Hi guys

I currently have an electric fuel pump on my EFI system in the car connected to the throttle body by 3/8" outside diameter aluminium tubing. I will be removing the EFI system and installing dual carbies.

I understand that I can't use the EFI electric fuel pump due to the high pressure and that I need to either install a new electric pump with reduced pressure or install a mechanical fuel pump.

I have the following question:

1. Ideally, I would like NOT have to replace the existing 3/8" aluminium tubing from the fuel tank to the rear. Can I simply bypass/disconnect the existing electric fuel pump, directly connect to the fuel tank, install a new mechanical pump and directly connect that to the 3/8" aluminium tubing? If so, are there any off the shelf "reducers" that will drop the diameter down to the correct size for the mechanical pump and fuel tank?

2. Is there a simple way to reduce the pressure in the existing electric fuel pump?

3. Any other suggestions?

Regards
Greg

Two to file under your option 3 I think Greg.

Presuming you have a return style system with TWO fuel lines running between tank and engine (one for supply, one for return), I would:

a) Replace the existing EFI pump with a low pressure electric pump and a good quality low pressure return style regulator and keep the lines as they are (my preference).

or

b) Leave the existing EFI pump as is, but replace the EFI regulator with a good quality low pressure return style regulator to step the 40+ PSI down to the 3.5 PSI that your carbs will like. This is similar but different to the "reducing the pressure in the pump" idea of option 2.

Technically you CAN do your option 1, but it's a bit of a hack IMHO and doesn't really gel with the "do it right" theme.

Thanks Dave

I didn't think you could use a "return" type system with dual carbies?

Regards
Greg

Hi Greg, I had a similiar scenario a while back.

My 70 Bug had an EFI rotary engine and had 2x 10mm fuel lines fitted through the tunnel and an electric pump under the tank.
Same deal, I didn;t want to run a new line or electric pump as I was fitting a stock VW engine back in.

I found 8mm-5/16" fuel hose had enough give to fit the 10mm rigid pipe so I capped one off and used the other as a supply fuel line.

Beside the gearbox I used a generic plastic fuel filter like this



That acted as a reducer allowing me to drop the fuel hose size back down to 5.5mm on the outlet side to suit the VW fuel line that comes through the firewall tinware from the fuel pump.

Hi Joel,

What did you do regarding the higher pressure electric fuel pump?

Regards
Greg

I removed it and ran the stock mechanical pump.

It had been fitted under the tank near the mastercylinder so I just ran a new hose straight from the tank to the line in the tunnel

Cool!

you could just take the hoses off of the fuel pump and put a z200 etc fuel filter in between them, just leave the return line as is .
just put a stock vw pump on the engine .

Thanks Ian

Regards
Greg

http://www.vollks.com.au/store/D.I.S.-Ignition-System-Compufire.html 
.

I'd go with Sides first idea as you can buy elec fuel pumps at the correct 3.5psi output. This then means that you don't have to worry about any overfuelling issue or having to shim the mech pump to reduce the pressure it creates.

Also, with the build quality of mech pumps these days you are also better off with the elec option for more reliable and troublefree motoring

How come no efi ?? Nothing wrong with dual carbs though. Use the larger line that's been installed and either step it down to the right size for a mechanical pump as that should supply your motor just fine and cap off the spare return line. The CB and empi inline electric pumps put out the right psi for webers, I think they are a walbro manufactured?? I think Rod has them on the shelf. Return style regulator systems are waaay overkill for what you are doing but good. DO not dead head regulate the efi pump down to 3 psi for a few reasons.

The little drag buggy I'm running has a cb inline electric pump and no separate regulator, works fine with 48 dells on a 2.3 160hp +

Hi Owen,

Whilst I would have really liked to have had the EFI system up and running it was going to take far too long with too much mucking around to get the car back on the road due to the fact that there would have been a lot or transporting of the new partly built motor and the car around from my place to Rod's place and to the Dyno etc. I was getting concerned that the initial run in of the cam and motor was also going to be compromised. Also, the cost kept adding up and it was looking to be economically impractical.

I really wanted to have a turn key solution so that Rod would supply everything (and be totally responsible and comfortable with the "technology" we are using), and get the entire motor properly configured and running so that all I needed to do was to unbolt it from his chassis dyno take it to my place, bolt it in and start her up! With the EFI configuration that just was not going to happen in a relatively short timeframe.

Having said all of that, I am still hoping to get the EFI configuration up and running sometime in the future once I have run the motor in and have had sometime to enjoy driving the car as the manifolds, linkages etc that we will be using for the dual carbs setup can be used with CB EFI Throttle bodies. So, I am planning to leave all of the wiring harness etc in the car.

Regards
Greg

Joel's suggestion seems OK too, but if there's the potential for going back to EFI then should also think about what's easier to do/undo.

When I built my car I put in a return style fuel system (with dual Webers) because I knew I'd likely one day go to EFI. Overkill yes, but it made the convert to EFI really easy for the fuel side of things at least... just a case of use the existing pump as the lift pump, add the swirl pot and EFI pump inline, change to an EFI regulator and plumb in the throttle bodies instead of the carbs and job done.

In all seriousness tho... since Rod's going to be doing so much of the work, what does he say you should do ???

Hi Dave

Rod and I discussed this yesterday and agreed that the simplest way was to install a new electric pump which he gave me yesterday.....I'm just doing some more homework.

I need to check how the existing EFI pump is connected as I have a feeling that it is connected to the ECU for shutting it off in the event of an accident. I need to see how it is wired and will be hopefully doing that today.

I'll let everyone know what transpires.

Regards
Greg

Hi Greg

To make your fuel pump operate safely you need to use either a special tachometric relay or a double through relay, have read of my long winded post http://forums.aussieveedubbers.com/viewtopic.php?tid=92649&page=1#pid862368 

Steve

Hi Steve

I'll definitely have a read.

I removed the tank to see how the currently installed fuel pump is installed and wired up. I traced the Positive terminal from the front of the car to the area under the rear seat where the ECU and Alarm system are installed.

It is attached to a Narva relay ( http://www.narva.com.au/products/browse/fused ) and is attached to terminal number 87 (that's the light grey wire in the attached photo marked A) in conjunction with a wire leading to Idle Control for the EFI (the green wire marked B).

There doesn't appear to be connected to the ECU but rather to the alarm?

Anyway, that's the update!

Regards
Greg

Hi Steve

The instructions I got with the fuel pump (it's packaged as EMPI but is stamped Carter) recommends a "safety circuit with oil pressure switch" be fitted.

Carter (not you mate!) seem to have such a switch ( http://www.jegs.com/i/Carter/180/A68301/10002/-1 ).

Regards
Greg

Hi Greg

When you get a chance to read my other post you will see that I used the stock oil pressure switch and only needed to fit a relay, it will be a Carter set up as well.

Steve

Thanks mate,

I had a quick read and missed the bit about connecting to the oil pressure switch.

Regards
Greg

Hi Steve

Just a quick update.

I fitted a Collision Safety Switch (purchased from Ebay) and a Peel CP30 Safety Switch from Peel Instruments ( http://www.peelinstruments.com.au ). both are about $30 each and are very easy to install and connect to the electric fuel pump.

The Peel CP30 basically provides power to the pump only when it detects a pulse from the tacho and for 2 seconds at start up in order to prime the pump. It also means that you can turn the key to "accessories" and the pump will not start.

Hopefully both of these switches provide enough protection in the event of an accident or other issue.

Regards
Greg