help !

[Melissa]

trying to get the old gal (1977 1126 839cc ) running smoothly..so far..new carb, points, condenser, changed oil, plugs leads dizzy cap & rotor arm..set up timing using dwell & tacho....so she now starts runs & sounds way better than ever before...no blank spots or spluttering on reving up & running...BUT..on idle the revs lunge from 750 to 1000 she sounds like she will die but then picks up & lunges again...tacho reading is odd & I have now run out of ideas! any help & suggestions very much appreciated cheers!

 

[jjad]

From my limited experience, could this be something like the float sticking in the carb?

 

[Melissa]

From my limited experience, could this be something like the float sticking in the carb?

although it was doing it with the old carb & is now doing it with a brand new shiny one! I might do a compression test see if that throws light on it.

 

[André4Renaults]

It might just be the mixture. It's possible it has not been set correctly and although it runs at speed OK the mixture being incorrect affects the tick-over speed more. Other thoughts are: dirt in the idle jet in the carb (although as the symptoms are identical with the other carb this seems unlikely.....) and uneven compression across the cylinders; dirty valves and/or stems?

 

[Melissa]

It might just be the mixture. It's possible it has not been set correctly and although it runs at speed OK the mixture being incorrect affects the tick-over speed more. Other thoughts are: dirt in the idle jet in the carb (although as the symptoms are identical with the other carb this seems unlikely.....) and uneven compression across the cylinders; dirty valves and/or stems?

I'll check those, thank you..I'm tending to think dirty valves/stems as the previous owner didn't really do the oil changes & I found the end of the mixture screw had snapped off & was stuck inside the carb in the opening! ..probably been like it for years so he'd been using the choke a lot !

 

[jcarruthers2]

Hi

Has yours got a small hose at the back and base of the carb? if so, this hose has a one way valve inside it. If valve defunct or hose split, revs fluctuate.

 

[Melissa]

Hi

Has yours got a small hose at the back and base of the carb? if so, this hose has a one way valve inside it. If valve defunct or hose split, revs fluctuate.

thanks but no it hasn't, I bought another carb which does though..same numbers but with a B instead of an A at the end, don't know what that means (it was v cheap!) this has a metal pipe/hose which I thought was for a vacuum advance

 

[mojobaby]

Hi Melissa
As mentioned above, it could very well be an air supply problem, too little air then too much causing the surging. Do as jcarruthers suggests and check your hoses to the carb for any splits and also check that they are completely clear-remove and wash them out with solvent and blow them clear with air. They tend to accumulate old oil.

might help if you put up a photo of your carb.

On my GTL there is a small tube(copper?) on the manifold between the manifold and engine. The hose from the rocker cover that leads to the top of the carb has a "T" connection and a small hose which has a restrictor in it, leads down to the little copper tube. If the restrictor is blocked you will get irregular running.

On my 845 there is a small copper tube on the base of the carb. It's on the wheel side of the carb.
Again, a small pipe runs from the "T" connection on the rocker cover/carb pipe. When I first started working on the engine, I found this tube to be blocked. I was told by someone on the forum that it runs better when it's blocked.

You could also try and run the engine with the air filter removed.

 

[Melissa]

Thanks Mojo, I will take a photo of my carb, I have disconnected choke, throttle & taken air filter off so eliminating those as culprits so far, think I will do a compression test today, I've a hunch I have a sticky valve, still she's running better than ever before so some progress is being made!

 

[Melissa]

Hi Melissa
As mentioned above, it could very well be an air supply problem, too little air then too much causing the surging. Do as jcarruthers suggests and check your hoses to the carb for any splits and also check that they are completely clear-remove and wash them out with solvent and blow them clear with air. They tend to accumulate old oil.

might help if you put up a photo of your carb.

On my GTL there is a small tube(copper?) on the manifold between the manifold and engine. The hose from the rocker cover that leads to the top of the carb has a "T" connection and a small hose which has a restrictor in it, leads down to the little copper tube. If the restrictor is blocked you will get irregular running.

