Fuel system questions

[carfixer24]

I have 2 separate questions:

1. What should fuel pressure be for a Weber-equipped S4 Elan? The car has an electric fuel pump, and I may need to install a regulator.

2. What is the resistance range of the fuel tank level sensor? The gauge reads empty with approx. 7 litres in it, and I've got an 0L reading between the sender feed terminal and ground. The car has been completely re-wired with non-oem wiring, but I want to confirm the level sensor before chasing wiring.

[MarkDa]

You should only have a few psi at the carbs, too high and you'll force the float valves open - so regulate to under 4psi.
The great advantage of the perfectly satisfactory mechanical pump is that flow increases with rpm along with demand.

[nigelrbfurness]

I use a 2.5psi regulator with the Facet pump on my car. All my Elans - and there have been a few - have been converted to electric pumps at some point. Makes starting much easier and reduces the load and wear on the starter motor and ring gear, this being the main reason for my preference for electric pumps and you can hear when the float chambers are full so starting is immediate. Also, if it fails, which is rare in my experience, replacement is much easier. You also have the option for a security switch to remove power to the pump when the car is parked, making theft slightly more annoying for the the thief. However you do need an inertia cut-out (I use a Peugeot item) and a fused feed and if it is mounted in the boot, regular inspection of the pipework for leaks.

In terms of delivering enough fuel at high rpm, the mechanical pump is indeed satisfactory when in good condition.

JMHO

Nigel F.

[MarkDa]

Good point about the quick prime of electrical pump particularly if not using the car very often and the safety in having an inertia cut out is very sensible
No such niceties on my old MG Midget - presumably they just expected us to turn the ignition off if we survived the crash!

[alan.barker]

I think with a MG Midget the electric pump is SU type which is low pressure and no regulator needed.
On my TVR 3000M i have fitted a Huco pump which is low pressure to be located near the fuel tank.
It is much quieter than a Facet and doesn't need a regulator + inlet and outlet can be orientated as you wish.
Alan

[carfixer24]

This is the pump currently in the car, with no regulator. I suspect it's putting out too much pressure causing the carbs to leak into the intake. I'm going to pick up a test gauge today to verify.

https://www.summitracing.com/int/parts/ ... /overview/

I have an inertia switch, fuse, relay and a manual switch installed, and all work correctly.

[carfixer24]

Update:

Confirmed fuel pressure at the carbs is almost 6 psi. Ordered an adjustable 1-4 psi regulator. Now we play the waiting game.

[ericbushby]

While you are waiting, I would expect the resistance of the tank sender to be approximately 20 ohms when full and 230 ohms empty.
I modified a Minivan sender to fit, which works fine, but others have had success with the Landrover type.
Sometimes the slider connection seems unreliable when tested with a meter, but is steady when tried with 12 volts and a small lamp.
Eric in Burnley
Blue 1967 S3SE DHC ( will be at Tatton park on Saturday)

[carfixer24]

Thanks Eric... I think I may actually have a sender lying around from my days as a tech... maybe I'll see if I can rig something up with that.

[alan.barker]

Update:

Confirmed fuel pressure at the carbs is almost 6 psi. Ordered an adjustable 1-4 psi regulator. Now we play the waiting game.

Or fit a Huco pump low pressure + no noise
Alan