifold, and only have one line running from the valve cover to the carb - all other pollution stuff is long gone.

Remember, mine's a Midget but I suspect the same applies
 
The factory fuel pump seems to be working fine but did not seem to change the performance of the carb at all. For now I'll leave it as is and keep the electric one on the spare parts pile. I found a cheap cannister on ebay and have it coming now. From what I've been reading on the carb and associated bits the cannister was just a means of catching stray petrol fumes from the tank and holding them in reserve until you start the car. So I doubt it will affect the perfomance at all if anything it will make me less of a fire hazard. I know how to get creative and bypass the EGR valve if needed but I would rather try and get it put back together correctly so that it will function as intended. I just got an email from the Little British Car Co. that related they have to back order the EGR now and it will hopefully be in by the end of the week. If this is a part you have been intending to replace it seems now is the time as this will be one of the latest parts found to be made of unobtainium soon if not already.
 
Nahh.. that EGR valve will be a counterfeit one, made in the backyard of some Tiawanese home and keep the family in rice rations for years to come. :wink:
 
Well I ordered the choke cable bracket from Moss to mount the choke cable properly but for the life of me I can't figure out how it mounts or what it mounts to. Anyone know?
 
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