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4GTL need choke to run smoothly

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Perkins

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Hi,

Could anyone out there throw some light on our rough running problem ?
We recently bought a 1986 4gtl 1108cc with about 50,000 on the clock. It is in great condition and uses no oil nor blows any smoke.

I have recently serviced it - new points (femsa) properly set, new plugs, new dizi cap, new air filter, timing checked and set to just before pinking under load. It is now running much more sweetly than before and all the plugs are the same colour, slightly sooty around the outer rim, but the central core burning clean.

My problem is that the engine will only pull well with the choke slightly out and when the choke butterfly 3/4 closed, suggesting to me an overlean mixture.

I have checked the gaskets around the Zenith 28 carb with oil and can find no air leaks, although you can only do this to the upper face of the engine head/inlet manifold joint. The fuel and fuel pump filters are both clean, as is the float bowl.

Over the years I have rebuilt and serviced many bike and car engines, so I have an inkling of what I am doing.

Any more suggestions would be very welcome as my last resort would be tinkering with carb settings which I don't like doing without the proper measuring gear. Any thoughts on the use of a Colortune ?

Cheers,

Perkins
 
Welcome to the forum. You've already done most of the things I'd have suggested.

I've had the same thing a couple of times. First time was due to a broken vacuum advance unit on the distributor, and second due to the mixture having been adjusted in the past to try and compensate for the choke being slightly stuck open. My bet is the vac unit - have you tried sucking the end of the pipe to see if it moves the distributor top plate?

The setting for the mixture is normally 1.5 full turns out from fully in. Worth checking where yours is as the cars are very sensitive to the mixture on low speed part throttle. The GTL is sensitive to mixture at the best of times - they are "tuned for economy".
 
is the little pipe on the carb conected at the bottom you know the one from the T bit that looks a bit like a C shape it seems to connect the very bottom of the carb to the plastic t thing at the top.when it comes off on daisy she runs like a bag of spanners,missin and backfiring all over the place and she loses power and wont even tick over:wink:
 
Wow, Clementine and Daisy, amazing quick replies. This is a great forum with loads of helpful info.

The pipe that you mention Daisy is OK and in place. The other breather pipes I nipped up with cable ties to make sure there were no leaks. I will give the vacuum pipe a suck too to see if it moves the top plate and take a look at the mixture screw.

Do you have any experience with a Colortune on these engines to set up the mixture. I once used one to set up an MGB engine and it was very effective (for a B!).

Another thought struck me that the valve gear is very quiet for a pushrod engine and maybe it has been set up with too little clearance, so I'd better check that too.

How do you go about checking inlet manifold gasket 'underneath' in situ as you can't get to it for the exhaust manifold ?

Thanks,

Perkins
 
Colourtune should work fine, but be sure to use the short reach extension (I didn't and got very confused).

Can't think of a good way to check the underside of the inlet manifold gasket without removing the manifold, though I've not known the inlet manifold to leak.

The valve gear will be quiet if you are used to MGBs, and it wears less so is normally neglected. Valve clearances can be set in much the same way as the MGB.
 
Thanks for the replies, I just tired the vacuum advance and the plate does move when the tube is sucked.

I also tried adjusting the mixture screw. It was set at just over 3 turns from base, I bottomed it out and tried at 1.5 turns but the car would barely run. I had to take it all the way upto 5 turns before it started to run smoothly.

As I assume turning the screw anticlockwise (out) is delivering more petrol to the mix, I can't help thinking the problem is elsewhere, as this is almost at the limit of the screw and will surely give a low mpg.

There must be air getting in somewhere. Looks like a bit more detective work and a tube of Hylomar are called for !
 
The 28IF is well known for giving these symptoms. I had to pull the choke out on my 4 to stop the pinking. There should be a short metal connecting pipe in series with the vacumn pipe at the distributor end. There is a little hole in it and this must be clear. This was the fix that Renault tried to stop the pinking in order to make the vacumn advance work more slowly.
As Clementine said, Renault did tune this engine for the sake of economy but they overdid it. You can try retarding the ignition slightly, or drill the main jet out with metric micro drills to one or two sizes up from standard. As far as the air screw goes, adjust it to achieve the optimum revs at tickover - I do mine by ear, but you can hook up a rev counter if you want to be 100% accurate.
The best fix is to fit the whole carb set up from the Mk1 Renault 5 and to chuck the 28IF in the bin where it belongs!! I'm sure that others may disagree, but it worked for me.
 
Hi Steve,
I'll take a look at that tomorrow, but I know the piece of pipe you mean.
One point I forgot to metion was that I have been unable to get the hotter of the two types of plugs recommended for the R4, and have had to make do with the Bosch W7BC instead of W8BC - do you think this will have any great effect as the Haynes manual recommends the hotter plug.
Even though we are in france, it's much easier to get parts elsewhere in the UK or Holland - the local renault dealer just seems to think it a great joke that we want to keep the old girl running and there is no such thing as a motor factor or a 'Halfords' type place !
I was quoted 38 euros for a set of Femsa points here and another 11 for the condensor - is that a record or can anyone beat it ?
 
