Getting the 4GTL running better!

[paulandpat]

Now the daytime temperature has gone above freezing, and before it starts raining again I think it might be time to have another bash at getting the 4GTL (1108cc / 1985) running a bit better. Symptoms are that it hesitates / jerks, as if its 'missing' at around 100 (we're talking kph here - anything less on the autoroute and you just get in everyone's way) - below it runs quite smoothly and above its OK but I don't like to push it - and the owner SWMBO usually complains as well! When we stop it then sometimes runs on.
Have replaced the breather pipe - that had given up and was causing similar symptoms as well as stopping the engine at almost every junction. Looking through it seems the timing is pretty crucial, what about the points gap - usually find it easier to take the distributor out and set that, someone mentioned the dwell - how do you measure that, and with what!
The other thing I cannot find in Mr Haynes manurial!! is which way do you turn the mixture screw to weaken / richen the mixture - is it in to weaken and out to richen or vice versa, I have often found that on a long run it takes only a few moments to open the bonnet, twiddle then go on until you get it right, why don't they put this useful piece of information in!
Any suggestions as to anything else to look for / do would be more than welcome!

 

[mr-reno-139]

hi have you got air intake set for winter so that carb is being fed hot air off exhaust pipe
as carb will ice up causing bad running

 

[malcolm]

For setting the mixture screw screw it all the way in (clockwise) then unscrew it by 1.5 turns. If it runs worse in that setting normally it's something else that's wrong.

I'd check the points gap (I've never used a dwell meter - I set the gap to 0.4mm and it seems fine). Cleck the points are clean, ignition adjusted to a point between the two marks on the gearbox casing. Check the vacuum advance is working (pull off the end from the carb and suck down the pipe - should feel air tight and the top plate of the distributor should move.

Cold air pipe on the manifold can make a big difference to running too.

 

[paulandpat]

New set of Feu Vert's finest plugs, reset of points, seems a bit smoother.
Followed Malcolm's advice to give it a good suck - vacuum part makes encouraging noises but does not move plate. Remove plate - its one of Femsa's finest - give it all some WD40 - another good suck - still no movement - conclusion its the vacuum advance unit.

Next question - can you get them seperately - if not and a complete distributor is needed which is likely to be the best type, when looking through before there were some very uncomplimentary remarks about Signor Femsa's products. Any advice before trawling EBay or La Vie de L'Auto websites would be appreciated.

 

[Steve Hennessey]

You can't buy the Femsa unit now so a good secondhand Ducellier, SEV, Marchal, Marelli distributor would be ok. Just the check that the vacuum is ok before you buy it. Donor cars would, of course, be a R4 and also the R5 TL early 1980's. As long as the car has an 1108cc engine, it will work.

 

[angel]

Adjusting the mixture screw will have no effect on the engine speeds you describe as it only controls idle mixture.
The GTL engines are rather sensible to ignition timing, so make sure it is set correctly (6 deg. BTDC @ 700 rpm with vacuum advance disconnected). When viewing from the front, the left mark on the bellhousing corresponds to TDC, the right one to 4 deg. BTDC).
The dwell angle is measured with a dwell meter, most timing lights have one built in. For peace of mind try to set the points gap by dwell measurement.
The R4 will not know the make of the distributor but will surely recognize the centrifugal advance/vacuum advance curve. Even though the engine will run, you will not get optimum results without the correct ignition curve. If you are sure the distributor is the origianl fitted, try to find one with the same ignition curve numbers (stamped on the distributor side Rxxx/Cxx).

 

[paulandpat]

Got outbid on a new distributor on EBay.fr last night, it started at 39.90 euros with 59.90 buy it now, rather than take BIN option tried to get if for less and it finished over 60 euros! C'est la vie!
To go back to the mixture setting I have put it at 1.5 turns out, before it was around 2.5 - 2.75 and the old plugs were a bit black, so am I right in assuming its out to richen the mixture / in to weaken it?

 

[Steve Hennessey]

The mixture screw setting is just a place to start and does not need to be exactly 1.5 turns. The carb is the last thing that you adjust when tuning an engine. So, make sure that valve clearances, compressions, air filter, all components of the ignition system and timing are ok. Connect a simple rev counter to the coil terminals and adjust the accelerator screw to approx 800rpm.
Then adjust the mixture screw to acheive the maximum revs and back off the accelerator screw as necessary.
If you find that the mixture screw needs to be turned out quite a few turns, or needs to be almost closed in order to enable the engine to tick over correctly, then this indicates a problem with the carb or an induction leak.

