Graham2755
Member
Hi all, sorry to post about issues no doubt covered many times before, but.......
My P6 3500 V8 automatic is running a Facet Red Top electric fuel pump, mounted under the car beneath the rear seat pans, with the reserve tap located nearby. I've driven about 800 miles with that set up, and all seemed fine until a couple of weeks ago, when I noticed drips of fuel from the offside carburettor overflow pipe. At first this was all, a couple of drips. On 3rd May, I did a 60 mile round trip, during which the idle speed started to surge, high then low without any input from me. The low speed, part throttle response was faltering, only clearing with a bigger bootful of throttle. On returning home from that 60 mile drive, and parking in the garage, a sudden torrent of fuel came from the overflow, not just drips, making a patch on the floor 2 feet across.
I disconnected the fuel return line from the carb and blew air through it at about 1 bar, and could hear bubbles in the tank, so I'm assuming the restrictor in the fuel return line fitting at the tank end is unobstructed.
Today (4th May) I started the engine with a bit of clear hose attached to the carb overflow, and initially there was no flow of fuel from the overflow, regardless of revs. However, as the engine warmed up and the temperature gauge needle climbed midway through the green bit on the dial, the fuel started to flow slowly up the overflow. As I had clear pipe attached, I could see that when I increased the revs to about 2500rpm, the fuel in the pipe started to suck back into the carb.
I've read a lot of posts on here about electric pumps needing a pressure regulator (I haven't fitted one yet) as the Facet Red Top puts out about 6 to 8 psi and the SU HIF6 carbs don't like anything more than about 3 psi. So the fuel pressure could be blowing the float valve open, leading to the overflow and surging.
I'm puzzled as to why I've driven so many miles without this being an issue and has suddenly started, and also why the overflow doesn't start immediately, but only when the engine is warm? I should also say that running the pump with the ignition on but the engine not running produces no overflow. If it were a fuel pressure problem, wouldn't the float valve be pushed off its seat straight away regardless of engine running or not or engine temperature?
Before I go ordering a set of new floats and valves, I thought I'd ask here for advice.
(The car is running a standard V8, 10.5:1 compression, with original manifolds and SU HIF6 carburettors).
Thanks in advance for any ideas!
My P6 3500 V8 automatic is running a Facet Red Top electric fuel pump, mounted under the car beneath the rear seat pans, with the reserve tap located nearby. I've driven about 800 miles with that set up, and all seemed fine until a couple of weeks ago, when I noticed drips of fuel from the offside carburettor overflow pipe. At first this was all, a couple of drips. On 3rd May, I did a 60 mile round trip, during which the idle speed started to surge, high then low without any input from me. The low speed, part throttle response was faltering, only clearing with a bigger bootful of throttle. On returning home from that 60 mile drive, and parking in the garage, a sudden torrent of fuel came from the overflow, not just drips, making a patch on the floor 2 feet across.
I disconnected the fuel return line from the carb and blew air through it at about 1 bar, and could hear bubbles in the tank, so I'm assuming the restrictor in the fuel return line fitting at the tank end is unobstructed.
Today (4th May) I started the engine with a bit of clear hose attached to the carb overflow, and initially there was no flow of fuel from the overflow, regardless of revs. However, as the engine warmed up and the temperature gauge needle climbed midway through the green bit on the dial, the fuel started to flow slowly up the overflow. As I had clear pipe attached, I could see that when I increased the revs to about 2500rpm, the fuel in the pipe started to suck back into the carb.
I've read a lot of posts on here about electric pumps needing a pressure regulator (I haven't fitted one yet) as the Facet Red Top puts out about 6 to 8 psi and the SU HIF6 carbs don't like anything more than about 3 psi. So the fuel pressure could be blowing the float valve open, leading to the overflow and surging.
I'm puzzled as to why I've driven so many miles without this being an issue and has suddenly started, and also why the overflow doesn't start immediately, but only when the engine is warm? I should also say that running the pump with the ignition on but the engine not running produces no overflow. If it were a fuel pressure problem, wouldn't the float valve be pushed off its seat straight away regardless of engine running or not or engine temperature?
Before I go ordering a set of new floats and valves, I thought I'd ask here for advice.
(The car is running a standard V8, 10.5:1 compression, with original manifolds and SU HIF6 carburettors).
Thanks in advance for any ideas!
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