Compression and Poor Running

[BlueS2]

My 1972 1.3S Coupe feels and sounds like it is running on 3 cylinders. The cold starting behaviour has been discussed in a previous thread and does not sound out of the ordinary. As previously noted, all ignition components are new and ignition timing is on the mark and plug gaps are within spec.

Today I ran a compression test to check for a dead cylinder. The readings were 105/105/110/100, which seem low but are within 10% of each other. I could not find what the compression readings should be in my Service Manual, Concise Service Manual, or Owners Manual. What should those numbers be?

The 1,2, and 3 plugs are a nice brown color, and 4 is slightly black. There is some oil smoke out of the tailpipe. Idle is reasonably smooth, it never threatens to stall, but it has a horrible flat spot between 1500 and 2000 rpm and the running never smoothes out regardless of revs. The car ran reasonably well until some remedial work was done (engine mounts, radiator etc). An inline fuel filter was added at the time in the engine bay. Could this be starving the fuel flow? I will be adding an electric fuel pump in the near future as recommended in the previous thread to aid with starting.

Any ideas on the cause of the poor running are appreciated.

Arno
1972 1.3S Coupe

[1,6 HF]

Arno,

I would think the compression numbers must be in the shop manual, but mine's at the shop--not at home--so I can't check. In any case, they're all close enough together that it's unlikely to be the problem.

A flat spot and rough running could be down to bad carb synch. But I'm not a great believer in coincidences, so if the rough running started after an inline fuel filter was added, I'd certainly suspect that. I'd try removing the filter (or the filter element) to see if that makes a difference. And I'd check the carb synch, too; a problem there would make any fuel flow problem worse--and vice versa.

[BlueS2]

Ed:

I would have thought that the compression numbers would be right there in the shop manuals, but I couldn't find them. There was a section on doing a compression test, but it only said that the cylinders should be within 10%. It did reference a chart which apparently relates to a Lancia special "recording compression test gauge", but the chart is not in the manual.

I will remove the filter and see if that helps. The carbs were not messed with at the shop as far as I know, but I will also follow the synching procedure and see if that helps. The problem is either spark or fuel, and I think I have eliminated spark as an issue.

Thanks,

Arno

[ncundy]

I suspect that one of these days someone will offer an interactive web based training session on how the hell you make sense of the relationships between the various Lancia documents. But I'll start with lesson one :)

Documents that are referenced with the prefix "DT" in the Overhaul Manual "Istrutzioni per le Riparatzioni" are notfound in that document. They are to be found in the Technical Data book "Dati Tecnici".

Thus the document you found referenced n.DT 01/0700 is on page 62 of that document. I have attached it below.

It's taken me years to get to this level of proficiency and I usually charge £40/hr for private tuition :D

[Peter Cripps]

Neil, thanks for the table, and also the list of instructions on how to get there!!!

As for compression tests, the figure quoted in the table for the 303 engine is 11.5 kg/sqcm. This converts to 164 lb/sqin. I actually measure 180-190 lb/sqin on my car ... hmmm??

To make the measurement, it's important to have the accelerator pedal fully depressed and to crank until the gauge no longer pumps up on each compression stroke.

People do say that these measurements are to be taken with several grains of salt. Gauge accuracy, speed of cranking, etc., all play a part. In fact I'm a bit surprised that Lancia even publishes figures ... I don't think many other manufacturers do.

Peter

[BlueS2]

Neil: Thanks for that clarification and the document. I guess if I am in the low 100's and the specification is closer to 165, that would explain why it was so easy to turn the engine over with a wrench on the crank pulley to get TDC while installing the 123 distributor.:eek:

Arno

[RdeMasi]

Those compression numbers are not different enough to cause the large discrepancy you are seeing between plugs 1,2 & 3 and number four. You might want to rerun the compression test with the previous advice of open throttle and insure the same number of turns for each cylinder or keep turning until the gauge no longer rises.

[BlueS2]

I did keep the throttle wide open and cranked the starter for exactly the same amount of time on each cylinder (4 compression strokes). I do plan to rerun the test since I did not have time to do the old "see if dropping some oil down the bores improves it" test.

Arno

[be-em]

I would suggest a leak down test over a compression test as you can listen to where the gas is escaping the combustion chamber. A hose to your ear into the intake, exhaust or crankcase tells you right away. It does require a different gauge and a compressor though. Brian.

