Zenith 28IF Problem

[jayar]

Vanessa is a 1987 Renault 4 F4 van (fourgonette, ex La Poste) fitted with 1108 cc engine with Zenith 28IF carburettor.

The original carburettor (Spanish built) was showing signs of wear, and last weekend I chanced upon a reconditioned French built 28IF carburettor, which although had minor differences in choke cable attachment and a slightly different body shape, fitted easily.

With the replacement carburettor it starts easily, idles well, and initially runs well out on the road. But after a short time it seems to run out of fuel, as if the float and/or fuel inlet valve is sticking and the fuel bowl is emptying. After a short time, it will start again but will not run for very long if the throttle is opened. To drive it home it will only run smoothly in second gear at low rpm, any application of accelerator will cause it the engine to quit again. It idles happily at any stage.

I took the top off, and the float and inlet valve seem to be fine and not sticking in any way. The mixture is adjusted at 1 ½ turns out, and as the old carburettor was working before I took it off I assume the fuel pump etc are working normally. I would prefer to leave this newer carburettor on if it can be encouraged to behave itself; but if needs be I shall need to put the old, worn carburettor back on.

I can find nothing like this in the forums, but I may have missed any similar problems. Any ideas would be appreciated

 

[Geoff in the Gully]

Have you checked the wire strainer filter where the fuel line goes into the carby?
If that's a bit blocked from sitting around for years it might slow the fuel flow enough to cause the effects you experience.

 

[jayar]

Thanks for the thought Geoff, even though the carburettor is ostensibly in new conditionm I have just checked it and it is all clear.

 

[DavidN]

If the carb is reconditioned, did you check back with the seller?
Nobody is perfect and maybe they did something wrong while working on the carb.

Ask me how I know ...
I changed my 28IF for a reconditioned one Yesterday.
The (older) guy who did the work on the carb forgot to fasten the fuel inlet piece (the one that is screwed into the carb with the filter screen inside.)
Fortunately I discovered that when I mounted the fuel hose to the carb.
(I don't want to think about what could have happened if petrol would have spilled onto the hot manifold.) :?

The second thing that was not to my satisfaction was that the lower flange was uneven from fastening the carb too violent onto the manifold by a previous owner.
That is a common/known problem of the R4 carbs and even though it kept unnoticed by the expert.
In the end I did the planing (?) by myself.

Other than that the shop did a good work and the car is running even smoother than before (with a carb cleaned by myself).

I would send the carb back to where you've bought it to have it checked again!

Cheers,

David

 

[Cornish4]

You've got to watch out for these "older guys" David, we can be a little forgetful at times you know, now, who am I?
Jayar, I would disconnect the fuel pipe and crank the engine over, just to make sure the pump has a good discharge, then maybe check all the gaskets are air-tight. Is there a good level of fuel in the float-chamber? I enlarged the main jet from .9mm to 1mm as my carb was running very weak and no amount of mixture adjusting would cure it. Your carb however should be ok in this area. Regards, Brian.

 

[mojobaby]

Your car idles happily and drives in 2nd gear at low revs and that means there is a happy mix of air and fuel. But at higher revs it dies, so to me it sounds like its getting the extra fuel when you accelerate, but not the air. its choking on excess petrol!

my mixture screw is turned out two and a half turns. i think the manual says 3 turns. I'm certainly not an expert so I'd like someone else's opinion on my thoughts.

 

[jayar]

Thank you for the replies. I must confess I am one of those older types too, and perhaps it is showing in this case!

DavidN - I bought the carburettor last weekend from a stall at a large fair in the south of France - it actually looks new, it was my assumption that it was reconditioned, as for the money I paid (not a lot) I could not believe it would be new! The vendor was actually selling an amazing array of gaskets of all sorts, but he had a bin with five new-looking carburettors, four Solex and just this one Zenith 28IF. With it in position everything seems to be working as it should, and the inlet pipe is tight (and the fliter inside is clear). I have checked the lower flange and it is dead square, and the gaskets are new.

Cornish4 - I have just been out and re-checked the fuel pump supply, there is plenty there. Drilling out the main jet is something I will leave until I have exhausted all other possiblities I think, as in theory it should be okay. and it would not run normally for that first 1 or 2 km if there was a problem there.....perhaps?

Mojobaby - it idles well at any time, and the engine revs normally with no load. It also runs/accelerates normally and well when starting off, but after about 1-2 km it starts dying as if it has run out of fuel....the throttle butterfly seems to be working fine, as does the choke butterfly.

I will report back if I stumble on the cause....thanks for your collective inputs.

 

[Cornish4]

To be fair, my carb was past it's best and the engine would only run properly with a bit of choke, hence the mod. This is a real head-scratcher isn't it, and it's not as if it's a complicated carb, very frustrating, so hope you come up with a solution. As for being one of the older types, nothing wrong with that, we can show some of the younger members of society a thing or two. Don't get me started,

 

[DavidN]

I didn't mean to bash old(er) people here. I am myself nearing 45 Years of age.

What I meant was that the guy who did the work on my carb is in business for decades, is specialized in carburettor repair and overhaul and that he should know what he is doing.

Jayar - Your Problem could indeed have to do with the fuel air mixture to be too rich.
I can drive perfectly with the choke out for about 2 Kilometers.
Engine would run fine. But when warmed up I have to put the choke in otherwise it will behave like you described!

