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1969 1750 Spider Veloce (Euro)
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Discussion Starter · #1 · (Edited)
Model: 1969 Spider 1750 Veloce (euro)

For several weeks, it was getting increasingly difficult to start the car. Eventually, it was impossible to start. Checked ignition dwell and timing. No luck.

Replaced distributor with 123Ignition electronic distributor (model 123/ALFA-4-R with advance curve “8” selected). Car finally started. However, the idle was rough (a lot of “putt putt putts” and we needed to keep the minimum throttle opening high (1,500-2,000 RPM) to prevent the engine from dying). Also, the engine would hesitate significantly when depressing the throttle pedal at low RPM. There was good throttle response above 2,500 RPM. We made sure the carburetors we’re properly setup (float levels to spec, throttle butterflies properly aligned, all four fuel mixture screws opened by about 1 screw turn from seated position). No obvious change in performance.

We noticed that fuel rather easily comes out of the back carb’s overflow hole, despite the floats being set up to spec

Next steps:
  • Play with ignition timing.
  • Check for air intake problems.
  • Try to figure out why fuel easily flows out of back carb
Any words of wisdom?
 

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But Mad North-Northwest
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Fuel pressure too high, perhaps? If you have a regulator on there maybe it's gone bad.
 

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Discussion Starter · #3 ·
Fuel pressure too high, perhaps? If you have a regulator on there maybe it's gone bad.
I don't think there's a regulator on this car. It does appear that the fuel mixture is too rich, at least at lower RPM.
 

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But Mad North-Northwest
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Start by verifying fuel pressure then. You should be able to get a cheap gauge and just dead-head it to the rubber hose to the carbs with a barb fitting to verify.
 

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Discussion Starter · #5 ·
I will. I have a mechanical pump, so I don't think there's a way to adjust the pressure. If the pressure needs adjusting, then do I need to buy something like this?
 

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But Mad North-Northwest
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Yes, the Filter King is a good choice.

I thought that all the Alfas that had the mechanical pump should've come with a filter/regulator unit installed as well, but I could be wrong.
 

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Discussion Starter · #7 ·
Yes, the Filter King is a good choice.

I thought that all the Alfas that had the mechanical pump should've come with a filter/regulator unit installed as well, but I could be wrong.
Thanks mate - I'll check to be sure.
 

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But Mad North-Northwest
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Around here most auto parts stores will rent you a fuel pressure gauge, may want to check if it's the same there.
 

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I suspect that the carb has a faulty inlet fuel valve needle or seat, which is causing a flooding/super rich problem for the engine at the fuel level is too high in the carb. Replace the needle and seat in both carbs and reset the float levels. This is where I would start. A pressure regulator is also a good idea as it will prevent wear from excess fuel pressure. You can check the pressure with a gage before the carbs. Since this is a euro model it should have a regulator between the fuel pump and the carbs.
 

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You should have a fule filter installed somewhere if you are using carbs. The Filter King also serves as a fuel filter.
Cheers, James
 

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Discussion Starter · #11 ·
Thanks folks. We just rebuilt the carbs last summer and everything looks good in terms of needle valves. Going to check fuel pressure next.
 

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If the fuel pressure was too high would not both carbs be flooding? You mention only the rear carb flowing fuel. That needle is shot.
 

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Discussion Starter · #13 ·
If the fuel pressure was too high would not both carbs be flooding? You mention only the rear carb flowing fuel. That needle is shot.
Possible, but would be surprising. Carbs were rebuilt with Centerline kit last year.
 

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Easy enough to check. Remove the carb top. Stand in front of a mirror. Blow through the gas inlet while pushing the float up. Does the needle stop the air when it's about level?
 

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I've used this in the past with a DCOE-2 setup with great success -


I had also put an inline gauge to the carbs ($15 on amazon) so that I can always keep an eye on fuel pressure, and an inline NAPA $3 clear plastic fuel filter.

Did you replace your carb mounts? Are you using a SPICA manifold or euro carb one?
 

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That regulator appears to be a Filter King unit without the attached filter. Blowing into the carb to check the needle function is ok but it can yield false results. I've had faulty needles with both SU and Weber carbs that seemed to work with the blow in method. The quality of needles is not what it used to be, or the current gas seems to ruin them easier than before.
 

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Discussion Starter · #17 · (Edited)
Easy enough to check. Remove the carb top. Stand in front of a mirror. Blow through the gas inlet while pushing the float up. Does the needle stop the air when it's about level?
Would love to try this, but I'm still learning. Not sure how to do this. Need to read more and watch more demonstration videos.
 

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Discussion Starter · #18 ·
That regulator appears to be a Filter King unit without the attached filter. Blowing into the carb to check the needle function is ok but it can yield false results. I've had faulty needles with both SU and Weber carbs that seemed to work with the blow in method. The quality of needles is not what it used to be, or the current gas seems to ruin them easier than before.
So, is there an alternative method to determine whether the needle valve needs to be replaced? The first step of course is to see whether the fuel pressure is too high. If not, then next step would be to check out needle valves.
 

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Discussion Starter · #19 ·
I’ve confirmed that the fuel filter apparatus indeed has a screw on top to adjust fuel pressure. Now I just need to measure the pressure.
 

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Discussion Starter · #20 · (Edited)
I thought I would update y’all on my progress.

I installed an in-line fuel pressure gauge, which showed that the fuel pressure is fine (about 3 psi).

After taking the carbs apart, I discovered that the rear carb’s float weighs 45 grams! The front one weighs the appropriate 26 grams. No wonder the rear carb has been overflowing, and no wonder the air/fuel mixture has seemed overly rich.

The heavy float looks identical to the other one. It even has “26” (grams) stamped on its tab. Nothing rattles when shaking it, and no fuel leaks out of it. Is it possible that fuel slowly seeped into it over the last 50 years and somehow solidified? So strange.
 
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