Lancia Motor Club

Now I've got my Fulvia running reasonably well there is one thing that is still frustrating - whenever I initially accelerate, either whilst already moving or when setting off there is a hesitation before the revs pick up. I've tried altering the timing but that didn't really make a difference and generally the carb setting seems reasonable with decent acceleration once past the hesitation.

Any thoughts on what it could be? As far as I know the carbs and engine are standard 1.3 S2, I've rebuilt the carbs and cleaned all the jets etc. in an ultrasonic cleaner so there is nothing blocked. The only thing I didn't change was the float settings as I preferred to leave them alone as I don't fully understand how to set them.

Maybe just take the airbox off, and have a look inside each venturi as you operate the throttle lever (engine not running). You should see fuel squirt into each one as the lever operates. I think that's probably the first thing I'd check. Is it better if you run with some choke?

I'll have a look at that, thanks. It doesn't run well with choke once it has fired up but I've not tried using it when warm - I will do next time I have it running, which might be a couple of days.

Fulvias are quite sensitive to valve timing which if not correct will leave a "hole" at  around 2200-2500 (just the revs normally used to pull away from a junction). This is  more noticeable on 1600's.

I doubt float levels will cause this but a quick and dirty way to check is t run the engine so the carbs are full. Take off the little cover on the top with  the domed breather cap and remove one of the middle "jets". With a black 3mm cable tie mark a datum 30mm from the bottom. Stick the cable into the hole where the jet was down to the mark and withdraw. See where the fuel is in the   tie notches and measure to the datum line. The gap should be c19mm+-1mm.

Thanks Tim, the valve timing is as accurate as I can get it on the basis my engine doesn't have the vernier cams. I think it would benefit from a new chain and tensioner which is a job for the winter I think. I'll try the cable tie trick and see how I get on.

How good is your distributor? With the engine off, remove the distributor cap and by hand move up and down the rotor arm to feel for free play. If there is a clear click (max axial play 0.1mm), then the shaft needs re-shimming otherwise you get erratic firing especially at low rev. The shaft needs regular oil lubrication via the purpose made hole in the distributor baseplate, Andrea

Thanks Andrea.

Bigger jets needed for modern petrol.  There is info. in the technical thread I think.

David, I have no problem with my 2c, however I fitted Dellorto 32 DHLB's years ago. :)
Brian
8227 8)

Pardon my ignorance of the Fulvia - what breed of carb does it use? I'd suspect a mixture issue, what you describe sounds like transition from slow running jet to main. Rolling road test might help or if you get really keen invest in an air/fuel ratio gauge which shows what the mixture is at all times. Certainly worked for me on my Augusta but pricey.

Mike

Solex breed?

I already started  a different post about possible solex carb problems as I have no power above 5000 rpm although fine up to that point.
I have the carbs off and am ultra sonically cleaning all the jets etc. I note my main jets are 120. What is the consensus amongst solex experts. Are these correct or should they be a bit bigger?  It is a series 1 1.3s The emulsion tube/air jet is stamped either 80 or probably 180 but a bit difficult to read as the tops are a bit mangled. I do have the feeling that the carbs are under fueled at high rpm/high throttle.
I do not need a rebuild kit but need some carb to manifold gaskets. Who supplies theses?
The timing is good so If the carbs are not the problem I will go to valve clearances and valve timing. I am fairly new to Fulvias so what is the fly wheel marking for No. 1 TDC?
Thanks.
Simon

Notin tech. thread but I knew it was somewhere....
I increased my fast idle jets to 60 via 55 with considerable improvement.  I am consideering increasing the main jets as well but currently am doing the bodywork.   I think it well worth your while experimenting, jets are cheap...

 
   
   
" Re: Carburettor tuning
« Reply #16 on: 22 October, 2012, 03:45:35 PM »
   Reply with quoteQuote
Hello David

I have been following the posts about your engine faltering on pick-up with some interest, as I experienced similar symptoms.  Having now seen that you have exhausted alternative suggestions, it is perhaps time to throw in my tuppence worth......

I am convinced that the viscosity and volatility of current petrols is so different to that of 40 years ago that the behavour of the fuel in Solex carbs is different from what the factory developed.  Admittedly both my 1600 Fulvias have altered ports and manifolds from standard, but on both cars I found idle was fine and main-jet running was good, but to get an adequate pick-up, the fast idle jet had to be significantly increased from the standard 50.  On one car I am using size 55 and the other, size 60 (states of engine tune/distributor advance curve/spindle wear etc. are different), but both now give good instantaneous pick-up. I had to do similar alterations on the 1300 engine, too.

Italian Carburetors of Corlo, Ferrara, Italy can supply new Solex jets in most sizes for a very reasonable amount, and offer a good service.  The url is :
http://stores.ebay.com/ALFA1750S-CARBURETORS-PARTS-STORE

They can also supply the diaphragms - which do seem to harden with age / degrade with modern fuels.  With the carbs off to fit the diaphragms, take the opportunity to try and adjust the drop rods to ensure the activation arm moves the same amount for each diaphragm.  Good luck.

Regards - Roddy
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Roddy Young
Dunfermline, Fife "

That is really helpful David, thanks.

I can't see fast idle jets from that eBay seller but will have a search and see if I can find them somewhere.

They have what ever you need. Just email them. They do a kit containing 8 jets - 4 of one size 4 of another. Suggest you order +5 and +7.5 to start. However as I said before real hesitation (a “hole”) is likely to be something else underlying.

I agree with Tim's message: carbs are often blamed when the problem is somewhere else. Andrea

I haven't had chance to try the cable tie measuring you suggested, hopefully will have a chance this week. The timing chain might take longer to investigate and sort.

