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

[turbo500]

Hello everyone,

I recently upgraded to a 28IMB, have new bakelite spacer, new gaskets, new fuel pump. I'm struggling to get her started properly without cranking for a while with the choke on. Even with the choke, it doesn't always start properly at first. Tends to lower revs and stop.

I was reading other members similar issues, and it seemed to point towards incorrect gap in the breaker points of the ignition. So today I tried setting them to 0,50, moved the pulley until the gap was at it's furthest, measured and then set the gap. Nothing changed.
I replaced the points with a new set I had, and that too didn't change a thing. I have a new condenser to install but I don't think that will make a difference...

I've uploaded some pics, maybe you guys can see if something is wrong? Could the rotor arm be worn out?

Thank you for your help

 

[Goldnrust]

I've not been around here too long, but I've already read of so many running problems that come down to the condenser on these engines... With the position of the distributer getting blasted with hot air as it exits the cooling system, the condensers have a hard time. I would suggest it's well worth your time swapping it out if you've got a replacement to hand, if only to rule it out.

 

[turbo500]

I've not been around here too long, but I've already read of so many running problems that come down to the condenser on these engines... With the position of the distributer getting blasted with hot air as it exits the cooling system, the condensers have a hard time. I would suggest it's well worth your time swapping it out if you've got a replacement to hand, if only to rule it out.

Yes, might as well at this point.
I'll also measure the coil resistance to see what coil I have (thinking forward to eventually getting a powerspark type ignition).

 

[bugsymike]

Looking at the photos , you could "drive a bus" through that points gap .
Regarding condensors in my experience they will give you an uneven misfire, but a good clue is to look at the set of points it has been running on , if the contact area is blue and pitted then replace the condensor and points as the condensor is there to prevent arcing at the points as well as giving a quick collapse of the current at the coil to give a good spark.
Another thought if someone has been too enthusiastic cleaning the rotor tip they can increase the gap to the distributor contacts making it hard to start. If you don't have a new one to compare try resting the rotor in it's correct position and see if there is too much of a gap to the contacts in the cap. We never used to file or sand them, just rub against the side wall of a tyre to clean them.
A common reason for condensor failure is leaving the ignition on without the engine running whilst working on it causing it to overheat along with the points and coil.

 

[bugsymike]

Before the carb change was it running well?

 

[turbo500]

Looking at the photos , you could "drive a bus" through that points gap .
Regarding condensors in my experience they will give you an uneven misfire, but a good clue is to look at the set of points it has been running on , if the contact area is blue and pitted then replace the condensor and points as the condensor is there to prevent arcing at the points as well as giving a quick collapse of the current at the coil to give a good spark.
Another thought if someone has been too enthusiastic cleaning the rotor tip they can increase the gap to the distributor contacts making it hard to start. If you don't have a new one to compare try resting the rotor in it's correct position and see if there is too much of a gap to the contacts in the cap. We never used to file or sand them, just rub against the side wall of a tyre to clean them.
A common reason for condensor failure is leaving the ignition on without the engine running whilst working on it causing it to overheat along with the points and coil.

Thanks for the explanations. The engine is not an original 110 engine. It has a 126 head, and I don't know about the internals. The stamping show 110, but who knows if that's original...
With that said, would the 0,50 gap i adjusted to (manual says between 0,47 e 0,53 mm) be wrong if it's not a true 500 engine or distributor? I was under the impression the 126 and 500 had the same gap spec.
Am I correct in adjusting the points when they are at the biggest opening point (or when the lobe around the center of the distributor) pushes them open?

I will look at the original points and see if there's any blue or pitting. How would I check if there's too much gap in the cap? I'm not sure what you mean by resting the motor. Sorry

I'll be changing the condenser just to be safe and report back.

 

[turbo500]

Before the carb change was it running well?

it's more the starting that has been an issue. I think it always struggled with starting without the choke. I really haven't gotten a chance to drive it properly since changing the carb.

 

[bugsymike]

Thanks for the explanations. The engine is not an original 110 engine. It has a 126 head, and I don't know about the internals. The stamping show 110, but who knows if that's original...
With that said, would the 0,50 gap i adjusted to (manual says between 0,47 e 0,53 mm) be wrong if it's not a true 500 engine or distributor? I was under the impression the 126 and 500 had the same gap spec.
Am I correct in adjusting the points when they are at the biggest opening point (or when the lobe around the center of the distributor) pushes them open?

I will look at the original points and see if there's any blue or pitting. How would I check if there's too much gap in the cap? I'm not sure what you mean by resting the motor. Sorry

I'll be changing the condenser just to be safe and report back.