[KeppelmanJ]

I concur with Be-em about the leak down. However, if the car runs the tool I would grab is the Colortune by Gunnison. Tells right away which cylinder(s) are running well and which badly. In case you're not familiar with it, it's a spark plug with a glass top which you put in place of each of your plugs holes successively, running the engine for each and viewing the color of the flame. Bunson blue is good, yellow orange is bad. It's particularly good for multiple barrel carb tuning/balancing, but also good for general diagnostics. Wont tell you why a cylinder is running badly, but will identify it and you can fiddle with carb adjustments as you view the combustion flame to determine if your problem is fuel or mixture related. Available at a number of sites including International autosports. The following site is good at explaining it's use:

http://www.gadgetjq.com/ctune.htm

[BlueS2]

Thanks for the reminder about the Colortune. I have been meaning to get one for a while and this may be a good excuse to do so.

Arno

[Dave Simons]

Concur with the leakdown test. Cranking compression can be a bit misleading as its very dependent on cranking speed. If the starter or battery are a bit tired you can get low readings. Keep cranking until the gauge maxes out.

One quick thing to check, which occasionally will give one duff cylinder, are the carb diffuser venturies. You can see them down the carb throats easily enough. Put a finger down the carb and try to wiggle the diffusers with the top of your finger - if it is loose on the doubtful cylinder, you may have found the problem. This is a Solex problem, doesn't seem to happen on Weber or Dell'orto, though I dont know why, this area is quite similar.

[BlueS2]

Concur with the leakdown test. Cranking compression can be a bit misleading as its very dependent on cranking speed. If the starter or battery are a bit tired you can get low readings. Keep cranking until the gauge maxes out.

One quick thing to check, which occasionally will give one duff cylinder, are the carb diffuser venturies. You can see them down the carb throats easily enough. Put a finger down the carb and try to wiggle the diffusers with the top of your finger - if it is loose on the doubtful cylinder, you may have found the problem. This is a Solex problem, doesn't seem to happen on Weber or Dell'orto, though I dont know why, this area is quite similar.
I spent some more time tweaking the car today. I redid the cranking compression test and got basically the same results, but the readings were marginally higher (in the 120 psi range). I put oil down the bores and the readings did not change, so it seems that the rings are not to blame and it may be a valve issue.

I also rechecked the timing on the 123 and made just the slightest adjustment. I also removed the inline fuel filter. I then took it out for a 25 mile Italian tuneup. The car does run much better now, but nowhere as well as other Fulvias that I have driven or ridden in. I wonder if the engine is gunked up from the previous poor state of tune. However, it seems to now run on about 3.75 cylinders (still has some hesitation and some chug/chug/chugging), and it seems to run better with a heavy throttle application versus light. Idle is smooth, and it is clean coming off idle, but then gets rough in the 2000 to 3500 rpm range. I have not yet ordered my Colortune but will do that this week.

Turning to the carbs, I did check the venturis and both 1 and 2 are very loose (like scary:eek:), but 3 and 4 (the suspected bad cylinder) are tight. How does one tighten these up? I looked at the Solex information that was posted on this site, and the exploded figure seemed to show a nut at the bottom of the carb body which I tried to tighten, but it didn't do anything to tighten up the venturis. I have not yet checked the carb synchronization.

As a side note, I took one of my 70's Alfa coupes out for a drive right before doing the Italian tuneup on the Fulvia, and I was shocked how different the two cars feel. I have owned this particular Alfa for over 15 years and the Fulvia for a little over one. The Alfa has more power (2 litre vs 1.3) but the steering and braking of the Fulvia is better. I also fit better in the Fulvia (I am 6 ft 4 inches tall).

Arno

[1,6 HF]

Arno,
Check the carb synch; if it's significantly off, the engine won't run smoothly, whatever else you do.

And the comparison between your Fulvia and your Alfa GTV doesn't surprise me at all. The GTV is considerably quicker in a straight line (as you'd expect from the difference in displacement), but the Fulvia is better balanced and better built.

