Technical New Carb, new ignition points - still struggling to start without choke

[turbo500]

With regard to mixture adjustment---some times it works better if, when you have got the engine 'sort-of' idling OK, you turn the mixture screw ANTI-CLOCKWISE (i.e. OUT) until it runs a bit rough and then turn the screw back in (clock-wise) until it smooths out

What I noticed was that if I did what you wrote, starting from it screwed out, it was super rich, to the point I could see slightly dark smoke from the exhaust when pushing the revs.

 

[bugsymike]

As hobbler above, plus generally if you gently increase the throttle, it revs then dies a little, can indicate a weak mixture, this would be to do with jetting as the external mixture screw is only for an idling adjustment. If your model carb has an accelerator jet, check that as you start to operate the accelerator linkage you get a steady jet of fuel into the carb as if not that can cause a hesitation.

 

[the hobbler]

As hobbler above, plus generally if you gently increase the throttle, it revs then dies a little, can indicate a weak mixture, this would be to do with jetting as the external mixture screw is only for an idling adjustment. If your model carb has an accelerator jet, check that as you start to operate the accelerator linkage you get a steady jet of fuel into the carb as if not that can cause a hesitation.

Apologies if I didn't explain myself clearly. Still start tart with the basic idle-speed mixture screw setting (1---1-1/4 turns out from fully in), but adjust it gently OUT until it runs unevenly, and then gently screw it back in untill the idle evens out.

 

[lazylobster]

Haha Daniel, I think I would have given up today if it wasn't for reading you post last night. I can't believe it but it actually turned on. Funny story is I spent 2 hours checking the carb, pulled it off completely, check the jets again, checked the points, checked the spark plugs with a multimeter, checked the voltage regulator (found a dodgy wire but no clue as what it's for, hanging on by a thread for now), checked fuel flow, etc.
I cranked it for a good 30 seconds on several occasions, and nothing happened. I have a battery charger that I resorted to 3-4 times today. Eventually I started filming a video so I could post it here to see if while cranking anything stood out to you guys, and it started


I spent about 15 minutes trying to get it to run smoothly, but I'm not sure I've gotten there. In an effort to reduce the sooty sparks I had with the previous carb, I found this guide from weber https://www.carburetion.com/Weber/adjust.htm, and it helped, but I don't know if there's a better way.

I turned the mixture screw fully closed (clockwise) and it actually sped up the engine and was running fast. So I backed it out, and I went too far because when accelerating the exhaust gasses were slightly dark. So I ended up about a turn or so from closed (turning counterclockwise).
Idle I followed the guide of turning clockwise until it starts to run rough, and then back it out 1/4 to 1/2 turn.
Throttle linkage screw, turned out until generator light starts to appear on the dash.

The problems I'm finding, is when moving the accelerator linkage, the initial acceleration I notice a few hiccups, then it rises smooth. Letting go of the accelerator it goes back down to idle, and sometimes wants to turn off. I also noticed a few spits and pops.



The biggest win is that it actually turned on, and seems to turn on after a half second or so, compared to before when it used to crank for a few seconds with the 28imb. I think I will attempt to adjust valves to see if that improves, but first want to get her going.
Anyway, a little picture dump, maybe someone can spot any issues (anyone know what the green wire on the left most voltage regulator coil thing would be?it goes into the passenger compartment?)

View attachment 420179
View attachment 420180

I would also, if it was me, replace the voltage reg with a new electronic one. Your mechanical one looks original, so 40 plus years old? They can be adjusted but it's quite an involved process. Get an electronic one, hassle free, no adjustment. You can engineer the mechanical cover to fit on the new one if you want the original look.

 

[dangfiat]

@turbo500: Good on ya! Always a great moment when you finally get it running well (or at least acceptably well)

Thanks for the weber link, good find!

My journey continues: the starter has decided it's job is definetly NOT starting the car. It's gone dead, even with the "poke it with a stick" approach. New (rebuilt) device on the way from the UK

+1 on the "replace regulator with a solid state version". They're cheap and work well. Unless you have a really special car, I'd go with driveability over origionality any day

Daniel

 

[turbo500]

Apologies if I didn't explain myself clearly. Still start tart with the basic idle-speed mixture screw setting (1---1-1/4 turns out from fully in), but adjust it gently OUT until it runs unevenly, and then gently screw it back in untill the idle evens out.

