Carburettor help

[bstark]

Not on the Seven - it's the Weber 28IMB fitted to our '66 Fiat 500.

 

When the car has been left for a few weeks it will simply turn over but not try to fire. Spark etc. is all fine. What I end up doing is removing the only external jet on the carb (think its the idle jet) and spraying a load of carb cleaner in. That's enough to get it to cough. Do that 3 times and it starts and then runs fine...

 

If you then leave the car till it gets properly cold again it all works fine on the choke ('cold start mechanism' on these carbs). Leave it a week or so and you're faffing around with screwdrivers and carb cleaner again. There's no accelerator pump so you can't just pump the pedal as you do a DCOE.

 

I can't believe they were like this new so does it sound like something obvious to the experts? I'm wondering if it's just worth investing the money in a new carb...

 

Th other thing to mention is that it's a 650cc engine from a later Fiat 126 and the carb has a fuel return not present in the original car so the tank isn't designed to take it. I've simply run this back to in front of the fuel pump and fitted a non-return valve to stop it draining to the tank and creating an airlock. Don't think this is the problem as it runs fine once coaxed into life but prepared to be corrected .

 

All help welcome!

 

Bob

 

[Markiebabes]

Bob

I'm no expert but had something similar on my aircooled camper 😳 could it be a worn jet ?

Try blowing the jet out with an air line ( the bigger the pressure the better) worked for me rather than just blasting with carb cleaner

 

HTH

[Roger King]

I have no knowledge about that carb type, but no accelerator pump? Really?

 

That would be the only way to prime the engine before cranking. Pulling out the choke won't prime it, it just puts more fuel in once it starts working.

 

I'd be inclined to simply block the return to the fuel tank rather than loop it back. Most carbs will work fine either blocked or with a return (its usual function is simply to prevent the fuel sitting around and overheating).

 

I'd also check that there is fuel in the float chamber after it's been standing for a while. If it's evaporating or leaking the engine won't even try to start unless you spray something like Easy Start in. Assuming you have a mechanical pump, you'll have to crank the engine for a while to get some fuel up.

[bstark]

Mark, could well be worn. The engine came from Poland without history via eBay 😬 but seems in good nick and works fine

 

Roger - yep, they cut cost everywhere! There's fuel in there alright but I assume something is causing an initial internal blockage?