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

[turbo500]

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.

I get this. But I don’t get why this issue is happening now randomly?

 

[the hobbler]

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…

Have you checked the timing yet?

 

[bugsymike]

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

I was thinking that about the carb also, as it does seem reading Forum that quite a few people have queries subsequent to fitting after market carbs, whether from differing quality or jetted for a different use.
With the popularity of classic cars and motorcycles several far eastern suppliers get on the parts band wagon with varying standards not quite to OEM spec. No doubt the experiences of other members is a good guide re this.

 

[smart51]

Have you checked the timing yet?

I was convinced mine was struggling with fuelling. It was points gapping that fixed it. Well, after I'd fixed the float height.

 

[turbo500]

I was convinced mine was struggling with fuelling. It was points gapping that fixed it. Well, after I'd fixed the float height.

I checked the points gap at 0,50.

Float height 8mm from spacer to float. Is there another measurement I should check on it?

 

[smart51]

I checked the points gap at 0,50.

Float height 8mm from spacer to float. Is there another measurement I should check on it?

Timing before TDC, idle speed (throttle stop) screw and idle mixture screw. Each one had an effect on mine.

 

[turbo500]

Timing before TDC, idle speed (throttle stop) screw and idle mixture screw. Each one had an effect on mine.

Sorry I meant on the carb float. Is there a min and max for the float? I’m trying to see if maybe too much or too little fuel is running through the carb because of it.

 

[smart51]

Sorry I meant on the carb float. Is there a min and max for the float? I’m trying to see if maybe too much or too little fuel is running through the carb because of it.

The float has two stops, fully open and fully closed. On the 28IMB they should be 8 an 16mm. I'm not sure what effect the open limit has.

 

[the hobbler]

The float has two stops, fully open and fully closed. On the 28IMB they should be 8 an 16mm. I'm not sure what effect the open limit has.

The easiest way to measure the "8mm" setting for the float, measured with the carb top hanging vertically---with the 8mm being between the top-cover gasket and the float, is to use a piece of 8mm rod, or if that is not available, the smooth shank of a 8mm drill bit.

 

[turbo500]

The easiest way to measure the "8mm" setting for the float, measured with the carb top hanging vertically---with the 8mm being between the top-cover gasket and the float, is to use a piece of 8mm rod, or if that is not available, the smooth shank of a 8mm drill bit.

Thanks but I’ve already done this.

Could it be the cap of the distributor or the distributor brush? How can I check if they’re in good working order ?

 

[bugsymike]

If a distributor cap is suspect often you may see what looks like a crack or tracking mark inside or even some times outside the cap, if so this is the path the HT voltage is using to short out or misfire.
Check also the neck of the coil and the rotor arm it's self for similar signs.
Another thing I check for is if some one has got over enthusiastic cleaning/sanding the contacts in the cap or the end of the rotor arm, I found one that had been filed to the point the spark had to jump a much larger gap from the distributor "brush as you called it" to the plug lead contacts in the cap. Any wide gap there or even at spark plugs has the effect of increasing the voltage provided by the coil to jump the gap, the result being like water it takes the easy route and shorts across somewhere else causing a misfire.
Generally unless the centre spring and "brush" are missing they are not usually a problem.
By the way re what I mentioned earlier about checking continuity on HT leads especially silicon ones I use a basic multimeter on OHM setting it doesn't have to be fancy.

 

[turbo500]

If a distributor cap is suspect often you may see what looks like a crack or tracking mark inside or even some times outside the cap, if so this is the path the HT voltage is using to short out or misfire.
Check also the neck of the coil and the rotor arm it's self for similar signs.
Another thing I check for is if some one has got over enthusiastic cleaning/sanding the contacts in the cap or the end of the rotor arm, I found one that had been filed to the point the spark had to jump a much larger gap from the distributor "brush as you called it" to the plug lead contacts in the cap. Any wide gap there or even at spark plugs has the effect of increasing the voltage provided by the coil to jump the gap, the result being like water it takes the easy route and shorts across somewhere else causing a misfire.
Generally unless the centre spring and "brush" are missing they are not usually a problem.
By the way re what I mentioned earlier about checking continuity on HT leads especially silicon ones I use a basic multimeter on OHM setting it doesn't have to be fancy.