[ncundy]

Turning to the carbs, I did check the venturis and both 1 and 2 are very loose (like scary:eek:), but 3 and 4 (the suspected bad cylinder) are tight. How does one tighten these up? I looked at the Solex information that was posted on this site, and the exploded figure seemed to show a nut at the bottom of the carb body which I tried to tighten, but it didn't do anything to tighten up the venturis. I have not yet checked the carb synchronization.
Arno

The nut is a lock nut, tighten that too tight and you will damage something. If you look at the parts list that is on here you will see items 93 and 98. Item 93 is a tapered set screw, tighten this to locate the venturi, then tighten the lock nut. Not that easy to do with the carbs on the car.

Something else to check (although I think it unlikely given the symptoms you describe) is the rubber gasket between the carbs and the manifold. It can crack if not supported properly and as the engine vibrates the cracks open and close giving erractic running (usually at idle though). You can check this by undoing the support strut under the carbs and with the engine running move the carbs up and down to see if the speed changes.

[BlueS2]

Thanks for the continuing help everyone. The rubber carb mounts appear very fresh, and the car idles pretty well, but I will check them as Neil suggests just to eliminate that possibility.

I suppose I should look into one of those Gunson carb balancing gizmos while I am getting the Colortune. I suspect this all has something to do with carbs and fuel given how the car behaves and its response to things I have done. I will also be adding the electric fuel pump, which can't hurt either.

Arno

[RdeMasi]

You said the idle and acceleration are good but it stumbles around 2500-3000 rpms. Does it then clear up as you rev even higher?

If you shoot your timing light at the mark on the flywheel at idle and then start reving the engine (be careful with the wires) does the timing mark move with the revs of the engine? If not the distributor isn't advancing and there might be a problem with either the weights or the plate that moves.

Once you get the Gunson you can do the same sort of test. Rev the engine to 2500-3000 and with the Colortune you'll be able to determine if any of the cylinders are being starved of gas by virtue of the color observed. If it looks like one or more of the clyinders are not getting a proper mixture let the engine run for a few minutes, shut off and remove the tops of the carbs. See if the level of the fuel is different between the two carbs. Make sure the needle valve washer is the same thickness on both covers.

By the way you can't run the Gunson spark plug for very long because you'll melt it so be deliberate and quick with your tests.

I good test of the rubber spacer between the carbs and manifold is to spray either carb cleaner or starting fluid on the area. If the revs change fluid is getting by the rubber and so is air.

[BlueS2]

You said the idle and acceleration are good but it stumbles around 2500-3000 rpms. Does it then clear up as you rev even higher?

If you shoot your timing light at the mark on the flywheel at idle and then start reving the engine (be careful with the wires) does the timing mark move with the revs of the engine? If not the distributor isn't advancing and there might be a problem with either the weights or the plate that moves.

Once you get the Gunson you can do the same sort of test. Rev the engine to 2500-3000 and with the Colortune you'll be able to determine if any of the cylinders are being starved of gas by virtue of the color observed. If it looks like one or more of the clyinders are not getting a proper mixture let the engine run for a few minutes, shut off and remove the tops of the carbs. See if the level of the fuel is different between the two carbs. Make sure the needle valve washer is the same thickness on both covers.

By the way you can't run the Gunson spark plug for very long because you'll melt it so be deliberate and quick with your tests.

I good test of the rubber spacer between the carbs and manifold is to spray either carb cleaner or starting fluid on the area. If the revs change fluid is getting by the rubber and so is air.
The distributor is a brand new 123 electronic one from Huib, and the coil, wires, plugs, battery etc are all new. The timing is spot on throughout the rev range as checked with a strobe.

Thanks for the additional hints on things to check on the carbs. I suspect the issue is with fuel delivery of some sort. It smoothes out somewhat at higher rpms but I can still feel the miss. It also seems to miss more with small throttle inputs as opposed to giving it a bootfull of throttle.

Quoting Maxwell Smart: "Ah yes, the old spray carb cleaner on the rubber trick..."

I guess I have plenty to keep me busy for the next few weekends...:D

Arno

[NMLancia]

I would suggest an igntion problem but it seems you have checked that.

