Technical Bubbles wont start...again

[usafstud]

Happy New Year guys.

My car wont start again. It ran great for about two months, 3 times a week. One cold morning (40-45 F), the engine died after 2 seconds of running.

I can get it to crank, but it wont fire. There is fuel and spark. Could it be the vlave clearence? I even put a new condenser even though I always had spark.

Inputs?

Thanks, Frank

 

[jjacob]

Hi Frank,

Can you give us a little more information. What did you do to determine that there is spark and fuel? Are you running points? Standard carb?

I would think the problem is something basic. Even if the valves were out of adjustment the engine would still start (run crappy, but still start).

Have you pulled a plug? Wet with gas?

John

 

[usafstud]

I pulled the sparkplug and had it grounded to the engine block while cranking, and there was spark. I pulled the fuel line from the carb, and fuel came out while cranking.

I'm using standard points/contact.

 

[jjacob]

OK Frank,

You have spark to the plugs and gas to the carb. You may have a flooded engine. If the float was to stick open or the needle valve inlet to the float chamber leaks, then you will flood the engine.
It could also be that the float or needle valve are stuck and there is no gas going into the carb.
There is a possiblity that the distributor is loose and you lost your timing, but unlikely. If you have spark I would think the engine would at least try to start.
If you are getting nothing, then sounds like fuel. Pull a plug and see if it is wet with gas. If it is then then carb is flooding. If it is dry, then most likely no gas getting through to the jets. Try shooting a little starter fluid into the carb and see if it starts. You can also try dribbling a little gas directly into the carb to see if it starts.
John

 

[usafstud]

The plugs are dry. It did start with starter fluid, but did not stay running.

Is a carb cleaning and new gaskets next to do? Any more new parts?

 

[jjacob]

Hi Frank,

Very good, we are getting to the source of the problem. The engine is not getting fuel. This can be caused by any or all of the following:

1) a stuck fuel inlet valve
2) a stuck fuel float
3) plugged jet(s)

I am assuming that you have a standard original type Weber IMB carburetor (single barrel).
First I want you to lightly rap the carburetor with a small hammer. This may free a stuck float or inlet valve. Then try to start again, giving the carburetor some time to refill.
If this does nothing then you need to proceed to the following.
Remove all of the attachment hardware to the top of the carburetor. Remove the screws that attach the top half of the carburetor to the bottom. What we want to do is to take this off carefully and see if there is gasoline in the float chamber. If there is very little to none then the float is sticking or the float valve is stuck (easy fix). You can remove the carburetor from the car if you wish before disassembling the top if that is easier for you. Just don't dump the gas out of the carburetor while removing it.
If the float chamber is full of gas then you need to disassemble and clean the carburetor and all of its jets and parts.
You don't have to take the top all the way off, just enough to see inside the float chamber.
Report back what you find (or if the rapping with the hammer works).
John

 

[usafstud]

I tapped around the carb and it started.

While doing so, I noticed fuel around the base of the carb and engine. Could the carb be leaking fuel?

 

[Bambino]

Over to you John - but I reckon it's time you stripped, cleaned and refitted the carby with new gaskets and a new fuel inlet valve. A new float might be in order also as the old one maybe leaking and filling with fuel thereby flooding the engine by not 'floating'.
I'd change the fuel filter as well.
All these parts are available and cheap.
Chris

 

[ianhunterv8]

Frank

While you are at it, unscrew the filler cap on the fuel tank. If you hear a hissing of air, your fuel tank isn't venting and that will prevent fuel getting through.

Caught me out - that's how I know!

Ian

 

[usafstud]

Thanks for all the help.

I went for a 5 minute drive and let the car idle in the garage for about 1 hr and it stayed on the entire time.

Over to you John - but I reckon it's time you stripped, cleaned and refitted the carby with new gaskets and a new fuel inlet valve. A new float might be in order also as the old one maybe leaking and filling with fuel thereby flooding the engine by not 'floating'.
I'd change the fuel filter as well.
All these parts are available and cheap.
Chris

Which of these repair kits should I get? They didn't list the items, so I don't know which has the fuel inlet valve. I don't know how that piece looks like. I don't think I see the float on either of the kits. I did replace the fuel filters by the pump and tank.

http://mrfiat.com/part.php?item=Cars/Fiat/Fiat 500/Fuel System/Fiat500NDFLWeber26IMBQuickRepairKitNew.html

http://mrfiat.com/part.php?item=Cars/Fiat/Fiat 500/Fuel System/Fiat500R126CarburetorRepairKitNew.html

http://mrfiat.com/index.php?car=Fiat&type=Fiat 500&cat=Fuel System

Frank

While you are at it, unscrew the filler cap on the fuel tank. If you hear a hissing of air, your fuel tank isn't venting and that will prevent fuel getting through.

