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Vapor lock or something else? Carbureted engine dying.

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Vapor lock or something else? Carbureted engine dying.

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khg30

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Hello- this is my first post and first visit to the site. I found the site as I'm at a crossroads on my next move and looking for some advice. Hopefully I'll become a frequent visitor after this repair!
Here's the situation (sorry for the long post)-
I've got a 1977 Campagnola that will die when driving. It has a 2L gas engine. It will idle all day but within 15 mins of driving, it'll start to lose power, start to miss, and eventually die. Then it won't restart again for 2+ hours. I'm thinking I have too much heat on the fuel system and don't have a return fuel line, leading to vapor lock. I'm running 4.5 psi in the fuel system and haven't noticed any leaks. About a year ago I had rust in my fuel lines so I cleaned the system, including stripping and sealing the inside of the fuel tank, and replaced the inline fuel filter.
I'm curious before I start replacing parts if anyone has any other suggestions?
Apparently some of these vehicles (later, 79+ from what I can tell), had the fuel return line right off the carb. Mine does not have that piece on the carb to connect a second line and if I can find the right carb with the piece, it would be several hundred dollars for something I'm not sure will fix the problem. Perhaps I could T off the fuel line before the carb and add a return line that way? This is all just guesswork at this point.. Thanks in advance..
 
khg30 said:
Hello- this is my first post and first visit to the site. I found the site as I'm at a crossroads on my next move and looking for some advice. Hopefully I'll become a frequent visitor after this repair!
Here's the situation (sorry for the long post)-
I've got a 1977 Campagnola that will die when driving. It has a 2L gas engine. It will idle all day but within 15 mins of driving, it'll start to lose power, start to miss, and eventually die. Then it won't restart again for 2+ hours. I'm thinking I have too much heat on the fuel system and don't have a return fuel line, leading to vapor lock. I'm running 4.5 psi in the fuel system and haven't noticed any leaks. About a year ago I had rust in my fuel lines so I cleaned the system, including stripping and sealing the inside of the fuel tank, and replaced the inline fuel filter.
I'm curious before I start replacing parts if anyone has any other suggestions?
Apparently some of these vehicles (later, 79+ from what I can tell), had the fuel return line right off the carb. Mine does not have that piece on the carb to connect a second line and if I can find the right carb with the piece, it would be several hundred dollars for something I'm not sure will fix the problem. Perhaps I could T off the fuel line before the carb and add a return line that way? This is all just guesswork at this point.. Thanks in advance..
Click to expand...

Hi and welcome to the forum.

While vapour lock is a posible cause of his sort of problems there are other possible causes. One is a failing condensor (capacitor) across the ignition points (breaker). Another is tight valve clearances.
What is the recent history of the car? Have you had it long? An recent maintenance or repairs?
You could try changing the condenser first as its relatively cheap and easy.
A vapour lock issue is unlikely to come on suddenly.
Adding a T and return line close to the carb may well help with vapour lock as can thermal insulation on the fuel line.

Robert G8RPI.
 
Last edited:
Thanks for the response. The car was imported 1.5 years ago from Italy and at some point prior to import, the 4 speed manual was changed to a 5 speed but the carburetor was not changed. Additionally, although I don't believe it matters, I was told the float in the fuel tank was off an older diesel unit but the supply/return lines are all either used or plugged. The ignition coil was replaced recently as there was oil in it. I've been told the fuel pump is not original either.
Since I've had it, the truck has always had issues staying running.
I'm sure engine work was done at some point but I have no knowledge of when that would have been.
 
