fuel pumps, whats the difference?

[hallsie]

Whats the difference between the barrel type fuel pump that most of us have on our wedges and a solid state facet type pump as seen in the below link.

http://www.mcgillmotorsports.co.uk/index.php?act=v...

Im going to be using the second on down on my Taimar to feed a 38 DGAS Webber carb, and removing the mechanical cam driven pump, but I was wondering what potential problems there could be running one on the V8 or V6?

Any thoughts?

Stu

[MrPicky]

This may already be obvious to you so I apologise if it is.

The fuel pump that is designed to feed injection systems runs at a much higher pressure than one designed for float chamber systems.

Float chamber valves can really only deal with a 3-4 PSI difference across them, the fuel injection pumps run at up to 50 PSI (which is bled down to 28-35 by the regulator.

A Lotus Turbo system we had on one car which had a sealed carburettor that was pressurised by the turbo had to have a special fuel pump that had a lower pressure regulator.

Hope this helps.

[mrzigazaga]

Hi Stu..I think Ralph also had a problem running the original 350i pump on a holley carb..There was way too much fuel pressure and it was flooding real bad..Ziga

[RCK974X]

There are in fact a range of pressures used on vehicles....

Carbs typically have about 3-5psi, and a mechanical or Facet type pump (or old SU works for these. Different sometimes for turbos etc.

Electronic fuel injection systems tend to be around 35psi.

'K' series injection (2.8 injection etc) use 75psi.

And there are others around too, for turbo, supercharged etc.etc.

So if going to carbs from injection, you will DEFINITELY need to change the fuel pump.

[hallsie]

Thanks all
Andy p, its for a Taimar running a webber carb, so the lower 3-5 psi should do it.

Stu

[ralph350i]

hallsie said:

Thanks all
Andy p, its for a Taimar running a webber carb, so the lower 3-5 psi should do it.

Stu

Hi Stu
Carbs need no more than 5psi and I run a red top facet pump on mine with a regulator, there a little on the noisy side but it works well, Cheers

[KelWedge]

Shell ones are Yellow/Red, BP are .............

Or dont I understand the question

[RCK974X]

I remember the extra pinning recommendation for the 38DGAS from a long time ago, as the brass inlet tube (fuel feed) can come loose - does that still apply ?

Also there are a few inertia switches around, which flip off in the event of a bump or accident as a safety feature. Not sure how common they are now, but such a unit used to be fitted to Triumph 2500 and TR6, and other injection cars too. They can be used for carby electric fuel pumps too, as an extra safety feature. Done that a few times.