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Ultra rich fuel mixture and flooding inlet manifold drains

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Walter74

Walter74

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Hello,
I have recently revised my BJ7 engine. The engine is running, but with extremely rich mixture. The drain pipes from the inlet manifold are pouring fuel when engine is running idle.
I have checked carbs, timing and valves but everything seemed to be correct. Needles and valve seats are new. Float chamber level is correct. Jet level is also ok. When lifting HS6 piston with the engine running nothing happens to the revs.
I am pretty desperate at the moment, so who can help me solve this issue?

Looking forward to your replies
 
Had a similar issue and found that the brass soldered floats had a leak in them that would only open up when warm. Floats got bogged down and fuel leaked from drain pipe. Replaced with nitrophyl floats and problem disappeared
 
MikeAH100M said:
Had a similar issue and found that the brass soldered floats had a leak in them that would only open up when warm. Floats got bogged down and fuel leaked from drain pipe. Replaced with nitrophyl floats and problem disappeared
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Walter--

Beyond checking for a sunken float make sure that the pin upon which the lever arm pivots is in straight and that the lever is not binding.
 
Be sure the tabs on the float are in the correct position on the mounting rod. If not on their correct position they will not have full travel and flooding happens.
 
Checked everything in the carbs and it all seems in good shape. I suspect it is something outside the carbs. Is fuel pressure a possible issue?
 
Don’t assume that just because parts are new they are good and work . Put the floats in hot water to expand them and check for bubbles .
If the needles and valve seal correctly then fuel pressure shouldn’t be an issue unless it’s crazy high . Normal fuel pressure is on around 2psi
 
Debris in needle and seat. Even the smallest of chunks can cause the flooding issues described. Also, is there fuel pushing out of the carb overflows? Only the front? Back? Both? Is an aftermarket fuel pump installed? Regardless, 3 to 4 psi max pressure.
 
Walter--

In your first post you seemed to indicate that both drain pipes are leaking fuel. That in and of itself might suggest fuel pressure, esp. since you have gone through both bowls, floats, etc.
What kind of fuel pump do you have installed and if aftermarket is there a fuel pressure regulator in the system?
 
I would remove the dashpots and pistons and, with the pump running, look to see how high the fuel is inside the jet. It should be just below the top of the jet when the pump is running. If it is flowing out of the jet and into the manifold, you know there is a problem with the float valve - either grit under the float needle seat, it's adjusted wrong, a sunken float, or too much pressure. I agree with others that "just because something's new, does not guarantee it's working properly"
 
Walter74 said:
The car has an aftermarket Pierburg fuel pump without pressure regulator. Pressure is 3.2 - 5 Psi. Could that cause flooding?
Click to expand...
Walter--

Most definitely.

Follow Red's suggestion and see where fuel is relative to the jet bridge. If fuel is flowing over it AND if you are confident that the issue is not debris and the floats are working properly I suggest that you either change to a 2-4 psi fuel pump or install a fuel pressure regulator or both. Google "Fuel pressure regulator" and you'll see several regulators with gauges.

I've never felt the need to install a fuel pressure regulator on my 100 but I have done so on SU or Weber-equipped race engines which generally operate at or near wide open throttle ("WOT") I've had good luck with Carter 4070 pumps set to 4 psi.

Good luck and please keep us posted on your progress
 
Walter--

As I said, I have never had the need to install a pressure regulator on my Healey but on my race cars I install them near the firewall and close to the carbs so it is easy to view the pressure and effects, etc. on the carbs. This location may not be your first choice from an esthetic standpoint but I think it more important to have the regulator and gauge close to the carburetors so you can see the effect of adjustments, etc. If this presents a problem you can always opt for the easier solution of simply changing to a 2-4 psi fuel pump,,,,
 
Walter,

I'm still curious what the fuel level is inside the jets. Is fuel pouring out when the pump is on? If you think pressure is the problem, you may find it much easier to simply replace the pump with a lower pressure one as Michael suggests, rather that mounting and plumbing a regulator.
 
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