I am not a Fiat specialist, just retired after 50 years in motor trade, gap looked wide to me visually more like 50 thousands of an inch than .5mm (some say .37 to .43mm in metric, generally around 15 thousands of an inch in imperial terms works for me and as you say when the lobe of the cam is pushing the points open the most.
By the way it was "resting the rotor" as in turning the distributor cap up facing you and positioning the rotor arm as centrally as possible so the carbon contact in the middle of the cap is directly over the normal contact area on the rotor arm to see if the gap between the end of the rotor arm and the terminal in the cap that goes to the plug lead is excessive as if someone has sanded or filed the rotor to clean it. It is only a rough guide , if you have another rotor arm you can match together to see if one has been sanded away.
Regarding the points, if working correctly the contact area will be a smooth grey surface on both parts.
Incidentally has the ignition timing been checked correctly also as that could be part of the problem too.
I tend to over explain as it's always difficult if you are not standing beside the engine listening to it etc.

 

[turbo500]

I am not a Fiat specialist, just retired after 50 years in motor trade, gap looked wide to me visually more like 50 thousands of an inch than .5mm (some say .37 to .43mm in metric, generally around 15 thousands of an inch in imperial terms works for me and as you say when the lobe of the cam is pushing the points open the most.
By the way it was "resting the rotor" as in turning the distributor cap up facing you and positioning the rotor arm as centrally as possible so the carbon contact in the middle of the cap is directly over the normal contact area on the rotor arm to see if the gap between the end of the rotor arm and the terminal in the cap that goes to the plug lead is excessive as if someone has sanded or filed the rotor to clean it. It is only a rough guide , if you have another rotor arm you can match together to see if one has been sanded away.
Regarding the points, if working correctly the contact area will be a smooth grey surface on both parts.
Incidentally has the ignition timing been checked correctly also as that could be part of the problem too.
I tend to over explain as it's always difficult if you are not standing beside the engine listening to it etc.

I measured the opening again last night and changed the condenser and its still the same issue

I spent a little bit reading around various forums and came across someones problem/solution; he fitted a new carb, and the float was set too high, meaning too much fuel was getting in, and the only way the car would start was with the choke, to burn off the excess fuel that was being fed into the combustion chamber. They adjusted the float, and it fixed the issue.

Don't know if this is what I'm dealing with, the carb is a brand new unit, so I'd be surprised its the issue...?
I turn on the car with the choke, and it often sputters and turns off. So it means I need to keep choke on for a bit.
The spark plugs are pretty dark last time I checked them after replacing the carb.
I adjusted the mixture to be as lean as possible without the car not being able to idle.
Maybe I'm doing something wrong.

 

[Toshi 975]

If you fitted a NEW 28IMB carb it will either be a rare bit of new old stock, a recent Spanish made carb or at worse a Chinese fake. The latter two have sometimes been a problem especially the Chinese one.
I recently examined a 28IMB where the owner had bought a full rebuild kit from a well known UK supplier. He could not get the car to run right and I found that some parts of the kit were very poor quality especially the fuel inlet needle valve which made the carb flood.

 

[bugsymike]

I measured the opening again last night and changed the condenser and its still the same issue

I spent a little bit reading around various forums and came across someones problem/solution; he fitted a new carb, and the float was set too high, meaning too much fuel was getting in, and the only way the car would start was with the choke, to burn off the excess fuel that was being fed into the combustion chamber. They adjusted the float, and it fixed the issue.

Don't know if this is what I'm dealing with, the carb is a brand new unit, so I'd be surprised its the issue...?
I turn on the car with the choke, and it often sputters and turns off. So it means I need to keep choke on for a bit.
The spark plugs are pretty dark last time I checked them after replacing the carb.
I adjusted the mixture to be as lean as possible without the car not being able to idle.
Maybe I'm doing something wrong.

Sounds strange carb flooding and giving more choke to fix it? To me that would make problem worse.
Never trust a new carb to be perfect, even if generally OK it could still have swarf in it blocking a needle jet etc.
Another thing often a new carb will "bog down" on choke or race, either way usually there is a linkage bar from the choke mechanism down to the throttle lever which can be adjusted or bent to give correct revs when warming up.
In the 1970s working at a Mazda Dealership we would have to adjust brand new cars as the fast idle on choke was so high on initial start up it was causing the engine bearings to rattle before the oil got around the engine! It only needed a few minutes to bend the rod link and the cars were fine.
If it was me I would get car running and once warmed up with choke off slow engine down on idle screw as low as possible then adjust mixture screw to get best running position. I would also check timing was correct by makers spec. and then if necessary adjust by ear and on the road to get optimum with no "pinking" / "pre ignition" as modern fuels are not as good as when the cars were made.
Finally I would set idle speed at makers spec. and recheck idle mixture adjustment.
All that would be after I had checked carb over completely and made sure correct jets etc. have been fitted.
After giving car a decent run another inspection of the plugs to make sure not too weak or too rich.

