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Air leak?

Ignas

Enthusiast
Messages
24
Location
Vilnius, Lithuania
Hi,

One month ago I cleaned my carburator zenith 32 IF replaced all gaskets also replaced intake manifold gasket, breather hose, I started up and it seemed to work properly by that time. I didn’t drive and let it sit for a while. I tried to start this morning and it couldn’t keep it idile without a choke. Even if she is completly warmed up, as soon as I shut the choke off the engine stalls.. I wonder is it could be air leak, or something else? I also noticed a bit of rusy in fuel filter, changed it already..
 
Is the vacuum pipe OK, I routed mine incorrectly after replacing the carb and it melted over the exhaust and did the same thing
 
Start the engine & let it run, even with the choke out, then spray WD40 or similar around the carburettor. If the engine's note or speed changes, you have an air leak somewhere. The normal source of this is the joint to the inlet manifold, although it could be somewhere else.
 
Probably you need to adjust tickover and mixture, start to adjust "so the butterfly close less" (amount of air possible to get through carburettor) so car can idle without choke, then adjust mixture screw so engine going cleanest. You can go back and forth halv turn on the screw and were highest rpm occur mixture is close to right. Then turn down idle screw to lower rpm and adjust mixture again repeat until engine idles nice. If you haven't touched ignition since carburettor change you don't need to bother about it.
Everything above with warm engine and clean jets.
 
Oh thanks for fast replies! ;) the vacum pipe seems to be OK, I will try spraying WD-40 as soon as I will get my alternator back from service and will be able to start engine. About a mixture. Need better investigation, but it seemed to me that mixture screw was kind of irresponsive at least not like it should be, It’s another clue I forgot to mention..
 
If the car cannot idle without the choke helping it the mixture is probably too weak, as the choke enriches it. Assuming the air leak at the gaskets has been eliminated as a problem, try screwing the mixture screw OUT from the carburettor body, which will enriched the mixture, as this will allow more petrol into the carburettor. Whatever adjustments you do MUST be done s-l-o-w-l-y and g-e-n-t-l-y, to allow the engine to adjust to the new settings and not to damage the delicate jets.
 
Sounds to me like a clogged idle jet. Remove it and spray carburettor cleaner through it.
 
Hi, I'm back again in my garage and I've got some news. I noticed that to make it idle without choke I need to unscrew idle jet just a little bit 1/8 of a turn. Is where some 'special' halls I should look for? Idle jet seems to be clean, so I assume that some idle jet canals clogged in carb itself? Just don't know where else I should clean, it looked that I already cleaned it quite well..
 
Keep adjusting out idle screw until you got rpm you want. Follow guide I wrote in #4 abowe.
Idle rpm.
1 Idle screw: how much air that engine can get. (Set to 8-900rpm)
2 Idle mixture screw: air/fuel ratio at idle (adjust to highest rpm)
3 Ignition: when spark occurs (can be adjusted to value in handbook or adjust to highest rpm)

Start with 1 then adjust 2. Probably you have to redo 1 and 2 again.
When you have smoot idle you can do 3 and if idle gets to high or low back to 1

Hope everything works out. I guess you start getting summer as we do in Sweden.
Best regards.
 
Hi, I'm back again in my garage and I've got some news. I noticed that to make it idle without choke I need to unscrew idle jet just a little bit 1/8 of a turn. Is where some 'special' halls I should look for? Idle jet seems to be clean, so I assume that some idle jet canals clogged in carb itself? Just don't know where else I should clean, it looked that I already cleaned it quite well..
The adjustment can be as fine as that. I have a small Daf and the adjustment is one quarter of a turn between smooth running and stalling all the time. Make a point of using a quarter turn as the measurement, based on a clock face to measure by how much I've adjusted the screw.
 
Do you unscrew the jet itself, or the idle mixture screw at the base of the carburettor?
 