Ok that makes sense. I'll give it a try and see if that works well.

I would also, if it was me, replace the voltage reg with a new electronic one. Your mechanical one looks original, so 40 plus years old? They can be adjusted but it's quite an involved process. Get an electronic one, hassle free, no adjustment. You can engineer the mechanical cover to fit on the new one if you want the original look.

Yes I've been considering it, one less thing to worry about. Ideally would like to get an electronic ignition as well, if the coil is reading over 3ohms I should be set to replace it if I remember well?

@turbo500: Good on ya! Always a great moment when you finally get it running well (or at least acceptably well)

Thanks for the weber link, good find!

My journey continues: the starter has decided it's job is definetly NOT starting the car. It's gone dead, even with the "poke it with a stick" approach. New (rebuilt) device on the way from the UK

+1 on the "replace regulator with a solid state version". They're cheap and work well. Unless you have a really special car, I'd go with driveability over origionality any day

Daniel

I've got a whole backlog of stuff to get done...rear bearings are shot, speedo dances, steering loose, wiring loom

 

[lazylobster]

Ok that makes sense. I'll give it a try and see if that works well.

Yes I've been considering it, one less thing to worry about. Ideally would like to get an electronic ignition as well, if the coil is reading over 3ohms I should be set to replace it if I remember well?

I've got a whole backlog of stuff to get done...rear bearings are shot, speedo dances, steering loose, wiring loom

re: Coil over 3 ohms, by how much? If it's still low 3's then nothing to worry about.

electronic ignition. Mixed bag. I run a powerspark (hall effect, accuspark and others are available), no problems yet. But others have had issues as they don't like the heat from the engine. So revert to points. If you do go points, invest in a top end condenser like swifttune:

Swiftune Competition Condenser

Swiftune Competition Condenser

swiftune.com

Normally condensers are the BIG issues in old style ignition systems.

Cheers
Rob

 

[bugsymike]

I agree with lazylobster re older points based ignition systems and condensors, it was all we ever had back in the late 60s.
However if you inspect the contact points surface area and they are a light grey even surface then condensor generally is good , if the contact area is "blue and pitted" that is a sure sign of a duff condensor. When I was at college I was taught the purpose of the condensor was to prevent arcing at the points, basically it allowed the voltage at the points to quickly collapse "make and break" without splashy sparking.
Leaving the ignition on without the engine running whilst fault finding elsewhere for example will quickly "knacker" the condensor, contact points and possibly the ignition coil due to overheating. I have seen coils with the oil bubbling out of them in the old days. Obviously if the contacts are open this will not happen.
When ever I did a service and was changing the points I would always look at the old set coming out and if the signs I mentioned were there then replaced the condensor.

 

[turbo500]

Ok I’m losing my mind. I got round to working on the 500, and it is a mess.

I tried starting it and recently it was fine. Now I start it and with choke on it just revs high and then almost sputters pretty low, if I turn off the choke it cuts out. So I don’t know what that’s about. It’s not keeping steady rpms.

I fitted a fuel filter because I was worried the fuel tank was dirty. I cleaned the carb jets (28 Imb), other than the choke jet and emulsion well that I don’t know how to remove.
The jets were all clean looking including the main jet. The float chamber was pretty clean. I can try and spray some carb cleaner when it’s running if that’s advisable?
As it stands my settings for the screws are:
-Idle jet screw (the top one) is screwed only 1/4 out, or is this supposed to be screwed in fully as it’s a jet???
-idle adjustment screw (the bottom one hidden inside the metal tube) is 2 turns out
-there is no other screw to adjust on the 28imb compared to the 26imb? I keep reading to adjust both screws on the fiat 126 forums?

I adjusted the points gap (again) to 0,50
I will attempt to adjust the tappets to 0,20 and 0,25 since it’s supposedly a 126 head.
Other than that the only thing left is the timing (which I have never adjusted, same with the tappets). But I would rather first see if it’s something in the carb that’s wrong or off.


Here is a video of it running (badly) with the choke off. It will idle but it sounds rough. More importantly it will not accelerate without huge drops in power. It’s almost impossible to get a good rev.



