FFuel overflowing at Intake Manifold

R

RonR

Jedi Trainee

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• Sep 4, 2019

• #1

Folks.

I have been having a problem with the excess fuel running out the intake manifold overflow tubes with the engine running.
The carbs are HD6.

I have installed new gross jets and adjusted the floats, as well as verified they are functioning properly.
I have a bit over 20,000 miles since I rebuilt the carbs, including replacing the jet and the jet bearings.

Any suggestions?

Thanks.

 

John Turney

Yoda

Silver

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• Sep 4, 2019

• #2

1. Use the SU float valves.
2. Did you clean the Grose jet float valves with acetone before installation? They come with a coating on them.

 

OP

R

RonR

Jedi Trainee

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• Sep 4, 2019

• #3

John,
Thanks for your reply.

The gross jets are shutting off the fuel supply.
I verified this by removing the piston cover, piston and needle, turning on the fuel pump. Not fuel came up through the Jet assembly, but did flow out the float bowel overflow tubes.

 

steveg

Yoda

Gold

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• Sep 4, 2019

• #4

Ron -
The rule for troubleshooting is something is either broken or changed. You've changed something by installing new Grose-jet float valves. Therefore they are likely the cause of the problem.

Suggest you reinstall the old float valves and see if the problem goes away.

 

Keoke

Great Pumpkin

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• Sep 4, 2019

• #5

a
If you did not do what John said:

2. Did you clean the Grose jet float valves with acetone before installation? They come with a coating on them

This may be your problem​

 

OP

R

RonR

Jedi Trainee

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• Sep 4, 2019

• #6

The problem existed, although not well defined, prior to installing the gross jets.

Originally, I assumed the excess fuel was caused by the old needle and seats not sealing. So, I replace them along with the float levers, adjusted the floats and put everything back together.
I will remove the gross jet and clean them again.

Now that I have verified that the problem is not with the amount of fuel flowing out of the float bowels , I am asking if it is possible that the jet assembly and/or needle could be worn out and causing the excessive amount of fuel in the intake manifold?

Or, is there somethign else that I am overlooking?

 

red57

Jedi Knight

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• Sep 4, 2019

• #7

RonR said:

The gross jets are shutting off the fuel supply.
I verified this by removing the piston cover, piston and needle, turning on the fuel pump. Not fuel came up through the Jet assembly, but did flow out the float bowel overflow tubes.

Click to expand...

If I understand you correctly, you have excess fuel coming out of both the manifold drains and the float chamber overflow vents?

Float chamber overflow vents:

Normally the fuel level in the float chamber is even with the fuel in the jets - the old 'water seeks it's own level' thing. The overflow tubes go into the float chamber cap which is much higher elevation than the jets so if fuel is not coming out of the jet but IS coming out of the float chamber overflow, the passages to the jets must be plugged/restricted, at least partially, in order fill the float bowls full enough to cause it to overflow without any coming out the jets.

Manifold Drains:
If the float chamber levels are set too high, it could be draining fuel (when not running) out of the float chambers and passages through the jets and accumulating in the manifold.
​

Or:
The fuel coming out of the manifold drains could be just a very rich situation where fuel is condensing out of the air stream and pooling in the manifold. If that is the case, the float jets would likely have nothing to do with the problem.

Besides that, I agree with Steve - always look at whatever you did last.....

Dave

 

John Turney

Yoda

Silver

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• Sep 4, 2019

• #8

RonR said:

John,
Thanks for your reply.

The gross jets are shutting off the fuel supply.
I verified this by removing the piston cover, piston and needle, turning on the fuel pump. Not fuel came up through the Jet assembly, but did flow out the float bowel overflow tubes.

Click to expand...

If fuel is coming out the float bowl overflow tubes, the Grose Jets are not shutting off the fuel supply. The bowl overflows are higher than the bowl inlet valves.
Are you sure it's the float bowl overflow tubes and not the intake manifold drain tubes?

Does the pump shut off when the float bowls are full?

 

steveg

Yoda

Gold

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• Sep 4, 2019

• #9

Also make sure the washers on the float cover banjo bolt are in the correct order, with the slotted fiber washer below the banjo and the aluminum washer and tag above.

 

Bob_Spidell

Yoda

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• Sep 4, 2019

• #10

Longshot, but I think you could have that problem if one of the jet diaphragms--the 'D' in 'HD'--is cracked or has a hole in it (I've seen them get brittle and crack around the edge). FWIW, I've had a new jet soaking in denatured alcohol--according to the label 'at least' 50% ethanol with other nasty organics--for over a year and it's still in pristine condition.

 

vette

Darth Vader

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• Sep 5, 2019

• #11

It can be all the above. But I agree that the fuel in the float bowls is probably too high and the float valve is not shutting off the fuel. A cracked diaphram could be doing it and also an extremely rich carb jet setting. As stated above.