Hello fellow Z'ers,

 

Recently started having an issue on my Z running really rich and I can  see fuel dripping from the nozzle into the barrels.

Car ran excellent for months; then suddenly went to start it and noticed my AFR in the 9's and noticed the drip.

The motor is not stock; has a .495 lift and 290 duration, so keep that in mind.

Idle Jets it ran - 65, but I also tried swapping in 62.5 and 60's and the AFR stayed the same. 

Mixture screws are 1.5 turns out. 

Fuel Pressure is right below 4psi (with 3.5 - 5psi spec) and was tested with two different gauges

Floats at 30mm (within 29-31mm spec)

Pump nozzle sizes tried: 40 and 50

It drips down from multiple barrels, not just one. Can't seem to figure out why this is happening since nothing was changed since it last drove fine.

Any ideas where to start next? Thanks!

 

 

Wild guess. Float needles...

 Ditto. Float needles. Either a worn tip or crud holding the valve open.

20 minutes ago, Mark Maras said:

 Ditto. Float needles. Either a worn tip or crud holding the valve open.

Just seems so sudden. Been running flawlessly for months, did a coffee run and on the way back problem occurred. Car was driven regularly throughout the week and hasn't sat for long. Odd that multiple needles have issues simultaneously out of the blue. Thinking maybe something in fuel line that spread across carbs and maybe clogged up something? Is that a thing?

Yes, it's possible you fed something into all the carbs at once. Trash out of fuel pump, blown out fuel filter...

I concur with Charles. Fuel pressure seems to have gone high.

What filter(s) are you running? A large (100um) from the tank to the pump and a small (less than 10 um) to the carbs?

Float needles get stuck. I have been adding Marvel oil to each fuel jug after the middle carb float stuck closed causing a lean and expensive incident. No issues since.

3 hours ago, gnosez said:

What filter(s) are you running? A large (100um) from the tank to the pump and a small (less than 10 um) to the carbs?

Float needles get stuck. I have been adding Marvel oil to each fuel jug after the middle carb float stuck closed causing a lean and expensive incident. No issues since.

Yup, larger filter by pump and small right before regulator in engine bay.

Hmm, wondering if maybe it was a batch of bad gas in there from my last fill up or maybe nasty junk in the gas tank that managed to get past the filters...if that's a thing. Thought the filters would keep stuff out, haha. 

 

Just odd that it all happen so suddenly and simultaneously throughout the Carbs - which is why I suspected fuel pressure first, especially since the car's health changed over it just sitting for a couple of hours after running healthy for several months. 

 

I'm no carb expert, but I suppose I might have to take these suckers apart - was hoping to avoid that. But I can't keep running the car like that until I fix it. Don't want fuel to make its way to the crankcase with how rich its running...

Overflowing fuel bowls is usually too much pressure from the pump.  It causes the fuel levels in the bowls to rise and the fuel easily runs down the pipe to the Aux Venturi.

 

Another reason to set fuel level 27mm to 30mm down rather than the internet myth of 25mm down (unless you run an old 4cyl Lotus it seems).

Once fuel sloshes to 23mm up, it pours into the throat of the carb.

Ok, so I tested my needles and all of them seat properly. Ran pump with one unseated top at a time and all the seated ones remained shut and never leaked.

My fuel pressure is still within spec and hasn't been an issue before...but what can I lower it to? 3psi?

I would think 3-4 psi should be good

44 minutes ago, Patcon said:

I would think 3-4 psi should be good

Lowered it to 3psi - still drips.

 

Could the size of the pump nozzle make a difference? I have one size smaller. I'll give that a shot and see if it does anything. 

On 5/7/2018 at 1:50 AM, 240260280 said:

Overflowing fuel bowls is usually too much pressure from the pump.  It causes the fuel levels in the bowls to rise and the fuel easily runs down the pipe to the Aux Venturi.

 

Another reason to set fuel level 27mm to 30mm down rather than the internet myth of 25mm down (unless you run an old 4cyl Lotus it seems).

Once fuel sloshes to 23mm up, it pours into the throat of the carb.

My floats are all set at 29mm

@240260280