What on earth is going on? I don’t understand what I’m doing wrong. Send help

P.s. someone on an Italian forum had something similar happen, they were saying it might be the air bleed jet (freno aria) Being too big on the 28 for the 500 engine??

 

[smart51]

Mine was running worse than that a couple of days ago. The gap on the points was too small. With that set it ran a little better. Similar to your's, a bit of choke made it run better. I wound out the mixture screw until it idled nicely. Mine is currently at two turns out.

Not idling well but improving with a bit of choke suggests a lean mixture. Either there is an air leak somewhere, or the emulsion tube is letting too much air in, or the fuelling is on the low side. What happens if you turn the mixture screw out a little at a time?

 

[bugsymike]

If you hadn't said the carb had been stripped and cleaned, when revved it is like a fuel blockage but I would also look to the ignition side, HT leads shorting distributor cap or coil tracking out even the rotor arm, I know that sounds like covering both bases but to me a old style mechanic would have covered most of it when doing a normal service.
Just a final thought are those silicon HT leads, it may be worth putting a mutimeter on Ohm settings and just check end to end on the leads for continuity, I have come across many that the caps have been yanked and broken the carbon string inside, so they run but struggle under load.

 

[the hobbler]

Mine was running worse than that a couple of days ago. The gap on the points was too small. With that set it ran a little better. Similar to your's, a bit of choke made it run better. I wound out the mixture screw until it idled nicely. Mine is currently at two turns out.

Not idling well but improving with a bit of choke suggests a lean mixture. Either there is an air leak somewhere, or the emulsion tube is letting too much air in, or the fuelling is on the low side. What happens if you turn the mixture screw out a little at a time?

The idle JET should be fully wound IN---if it isn't, air can intrude. The screw for the throttle-link adjustment is for adjusting the idle SPEED---I would start by screwing it out until it no longer touches the cating on the carb, and then turn in in (clockwise) 1-1/2 turns from when it JUST touches that casting. The idle MIXTURE screw is the one that goes into the side of the carb (and is surrounded by the ally casting) Personally, i would start with this 1-1/2 turns OUT from fully in. GENTLY turn this mixture screw fully clockwise until it stops---and then turn it out (anti-clockwise) 1-1/2 turns. This should give you a good basic setting .
You say that you have never touched the timing---this needs to be checked and (if required) corrected. With points-ignition this can be set statically with a test-lamp-----obtain a test lamp with a 12 volt bulb in it. Remove the rocker cover and check that both valves of No. 1 cylinder (the rear-most cylinder) are shut---you should be able to move both of the no. 1 cylinder rocker-arms, and the no. 2 cyinder valves should be "on the rock" (i.e.--1 valve shutting and 1 valve opening). Attach 1 wire of the test-lamp to the DISTRIBUTOR side of the coil and 1 wire to earth. Turn the engine until the timing mark on the pulley alignes with the first timing mark on the timing-chain cover. Ensure that the rotor arm is pointing at the 'No. 1' terminal on the distributor cap. Disconect the king lead either from the coil or the distributor. Turn on the ignition. Does the bulb in the test-light come on? If the answer is YES, the timing is too far advanced, if the answer is NO, the timing is too far retarded. If the light is on, loosen the distributor clamping bolt and turn the distributor ANTI-clockwise until the bulb goes off, and then clockwise until the light comes back on up. If the bulb is NOT illuminated, turn it gently clockwise until the bulb just lights up. Tighten the clamping nut. Turn the engine anti-clockwise until the timing light is out, and then clockwise until the light just comes on. It should come on just as the timing marks align. If all is correct, turn the ignition off, and refit the king-lead. On a 500, the points gap should be between 18 and 20 thou, and the static timing is 10deg (13mm) BTDC (Before Top Dead Centre).

 

[bugsymike]

Excellent points as usual from @ the hobbler , the only thing I would add, is due to the fuel quality these days it may be necessary to alter/retard timing slightly after a road test when warmed up to prevent "pinking/detonation" .
The timing with valves "on the rock" reminded me of my college days in the late 60s when the lecturer presented us with an engine with all timing marks erased for valve and ignition and we had to get it running for a dynamometer test, an a good way for him to see who hadn't been listening.

 

[turbo500]

Thanks to everyone who has chimed in.

