32ADF dries out over night

[SteinOnkel]

Hello Gang,

pretty much as the title suggests. I've rebuilt the carb, but there's just not enough fuel in the bowl in the mornings to start it AND keep it running. It'll catch, die, then you crank it some more and boom it fires right up.

I've opened the bowl up when it exhibits these symptoms only to find it empty.

Running the mechanical fuel pump w/ Jeep fuel filter (integrated pressure regulator).

Any ideas?

Cheers
Steiny

[18Fiatsandcounting]

Steiny, I always have ideas, and a precious few might even be helpful...!

Sounds like your fuel pump is fine. The float bowl shouldn't be emptying that quickly. Two possibilities:

1) (Less likely) A leak/crack in the float bowl reservoir that is allowing fuel to slowly leak out.
2) (More likely) An improper float bowl venting hole that is either open to the atmosphere, or worse, pulled on by a vacuum that is developing as the engine and fuel tank cool down overnight.

-Bryan

[SteinOnkel]

Steiny, I always have ideas, and a precious few might even be helpful...!

Sounds like your fuel pump is fine. The float bowl shouldn't be emptying that quickly. Two possibilities:

1) (Less likely) A leak/crack in the float bowl reservoir that is allowing fuel to slowly leak out.
2) (More likely) An improper float bowl venting hole that is either open to the atmosphere, or worse, pulled on by a vacuum that is developing as the engine and fuel tank cool down overnight.

-Bryan

Bryan,

I would not discount point 1). There is something inherently wonky about this particular carburettor. I have to turn the mixture screw way out or else it will start to slowly drip fuel from the main jet's venturi at idle. This issue I have been trying to trace down for month to know avail. I've thrown the book at it. Also, my idle will not smooth out. It IS possible that the dpo installed a hot cam...

As for 2) I will check that at lunch today. It's entirely possible that it is open.

Cheers
Steiny

[18Fiatsandcounting]

Is your float level correct? Some of the symptoms you describe might be traceable to an incorrect float level (wonkiness, idle, main jets coming on too soon, etc.).

-Bryan

[SteinOnkel]

As I said, I've thrown the book at it

Is the float level that critical on these Webers though (I'm more familiar with Solex-Pierburg)? One Redneck Test I've done is to set it to so that it drips out of the main jet and then clamp the feed line to the carburettor shut. If the float level/fuel pressure were incorrect, it should go like this: Drips....Stops Dripping....Dies when the bowl runs dry. But alas, it keeps dripping until the bitter end.

I wish I could slap on a spare 32ADF, but my goodness are used carburettors expensive for these cars.

My next step is most likely to put this bucket on the shelf and install the spare rack of bike carbs I have. It ran pretty well on my 1.6 16v so it's most like jetted close-ish for a 1.8 8v. Already confirmed that the spacing is dead on

[18Fiatsandcounting]

I'm going by memory here, but on my Webers of the style you have, the float bowl normally has about an inch of fuel in it. Half and inch would be too little, and 1.5 inches is probably too much. It's not necessary to be exactly right, but getting it close does eliminate one issue when you are experiencing carb issues.

As for the lumpy idle? Yes, it could be hotter cams than stock. My '69 spider has the stock 26/66 cams, and it idles reasonably well but there is a bit of lumpiness. Later model years, like mid 70s onward, seemed smoother.

You know, in thinking more about your issue, it sure sounds to me like your idle circuit is not working. Because of this, you have to open the throttle to get fuel from the main jet to keep it idling, which explains the dripping, and also the wonky idle because the main jet is not designed for idling. If you have an electrical idle cutoff switch, it is stuck in the off position? Are you sure your idle jet and idle passageways are clear? I've seen one little speck of rubber in just the right place block an idle jet and prevent the engine from a proper idle.

-Bryan

[SteinOnkel]

Bryan,

I've dismantled and cleaned this carburettor more times than I can count. The solenoid is working properly and the idle circuit works. This I base on the fact that it DOES react to the idle mixture screw. Speaking of the solenoid, this is where I like Solexes better. On those solenoids you can simply take a pair of bolt cutters to the plunger et voila, it doesn't matter if it's energized or not, it simply cannot interfere with the idle circuit. The only cars I've ever had diesel on me were super old, piping hot VW flat fours that did not have that solenoid.

