Weber fuel problem

[Scott R]

I hope this is an easy one, my idle is perfect. carbs respond to idle adjustment very well. My problem is with full acceleration, I have a lot of fuel coming out of the mains, so much that it spits onto the sound deafening mat on the engine bay roof.

I can take the accel pumps out of the picture and it still does this. The mains were 140's I went down to 130's same issue. Also of course this causes serious bogging. I removed the left bank today, inspected all the passageways, checked the floats and float levels, everything seems to be ok. I'm stumped.

[avendlerdp]

What are you using for air filters?

[Steve@Rennsport]

Originally Posted by Scott R

I hope this is an easy one, my idle is perfect. carbs respond to idle adjustment very well. My problem is with full acceleration, I have a lot of fuel coming out of the mains, so much that it spits onto the sound deafening mat on the engine bay roof.

I wouldn't worry about that for the moment; thats usually due to reversion. I hope you are using air cleaners,................

I can take the accel pumps out of the picture and it still does this. The mains were 140's I went down to 130's same issue. Also of course this causes serious bogging. I removed the left bank today, inspected all the passageways, checked the floats and float levels, everything seems to be ok. I'm stumped.

Does it stumble every time you accelerate from low and mid-RPM?

Do you have 3.5 psi of regulated fuel pressure?

Are your float levels absolutely perfect?

[Scott R]

Originally Posted by Steve@Rennsport

I wouldn't worry about that for the moment; thats usually due to reversion. I hope you are using air cleaners,................



Does it stumble every time you accelerate from low and mid-RPM?

Do you have 3.5 psi of regulated fuel pressure?

Are your float levels absolutely perfect?

I'm using the K&N air filters sold by our host; the rainshield kit from PMO. I have slightly more than 3.5PSI according to the PMO fuel block/gauge but it's dialed down as far as it can go. And yes it stumbles badly, and I have black smoke and extreme hesitation on heavy accel. In fact when it's cold full accel will simply kill the engine.

I'm going to go over the float levels again, but in the carb that displays the most fuel "spitting" (number 1 cylinder) I did out my PMO gauge on it today and the meniscus was between the lines.

[911pcars]

Originally Posted by Scott R

I'm using the K&N air filters sold by our host; the rainshield kit from PMO. I have slightly more than 3.5PSI according to the PMO fuel block/gauge but it's dialed down as far as it can go. And yes it stumbles badly, and I have black smoke and extreme hesitation on heavy accel. In fact when it's cold full accel will simply kill the engine.

I'm going to go over the float levels again, but in the carb that displays the most fuel "spitting" (number 1 cylinder) I did out my PMO gauge on it today and the meniscus was between the lines.

Has this been a constant symptom since the conversion or a sudden occurrence? Are you still using the factory fuel pump rather than a low pressure unit?

I''ve left my conclusions out. Your answers to the above might reveal the solution.
Sherwood

[Scott R]

Originally Posted by 911pcars

Has this been a constant symptom since the conversion or a sudden occurrence? Are you still using the factory fuel pump rather than a low pressure unit?

I''ve left my conclusions out. Your answers to the above might reveal the solution.
Sherwood

Constant symptom since the conversion, yes. And Yes I'm using the factory pump with the PMO pressure regulator.

[avendlerdp]

Disconnect the fuel pump and go for a short spin. Is it runs right just before it runs out of gas then you can count on some sort of fuel pressure overload. How have you routed the return line to the tank from the FPR?

This is not a jetting thing I bet. Go back to the right jets so you are not fixing a car that's both flooding and running lean too.

[Scott R]

OK, finally had some more time to work on this today. Funny solution, but you guys were right, it was excessive fuel pressure. Now the weird part... I had my carbs setup with one fuel filter between the PMO fuel block and the carb. I removed the filters and put just on filter between the inlet line and the PMO fuel inlet on the block. Now I can keep it spot on at 3 psi and it's not spitting fuel anymore. So thanks guys! Now I'm on to bigger jets.