Yea I see some confusion about that. Maybe I don’t know the right names in english. I’ll try to explane: As I understand the idle jet is near the top of the carb and it should be completely closed, so mine is a little bit open to make it work. Probably in that way the aditional fuel gets through this jet. The mixture screw, the one at the bottom is for adjusting mixture, but in my case it’s not very responsive, I think because more fuel comming from idle jet at the top. The question is there any way that I have damage that jet? Or what part of the carb I should look more closly, as I already clean it?

I will take a photo later.
 
The fact that it works when you loosen the idle jet means a) that the idle circuit inside the carburettor is not clogged, b) that either the jet does not allow fuel to pass through it, or is an incorrect one blocking the fuel passage in the carburettor when it's tightened down.
Post a picture of the jet please, it may clarify things a little.
 
Here is a picture of the jet.. It has a little crack You can see in a pictures. I would order a new one, if I could find it..

8E3D9FF6-4733-4A5B-BA9B-57813AC1E9F2.jpeg DA717545-EA3B-45D3-90D9-45B47BAD151B.jpeg 947E15B1-207D-4090-90FD-DE63E8977BCD.jpeg
 
In my opinion that jet is damaged beyond repair. You'll have to replace it before you'll be able to set the carburettor properly, as the worn thread and the crack suggests it would leak air no matter how it were adjusted. The crack in the screw head makes it look like it's been forced into the carburettor body far too hard. As it's a Zenith carburettor you shouldn't have any trouble finding parts for it.
 
Make sure that when you spray carburettor cleaner in the hole at the front of the jet, it flows freely from the holes around the jet.
Look also at the bottom of the hole in the carburettor body where this jet screws in. There is another hole there that picks up fuel from the main circuit, passes it through this jet to the idle circuit. If the idle jet has been forced in, the hole in the carburettor body may have been damaged somehow, blocking fuel flow to the jet when it's tightened.
If you have trouble finding such a jet, you can turn down a Solex's idle jet thread to Zenith size (if I remember correctly, Zenith is M6 and Solex M7), Solex jets being more widely available.
 
Been online searching for availability of Zenith 32 if carb parts online due to fitting a 32 IF 8 on my van and most of the info online does indeed come from Angels old posts on how to set up regarding the only If 8 stuff, but this place here in Spain does seem to have a supply of NOS Zenith 32 parts, link to one advert, they have a good stock of Renault parts.
https://www.ebay.es/itm/224215004208?_trkparms=amclksrc=ITM&aid=111001&algo=REC.SEED&ao=1&asc=20160908105057&meid=05fec66928fa4e3a944ababfd0f3d585&pid=100675&rk=1&rkt=15&sd=224215004208&itm=224215004208&pmt=0&noa=1&pg=2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci:1420020d-c59a-11ec-98d3-4e986ef55509|parentrq:676c8f031800aaf33e05ccdbfffbdd4e|iid:1
 
Wow! thanks for the link. And thank you all guys for advices and very fast response time. All in all I had adjusted the mixture quite well now, and it idles smoothly. I will try to replace the jet with the new one, and see what happens. But, as angel said, it could also be that the jet has been forced and the hole in a carb has been damaged, or somehow not in line with the jet. In that way either to buy new carb, or keep driving as it is, just need to put lock tightener on that screw. ;D
 
I tested on mine R4 the airleak test decribed here, rpm's did not rise when spraying carb cleaner into carb throath.

Anyways, the always present starting&running problems still continue with my precious Zenith 24IF, i adjusted ignition to 8th degr advance with strobo(i have electronic ingnition kit installed inside old distributor), now when it starts nicely every time it is difficult to add revs-it atteptms to stall.
Is the reason in acceleration nozzle jet or channels(partly clogged due ethanol resins? I use frequently petrol additives.Should i try bigger nozzle?

Another thing is leaking exchaust joint, it's a clamp model and corroded during the years, i did wrap around the joint with aluminium vapor barrier / aluminum tape 0.2mm and fix the clamp back.The joint is currently much more better without constant exhaust flow inside the engine bay. I guess 4stroke motors do not mind the back pressure as 2stroke motors do?
 
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