Unfortunately I still have not resolved anything after spending the morning in the garage.

-I started by screwing in the top idle jet, and mixture screw turned out to 2 rotations. Then started it, with choke, and it still struggled with getting a steady idle. When I did get it there and turned off choke, I tried spraying wd40 around the base of the carb and around the base of the new Bakelite spacer. No change in revs and it didn’t seem to get pulled into the engine.

-I disassembled the top of the carb and got the emulsion tube out. It was clean. As was every other jet including the main jet. I cleaned them all out. I checked float level, 8mm as I had done previously. The only thing left on the carb I didn’t clean (again were talking about a carb that has done maybe 1 mile) is remove the choke jet with the spring but it shouldn’t matter.
Is there any other point that could be creating a blockage?

-I then checked the points gap, 0,50, lubed the cam with lithium grease.

-I checked the tappet clearances. They were all over the place.
1 - 0.30
2 - 0.10
3 - 0.07
4 - 0.20

Set them to the 126 spec since I have a 126 head, 0,20 for intake and 0,25 for exhaust. Didn’t make any difference on running either way.

-checked the leads but my multimeter doesn’t run high enough to check continuity on leads, I tried with another cars lead and it it too didn’t work. Again I don’t think it’s the leads.

-checked the distributor cap, just to eliminate any confusion, the lead that goes to the spark plug closest to the back of the car, is the one that goes into the plug labelled 1 on the cap. And this is closest to the condenser. The one labelled 2 is towards the top of the engine, and is the spark plug that is closest to the interior cabin.

-I tried starting it during each step to see if anything changed and it didn’t.

-I then pulled the plugs and cleaned them from the soot. Put them back started it and it seemed to finally run well. I could accelerate perfectly and it wouldn’t trip over itself. Then after a minute or so it started again.

At this point what’s left is checking the timing. But could it be a fuel flow issue? Lack of fuel or too much fuel? I haven’t changed anything fuel related (It was already having this issue before the fuel filter addition)
Can I check the fuel pump? It’s a brand new bcd pump i bought in italy. Again wasn’t an issue before. Could there be some obstruction?


Here are the videos from today:

First video is is starting with choke fully pulled. Struggling to run smooth. Again could this be a fuel starvation issue?


Second video of it running after all the above was done. Struggling to pull any revs. Tripping over itself.

 

[fiat500]

Thanks to everyone who has chimed in.

Unfortunately I still have not resolved anything after spending the morning in the garage.

-I started by screwing in the top idle jet, and mixture screw turned out to 2 rotations. Then started it, with choke, and it still struggled with getting a steady idle. When I did get it there and turned off choke, I tried spraying wd40 around the base of the carb and around the base of the new Bakelite spacer. No change in revs and it didn’t seem to get pulled into the engine.

-I disassembled the top of the carb and got the emulsion tube out. It was clean. As was every other jet including the main jet. I cleaned them all out. I checked float level, 8mm as I had done previously. The only thing left on the carb I didn’t clean (again were talking about a carb that has done maybe 1 mile) is remove the choke jet with the spring but it shouldn’t matter.
Is there any other point that could be creating a blockage?

-I then checked the points gap, 0,50, lubed the cam with lithium grease.

-I checked the tappet clearances. They were all over the place.
1 - 0.30
2 - 0.10
3 - 0.07
4 - 0.20

Set them to the 126 spec since I have a 126 head, 0,20 for intake and 0,25 for exhaust. Didn’t make any difference on running either way.

-checked the leads but my multimeter doesn’t run high enough to check continuity on leads, I tried with another cars lead and it it too didn’t work. Again I don’t think it’s the leads.

-checked the distributor cap, just to eliminate any confusion, the lead that goes to the spark plug closest to the back of the car, is the one that goes into the plug labelled 1 on the cap. And this is closest to the condenser. The one labelled 2 is towards the top of the engine, and is the spark plug that is closest to the interior cabin.

-I tried starting it during each step to see if anything changed and it didn’t.

-I then pulled the plugs and cleaned them from the soot. Put them back started it and it seemed to finally run well. I could accelerate perfectly and it wouldn’t trip over itself. Then after a minute or so it started again.

