Technical Mysterious Stalling Issues

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Technical Mysterious Stalling Issues

Epicsockzebra

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Heyo folks, So recently I got myself a 1979 Fiat x1/9 and the car has made a lot of progress and its nearly drivable but still encounters some residual issues.

I've replaced the throttle cable, done a full tune up, made the swap to an electric fuel pump, stuff that I thought would solve the issue as when I drive the car it'll do so fine until after 10 or 15 minutes maybe the car will stop responding to my throttle inputs and the revs will drop until the car ultimately stalls. I can restart the car with no problem, it holds an idle just fine and I can really only drive it by slipping the clutch until it starts to move and then chug along at like 5mph

I'm drawn to believe its a carburetor issue as after the most recent drive the car limped home, I popped the hood and there was a distinct sizzling coming from the carbuertor, I couldn't exactly locate it but it was there.

Although I did notice something peculiar as I pulled it into the driveway, with the clutch pressed in I could tap the gas and it would rev up just fine when just moments earlier it would try and buck and kick if I gave it gas while chugging along in first

Also if it helps for whatever reason, I've noticed that the car feels and drives fine but at around 4k rpm it starts to take off and has significantly more power (the secondary kicks on I presume and its a Weber 28/30 I believe)
 
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Hi

The x1/9s do suffer from fuel vapour lock in the carb due to the exhaust manifold making the area very hot.

Fiat originally fitted a carb cooling fan to try and help the problem. I think the issue is worse now the cars are old, most have lost their exhaust heat shield which probably rusted away long ago. So replace with something if you can.

If the cars been put back on the road its always a good idea to replace the fuel lines to reduce the risk of leaks and engine fire. A very good idea is to add insulation to the fuel lines to try and reduce the heat transfer.

The electric fuel pump will help as it will circulate fuel more quickly.

The carb might benefit from a rebuild? And a fresh in-line fuel filter is a good idea if you don't already have one.

Let is know how you get on
 
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I have two new fuel filters already, with new lines as well. I've been thinking about getting some insulation as well because the way I have the lines routed means that they're experiencing a fair bit of heat once the engine gets hot.

I'm definitely considering a rebuild at the point and have already called oreillys to get them to have a rebuild kit shipped in, but I've also been doing some reading that suggests that I might need a thicker gasket on the base of the carb? Apparently this might help reduce the amount of heat that gets transferred to the carburetor from the manifold and I'm thinking its something to do with this given the distinct sizzling sound which could be heard coming from the carb

Also I checked and the exhaust heat shield is still in place although I find the location of the exhaust manifold to be weird given how close it is to the carb
 
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There should also be a plastic drip tray between the carb and the manifold. I think this means there are two paper gaskets.
 
hi, hope u have found the problem, sounds like it could be a blocked fuel filter or pick up feed, im having the same troubles with mine will check mined not blocked tomorrow;)
 
I had a similar issue with my old car, after new plugs, fuel pump and carb rebuild, I eventually found that the problem was with the coil unit.

I am having new issues with my current car though, which is fuel starvation when going uphill at higher revs. I have fitted electric fuel pump and electronic ignition, new coil etc but I have been told it might be carb related.
Apparently the float might not be weighted properly - the science bit was explained to me by modern fuel being less dense than back when the car was built, causing the float to sit higher and therefore closing off the fuel supply prematurely.
A job for winter is to get the carb rebuilt and/or place additional weight on the float to see if that helps matters... a friend also suggested extending the fuel pick up pipe to sit lower in the chamber...

Both could be worth investigating, although the coil would be the cheapest and easiest solution.
 
I had a similar issue with my Fiat after going through the carborator and electrical it ended up being the immitions canister in the back left of the engine compartment that feeds the intake manifold below the carborator had a small tear in it.
 
Hi I've been having the very similar issues with hesitating/surging for a while, I've tried cleaning carbs etc, my last hope is the sensor in the flywheel area of the transmission which I can only guess is a speed sensor/crank position sensor, from what I remember it seems to be linked to the ignition circuit, the symptoms online describe mine, but then so do a lot of things... I'll have a look at mine tomorrow and let you know
 
ignore my last message, I was clutching a straws at that point. I have mine running now as I found the carb had warped considerably between the top and bottom half, and the base, thus leaking float bowl and leaking primary/secondary. I sanded the float bowl half with 600/800 grit and a glass plate to get it flat, the top half is tricky as there are many obstacles, I used a thin strip of glass to get it fairly flat the bronze vacuum dowel things can be removed but if u use pliers dont use too much pressure as they break quite easily as I found out. Also would help to remove the auto choke assembly with the three screws behind the fast idle cam, dont lose the o ring/seal for the vaccum advance at the back. Good luck hope this helps
 
also if u need I have a few different manuals including the original workshop manual which has all the carb set up info, just send me your email adress
 
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