My Fulvia tends to foul plugs, but its usually on cold start and then clears with an "Italian tuneup". Is the #4 plug oil fouled or wet with gas? Have you rebuilt/cleaned the carbs? Have you checked the valve clearance? The Fulvia may not have the power of the Alfa Nord but it should be very smooth "sewing machine like" at higher revs. At 1100' I dont think you should have to rejet the carbs (especially since 1,2&3 seem ok) but I do believe your problem might lie in the carburetor.

Nice color by the way. We should meet for a Photo op.

[BlueS2]

I have a Gunson Colortune and a Carbalancer on order, so I am anxious to check the carburetion when they arrive.

NMLancia: Yes, I really like the blue on these cars. However, since mine was apparently repainted in Italy in the early 90's, the color doesn't quite match up with any known off the shelf formulation or paint code. I went to the paint store a few days ago to buy a pint of paint to repair some damage to the front valence under the bumper, and I brought them a chunk of the filler:eek: that came off the damaged area that was painted. They had to send it off to be computer color matched.

Apparently whoever repainted the car back in the early 90's thought it was more expedient to repair a dent in the valence by covering it up with a half inch of filler applied with a masonry trowel, sanding it with what looked like a garden rake, and painting the area. This was stupid because I was able to reach behind the dent and push it out with my hand (a simple oil can dent) which is why the filler popped loose. It only needs a light skim over the area to smooth it out, and then I will paint the whole valence to make sure it matches up. A nice easy New Years weekend project.

Arno

[NMLancia]

Mine was repainted also and I dont think its an actual Lancia color, its very dark, looking almost black at times.

I hope the New Year brings you good luck with your tuning issues.
If you need carb parts I have had good luck with "Alfa1750-carburetor-parts" an ebay store. He has all the Solex parts.

[1,6 HF]

Mine was repainted also and I dont think its an actual Lancia color, its very dark, looking almost black at times...

Blu Lancia is indeed a very dark 'midnight' blue, and does tend to look black unless it's in strong light. So yours could be correct.

[NMLancia]

Ed

The engine compartment and the inside of the doors (behind the door panels) are a little bit lighter than the exterior color which is why Im suspect... Original or not I like it!

[1,6 HF]

Stephan,

Don't forget that we're discussing Lancia, here; they could both be correct. I have a Glasurit swatch book with about 15 years' worth of colors; it has at least 2 slightly different versions of Blu Lancia. And I have factory color cards, which also have slightly different versions of Blu Lancia. So the exterior color may simply represent a later "official" factory Blu Lancia than the original.

[NMLancia]

Ed

Im affraid we may have hijacked this thread but if I ever get my car out to the west coast I would love to compare your samples to my car.

Stephan

[1,6 HF]

Stephan,

Any time; I'd love to see the car. And I hope the fact that we've managed to hijack the thread means that Arno's got his rough running sorted out.

[NMLancia]

Ed

I'm shooting for Best of France and Italy, a show I've always wanted to see. Maybe I can get some Az. Lancisti to join me.

Stephan

[1,6 HF]

I'm shooting for Best of France and Italy, a show I've always wanted to see. Maybe I can get some Az. Lancisti to join me.

Stephan, that sounds great! Hey, Arno, what about it? (it's not until next November; you've got 10 months to sort things out.)

Maybe the ALC WC Reunion will be down south this year; that's even sooner, and even better than Best of France and Italy.

[fay66]

Ed

The engine compartment and the inside of the doors (behind the door panels) are a little bit lighter than the exterior color which is why Im suspect... Original or not I like it!

Like yourself I have found places tucked away where the original colour is lighter than the exterior, but I think it's only the difference of the exterior being exposed to the elements, whereas the lighter colour hasn't been.


brian

[BlueS2]

Ed

The engine compartment and the inside of the doors (behind the door panels) are a little bit lighter than the exterior color which is why Im suspect... Original or not I like it!
Funny, I have exactly the same situation on my car. Whoever painted the car also did the engine bay, but missed a few spots where I can see that slightly lighter blue. Fortunately you have to look pretty hard to notice it.

Thanks for the tip on sourcing Solex parts. Hopefully I won't have to replace anything, but it is nice to know that parts are available. Hopefully my Colortune and Carbalancer arrive by the weekend.

Speaking of which, is there an English translation of the carb synching procedure available anywhere? All my documentation is in Italian.