As you have already identified that your vacuum unit is knackered, you really can't do any more until this is rectified. You can still get a new distributor from Renault, but they are not cheap!

Good luck!

 

[John Doe]

With all this cold air over here the car runs even better. At this moment it's -5 degrees of Celsius.

 

[paulandpat]

Managed to find another source of new distributors - www.prixusine.fr - total including postage 78.03 euros - bit more than the one on Ebay, but we reckon the car does not owe us much so we can afford to treat it!
Will keep you posted with progress - Pat took it to the shops this am and it kept stopping at the junctions so maybe weakened??? it off too much yesterday.

 

[Steve Hennessey]

That's not a bad price! As for the stalling, please refer to my previous post. Because the vacuum unit has a hole in it, this is an induction leak in itself. As the vacuum unit does not work, remove the pipe and plug it with something suitable then screw the mixture screw in or out until you can hear the optimum revs. This will do until you get your distributor.

 

[seujimmy]

Got outbid on a new distributor on EBay.fr last night, it started at 39.90 euros with 59.90 buy it now, rather than take BIN option tried to get if for less and it finished over 60 euros! C'est la vie!
To go back to the mixture setting I have put it at 1.5 turns out, before it was around 2.5 - 2.75 and the old plugs were a bit black, so am I right in assuming its out to richen the mixture / in to weaken it?

Were you born in yorkshire?

 

[paulandpat]

The wife was - I suppose you're going to repeat the old thing about Yorkshiremen being just like Scotsmen with all the generosity squeezed out!

 

[seujimmy]

The wife was - I suppose you're going to repeat the old thing about Yorkshiremen being just like Scotsmen with all the generosity squeezed out!

Yes and what do you mean,the wife was!Once a yorks lad/lass always a yorks lad/lass.My best mates a yorkshireman and it's painfull when we go to autojumble's. Last time he openen his purse he still had coins with Queen Victoria's young head on them. A Lancashire lad living in Scotland.

 

[paulandpat]

Distributor turned up on 31/12/07, we were out so had to collect it from Bureau de Poste yesterday - its a new ducellier unit.
Fitted it today and the car runs a lot smoother - so its just the carb to sort out now, it seems to still 'hunt' (I think thats the term), will whip a plug out tomorrow and see what colour it is. So whats the answer is it unscrew to weaken?

 

[Steve Hennessey]

Please see my previous post 24 Dec:

The mixture screw setting is just a place to start and does not need to be exactly 1.5 turns. The carb is the last thing that you adjust when tuning an engine. So, make sure that valve clearances, compressions, air filter, all components of the ignition system and timing are ok. Connect a simple rev counter to the coil terminals and adjust the accelerator screw to approx 800rpm.
Then adjust the mixture screw to acheive the maximum revs and back off the accelerator screw as necessary.
If you find that the mixture screw needs to be turned out quite a few turns, or needs to be almost closed in order to enable the engine to tick over correctly, then this indicates a problem with the carb or an induction leak.

As you have already identified that your vacuum unit is knackered, you really can't do any more until this is rectified.

 

[paulandpat]

Got the local garagiste to have a look at the car because its still not running right. He has checked out the timing, carburettor etc (carb gasket was past its best so this was changed for another), now it runs better on the road up to about 85 kph, but could still be smoother, but it will not tick over - even with the slow running screw turned in right against the stop. He admitted he was baffled, his thought was that it could be a problem with the timing chain. Distributor is new, and Jean Michel tried substituting another coil so I suspect we can eliminate the ignition.
I am going to try substituting another carb, (once I've mucked it out), but any other suggestions - preferably cheaper than changing the timing chain would be greatly appreciated.

 

[renault4mad]

didnt there used to be a small breather pipe off the manifold which used to block up with carbon.
i remember drilling out with a fine drill bit

 

[malcolm]

Good point - If the breather pipe isn't fitted with the restrictor there would be a massive vacuum leak and the engine might not idle. It's OK to block the breather pipe from the manifold for a test.

I'd go for blocked jets or a massive vacuum leak if the thing won't idle. Well worth trying a different carb or blocking off the pipe from the manifold.

It's definately not the timing chain. Mechanic is thinking cam belts not chains, but even then he's being hopeful.

 

[paulandpat]

Will try the breather pipe - thats the bit from under the carb that used to keep falling off - we replaced it with a new one, but I must admit I just put it on - should there be some sort of insert in it to restrict the flow?
We always knew when the old one had fallen off - every time we came to a junction the engine would stop.
Perhaps the new one did not come complete.