Whenever I'm in that boat, it usually ends up being a tiny speck of something stuck in a carb passageway... Man, I hate these searches to figure these things out.. Best of luck to you!
E3 2500 Zenith Cold Start Rough Running
- Thread starter E3_UK
- Start date
it will be nice to see the full setup with photographs to be able to address you to a solution
there are many models of the zenith carbs including two different auxiliary air valves, or even no aux valve
funny to see the temp sensor in your setup that activates the relay
which year is your car ?
answering one of your questions, the choke mechanism it has a combined heating from the electric solenoid and the coolant that affects a bimetalic spring, many things can go bad inside that little circular box, it is probably worth a check as you have said that there is no opening of the top buterfly in one carb
just one thing that i have not read from your posts, are the anti self running valves working well ?
i wonder if you even have them, again depending on versions,...
the whole sequence for cold start up starts with the ignition on, in that moment you must hear the two anti self running valves click that opens the fuel passage for iddle, if one of those valves is stuck, or defective,...
then you must find both carbs top buterflies wide open
then a kick in the accel will close both
start engine without touching the accel
once engine start you must see inmediately that buterlies open just 3mm due to engine vaccuum
warm up process will progressively open the burpterflies and revs will rise
a final kick in the accel pedal will bring revs to 900 iddle
anything else is wrong, please describe your situation
there are many models of the zenith carbs including two different auxiliary air valves, or even no aux valve
funny to see the temp sensor in your setup that activates the relay
which year is your car ?
answering one of your questions, the choke mechanism it has a combined heating from the electric solenoid and the coolant that affects a bimetalic spring, many things can go bad inside that little circular box, it is probably worth a check as you have said that there is no opening of the top buterfly in one carb
just one thing that i have not read from your posts, are the anti self running valves working well ?
i wonder if you even have them, again depending on versions,...
the whole sequence for cold start up starts with the ignition on, in that moment you must hear the two anti self running valves click that opens the fuel passage for iddle, if one of those valves is stuck, or defective,...
then you must find both carbs top buterflies wide open
then a kick in the accel will close both
start engine without touching the accel
once engine start you must see inmediately that buterlies open just 3mm due to engine vaccuum
warm up process will progressively open the burpterflies and revs will rise
a final kick in the accel pedal will bring revs to 900 iddle
anything else is wrong, please describe your situation
Thanks for the reply. Regarding the starting sequence you describe, this is what I have always done and until now it has worked perfectly. It does have the fuel shut off valves and these are both working however I noticed that disconnecting the rear one causes the engine revs to drop a little but disconnecting the front causes it to stall, indicating that the rear carb is doing a lot less than the front.
The car was built late 72' UK market. The problem with a lot of the technical information available is that they describe systems specific to the US market making it quite confusing figuring out what setup I have. The wiring diagram is from the original handbook therefore I know this is correct. The issue is that I don't know if it's a cold start problem or something else as even when up to temperature it runs rough. Here are some photos of the engine bay.
20180511_120604 by Robin Derrick, on Flickr
20180511_120557 by Robin Derrick, on Flickr
20180511_120216 by Robin Derrick, on Flickr
20180511_120551 by Robin Derrick, on FlickrOne thing that does confuse me is that one section of the manual states to close the choke Flap fully by hand then adjust the rod inside the housing, then another section shows setting a flap gap with a 2.5mm drill. If I had a clear understanding of the setup process I'd run through this first. The one issue that is apparent is that the rear carb flap isn't opening with the electrical element element over time (it does have electrical feed), however it does open with increase in coolant temperature but I don't know if it has always been like this as I've never removed the air cleaner during startup before. The electrical side does baffle me though. Ultimately the way the car runs suggests that only one carb is operating correctly, presumably the front one.
Thanks for the reply. Regarding the starting sequence you describe, this is what I have always done and until now it has worked perfectly. It does have the fuel shut off valves and these are both working however I noticed that disconnecting the rear one causes the engine revs to drop a little but disconnecting the front causes it to stall, indicating that the rear carb is doing a lot less than the front.
The car was built late 72' UK market. The problem with a lot of the technical information available is that they describe systems specific to the US market making it quite confusing figuring out what setup I have. The wiring diagram is from the original handbook therefore I know this is correct. The issue is that I don't know if it's a cold start problem or something else as even when up to temperature it runs rough. Here are some photos of the engine bay.
thank you for photos
perfect stock including original hoses, (i would replace them just in case a 45 y.o. fuel hose,...) they are not forever
have you ever rebuilt them ? clean and new gaskets ?
i will direct you to my video on the adjustment
you will need to learn spanish first, nothing wrong with that, it always helps
(just kidding, you will understand throught the images)
Thank you I'll review your video, very useful. To answer your question, in my ownership the carbs haven't been overhauled, all i have needed to do is adjust mixture and idle screws to make ir run corrcorrectly. There is no mention in the original owners comprehensive notes regarding any carb work. As it was starting and running perfectly last year it's unlikely to be an adjustment issue, more like component failure or blockage. However as i have never done so i would like to set up the choke correctly to eliminate this from the equation . The rear carb heating element must have failed however I'll try to verify that once i have removed the cover.
definitely replace those fuel hoses and the plastic tee!
impossible on grey textile, possible on black
your hose´s rubber will be not too far away from dissintegration, it is possible that rubber debris has made its way into the carbs,
when you replace fit a filter and an anti-return valve
IMHO, setting choke correctly with the carbs on the engine will be tricky,
choke solenoids are strong, however the wire can break with vibrations, and the contacts detereiorate with rust (green rust over copper terminals usually)
i strongly recommend you a complete ovrhauling, once you take spanish lessons my nine videos will pave your path to a smooth DIY experience ;-)
i have overhauled 6 sets of these carbs, and despite i agree with your NASA-calification for them, they are very comprehensive and doable.
yeah, the whole damn world is going south,...;-)
Search for Cohline or Continental:
https://www.belmetric.com/braided-metric-hose-oem-c-14_138/?zenid=iq4qmprlhkf1eqps0uvf76tus4
https://www.belmetric.com/braided-metric-hose-oem-c-14_138/?zenid=iq4qmprlhkf1eqps0uvf76tus4
Thanks Steve, do you know the diameter of hose required ?
ID is 7.5mm
Thank you
The rubber hose starts at the driver frame rail just inside engine bay, a bit hard to access the hose clamp, easier if expansion tank is moved out of the way.