What is the size of your main jet? On both of my 28IF's it is marked with a "90" which I suppose to be a 0.9mm bore.
The idle jet has been a 40 (0.40mm) on my old 28IF, the new, overhauled 28IF came with a 35 (0.35mm) idle jet which runs just fine as well.

Cheers,

David

 

[Cornish4]

David my friend, it's just my silly British sense of humour, take no notice.

 

[DavidN]

I am perfectly fine with that!

 

[jayar]

Thanks DavidN - no bashing taken!
It rained with a very cool northerly wind here this afternoon so I haven;t done any work on her today, but I shall have a look at the jet sizes tomorrow and let you know. Appreciate your observation about the fuel/air mixture, I think everything is working as it should but will double check tomorrow (they predict sunshine).

 

[angel]

Check the fuel level, too. Distance from carburettor top cover to needle valve ball should be 8.4mm, with needle valve seated but ball not pressed in. This measurement should be taken without the gasket fitted on the top cover.

I came across an instance where the float level was 1 - 1.5 millimeters lower than specified, and the car behaved just like yours.

On the GTL engine i have found it beneficial to decrease this disatnce to 7,8-8,0 mm (by fitting thinner sealing washer), to raise the fuel level, as opposed to boring out the main jet. It gives cleaner acceleration in the mid range with no effect in fuel consumption.

 

[jayar]

Many thanks Angel - I shall check that tomorrow,

 

[jayar]

Angel - I checked the fuel level as you suggested, and as best as I could tell with my plastic micrometer, it was close to 8.4 mm. I checked that the main jet was clear, and as there were small differences in the float shape and size between the old and the new, I decided to put the old float in the new carburettor and see what happened. Whether or not that was the answer, or I beneficially disturbed something else, I took her for a 10 km run and she never missed a beat! Early days of course, but very encouraging!

The other thing I noticed was that even though I was fully closing the choke, there seemed to be some creep for the butterfly to close a littleand affect the mixture, so I have adapted a small spring which has solved that problem.

Thanks to everybody for their inputs, appreciated.

 

[orsome]

Idle jet jamming

What is the size of your main jet? On both of my 28IF's it is marked with a "90" which I suppose to be a 0.9mm bore.
The idle jet has been a 40 (0.40mm) on my old 28IF, the new, overhauled 28IF came with a 35 (0.35mm) idle jet which runs just fine as well.

Cheers,

David

Hi David, jut wanted to take oppornity to check my situ according toyour msg from 2010

My problem is that car stood 23yrs with petrol inside tank.I tried to empty tank with air flush, reast petrol smelled like a skunk.

took the car to a proffs which again emtied the tank from bottom drain.
a full tank of new petrol in (shell formula).

after tiding the carb again and again i can run only about 5miles and idle jet(0.3mm) jgets jammed of the incoming fine debris.I have now two inlet petrol filters.

what should i do?

 

[DavidN]

Hi Orsome,

I would flush the gas tank again!
Fill it halfway up, give the car a good shake and open the drain plug.
Then clean the filter screens inside the fuel pump and inside the carb.
Clean your carburettor again and use two new inline petrol filters (one in front of the fuel pump, one between the fuel pump and the carb).
Use filters with a clear housing and change them as soon as a considerable amount of dirt has built up inside the filter.
That way you should prevent your jets from clogging.

Good luck!

Cheers,

David

 

[orsome]

idle jet jamming

Hi DaviD and thanks for your help, from local finnish R4 sites i received one good tip which worked. Guy said it must be water-soluble dirt if double filtering wont stop it, then he tipped me to dump some 100% alcohol in the tank and start up. I put two bottles of Masinol in tank and also flushed all jet ends seen from top of the carburettor with pressure air plus with alcohol+gasoline(used a nursing needle).
After a while she started with coffing and banging but could not bear more gas than just idle running. After ten minutes flapping of acceletor pedal she finally run also top revolutions.
I was happy as a drunken duck, i could drive 25 kms without any troubles. Now she is resting over winter and will be taken into use first of april next year.
She was MOT tested and taken back to registration after been out from it for 22years.
So you can imagine that the whole family will be waiting for sunny and warm spring time!

 

[DavidN]

Great to hear that everything is sorted out!
I recommend to use the two-filter-setup though.

Cheers,

David

 

[orsome]

carb problems continue

Check the fuel level, too. Distance from carburettor top cover to needle valve ball should be 8.4mm, with needle valve seated but ball not pressed in. This measurement should be taken without the gasket fitted on the top cover.

I came across an instance where the float level was 1 - 1.5 millimeters lower than specified, and the car behaved just like yours.

On the GTL engine i have found it beneficial to decrease this disatnce to 7,8-8,0 mm (by fitting thinner sealing washer), to raise the fuel level, as opposed to boring out the main jet. It gives cleaner acceleration in the mid range with no effect in fuel consumption.

Hi Angel, i tied to send y reply to a prit msg but it seems not to be working.So i answer hereby; my problems occur when engine is cold, cannot tolerate any choke nor gas pedal.I have to start on idle and its really annoying.When warm can start on 1st attempt.

I purchased a new tank+meter, its better now.

I have no sump connectin from my carb, its plugged.

I am missing the small cup on the four sided tower on carb top.
I did purchase a new carb repair kit and cahnged the needle valve as well as the sealing.Maybe its legth is wrong, must i change back to the old needle valve?

This is very mysterious to me??