Thanks,

Arno

[NMLancia]

Arno

My shop maual is in English, unfotunately I'm out of town until Sat but if you still need it I can send you a scan. You could also search the alfabb (carburation) it mostly talks about webers but the principle is the same. viva-lancia also may have some info.

Stephan

[jackois]

just to throw my tuppence worth in on the hesitation/poor running part of the thread...

I've now replaced or overhauled 99% of my fuel system.

New tank, carbs (solex) overhauled by Gowers, electric fuel pump & pressure regulating filter king and finally the main fuel pipe from rear to front.

The final item was changed after I was still struggling to get fuel pressure even after all the other bits. The pipework that was in view under the bonnet looked like new, but once removed, the stuff under the car was found to have various pinholes which I think were allowing air in.

The car now runs well, starting pretty much instantly from cold & doesn't suffer from the gradual loss of power/torque that it did before. It still, however, hesitates at around 2,500 to 3,000 revs before powering on smoothly through to the red line & clips along nicely between 70 & 80 mph where appropriate. I suspect the hesitation is where the carb changes choke from primary to secondary.

The only thing I can think to change out now are points & condenser, specifically condenser, just in case the spark is fluctuating.

With tuning, I can recommend the colortune unit as easy to use along with a flowmeter for carb balancing and have posted here about how it was done - http://www.lancisti.net/forum/showthread.php?t=3110

Hope this is of help.

[BlueS2]

Update:

I spent quite a bit of time on the car this past weekend, and although things are improved somewhat it is still definitely missing on one cylinder.

The first thing I did was use the Gunson Carbalancer to synch the carbs per the service manual procedure. The balance was way off with the front carb sucking a lot more air than the rear. Once balanced the stumble and flat spot between 1500 and 2000 rpm was mostly eliminated.

I then used the Gunson Colortune to check the mixture, and all four cylinders were running rich (yellow flame) throughout the rev range. There was a spot around 4000 rpm where the flame appeared to lean out but above and below that level it was rich. However, number 4 seemed to have a weak flame (recall that all ignition components are new, and the 123 distributor and coil put out one heck of a strong spark).

I then did the "Slow Running Adjustment" per the shop manual adjusting the 4 small screws on top of the carb bodies. This made very little difference. Is there an additional mixture adjustment I should make? The shop manual is not very clear on this.

Another thing to note is that I seem to have significant oil blowby coming out of the breather that goes to the air filter assembly, and the crankcase must be pressurizing since the dipstick pops out when you rev the engine hard and spills oil around it.

Overall, it is now a responsive 3 and half cylinder car. I am thinking I should pull the head and see if I have a broken valve or something and maybe drop the pan and pull at least number 4 piston and see if the rings are broken.

Ideas??

Thanks,

Arno
1972 Fulvia 1.3S
Assorted Alfas

[1,6 HF]

...
Another thing to note is that I seem to have significant oil blowby coming out of the breather that goes to the air filter assembly, and the crankcase must be pressurizing since the dipstick pops out when you rev the engine hard and spills oil around it.

Overall, it is now a responsive 3 and half cylinder car. I am thinking I should pull the head and see if I have a broken valve or something and maybe drop the pan and pull at least number 4 piston and see if the rings are broken.

Arno,

Sounds like some improvement. I don't know what to make of the oil blowby. First I'd check the oil level to make sure it isn't just overfilled. I'd also check the breather to make sure it isn't plugged up.

The compression test already told you most of what you need to know about the rings; number 4 isn't much different than the other three.

And before you pull the head to check the valves, do the leakdown test that several folks were recommending at the beginning of the thread. It'll tell you much the same thing with a lot less effort.

[BlueS2]

Arno,

Sounds like some improvement. I don't know what to make of the oil blowby. First I'd check the oil level to make sure it isn't just overfilled. I'd also check the breather to make sure it isn't plugged up.

The compression test already told you most of what you need to know about the rings; number 4 isn't much different than the other three.

And before you pull the head to check the valves, do the leakdown test that several folks were recommending at the beginning of the thread. It'll tell you much the same thing with a lot less effort.
The leakdown test is next on the list. Trust me, I really don't want to pull anything apart if I don't have to. I just need to beg/borrow/steal a leakdown tester from a friend, although this might be a good excuse to get one for the toolbox:D

The oil is at the right level, at least per the dipstick. The previous owner told me that the car burned some oil so I knew that going in. With the new hot ignition system it seems to be less oil smoke out of the tailpipe, but the amount coming out of the breather hose when I removed the airbox was really something. The term mosquito fogger is appropriate here.

