cutting out resolved
Posted: Tue Sep 29, 2009 9:31 pm
Just been having nightmares with my engine (stock EX with weber in a '92 GT11) cutting out at 50-60 mph... Learned some stuff as I fixed it though, so this may be of interest...
I'd just get on a hill at cruising speed of 50 - 60, and the engine would stutter once, then die. This all started after spottining the rotten filler neck... Rust had clogged the filter solid, so a new neck went on, blew the fuel lines out with compressed air, ran a magnet over the bottom of the tank, put a new in line filter on, and expected the problem to be a thing of the past... It wasn't!
Next, I suspected the part which is variously described as a "swirl pot" or "fuel reservoir"... So I changed it, changed the fuel hoses under the bonnet... and went for a drive. Got about 2 miles again before it cut out. Got back home and took the carb off and cleaned it to within an inch of it's life. And thought I'd fixed it...
At this point, I drove it down to a garage who's good with this sort of thing, and left it with him. Later that day, £60 changed hands, and he regailed me with tales of how badly set up the cardb was, how it was icing, and how I should get more hot air into the carb... So I headed home and piped lots of hot air in... Went for a drive, and broke down again.
Next bit of useful advice was to put some hotter plugs in... which I did... and the engine died again on the way home.
At this point, I was suspecting electrics, so chaged the ignition module for a used spare, and got a new coil and fitted.
As you may have guessed, the problem persisted.
The fuel pump looks like new, so I had no reason to suspect it. Thought it best to check the output pressure though, so took it down to a guy who could measure it... Really good pressure (think it was 4.5 or 5 PSI) at the pump... but only 0.9 PSI at the carb !!!!! As a "it'll get you home" fix, he took the return pipe off the fuel reservoir and blocked it up (which messed up the mixture settings mightily)
At this point, I wondered just what was actually inside the fuel reservoir... so I took the grinder to the old one.
It really is just a pot with 3 pipes in, with a filter aroud the one which enters through the top. It seems the real use for it is to prevent vapourisation of the fuel (which can apparently be a problem with any car with the fuel pump mounted at the front, and not when the lines are all pressurised by a rear mounted pump.) and to allow re-circulation.
Obviously, in my case, too much fuel was re-circulating, and too little going to the carb, so I've put a tight fitting piece of brass bar with a 1mm hole drilled through it in the re-circulating pipe to reduce the re-circulting flow, and hence increase flow to the carb. A tweak of the idle screw, and I drove it home without breaking down.
... I'd almost forgotten what it was like. 
The real question is what's changed? I've run the car for a year - through the snow, through the rain, through the "summer", and then, suddenly, fuel pressure issues. Cars.
I'd just get on a hill at cruising speed of 50 - 60, and the engine would stutter once, then die. This all started after spottining the rotten filler neck... Rust had clogged the filter solid, so a new neck went on, blew the fuel lines out with compressed air, ran a magnet over the bottom of the tank, put a new in line filter on, and expected the problem to be a thing of the past... It wasn't!
Next, I suspected the part which is variously described as a "swirl pot" or "fuel reservoir"... So I changed it, changed the fuel hoses under the bonnet... and went for a drive. Got about 2 miles again before it cut out. Got back home and took the carb off and cleaned it to within an inch of it's life. And thought I'd fixed it...
At this point, I drove it down to a garage who's good with this sort of thing, and left it with him. Later that day, £60 changed hands, and he regailed me with tales of how badly set up the cardb was, how it was icing, and how I should get more hot air into the carb... So I headed home and piped lots of hot air in... Went for a drive, and broke down again.
Next bit of useful advice was to put some hotter plugs in... which I did... and the engine died again on the way home.
At this point, I was suspecting electrics, so chaged the ignition module for a used spare, and got a new coil and fitted.
As you may have guessed, the problem persisted.
The fuel pump looks like new, so I had no reason to suspect it. Thought it best to check the output pressure though, so took it down to a guy who could measure it... Really good pressure (think it was 4.5 or 5 PSI) at the pump... but only 0.9 PSI at the carb !!!!! As a "it'll get you home" fix, he took the return pipe off the fuel reservoir and blocked it up (which messed up the mixture settings mightily)
At this point, I wondered just what was actually inside the fuel reservoir... so I took the grinder to the old one.
It really is just a pot with 3 pipes in, with a filter aroud the one which enters through the top. It seems the real use for it is to prevent vapourisation of the fuel (which can apparently be a problem with any car with the fuel pump mounted at the front, and not when the lines are all pressurised by a rear mounted pump.) and to allow re-circulation.
Obviously, in my case, too much fuel was re-circulating, and too little going to the carb, so I've put a tight fitting piece of brass bar with a 1mm hole drilled through it in the re-circulating pipe to reduce the re-circulting flow, and hence increase flow to the carb. A tweak of the idle screw, and I drove it home without breaking down.
... I'd almost forgotten what it was like. The real question is what's changed? I've run the car for a year - through the snow, through the rain, through the "summer", and then, suddenly, fuel pressure issues. Cars.