Q: open pipe on Zenith 28IF - what to do?

[CrCa]

Hi 4 fans,
I'm new here so don't beat me too hard but I'll start from a problem. CO and HC as always. The question is that I dunno what is that small pipe (green arrow) for, see pic, stolen from post of Clementine in http://www.renault4.co.uk/forum/about159.html. Head ventilation hose goes right below the carb into the inlet manifold and is in good condition, not clogged, so what is that spare for - I had it plugged with a cork when I got my R4. To go on emission, first I have to find this out. Thanks!

 

[malcolm]

Welcome to the forum CrCa,

On my 1984 car there is a plastic fitting with a T-piece on that pipe (arrowed). The pipe to the engine breather fits to the end of the T piece, and the pipe to the inlet manifold connects to the side.

I don't know why Renault set the breather up in this way. It seems more complicated than would really be necessary.

 

[CrCa]

Thanks for the welcome Clementine,

there were three types:

• vent to atmosphere,
  single circuit,
  dual circuit (aka T-piece).

Yeah, this T-piece rebreathing system is the most complicated on R4. My problem I guess lies here. This circuit has 2 different calibrated jets, I've got one (see pic, blue short-cut line, blue dot = cork), did not ckeck the jet size though, so I'll have to make missing parts myself as I can't get parts like these here in my country. My next check will be float level. More help needed here. Can somebody remember that dimension for Zenith 28IF?


Thanks.

 

[malcolm]

Here's the float height dimension. The manual says to screw the needle valve down tighter if it is too high, or to replace the seal if it is too low. The manual didn't give any tolerances.

 

[CrCa]

Thanks again Clementine,

I've found this dimention too but to be precise it has to be 8.4 or 8.9mm depending on the Zenith 28IF modification. I'll have to check this out.

 

[CrCa]

End of the problem. The car passed emission test with low CO, HC. I'll tell the sequence I did.
The float level on my Zenith 28IF modification had to be 8.9mm and was ok. Problems were with points that had cracks and pits. You have to dismantle to notice that. Then regaped to ~0.4mm, cleaned carb jets with compressed air, checked the sparks' gaps, adjusted ignition timing and idling to 700(+-25)rpm. Still had unstable idling. Here you have to use old method assuming that air is leaking somewhere at the intake. The first suspect was the missing T-piece connector and pipe in the oil rebreathing circuit (as shown in my prievious pic). Ok, made the missing parts with calibrated jets, 5mm from head cover to T-piece and 1.3mm from T to inlet manifold. Still uneven idling. The old method mentioned is to spray carb cleaner on the suspected for leakage areas while runing the engine. Rebreather and connections - ok. On to the carb. One leaking gasket found + fixed = no result. Carb is airtight. On to inlet manifold and here you go, engine as if wakes up for a moment of a spray. Despite the minor air leakage mentioned above the main problem was inlet-outlet gasket. The construction of inlet-outlet manifold as single piece is bad as one part heats up much and other has to stay cool. There is the problem = different parts of the same piece have different temperatures what leads to uneven expansion and as a result you have a torn gasket and great air suction. Fixed. Hey, I could even adjust idle speed below 700rpm = nice. So, these are procedures I carried out for CO+HC problems.

 

[Chris H]

on the one I have there is no restrictors in the breather pipes.

I am having to buy a new T piece as the one I have is broken - again :roll:

 

[jjad]

This page has some useful information on needle heights for the various Zenith 28 IF carbs:

http://www.la4ldesylvie.fr/index.php?option=com_content&view=article&id=47

 

[iMacThere4iAm]

Thanks for posting that jjad, they are wonderfully clear instructions for overhauling the carb.

 

[r4 spain]

Welcome to the forum CrCa,

On my 1984 car there is a plastic fitting with a T-piece on that pipe (arrowed). The pipe to the engine breather fits to the end of the T piece, and the pipe to the inlet manifold connects to the side.

I don't know why Renault set the breather up in this way. It seems more complicated than would really be necessary.

Hi do you know the part number for the t peice im desperately trying to find one for my car

 

[r4 spain]

on the one I have there is no restrictors in the breather pipes.

I am having to buy a new T piece as the one I have is broken - again :roll:

Any idea where to but the t piece

 

[Cornish4]

Hi there, check out R-quatrelle.nl, they list this part as well as many others. I've bought stuff off them in the past, and their service is excellent.