Twin Fuel Pumps K Series

[A7 OOH]

I have had a look through the archives regarding fuel pumps fitted to the K series and the need to drain, or remove the tank to replace.

Has any member fitted and additional pump(Facet) and filter unit to run via a change over switch for use in the event of a pump failure.

If so details would be appreciated

Cheers

Gordon

[revilla]

I don't think a Facet type pump would be of any use. They are generally low pressure pumps providing 2-4psi pressure and are really designed for simply delivering fuel, for example to carburettors. The tank pump used on the K Series is a high pressure injection pump and pressurises the whole system up to the fuel rail to 3 bar, which is more like 44psi. The pump itself will be rated even higher, probably 3.5 or 4 bar which is close to 60psi; the regulator at the far end of the fuel then bleeds off fuel to regulate the pressure down to the 3 bar rail pressure for which the injectors are calibrated. For a backup pump you would have to look at something like a Bosch high pressure injection pump, a Facet simply won't run the engine as it won't provide the pressure needed for the injectors. However, I'm not sure how practical it would be to plumb it in. Firstly I'm not sure how well a "dead" pump will pass fuel, i.e. whether the dead pump will act as an obstruction. Secondly the injection pumps are generally designed to run immersed in the tank. They tend to have a large (e.g. 16mm) inlet which is not really designed to be mated to a fuel line. In addition, although they are very good at providing positive pressure on the output side, being turbine pumps they generally have very poor lift capabilities and won't suck fuel up from the tank unless they are primed; when installed outside of the tank you would probably need a Facet type pump in addition just to prime it. When I built a test rig for running my spare engine, this was the system I ended up with - a Facet pump priming a Bosch, with a bit of a mess of silicone hoses, reducers and clamps to mate the Bosch to a fuel line and run it externally.

[revilla]

Like this:

http://www.revilla.plus.com/Facet%20&%20Bosch%20Pumps.jpg

[Mankee]

Sounds like more weight and complexity. When my pump failed, it did so gradually, rather than just fail to work, i.e. it couldn't provide the required fuel pressure at high loads. If you are paranoid, just bung in an uprated pump for about £90 from Merlin, which will provide years of service as well as future-proof yourself if you go nuts with power upgrades.

[elie boone]

There is no need to have a Facet before the injection pump, almost all performance external injection pumps are capable to overcome a 50mm height without aid.

[revilla]

@elie boone - I stand corrected if the pump can be installed with that little height difference.

[A7 OOH]

Thanks to all you Guys

Your explanation Revila was on the ball, I see now, why unlike my classic car installation the dual pump option on injection sytems is more complex.

Mabye its fix when necessary.

Cheers

Gordon

[elie boone]

Oeps it should have been 50cm.

[revilla]

I can't find the specs right now but I'm sure that the spec sheet that came with the injection pump I purchased specified a maximum lift height of 300mm.

[John Vine]

This idea sounds very like what Henry Royce did in the 30s on cars like the 25/30.  But in those days, of course, pumps did fail frequently, and the extra weight/cost was negligible.

JV