Do you have a vacuum gauge? It is worth checking idle vacuum. Also check that the idle jet and all idle circuit passages and progression holes are clear, blow through them with compressed air to be sure.
The Colortune works very nice on any R4 engine. On MGBs (4-cyl) I have noted that, when you set the carbs with the aid of the lifting pin, the Colortune reads rich, when I try to make it read blue, the engine runs too lean, an exhaust analyzer confirmed it. Strangely enough, on other engines with double SU it works very well.
It may be cheaper in the long run to buy a Ducellier distributor!
 
There should be a restrictor with a very small hole in the breather from the rocker cover, without it the engine sucks air from the cover, perhaps the hose has been replaced without this restrictor. My local friendly Renault garage reckons Femsa distributors are no good, it may also be a weak diaphragm in the dist, causing too much advance, a Crypton type tune will show the advance curve
Allan
 
hi everybody hope my suggestion may be of some use as i feel sure given the symptoms that this willl cure problem
if you remove air filter and mounting bracket you will see a small bowler hat shaped cover about 16mm dia riveted to top of float chamber use a drill carefully remove rivet ,under neath is a gauze filter which will be blocked with petrol residue remove clean or for non dusty countrys throw away
(this will allow air to vent into carb) re adjust mixture on idle ,road test found best timing setting is to ignore actual setting other than as initial reference(put paint mark dist body/ block) advance as much as will allow without pinking in top gear low speed pullaway
Having worked on R4 s for many years this problem only occurrs on 1108 models becaus e under bonnet temp tends to boil fuel ,850s fan runs constant blowing air around carb
of course R5 mk1 carb is better as suggested but most donor cars are now long gone
Good luck Paul
 
Hi,
Thanks for all the suggestions. I cleaned out the tiny breather in the vacuum advance tube and at the same time I also removed the carb and reseated both gaskets on Hylomar.
The engine now seems to run a lot sweeter and pulls better with less choke, although it still seems to need some and is not perfect.
One point I did notice was that when the engine was really hot ie it had been idling for 15 mins and the fan kept cutting in, it ran like a swiss watch !
This leads me back to the question as to whether the plugs are too cool, as I have not been able to find the hotter ones here ie the Champion L92YC, rather than the L87YC which I think are cooler and all I have been able to get my hands on.
Once the car is back to 'normal' temp, the problem reoccurs although not as bad as previously.
I will try cleaning the small filter in the carb as suggested.
It wouldn't be such a grave problem, apart from it is my wife's car and as she has no mechanical sympathy, I fear the choke will be fully out 100% of the time, with her hand bag swinging merrily from it - or maybe I'm just being sexist !!
 
Hi
Could be just dirt in the main or idle jet
It is also always a good idea to put a inline filter between the pump and the carb The fuel tanks are made of metal and corrode inside as well as out and a lot of muck can come up the fuel inlet

Where abouts are you in finistere I am near Caulness dept 22 just of the N12
I have loads of spares and about 14 cars and 2 vans now I have just completely broken a R1126 as it had no carte grise and was heavily corroded
Let me know if you are ever after anything
Regards
Martin
 
Hi Martin,
We are just west of St Renan, off the coast of northern finistere about 15 mins from the end of the N12.
Do you have an e-mail address for future use.
Thanks as parts seem difficult to get hold of here, as we are 'the end of the line' !
 
mguez

Wow! After meeting malcolm and Steve on the Kent run ,all this carburettor talk on the forum is very helpful to me as I struggle currently with running problems.You guys really know your stuff and thanks for sharing your expertise. I really enjoyed last Sunday and meeting the other owners.My favourite car was that 1968 one ,blue with the beefy engine..the guy from Hertfordshire I think...
 
I have just finished another session on the 4. Whilst replacing the gaiters on the steering rack (piece of cake with QH extra stretchy ones with plastic guide), I also drilled out the breather cap on the 28IF carb as per the advice of Mr-ren-139.

He is dead right, the small gauze filter was gunged up to the eyeballs. I cleaned it off with thinners and then replaced it all with a very small pop-rivet. Amazing, it now runs perfectly with no choke !

Thanks for all your advice - my wife's handbag now resodes safely on the passenger seat.
 
glad to be of help had almost forgotten about that trick. used to be normal problem when R4s were more commonly seen in my workshop instead of all this electonic nonsense of todays renaults
(any body else want to test my aging brain cells)
cheers paul
 
Well done Paul! I swapped a carb over last year because of similar issues. The car had the normal inline fuel filter, but the filter in the carb could well have been gunged up. Maybe that carb is a good one after all.

Another of my cars had great trouble starting from cold. I burned a valve before figuring out the problem (4000 miles at high speed across europe in 3 weeks) so swapped the whole engine. Occurred to me later on that the problem might have been a blocked choke jet, though I've no idea if these things have seperate choke jets. If your brains need picking I'd be interested in your thoughts on this one.
 
I had an annoying experience with the air pipe from the carb. Small pin prick hole in it making it run rough, I only found it by chance.
 
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