I see an earlier post of mine from some years ago has been resurrected, and it is perhaps relevant to revise my views.  Richening the slow running jets did effect some sort of remedy at the time but it was not the proper solution. Almost by accident, when the carbs were off the engine, I noticed that there was quite a lot of 'play' in the butterfly spindle shafts in the their bushes. I did have a pair of overhauled Solexes on the shelf that had had new bushes and spindles fitted, and swapped them over.  Instantly the problem of faltering on pick-up was gone and I had to revert to the standard size of jets to avoid fouling plugs.  I can only surmise that the worn spindles/bushes were allowing air to enter the manifold that had not flowed through the venturi to pick up the requisite amount of fuel dispensed by the slow running jets. Once the butterflies were opened further and the main jets operating, the fuel/air ratio sorted itself out.

Hope of some interest / use?  Regards -

 

Andy

It seemed to go alright on  your video

https://www.youtube.com/watch?v=PY0LKThzh84

Tim

Thanks for watching my video. I understand what it does well enough now for me to be able to drive around it and it not be an issue, I'd just rather not have to do that! Once past that hesitation it does go well.

My carburation problems solved. All jets ultrasonically cleaned and I changed one float valve as it felt a bit “gritty” when pushed up.
The car now runs the best ever. It revs to eternity and back instead of running out at 5,000 rpm. I can really recommend investing in an ultrasonic cleaning tank. They are cheap and they work!

Well done and thanks for the ultra sonic  tip.

Mike

Hello All, Read this thread with interest. I have been chasing a flat spot between 1800-2000rpm on my S3 coupe, very late 1976 car. I have 55 slow running jets, which helped but not completely. Pertronix points and a higher output coil also helped.
But the following might be of interest. By the way my car is very low mileage, 18000 from new!
My carbs are Solex C35PHH E3 (the E3 stamped on the top cover). The standard jets for these (as confirmed in the car handbook) are Slow running 52, main jet 115 air corrector 180. I changed the 52 to 55 with some improvement as mentioned.
The slow running screws have M5 x 0.8 threads and a very fine point, more or less parallel 1mm for the last 4mm, not like the conical "biro" tip shown on the cross section drawings I have found for the C35PHH carbs. I'll try to add a photo.So I am thinking the tuning advice given in R C Pack's Brooklands Books manual may not apply i.e. unscrew these about 2 turns as a starting point. Mine are at 3 turns out now and I will try more.
Where does anyone else with the E3 carbs find they have to set them?
Then as to fuel level and emulsion tubes. As per a forum comment of a good few years ago, mine have the open ended tubes. 4 pairs of cross drillings, the top ones 20mm below the tube seating flange. The "tide line" fuel level is 17 mm below the flange - so above all the cross holes. Confirmed by the "cable tie" dipstick method. The tubes screw into brass bushes in the carb body, not directly into the alloy. The float arms have not been bent, and weigh 10gm.
So is this correct for fuel level? I have never seen a fuel level given in the Solex literature, only comments in the forum that it should be 19mm below the alloy body surface. If I take account of the brass bush thickness about 1.7mm mine would be 15.3mm. But this level must surely depend on the type of emulsion tube, so maybe all is correct on mine.
I'll add a few photos. Any comments would be very welcome, particularly on number of turns for the slow running screws. And for recommendations regarding good Solex books or manuals.
Henry.

You are correct that most of the information and settings available refer to the earlier carbs. I have the E3 carbs on both my cars and use 55 idle jets on one and 57 on the other, the mixture screws are at least 4 turns out maybe more depending on any air leaks. I measured the emulsion tube inserts at 2mm so to check a fuel level of 19mm I make a bend in a bit of wire to leave a leg of 21mm to poke down the well  till it touches the fuel surface. I am experimenting with 125 main jets to try and improve a sensation of weakness during transition at 3000rpm, feels like an improvement and AFR is in the 13's but needs more road testing.

Sean

My experience is that E3 Solex carbs are troublesome and, if possible in terms of cost and availability, they should be replaced by earlier carbs. Andrea

for what it is worth I attach the data sheet for the C35PHHE 3. It does not show a brass shoulder for the emulsion tube housing but the data sheet could be wrong....

I agree with Andrea best solution is to change to earlier non emission solex's.

The diagram is a generic version of the early carb just to show where the main components are. The E3 body has many differences, the idle jets feed from the well not the float chamber, the top cover has extra screws and return spring, the mixture screws have narrow taper, the pump membrane is bigger, there are vacuum ports and the idle bleeds are 2mm.  The emulsion tube inserts are compensated by a longer tube which lets the 19mm fuel level fall just below the top hole.

Sean

Thanks for the above info everyone. Its very helpful to know what others have actually done.
I do not want to change the carbs, mine are in good condition and I'm sure worked well when the car was new.
I have been out for a test run today after resetting slow running to 3 1/2 turns out. It idles nicely, but sounds a bit rich at 4 turns, no increase or decrease in idle speed though, so I left them at 3 1/2. It goes well, pulls well through the offending range so I'm pleased and will leave it like that without doing anything else.
Does that mean you think the fuel level in mine is right or too high. The E3 spec sheet has 19mm so I suspect mine actually is too high.
Has anyone checked the weight of their floats? I may get a pair of new floats at some point.
Henry.

The 19mm is measured from the top face of the body, you can either take the top cover off and measure that way which is a bit of a faff or add 2mm (or 1.7mm) to account for the insert and use the dipstick method down the emulsion tube well.

Sean