On my 845 there is a small copper tube on the base of the carb. It's on the wheel side of the carb.
Again, a small pipe runs from the "T" connection on the rocker cover/carb pipe. When I first started working on the engine, I found this tube to be blocked. I was told by someone on the forum that it runs better when it's blocked.

You could also try and run the engine with the air filter removed.

Any idea what the A & B mean at the end of the numbers on the carbs btw?

 

[jcarruthers2]

Hi Melissa

Further to my last thread regarding the hose with the one way valve in it which could cause fluctuatons in revs if faulty. In fact, there are other reasons for erratic air intake which could cause the same problem including: worn carb base gaskets which you may have already changed, loose manifold nuts, worn manifold gasket or the manifold itself being cracked.

 

[André4Renaults]

Hi Melissa

Further to my last thread regarding the hose with the one way valve in it which could cause fluctuatons in revs if faulty. In fact, there are other reasons for erratic air intake which could cause the same problem including: worn carb base gaskets which you may have already changed, loose manifold nuts, worn manifold gasket or the manifold itself being cracked.

A good way to ascertain if there's an air leak in the carburettor base gasket is by spraying say, WD40 around the base area when the engine's idling. If this produces a change in the engine revs, then there's a leak there. Loose manifold nuts are often sorted by removing the carburettor and making sure the bolts are significantly proud of the carburettor base before tightening the nuts down. Judicial use of silicon sealant helps, too.

 

[Melissa]

Eureka! Stripped the dizzy & there are 2 springs..someone has been here before me & put in the wrong spring on one side which doesn't hold the parts tight & the other original spring is corroded & does not operate freely at all until the car would be cruising along..accounts for erratic idling & sooty plugs due to having to keep it running with choke out at idle without it cutting out. So...now to get some new springs & I reckon my problems are cured.

 

[mr-reno-139]

Pretty sure there is supposed to be two odds springs in there I would be double checking the tappet clearances and probably manifold gaskets other issue I've had which is common on Renault force that don't idle correctly is back to carburettor related look down the top of the carburettor when it is running and see if you can see petrol pouring into the opening when it starts messing about as you haven't started with a brand new carburettor and this is a common problem

 

[Melissa]

thanks Paul, tappets is next on my list, re the carb it's doing the same thing with 2 different carbs so I'm thinking it's not the carb..she sit at idle but the revs lunge to 1000 then back to 750. The long spring doesn't hold the arms tight at all, it flaps about away from the centre by about 6mm..photo doesn't show it.

 

[Melissa]

Pretty sure there is supposed to be two odds springs in there I would be double checking the tappet clearances and probably manifold gaskets other issue I've had which is common on Renault force that don't idle correctly is back to carburettor related look down the top of the carburettor when it is running and see if you can see petrol pouring into the opening when it starts messing about as you haven't started with a brand new carburettor and this is a common problem

took my dizzy to a French old Renault chap today..there should def be two identical springs in there, one doesn't work until throttle would be down & one flaps about at idle..they are both pretty done for..new dizzy on its way from ebay fr.

 

[mr-reno-139]

Willing to bet the new distributor you buy will also have to two odd Springs fitted as standard
I'll be very surprised if this cures your problem however without me standing next to the car diagnosis by internet is very tricky

 

[mr-reno-139]

I could also mention that I have been exclusively working on Renault cars since 1974 but then you might think I'm being I know it all -)

 

[Melissa]

Ha! no not in the slightest! I'm learning daily about these cars so every bit of advice you experienced peeps can give is very gratefully received. It's just what my Monsieur Renault told me, I can't find a diagram for my dizzy anywhere.

 

[mr-reno-139]

I've got no idea where you are in the world as I don't think we've chatted directly before there is several different makes of Sev and ducellier being the most common there is two different sized of the last one I mentioned and definitely not interchangeable between 11 and 8 engines and 8:45 so make sure you're buying the right one to use as a paperweight