Thank you I will inspect the items you mentioned and report back.
I will also check the filter in the fuel tank to make sure it is not clogged up and reducing flow.
On the Italian forums someone with a similar issue disassembled their fuel pump and found buildup that was obstructing the valve from functioning properly. I would like to avoid opening a pretty new fuel pump but might have to if I don’t find a solution soon.

Also, for the ht leads, I tried using my multimeter, and with continuity in the “sound” mode, it wouldn’t make any sound when touching both ends of the leads. I tried with a set of brand new leads of another vehicle and it did the same. If I turn it to continuity mode without sound, it registers some values. I will test again and compare.

 

[fiat500]

Thanks but I’ve already done this.

Could it be the cap of the distributor or the distributor brush? How can I check if they’re in good working order ?

Did you temporarily refit the old pump? The workshop instructions regarding the actuating-rod from the camshaft only make sense with a genuine, original pump or one that is made exactly to the original dimensions.

 

[bugsymike]

Re the multimeter readings if you are getting any reading then you have continuity, it is only if no reading then carbon string in leads are broken, never a problem in the old days with copper HT wires.
Re varying Ohm readings the longer the HT lead the more resistance in the circuit.
Don't forget to check the Coil HT lead to Distributor as well as the plug leads.

 

[turbo500]

Did you temporarily refit the old pump? The workshop instructions regarding the actuating-rod from the camshaft only make sense with a genuine, original pump or one that is made exactly to the original dimensions.

No not yet. It’s one of the things I’m planning on trying.

 

[turbo500]

Unbelievable. I spent another morning in the garage going through all the items.

I was about to pull the fuel pump when I said before I get into that whole situation let’s try some of the other newer items I installed at the beginning of this thread…fitted the old condenser and it fired up right away and seems to be revving great, no hiccups at all. The condenser I fitted with the new points was a brand new Marelli, really surprising to have this silly part drive me up a wall.
At least it forced me to adjust the valves and learn some new skills

Thanks for everyone’s input and time to help me resolve this. I’ll report back once I take her for a ride. Fingers crossed it was really just that.

 

[bugsymike]

Keep a spare set of contact points handy as the condensors job is to prevent arcing at the points and often cars with a duff condensor have pitted points.
By the way I may have mentioned previously often when working on cars the ignition is left on. If points are closed at that time it can quickly damage condensors ,points and even coils through overheating.

 

[turbo500]

Keep a spare set of contact points handy as the condensors job is to prevent arcing at the points and often cars with a duff condensor have pitted points.
By the way I may have mentioned previously often when working on cars the ignition is left on. If points are closed at that time it can quickly damage condensors ,points and even coils through overheating.

Thank you for your tips! Very appreciated.

Would you recommend going with a powerspark/accuspark electronic ignition to avoid all these issues?

 

[Goldnrust]

Excellent news. that you've got the problem sorted.

Unfortunately, modern condensers are often not great quality. Finding good NOS parts is one route (which is what I'm using for now) the other is expensive 'performance' condensers, many members on this forum have good experiences with the 'swift tune' condensers intended for racing Minis.,

Ultimately, no fitting an electronic pickup doesn't seem to have the best reputation because the distributer in the 500 is in the path of the hot air coming off the cooling system, and the heat seems to cause problems with the electronics over time. Many members go back to points after trialing electronic pickups.

 

[the hobbler]

Keep a spare set of contact points handy as the condensors job is to prevent arcing at the points and often cars with a duff condensor have pitted points.
By the way I may have mentioned previously often when working on cars the ignition is left on. If points are closed at that time it can quickly damage condensors ,points and even coils through overheating.

The problem with a lot of modern, and often "pattern", condensors is that they are VERY cheaply made. The continual blast of hot 'engine-cooling' air over them makes them wilt quite quickly. One option is to fit a modern condensor from either "Swiftune" or from "Shacktune". Both of these condesors have a long 'feed' lead AND a long 'earth' lead, which enablesthemtobe mounted up by the coil, and away from the heat. Alternatively, "Distributor Doctor" can supply a high quality (made in the UK) Condensor that, with a bit of twaeking of the mount, can fit onto the distributor in the normal condensor location---part number:--484249 (use the long bracket). The condensor that you have refitted is probably the original which, whilst old, is probably better made than most modern ones.