I'll tinker some more this weekend.

Arno

[ncundy]

When you do the leak down test first pressurise the piston and then turn the engine to see if you get a sudden leak at a certain position, probably TDC as this is where the worst bore wear occurs. If you can identify a certain position re-run the test. You only need to run this on each piston around the position where both valves are closed. Do this with the cover off and you can see when the valves are off the cam.

However even if you find nothing (and a static leak down test will not always show up leaks) you will ultimately have to take the head off to measure the bores and look for damage. And then at the least the pistons out to change the rings. In 25 years of professionally dealing with rail engines the one test which is consistent across the patch and never lies is measuring crankcase pressure. If it rises and there is no water in it, you have to change the rings or liners. Always.

Personally I would cut your losses and at the very least take the head off and gauge the bores. But you will have to remove the pistons eventually.

The only other thing which is worth checking is are you getting water in the sump. It is possible although unlikely that the head gasket has gone.

[RdeMasi]

You might try closing the idle screw (clockwise) for cylinder 4 while the car is idling and see if that affects the mosquito fogger effect you're getting from the crankcase. Note the screw's setting so you can put it back to the original position.

[BlueS2]

You might try closing the idle screw (clockwise) for cylinder 4 while the car is idling and see if that affects the mosquito fogger effect you're getting from the crankcase. Note the screw's setting so you can put it back to the original position.
Sorry if this sounds dumb, but exactly which screw is that? Neither the Tavola or the DHLB information in the downloads section uses the term "idle screw". To be sure that I don't turn the wrong one, can you either reference the number on the diagram or describe which one it is?

Thanks again everyone for your help and advice.

Arno

[1,6 HF]

It's not the "idle screw"; it's the "idle mixture screw"--a screw with a spring under the head, located on top of each barrel, near the throttle plates.

And "idle mixture" is a bit misleading. The screw controls the mixture for everything under about 2500 rpm, at which point the main jets come into play.

[BlueS2]

It's not the "idle screw"; it's the "idle mixture screw"--a screw with a spring under the head, located on top of each barrel, near the throttle plates.

And "idle mixture" is a bit misleading. The screw controls the mixture for everything under about 2500 rpm, at which point the main jets come into play.
This is the same screw that is used to do the "slow running adjustment" in the service manual, right? If so, then someone previously had the same idea that RdeMasi had since that screw was backed down all the way.

I find it interesting how different these carbs are from the Solex 44PHH that are on my Alfa 2000 Touring (and the downdraft Solex on my 60's Beetle :D). This has been quite the learning experience...

Arno

[RdeMasi]

I noticed that a few posts back you said you did the slow running adjustment with four small screws but you are now saying the screw was all the way in or closed as far as passage of the fuel. Well that's the same screw (for cylinder 4) that I'm suggesting you to adjust and as Ed noted it's brass colored and has a spring (hopefully) under it to prevent movement after being set.

You said in your post that these didn't make much of a difference to the running of the engine. With the Gunson Colortune installed and the engine idling you should have been able to adjust the idle mixture screw and observe the sparks color change from yellow to blue as the mixture for that cylinder went from lean to perfect. I don't remember that exact colors for each condition but you get the idea.

I will look for a photo or sketch of the carb to insure you are adjusting the right screws. In the absence of a Colotune tool the method of approximately adjusting the idle mixture screws is to set them so that any further movement of the screw either clockwise or counterclockwise would result in fewer RPM's. You're looking to achieve the highest RPM possible with each screw. You can either use your hearing or a tachometer to determine the RPM.

Once that's done to all four screws then you can readjust the idle set screw which is the one between both carburettors and moves the throttle plates of both carbs. Don't mix this one up with the screw used to adjust the BALANCE of the two carbs.

Again, like Ed mentioned, this idle circuit will serve the motor's requirements until the main circuit starts to come into action.

[fay66]

I noticed that a few posts back you said you did the slow running adjustment with four small screws but you are now saying the screw was all the way in or closed as far as passage of the fuel. Well that's the same screw (for cylinder 4) that I'm suggesting you to adjust and as Ed noted it's brass colored and has a spring (hopefully) under it to prevent movement after being set.