Is there an easy way to identify hotter cams on these cars? Many moons ago this car was owned by an independent Fiat mechanic in the area. It's highly likely he modified the engine a bit. The rest of the car is stock from what I can tell.

It'll be interesting to see how it idles with the bike carbs. If it's silky smooth, we know for sure it's an issue with the Weber.

Cheers
Steiny

[18Fiatsandcounting]

I have to admit that you have me stumped. As for the question on how to tell one cam from another, I'm not aware of an easy way. If there is a Fiat part number stamped on the cam, you might be able to cross reference it to the type of cam. If there's no number, then it could be almost anything. There are shops (perhaps racing shops) that can measure the cams, but my guess is that it requires a lot of specialized equipment.

You might (and that's a very big "might") be able to get some indication by measuring the angle at which the intake cam opens the #1 cylinder. I believe a stock engine for the '78 spider has an intake cam that opens 5 degrees before TDC and closes 55 degrees after BDC. So, if you remove the intake cam housing cover and rotate the engine (by hand) until the cam lobe on cylinder #1 looks like it just starting to depress the valve shim, then that should be 5 degrees of rotation before TDC. Continue rotating the engine by hand, and the intake lobe for cylinder #1 would have just let the intake valve fully close at 55 degrees after BDC. I believe these degree measurements are for crankshaft rotation, and so for the camshafts which turn at half speed, they would open 2.5 degrees before the crankshaft is at TDC and close 27.5 degrees after the crankshaft has passed BDC.

Same story for exhaust cams. However, I've never done the above, and it might not be accurate enough to get a good reading on what cams you have.

-Bryan

[SteinOnkel]

Brian, that might be worth a look. Armed with the stock specs we might be able to figure out what's in the engine. Most aftermarket cam manufacturers stamp their work...

Interesting side story. My VW sports the stock cams and it has VVT with open-source efi. It would be interesting to know the cam duration and other specs etc. The engine is from 2001, so not exactly fresh off the assembly line, but not ancient history either. Back in the day (80's, 90's) you could find these specs in any run of the mill haynes manual and certainly in the factory manual. 2001. Could not find a damn thing for my engine. Google spits out nothing in this regard, only the specs for the aftermarket cams. So I thought, well why don't I e-mail the factory (VW has an outstanding support team, especially for their vintage and vintage-ish models). Had to wait six weeks and the response had me floored. It was basically "Look, buddy, we went digging in every database and file cabinet we could think of...we can't find the specs...we even spoke to the engineering team of that engine, they can't remember". How decidedly un-german of them

[18Fiatsandcounting]

How decidedly un-german of them

Schade. Die sind total verrückt, diese VW ingenieure...

-Bryan

[manoa matt]

Similar issues as you. I like a mechanical fuel pump for the reliability and safety aspects, also quieter. I've had hard starts after driving, shutting it off, then re-starting after 1/2 hour or more. I know the carb is setup properly and not cracked. I've installed an inexpensive cube pump near the tank that is wired to a switch in the foot well.

When I want to start up, I flip the switch and the pump will push gas up to the engine. When the float bowl is filled and the needle valve shuts off, the pump quiets down. I switch off the electric pump via the switch. Pump the pedal twice, and it starts right up.

[18Fiatsandcounting]

Manoa, that is odd but I've heard of this problem with Fiats. Unless the float bowl is totally open to the atmosphere, it's hard to imagine gasoline evaporating that quickly (even where you are). The gas in my carb's float bowl will eventually evaporate away, but that takes weeks.

Is the engine perhaps partially flooded? Gas dripping down into the intake manifold when you shut it off? Try holding the gas pedal to the floor (no pumping) when you crank it, and see if it behaves any differently. If it cranks for a few seconds and then fires, chances are it was flooded.

-Bryan