Caught me out - that's how I know!

Ian

The tank vents. I already dealt with that issue with my 71 Vespa 50.

 

[jjacob]

I tapped around the carb and it started.

While doing so, I noticed fuel around the base of the carb and engine. Could the carb be leaking fuel?

Great! I have started many cars that have sat for awile by giving the carb a whack or two. Glad we were able to work this through together.

Your float or inlet valve is sticking.
Sometimes the inlet valve sticks open and you end up with flooding, or the float sticks down or fills with gas and you flood. That is not the case here.

In your case the inlet valve or float are sticking shut, so no gas into the carb. It will most likely do this again, especially if the car sits for longer periods of time.

You have a few choices at this time:
1. You can just replace the carburetor with a new one if you want. About $200 I think?
2. You can do a complete tear down, cleaning and reassembly. Installing new components and gaskets from a kit. Kits are cheap.
3. You replace just the gaskets and the inlet valve if you are not up to doing a complete tear down. This preserves your current settings.

My recommendation is that you do a complete tear down, cleaning and replacement of gaskets and parts. The standard carburetors are very simple. If you count the number of turns it takes to remove the idle mixture screw during disassembly you can get it back close to the original position before fine tuning it.

If you have never done this before let us know and we can give you some pointers and advice.

The slight wetness at the base of the carburetor is normal.

John

 

[Bambino]

The inlet needle valve parts are the two brass looking bits in bottom right hand side of the attached photo. That kit contains the main gasket, internal fuel filter, float pin, various o-rings and seals and the needle valve. A more comprehensive kit is also available the contains jets etc.

Floats are available here and should come with setup instructions - http://www.fiatplus.com/weber-carburetor-float-pr-279316.html

Diagram and explanation is here - http://www.fiat500america.com/2009/06/weber-carburetors-type-26-imb1-26-imb3/

Good luck,

Chris

 

[jjacob]

Which of these repair kits should I get? They didn't list the items, so I don't know which has the fuel inlet valve. I don't know how that piece looks like. I don't think I see the float on either of the kits. I did replace the fuel filters by the pump and tank.

Frank,
My opinion is that you do not need to replace your fuel float. You did not have a flooding condition.
In your pictures I cannot determine the model of your Weber. There were three models typically used. The 500cc 500F and 500L cars used a Weber 26 IMB. The 500R used a 24 IMB and the 126 used a 28 IMB. Look on the side of the carburetor. You most likely have a 26 IMB, and that would be the kit to get.

On Mr. Fiat the kit you want is the $28 quick repair kit for a 26 IMB, if that is the carburetor you have. This includes the inlet valve pieces and gaskets. I have circled them in the attached picture. The brass pin is for the float to pivot on.
John

 

[jjacob]

Sorry Chris, we must have been writing replies at close to the same time. I should have refreshed my page first.
John

 

[usafstud]

John, I have a 500L. So I'll get the 26 IMB kit.

Do you think this could fix another issue I have been talking for a while? The air/fuel mixture screw doesn't seem to make any effect on the carb.

 

[jjacob]

Yes, if your fuel mixture screw has no effect at idle then the carb most likely needs a good cleaning. Your mixture screw or even the internal seat in the carburetor base could be damaged also (usually from overtightening). Keep in mind that the mixture screw only has an effect at idle speed. Anything above idle speed, and the idle mixture screw and its circuit is bypassed.

If you rebuild the carburetor yourself, I would recommend that you do not remove the throttle plate and rod from the carburetor lower base. This can sometimes cause more problems.

Will send another email maybe tomorrow with some pointers if you would like that. I am sure others will give some advice also. If you like, I can send you a PM with my phone number in case you run into problems or have questions. We are on the same continent and time zone.
John

 

[Bambino]

Frank,
My opinion is that you do not need to replace your fuel float. You did not have a flooding condition.

I agree - the only reason I mentioned buying a new one was in case the old one is damaged (dented, bent, twisted etc.) but still floating.

Chris

 

[jjacob]

Frank,

Once you start to take the carburetor apart you can post pictures of the idle mixture screw and the float for us to look at to see if they are damaged.
John

 

[usafstud]

Thanks everyone. I'll provide updates in two weeks. I gotta go to wyonne and ohio for two weeks for business.

 

[usafstud]

Where does the rubber o-ring and brass ring go? Are they spare parts?