You said in your post that these didn't make much of a difference to the running of the engine. With the Gunson Colortune installed and the engine idling you should have been able to adjust the idle mixture screw and observe the sparks color change from yellow to blue as the mixture for that cylinder went from lean to perfect. I don't remember that exact colors for each condition but you get the idea.

I will look for a photo or sketch of the carb to insure you are adjusting the right screws. In the absence of a Colotune tool the method of approximately adjusting the idle mixture screws is to set them so that any further movement of the screw either clockwise or counterclockwise would result in fewer RPM's. You're looking to achieve the highest RPM possible with each screw. You can either use your hearing or a tachometer to determine the RPM.

Once that's done to all four screws then you can readjust the idle set screw which is the one between both carburettors and moves the throttle plates of both carbs. Don't mix this one up with the screw used to adjust the BALANCE of the two carbs.

Again, like Ed mentioned, this idle circuit will serve the motor's requirements until the main circuit starts to come into action.

In my Fulvia Manual for solexes Lancia Call them Volume adjusting Screws, shown as 2 in Diagram.

Brian

[BlueS2]

I noticed that a few posts back you said you did the slow running adjustment with four small screws but you are now saying the screw was all the way in or closed as far as passage of the fuel. Well that's the same screw (for cylinder 4) that I'm suggesting you to adjust and as Ed noted it's brass colored and has a spring (hopefully) under it to prevent movement after being set.

You said in your post that these didn't make much of a difference to the running of the engine. With the Gunson Colortune installed and the engine idling you should have been able to adjust the idle mixture screw and observe the sparks color change from yellow to blue as the mixture for that cylinder went from lean to perfect. I don't remember that exact colors for each condition but you get the idea.

I will look for a photo or sketch of the carb to insure you are adjusting the right screws. In the absence of a Colotune tool the method of approximately adjusting the idle mixture screws is to set them so that any further movement of the screw either clockwise or counterclockwise would result in fewer RPM's. You're looking to achieve the highest RPM possible with each screw. You can either use your hearing or a tachometer to determine the RPM.

Once that's done to all four screws then you can readjust the idle set screw which is the one between both carburettors and moves the throttle plates of both carbs. Don't mix this one up with the screw used to adjust the BALANCE of the two carbs.

Again, like Ed mentioned, this idle circuit will serve the motor's requirements until the main circuit starts to come into action.
I need to redo the slow running adjustment since I now think that I didn't turn the screws out far enough to reach that max rpm, and I didn't do it with the Colortune in place like it makes sense to do. I used the Colortune to check the original mixture but then put the plugs back in.

I am still awaiting the arrival of the leakdown tester I ordered, so I still have lots of fun stuff to do.

Arno

[Jeff_B]

What was the resolution to this story?

[BlueS2]

Jeff:

The car runs like a champ now. After all the head scratching, carb tuning ad infinitum, it appears that I had some stuck compression and oil control rings on #4. Keep in mind the car sat around for a long time prior to my ownership, and it didn't get driven that much for quite a while after I bought it while I sorted out a bunch of cosmetic and mechanical items. One day a few months ago I started it up and there was an almighty cloud of blue smoke (at which point the air got blue too...) and as the car idled the smoke started to clear (probably when the rings finally freed up) and it ran smoothly. The more I drove it the better it got. I have put probably 300 miles on the car this month alone with no smoke, no flat spots on acceleration, no oil burning or other issues. I think that the carb tuning and 123 ignition/Beru coil help a bunch, but having it actually fire on all 4 is the secret...

In fact, I just took it out to run some errands and it was great.

[fay66]

Very lucky you got away with that, in a similar situation I finished up with a broken ring, a scored bore, a rebore, oversize pistons and a £1000+ plus bill.:'(

Brian

[BlueS2]

Very lucky you got away with that, in a similar situation I finished up with a broken ring, a scored bore, a rebore, oversize pistons and a £1000+ plus bill.:'(

Brian

Ugh, that must have been an eye opener. Better lucky than good sometimes...

[fay66]

Ugh, that must have been an eye opener. Better lucky than good sometimes...

Yes, it did hurt somewhat at the time!

Brian