Lotus Elan and Lotus Elan Plus 2 Forums

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.

can you fit a fuel pressure gauge just before the carbs?
float height okay?

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

https://www.mactools.ca/en-ca/NoValue/N ... ark-Tester

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?

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.

Neil

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.

How is the dual feed arranged, maybe the first carb to be fed is relieving the pressure on the second carb by continual discharge.

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.

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.

With better weather now here I am back to tackling this issue. Today the carb was tested with the new pressure gauge set at 2.5 psi. Fuel line is direct to the front carb only, obviously the engine is not running. I still have a trickle of fuel from the overflow. Carb has been out, floats are in good condition (replaced by po). Floats have been set and tried at 17mm and 18mm WITH the gasket in place. The original needle valve does appear to be sticking (original issue?) and so I have replaced with a valve from a spare CD175 carb. The valves are different, interchangeable? The original is stamped 1.75. The sealing washers are not the same, I have .060, 061 and 063. Currently the .060 is fitted. Thoughts ?

Definitely buy some good quality float valves before wasting your time. Triumphs use those carbs and have similar problems. One of the valves shown is aftermarket.junk. Try to obtain OEM parts. Probably Burlen fuel systems have them. Last year one of my customers brought a neat kit for his car with adjustable main jets. Original calibration does not work well with modern gas.

I have same fuel leaking/pumping from rear Stromberg condition (Federal S4). Carbs were sent out and rebuilt last year. It started (Pertronix distributor), but then the water pump failed and fuel sat in carbs for months. I had the head off for the water pump rebuild, and the cam gear timing marks are facing each other. When water pump was rebuilt and reinstalled I tried to start it, but got little/no fuel pressure so I sent the original AC pump out for rebuild. As replaced pump parts were returned with no spring, I assume original pump spring was re-used. I pulled the carbs and checked the float height and float valves as OK. Removed float valves, squirted carb cleaner through each, blew through them and replaced them.
I got it all back together and I am having the same problem.
Initially it will run rough with occasional backfires and eventually very rough and starts spitting out fuel. I checked the timing and reset the distributor a couple of times. I started with rotor pointed at no.1 plug wire and advanced the spark to maybe 15 degrees once I got it running. I'm using 90 octane no alcohol gas.
Any suggestions before I reluctantly pull the carbs again? I expect to find clean float bowls and clean float valves again.
Dick