khg30 said:
Hello- this is my first post and first visit to the site. I found the site as I'm at a crossroads on my next move and looking for some advice. Hopefully I'll become a frequent visitor after this repair!
Here's the situation (sorry for the long post)-
I've got a 1977 Campagnola that will die when driving. It has a 2L gas engine. It will idle all day but within 15 mins of driving, it'll start to lose power, start to miss, and eventually die. Then it won't restart again for 2+ hours. I'm thinking I have too much heat on the fuel system and don't have a return fuel line, leading to vapor lock. I'm running 4.5 psi in the fuel system and haven't noticed any leaks. About a year ago I had rust in my fuel lines so I cleaned the system, including stripping and sealing the inside of the fuel tank, and replaced the inline fuel filter.
I'm curious before I start replacing parts if anyone has any other suggestions?
Apparently some of these vehicles (later, 79+ from what I can tell), had the fuel return line right off the carb. Mine does not have that piece on the carb to connect a second line and if I can find the right carb with the piece, it would be several hundred dollars for something I'm not sure will fix the problem. Perhaps I could T off the fuel line before the carb and add a return line that way? This is all just guesswork at this point.. Thanks in advance..
Click to expand...

As Robert posted I found a condenser exhibiting very similar symptoms to your problem recently, it was a new condenser so don't assume because it's new it's good.

Plus if you have an electric pump you could try disconnecting fuel pipe at carb , putting pipe into a fuel can and running the pump for a good while looking to see if there is a reduction in flow.
 
jackwhoo said:
...Plus if you have an electric pump you could try disconnecting fuel pipe at carb , putting pipe into a fuel can and running the pump for a good while looking to see if there is a reduction in flow.
Click to expand...

I'm pretty sure I have a reduction in flow. The old fuel filter was clear and I could sit and watch it go from full to nearly empty as it ran- almost like it was surging at points.
If the reduction isn't caused by the fuel lines or tank, would it strictly be pump related?
I took my distributor apart and the condenser looks okay but need to put a multimeter on it.
 
khg30 said:
I'm pretty sure I have a reduction in flow. The old fuel filter was clear and I could sit and watch it go from full to nearly empty as it ran- almost like it was surging at points.
If the reduction isn't caused by the fuel lines or tank, would it strictly be pump related?
I took my distributor apart and the condenser looks okay but need to put a multimeter on it.
Click to expand...

You cannot tell the condition of a condenser by looking at it.
Neither is it practical to check a condenser with a multi meter.
Condersers are cheap by a couple of the best quality you can find and fit one.

You could run engine till it cuts out then see if you are getting any fuel at carb by disconnecting pipe and cranking on starter- only do this if you can do so safely!

Is it mechanical or electric fuel pump?

How old is fuel pump?
 
The fuel in See through fuel filters doesn't always look like you think it should.
Look at one on a perfectly running engine and you will be surprised how much air there is in there.
 
jackwhoo said:
You cannot tell the condition of a condenser by looking at it.
Neither is it practical to check a condenser with a multi meter.
Condersers are cheap by a couple of the best quality you can find and fit one.

You could run engine till it cuts out then see if you are getting any fuel at carb by disconnecting pipe and cranking on starter- only do this if you can do so safely!

Is it mechanical or electric fuel pump?

How old is fuel pump?
Click to expand...

I'll see if I can find a replacement; parts for this engine/truck aren't the easiest to find and usually I have the best luck buying from Italy.
The past couple times it has died on me while driving I've checked the fuel filter immediately and it still has fuel in it. I have not been able to successfully check if it is making it the carb when it cuts out however. That was one of my next steps..

It is a manual pump. I'm not sure how old; I thought it was original until a guy in Italy saw a picture and said it wasn't. Doesn't look new..?
 
khg30 said:
I'll see if I can find a replacement; parts for this engine/truck aren't the easiest to find and usually I have the best luck buying from Italy.
Click to expand...

Just purchased a new condenser from ebay. $15 and it'll be here in about a week..

Thanks for that advice. I'll continue trying other solutions too but that's cheap enough to try!
 
khg30 said:
Just purchased a new condenser from ebay. $15 and it'll be here in about a week..

Thanks for that advice. I'll continue trying other solutions too but that's cheap enough to try!
Click to expand...

Check the fuel pressure at pipe at carb before and after it cuts out.
And do the fuel delivery check.

Vapour lock used to make cars hard to restart after they had been running rather than stop running once they running.
 
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