At this point what’s left is checking the timing. But could it be a fuel flow issue? Lack of fuel or too much fuel? I haven’t changed anything fuel related (It was already having this issue before the fuel filter addition)
Can I check the fuel pump? It’s a brand new bcd pump i bought in italy. Again wasn’t an issue before. Could there be some obstruction?


Here are the videos from today:

First video is is starting with choke fully pulled. Struggling to run smooth. Again could this be a fuel starvation issue?


Second video of it running after all the above was done. Struggling to pull any revs. Tripping over itself.

Pulling the throttle doesn't seem to do anything.
It sounds regular enough on tickover, so you might be onto something with fuel starvation.
Have you check both tolerances on the float-arm level?
The activating-lever of the fuel pump may not have the geometry that allows a full stroke with each turn of the camshaft. I once had starvation when at top speed on bumpy roads; the float bowl was barely filling with fuel and that combination of events temporarily starved the engine.

 

[turbo500]

The idle jet should be scre

Pulling the throttle doesn't seem to do anything.
It sounds regular enough on tickover, so you might be onto something with fuel starvation.
Have you check both tolerances on the float-arm level?
The activating-lever of the fuel pump may not have the geometry that allows a full stroke with each turn of the camshaft. I once had starvation when at top speed on bumpy roads; the float bowl was barely filling with fuel and that combination of events temporarily starved the engine.

Yes so float on carburettor I measured closed (resting on pin) 8mm and open 15.6mm

The problem is that since I installed the new pump last year, I used the car a little and it has never given this problem until a few weeks ago. So could there be something wrong in the fuel tank with the fuel siphon? I took it out and it looked ok when I installed the online filter. The online filter also has fuel in it, but never fills up (it’s on its side on top of the fuel tank).

 

[fiat500]

Yes so float on carburettor I measured closed (resting on pin) 8mm and open 15.6mm

The problem is that since I installed the new pump last year, I used the car a little and it has never given this problem until a few weeks ago. So could there be something wrong in the fuel tank with the fuel siphon? I took it out and it looked ok when I installed the online filter. The online filter also has fuel in it, but never fills up (it’s on its side on top of the fuel tank).

I've never fitted a filter, but I hear that they always look like that. I would remove it. Fitted at the tank like that there is a chance that air is being sucked in.
Remove the fuel delivery pipe at the carb and get someone to crank the engine with the ignition switched off, and let the fuel flow into a jam jar.
There should be a real gush of petrol far in excess of what will ever be needed by the engine. If it's feeble or spluttery then you're onto something.

 

[bugsymike]

If you think it may be fuel delivery as a quick test try running it from a gravity fed supply whilst in workshop if it can be done safely.

 

[the hobbler]

Pulling the throttle doesn't seem to do anything.
It sounds regular enough on tickover, so you might be onto something with fuel starvation.
Have you check both tolerances on the float-arm level?
The activating-lever of the fuel pump may not have the geometry that allows a full stroke with each turn of the camshaft. I once had starvation when at top speed on bumpy roads; the float bowl was barely filling with fuel and that combination of events temporarily starved the engine.

According to the 'book of words', the fuel-pump has a specific fitment measurement. With the inner gasket fitted, and then the spacer, gaskets should be added until when at the START of its outward movement, the fuel-pump operating rod protrudes between 1 and 1.5mm. If it protrudes too much, add a gasket (they can be purchased with differing thicknesses). The fuel-pump will need to be removed to check this measurement. It will be easier to check for operating rod movement if you have a 'spare' hand who, whilst you are slowly turning the engine, can push against the operating rod and then feel when the rod is just about to start coming out. The protrubence ofthe rod can be checked with feeler-gauge laid flat across the fuel-pump mounting spacer/gasket.

 

[turbo500]

I've never fitted a filter, but I hear that they always look like that. I would remove it. Fitted at the tank like that there is a chance that air is being sucked in.
Remove the fuel delivery pipe at the carb and get someone to crank the engine with the ignition switched off, and let the fuel flow into a jam jar.
There should be a real gush of petrol far in excess of what will ever be needed by the engine. If it's feeble or spluttery then you're onto something.

Thanks. I’ll try that. But you don’t think the issue of higher rev fuel delivery would not be replicated with just cranking the ignition?

I might try and fit the old fuel pump just to remove one more doubt from the puzzle…