Fuel starvation?

[droopsnoot]

I went for a Facet Silvertop, but that's because I wanted it in the engine bay as I didn't want to remove all the interior to run a wire to the back. Turned out it probably would have been quicker to do that.

The regulator is, I believe, a Malpassi Fuel King - like a "Filter King" but without the filter as I have a separate one.

I think the key to what it suits is more down to the pressure regulator, as some of these electric pumps send out too much fuel and overwhelm the needle valve in the carb, leading to overflowing. I'm on twin Stromberg CD175s and it's been fine on those. I don't have a fuel pressure gauge in the system so I don't know what it's set at, just that nothing has overflowed.

I took the opportunity to swap all the fuel hose for new-spec stuff (even though the car was only rebuilt a few years ago, it was with old-spec fuel hose) and that's what took most of the time. The new 1/4" pipe has a larger outside diameter and a smaller bore, so it was pretty difficult to persuade it on to the various fittings in some parts.

[reb78]

Thanks for that. That seems like a good setup. The Filter King or Fuel King look like they will do the job. How do you work out the ideal stock pressure for the carb? Is it listed anywhere like Autodata or Haynes? I have a copy that covers the Magnum but they are in the workshed and I am inside! Or is it just a case of tweaking the pressure with these adjustable regulators until you get it running well?

[droopsnoot]

I think the data you want is for the carburettor more than the car itself, I seem to recall reading about it on various Triumph-related pages when I was looking for information on how to set my carbs up, as they used Strombergs in some markets. I've read similar information for the Dellortos that I have on the Firenza. As yours is a Zenith, maybe Burlen Fuel Systems would be able to offer advice on ideal pressure.

As I don't have a gauge, though, I got it running and just kept turning it down - I don't think I ever reached a point where it made any difference, but I haven't done much road testing of it in terms of sustained high-speed running which is where I might discovered I've turned it down too far. A gauge would be ideal, but because the fuel pipe is so difficult to get on and off the various connections, I don't relish the thought of fitting it, so as everything seems to be working it can stay as it is.

The one thing I have yet to do is fit the inertia switch to cut off the fuel pump in the event of a shunt. I've got the switch, made a bracket, just haven't yet sorted out the special connector it needs to wire it into the car. That's on the list for over winter.

[reb78]

Good point ^^^ . There is some good info here that could help with my question I think - http://zenithcarb.co.uk/zenseriesiv/?___store=zenith

Even though the pressures arent stated, they do mention some useful info under the Petrol Level section that I think could be used to set the pressure correctly? Copied below:

'Petrol level

This is set at the Factory 15.5 mm. down from the top edge of the f1oatchamber. It should be explained that this level is that which should result when the top half carrying the float is in position on the carburetter,
and the float is holding the needle closed against the pressure of the petrol in the fuel line. When the top half is taken off and the float is lifted out of the chamber the level will fall.

To check the level remove the top half and leaving the float in position reverse the cover so that the float arm closes the needle, then measure from the face of the gasket to the highest point of the float, which should be 32-33 mm.

The level can be altered by bending carefully the tag on the float arm that contacts the end of the needle or an easier method is to vary the thickness of the washer under the needle seating, a thicker or an additional washer lowers the level. Needle valves and seating’s These are calibrated in millimetres, the size being stamped on one of the flats of the hexagon. This size depends on the fuel pump pressure and the capacity and power of the engine.'