 

[turbo500]

If you fitted a NEW 28IMB carb it will either be a rare bit of new old stock, a recent Spanish made carb or at worse a Chinese fake. The latter two have sometimes been a problem especially the Chinese one.
I recently examined a 28IMB where the owner had bought a full rebuild kit from a well known UK supplier. He could not get the car to run right and I found that some parts of the kit were very poor quality especially the fuel inlet needle valve which made the carb flood.

Its a Spanish brought from an official Weber reseller in the USA. The car ran fine it’s the starting that’s the issue.
I’m trying to think what I could check without taking the carb apart. I’m thinking of starting with making sure there are no gaps in the gaskets, with some tape.

 

[turbo500]

Sounds strange carb flooding and giving more choke to fix it? To me that would make problem worse.
Never trust a new carb to be perfect, even if generally OK it could still have swarf in it blocking a needle jet etc.
Another thing often a new carb will "bog down" on choke or race, either way usually there is a linkage bar from the choke mechanism down to the throttle lever which can be adjusted or bent to give correct revs when warming up.
In the 1970s working at a Mazda Dealership we would have to adjust brand new cars as the fast idle on choke was so high on initial start up it was causing the engine bearings to rattle before the oil got around the engine! It only needed a few minutes to bend the rod link and the cars were fine.
If it was me I would get car running and once warmed up with choke off slow engine down on idle screw as low as possible then adjust mixture screw to get best running position. I would also check timing was correct by makers spec. and then if necessary adjust by ear and on the road to get optimum with no "pinking" / "pre ignition" as modern fuels are not as good as when the cars were made.
Finally I would set idle speed at makers spec. and recheck idle mixture adjustment.
All that would be after I had checked carb over completely and made sure correct jets etc. have been fitted.
After giving car a decent run another inspection of the plugs to make sure not too weak or too rich.

I already adjusted the throttle linkage with the adjustable screw to make sure it didn’t big down.

I’ll have to start again because the car seems to idle fine and run fine. It’s just the startup that seems to be the issue.
I’m out of my element with timing so I might resort to finding someone who’s more knowledgeable than me.

I usually let the car warm up, then turn it off, close the air mixture screw completely. Then unscrew it about a turn or a turn and a half. I then turn on the car, and adjust the idle screw until the car idles normally.
Then I adjust the air screw to make sure it runs well.

Maybe you guys have a better way?

 

[bugsymike]

Its a Spanish brought from an official Weber reseller in the USA. The car ran fine it’s the starting that’s the issue.
I’m trying to think what I could check without taking the carb apart. I’m thinking of starting with making sure there are no gaps in the gaskets, with some tape.

If it runs fine once warmed up and you are happy with that, then I would refer you back to the bit I said about the linkage on the choke mechanism that alters the throttle giving more revs as you pull the choke lever further out.
If you disconnect the choke cable at carb with air cleaner off, you should see that as you move the choke mechanism at carb it also is connected to the throttle lever and increases the idle speed.
With a new carb quite often they need a little fine adjustment, as I said about the new Mazdas.
So not unusual to need to set it to suite local conditions, it is trial and error , in your case you may need to adjust the connecting lever from choke flap down to where it pulls on the throttle spindle. Some have a screw separate to the normal idling adjustment and some you simple have to bend the rod a little or straighten it. Bending it shortens and increases the engine speed when on choke and vice a versa if you straighten it.
The other thing to check is that the choke flap is spring loaded and moves to the off /open position if you lightly press the choke flap in top of carb.
This is because as you rev the engine it needs more air regardless of where the choke lever is.
I have just looked at a picture of your carb which seem to do the choke side by controlling air flow through jets internally, which is a different method to which I was speaking about, so I would check the operation inside that area.
Although if it is new maybe the supplier can advise.
Re your last bit, as I said if engine runs fine when warm and choke right off don't alter anything but the choke side and leave timing or general mixture where they run best normally.

 

[turbo500]

So I'm pretty sure the engines flooded...

It's pretty much gotten to the point the car is refusing to start. So I took out the spark plugs and they were wet, I cleaned them well, put them back in and tried to start them. Nothing. I took them out again and could definitely see they were wet.

Fist time experiencing this, so I have no clue what to do and where to begin?
I've read somewhere that if you have a flooded carb, take the plugs out, try and let the chamber dry. Then when you go and start it, put the gas pedal to the floor? Any tips?

