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Zenith 28IF problem solving

hi Mario - how was the carburettor cleaned? If it was cleaned by soda blasting or another sort of blasting, there could be small particles stuck in a small pipe inside the carburettor. If so, try blowing carburettor cleaner through all small internal pipes.
 
Hello Mario
There are 2 things to consider when having a carburettor problem.

Firstly, the air/fuel mixture screw only applies to idle. When the revs get higher, the fuel comes into the carb through the main jet and the air flows through from the top of the carb body, past the choke flap and into the venturi section of the carb.

Secondly. as per the Heynes manual, the flow of petrol is fixed by the jet size and therefore the tuning of the carburettor is controlled by the rate of air flow through the carburettor.

So presuming that you have cleaned your carb very well, all the tiny passages, filters and jets, you should start looking at air flow.
Make sure that the rubber tube leading from the rocker cover is clear of oil and dirt. Also check that the small restrictor tube is present in the rubber hose that leads to the base of the carb. also that the small hole is open and not blocked.

The small restrictor tube should have an opening of 1,3mm. Have a look at the post that JdeW put up recently:
http://www.renault4.co.uk/forum/threads/electric-fuel-pump.8790/#post-59583

Lastly, my mixture screw is turned out 4 complete turns. I also run better for some reason if my choke is pulled out by 1cm. I'm quite happy with that and I check my spark plugs often. If your mixture is too rich, the plugs will be black.
 
Thank you for answering!

I am not sure how was carb cleaned, but I know that I took it to the best guy in town to clean it. Member petak was also there few years back with his carb, and he took 500 km trip to this guy, so I believe that he knows what he is doing. After him carb was ok, little to high idle, so I bring it down just a little bit and then I started to experiment how would car behave on different setting because I had problems with engine shaking on idle. When engine stopped shaking, I left it on that setting and then, after some period I realize car was slow.

Yesterday I set carb on 1,5 turn to the left, low idle and engine was turning off while breaking, it was shaking, not pleasant to drive. Then I took it to the open road, drove about 20 km with full throttle, and in some point when i put it in neutral it turned off but after that, when I get back in town, it was more calm on idle, but still shaking (not turning off even on low idle) while breaking. Today I made a short test drive, it started up with no choke after a night in garage, feels better to drive, but still little problems while breaking.

I believe the car is congested because it sat down for 6 years and the first owner was older woman for which I believe did never took it in higher rpm. Now I put 100 octane fuel in it and I will see how it will behave in further days.

If you think different, please tell me, because I don`t want to damage the engine (although we all know it is unbreakable :D ) while forcing it.
 
The "it started up with no choke after a night in garage" statement suggests to me that the idle mixture (petrol/air mixture) is too rich. The engine would normally need some choke (mixture made richer) to start from 'cold'. If the mixture is too rich, then the engine will not run correctly.

I have read that the mixture screw (at the lower left side of the carburettor) is an air valve - unscrewing makes the mixture weaker. This is unusual. Can anyone confirm this ?
 
Hello Mario, perhaps 1,5 turns outwards is not enough. Mine is turned out 3,5 turns. Have a look at Harbourseal's video on page 2 on how to adjust the mixture. Did you find any blockage in your restrictor tubes?

Adam, the mixture screw controls air and fuel mixture, but only for idle. Unscrewing it makes the mixture richer
 
I replaced the carb and now is much better. I will clean the old one and try to figure out what was wrong. This one, which is on car now is not perfect, but much pleasant to drive.
 
Hello, I have problem with my brand new Zenith 28IF. Few days ago I put it on my car, but I could`t set the mixture properly. Yesterday I unscrewed mixture screw and I figure out that the needle in the end is broken. I screwed another screw from my previous carb in but that broke too. The needle from the original screw stuck inside. Do you have any idea how to get it out without destroying the hole? Where I can get another screw? Thank you very much.
 
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I could try, but I`afraid if I destroy the hole because it is very sensitive. I didn`t buy it, I got it with my last R4 with other NOS parts :D
Now I`m not sure if I broke it or it was broken earlier. I have done carb settings for a dozen of times, but nothing like this never happened and I never heard that someone broke it.
It would be a shame to destroy it since it`s almost impossible to find NOS carb in these days.
 
I think you correct, it looks very sensitive, It looks like it could be brass.
Perhaps spray carb cleaner in there to loosen the needle and then try blow it out with compressed air.
If you have a pointed plastic piece, not a metal pin, that won't harm the brass nozzle.
A can of carb cleaner usually comes with a long thin plastic tube, try and push it gently with that.

Good luck Mario
 
I reckon that if it has stuck enough to break the end off then it will need a sharp tap or a reasonable clamping force from something to shock it out of it's wedge. Once it has moved at all it should fall out - try a small clamp or pliers or grips to press the end that is showing out of the hole.
 
Hello all,
Got a bit of a running problem - car isn’t returning fully to tickover so the engine races when idling. The throttle linkage comes to rest a couple of mm open when the accelerator pedal is released. I can close it with gentle pressure in the linkage on the carb.
Looks like it has been a problem for a while, as a spring has been stretched from the linkage to the inner wing - see pic.
A new throttle cable is on the cards but wondering if there other things I should look for/ do? Any thoughts appreciated -
Many thanks, Simon.

A8E48156-8B8A-4C1B-99BF-0719E19BB07C.jpeg4EE68918-5078-4A27-A91B-35255E7972A6.jpeg
 
To me it looks like the spring isn’t attached in the right spot on the half moon where the throttle cable sits in.
Apart from the state of the spring itself.
Maybe you can make some photos of the throttle cable to.
From the attachment on the accelerator paddle up to the carb.
You might be missing some parts to.
 
Sealant between the carb and the manifold as well as anywhere on the carburettor is a no-no...
 
Ok got some pics:

Attachment of spring at inner wing
54D64CCE-3108-4720-9879-2C4938BA6E3E.jpeg

...and at carb end
6B5C5CDE-8021-43E1-AD1E-A504A49BCBCC.jpeg

Adjuster snapped during our engine service
D3416FB4-FA8B-47DD-98AB-6803DDCDE406.jpeg

Bulkhead mounting - saw a strand of frayed cable here so will replace it
8CA6F196-CE22-4448-B379-34A241DA468F.jpeg
16C967AE-A706-4D37-8DAD-EAF8E501FA35.jpeg
7CBE9CD0-183D-46E0-ADC4-8E24FFA59146.jpeg

Harbourseal, I’ve put the spring to the other hole in the half moon - looks happier, but spring and choke mechanisms now interfere a bit when the choke is out
31574307-8BF7-4773-884C-62702F9B9A3E.jpeg

Hello Angel - hadn’t noticed the sealant there. Vendor told me the carb had been replaced
 
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