Lotus Elan

Stromberg, fuel out of the vent hole

PostPost by: lotusbc » Wed Oct 14, 2020 7:51 pm

I have just replaced a fuel pump, Delphi electric rated max 5psi, and now have fuel pouring from the vent hole on the carb front face. I was previously experiencing poor running, no pick up, stalling. My carbs are the fixed needle type. I have read through some other threads for tips and as the needle valve seems to stick and as I have a spare set, adj. needle type, I tried the valve from one with the same results. I have checked float condition and height and all appears ok. See photo, are these valves interchangeable? The original is on the right with two holes and 1.75 stamped on the side. Also I have an inline pressure regulator set at 2.5 but I can't be sure of it's condition as it was fitted by a PO. Scratching my head as to where to look for problems.
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PostPost by: h20hamelan » Wed Oct 14, 2020 11:45 pm

can you fit a fuel pressure gauge just before the carbs?
float height okay?
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PostPost by: h20hamelan » Wed Oct 14, 2020 11:52 pm

also, 99% of carb problems are electronic
have you tested spark

https://www.mactools.ca/en-ca/NoValue/N ... ark-Tester
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PostPost by: Evante » Thu Oct 15, 2020 1:32 am

I had a similar problem earlier this year. It turned out to be the timing.

Before coming to this, I also changed. The needle valves and adjusted the float levels.

You said you were getting poor performance and stalling. Why did you change the fuel pump?
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PostPost by: Neil D » Thu Oct 15, 2020 2:45 pm

I recently had the same issue with the rear Stromberg. The fuel pressure was too high due to a failed pressure regulator. If this has just started after fitting the electric pump the you'll need to fit a pressure regulator as 5 psi is too high I thing mine is set between 2-3 psi.

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PostPost by: lotusbc » Thu Oct 15, 2020 3:12 pm

I fitted a new pump as the old pump (Facet) had a very weak flow and no other issues were found. The car ran great one day and terrible the next. I ran the car about 25 miles after fitting the pump and it ran well, no fuel smell. The fuel is coming from the front carb only. I do not have a pressure gauge of any kind to test.
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PostPost by: Craven » Thu Oct 15, 2020 7:19 pm

How is the dual feed arranged, maybe the first carb to be fed is relieving the pressure on the second carb by continual discharge.
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PostPost by: Neil D » Thu Oct 15, 2020 7:48 pm

I have to say this sound like too much fuel pressure. When the regulator failed on mine nor the rear carb was affected, fuel just pored out of the float chamber overflow. Rebuilt cabs and found the regulator failure which I replaced- problem solved.
Put the old pump back on and I bet the issue goes away.
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PostPost by: lotusbc » Wed Oct 28, 2020 5:56 pm

An update. I have had the carb off again. I had the the float out and it floats as it should and is set at 17mm. The slightly sticky original needle valve is replaced from my spare carbs. Had the pressure control valve out, it's the commonly used type (Filter King) with the .5-5 psi dial on the top. I don't have a pressure gauge to test it but blowing through the valve it does increase and reduce the pressure. All fitted back on and fuel still runs out of the overflow hole. Not as much as before, more a trickle than a stream. So, put the old fuel pump back in and it is the same. Has to be the carb or the regulator. I'm leaning toward the regulator as culprit.
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