 

[Goldnrust]

Wet plugs can also be a sign of a lack of spark, as the fuel will build up on the plug if it’s not sparking and burning it off.

As to flooding; turning the choke off, opening the throttle fully and cranking the engine over a few times can help clear it if it’s not too badly flooded. A more heavily flooded engine one approach can be to disconnect the 12v from the coil,so there will be no spark, and then crank the engine over with the spark plugs out so any fuel trapped in the cylinder gets shot out the spark plug holes. Can be messy and obviously there’s fuel vapour about so be careful of fire.

That was always the approach that saved the day for me with my old Mazda Rx7, the rotary engines being particularly prone to flooding issues on a cold morning. I don’t know if I reccomend this, but I would also go one step further with that engine and would warm the spark plugs after it flooded, any fresh fuel hitting the warm plug when attempting the next start would be more likely to evaporate that way instead of fouling the plug straight away.

If you think flooding is a potential issue, then I would investigate your float height further. Also make sure the needle is seating properly as if it’s not the fuel pump may force fuel past it and that will just overflow through the carb and down into the engine.

 

[bugsymike]

Wet plugs can also be a sign of a lack of spark, as the fuel will build up on the plug if it’s not sparking and burning it off.

As to flooding; turning the choke off, opening the throttle fully and cranking the engine over a few times can help clear it if it’s not too badly flooded. A more heavily flooded engine one approach can be to disconnect the 12v from the coil,so there will be no spark, and then crank the engine over with the spark plugs out so any fuel trapped in the cylinder gets shot out the spark plug holes. Can be messy and obviously there’s fuel vapour about so be careful of fire.

That was always the approach that saved the day for me with my old Mazda Rx7, the rotary engines being particularly prone to flooding issues on a cold morning. I don’t know if I reccomend this, but I would also go one step further with that engine and would warm the spark plugs after it flooded, any fresh fuel hitting the warm plug when attempting the next start would be more likely to evaporate that way instead of fouling the plug straight away.

If you think flooding is a potential issue, then I would investigate your float height further. Also make sure the needle is seating properly as if it’s not the fuel pump may force fuel past it and that will just overflow through the carb and down into the engine.

If everything else was OK prior to fitting the new carb, I suggest contacting supplier and telling them you want another carb as this one appears faulty.

 

[Ant Knox]

Not sure if this is any help or not, but I used to run classic Vespas and the majority of flooding issues with their dellorto carbs was down to poor float needle sealing. They were originally fitted with needles that had rubber tips, these degraded quickly, so it was common practice to replace them with viton (red) tipped ones.

 

[turbo500]

Wet plugs can also be a sign of a lack of spark, as the fuel will build up on the plug if it’s not sparking and burning it off.

As to flooding; turning the choke off, opening the throttle fully and cranking the engine over a few times can help clear it if it’s not too badly flooded. A more heavily flooded engine one approach can be to disconnect the 12v from the coil,so there will be no spark, and then crank the engine over with the spark plugs out so any fuel trapped in the cylinder gets shot out the spark plug holes. Can be messy and obviously there’s fuel vapour about so be careful of fire.

That was always the approach that saved the day for me with my old Mazda Rx7, the rotary engines being particularly prone to flooding issues on a cold morning. I don’t know if I reccomend this, but I would also go one step further with that engine and would warm the spark plugs after it flooded, any fresh fuel hitting the warm plug when attempting the next start would be more likely to evaporate that way instead of fouling the plug straight away.

If you think flooding is a potential issue, then I would investigate your float height further. Also make sure the needle is seating properly as if it’s not the fuel pump may force fuel past it and that will just overflow through the carb and down into the engine.

So I removed the sparks, let the chamber 'evaporate' and tried it after a few days. I cleaned the spark plugs, and cranked both with the choke and without and pedal to the floor. Nothing. I checked the spark plugs again after this and they seemed dryish. I'm starting to think maybe a main jet or something is clogged inside the new carby or float issues. Thanks

 

[turbo500]

Update on this since it's been a few weeks and didn't get round to it until now.

I decided to remove the top of the carb because all signs point to that (I've checked coil, cleaned sparks, charged battery, rechecked points). Upon removing it there was a nice surprise covering the starter valve (looks to be some piece of extra gasket (Remember this is a brand new Spanish made weber).
I then checked all the jets, and nothing seemed to be obstructed. There was some gas in the carb, so I dried that out, and removed the trace sediments, the only one I couldn't get to is the one at the bottom of the float chamber.

Before starting it again, I'm going to measure the carb float to make sure; for the 28IMB its 8mm closed and 16mm open right? (measurement should include the gasket and closed is pushing the float towards the gasket, and open is it just touching the ball bearing of the inlet jet)