MFI & fuel pump relocation

elflamo · 02-09-2007, 10:48 AM

Hi all, I'm about to relocate the fuel pump from the rear to the front on my MFI car. I have two Q's:

- As the pump has two lines attached to the fuel filter, is it correct to simply extend these lines by using the existing 2 two hard lines in the tunnel and then attach to the front mounted pump?

- I guess I need to do some wiring to the pump. Can I tap directly from the front relay box, or do I need to extend the current wiring in the rear all the way to the front?

Thanks

Dennis

pjh69911 · 02-09-2007, 03:58 PM

Dennis,
You should tap into the wiring, via a relay and don't bother with the wiring at the rear of the car. If the fuel lines through the tunnel are in good shape, use them. You will have to adapt to go from the outlet of the tunnel to the fuel filter console, metal and or fuel injection grade hoses. You may need an adapter to transition from the larger 9mm pump outflow line to a 7mm line feeding the fuel filter console at some point. For connecting to the fuel pump up front, new rubber hoses. You might consider an alloy front crossmember as a good way to mount your fuel pump. Good luck. Paul.

Howard Taylor · 04-27-2007, 09:04 PM

Any photos available of the mounting location, electrical source and wire routing for the pump relocation?

rching · 01-29-2009, 08:49 AM

Photos bump

Grady Clay · 01-29-2009, 11:07 AM

There is a set of pieces that were on the ’69-’70 911E & 911S and ’70 911T . These bolted on the steel front cross member and supported the Bosch fuel pump. I think there may have been a ‘different’ front pan to clear this bracket. I doubt those are easily available.

Today I would use your existing fuel pump support bracket (911.608.120.00) and the two rubber vibration/sound isolators. You can weld two small ‘ears’ on the steel cross member to duplicate the mounting (angle) in the ‘fuel pump cradle’ that is welded to your left rear frame & torsion bar tube. These can simply be two pieces of steel ~20 x 20 x 5 mm and a 6 mm hole for the isolator fasteners. This keeps the pump easily serviceable with the screw-clamp.

If you have installed a cast alloy front cross member, you can make two angle brackets to bolt to the cross member. This configuration has more room for hoses, etc.

Your fuel tank outlet fitting (with screen filter) should have the larger 9 mm hose size to fit the inlet of the pump. Now it is just some 9 mm hose to the chassis fuel pipe.

The outlet of the pump is 7 mm and your two chassis fuel pipes are 7 mm and 9 mm. There is a VW hose about 12 cm long that is 7 mm on one end and 9 mm on the other. This makes a good adaptor.

The safety pressure relief in the fuel pump needs to be ‘teed’ into the return hose before the return to the fuel tank banjo fitting at the tank drain.

You should make the two hoses from the tunnel rear to the fuel filter console continuous although you will need to repeat the 7-to-9 mm hose adaptation. Put the adaptor where it is serviceable. I would run both hoses between the rear shock cross member structure and the firewall. There is foam insulation stuffed in the gap. It is useful to cover the hoses with an insulating sleeve. Aeroquip ‘FireSleeve’ works well. Be sure and zip-tie the hoses up to the chassis to not interfere with the axle or throttle linkage. Position the hose clamps so the screw is accessible with everything installed.

Absolutely use the pinch-bolt type Norma-Schellen hose clamps – not the common worm-screw type.

The control power for the pump relay can come from the ‘hot’ side of fuse 7 of Fuse Block I (10-terminal). The red/green power wire for the rear mounted pump is connected there. It can be disconnected and left ‘free’. I would tag it so someone knows what it was for.

The power for the pump should come directly from the battery B+ terminal. It is prudent to put a 20-25 Amp in-line fuse in the power circuit. The plug and wires at the rear are a separate ’pig-tail’ connected to the main harness. You can use this pig-tail harness at the front but you will need to extend it. This allows you to continue with the polarized plug. The pig-tail wire colors are black (ground) and blue (power). You can use this or change to the brown (ground) and red/green (power) used in the main harness (yes there is a color change across the connector to the main harness). I would use the common ground terminal under the cowl at the left. Use the proper brass 8 mm ring ground terminal. All the wiring is 1.5 mm, which is adequate.

I think any relay will do but there is a high-power (red) relay that may give more current capacity ‘safety factor’. There is a relay socket common to many models that has a single rubber mounting ‘tit’ on the back and the wired at the side. This is ideal for mounting in a single hole. A good location is in the trunk under the cowl, above your left knee. An extra relay and fuse is a good addition to your tool kit.

On my next iteration of this, I intend to silver-solder metric screw-type fittings on the chassis fuel pipes. I intend to use a CIS in-line fuel pump and an in-line filter (both with screw fittings) mounted to the front cross member. If needed, I’ll add a ‘bypass-type’ pressure regulator. This will allow most connections screw-type and higher quality hose. I’m not too concerned with exact originality with MFI in a ’68 or 914-6.

Best,
Grady

elflamo · 01-30-2009, 02:09 PM

Hey thanks for the replies.

Quite funny, I was just browsing the forum and came across this fuel pump relocation question that interested me. Turns out to be my own question from 1.5 year ago....

rching · 01-30-2009, 06:57 PM

And...... did you relocate that pump and how did you do it?

elflamo · 01-31-2009, 11:54 AM

Well..... my 911 project is not progressing terribly fast. It's not that I've had to battle too many motivational dips, but just too many other things that require time.

Anyway, I'm finally finishing up all the welding on the body and haven't even gotten to other stuff. March 16th the painter is coming to pick up the car though...

And yes, I have removed the fuel pump bracket and will move the pump to the front. Will update this thread then.

Cheers

Dennis

elflamo · 02-02-2009, 12:49 PM

Hi guys, I tried to draw up a little diagram with the fuel lines and connector sizes. Is this correct?

Thanks

Dennis

elflamo · 02-02-2009, 12:53 PM

Also, I was wondering where I can get the mentioned VW fuel line that goes from 9mm to 7mm?

Thanks again

Dennis

Zeke · 02-02-2009, 01:03 PM

I don't think there's an actual factory part that reduces the size on the line. You would do this with hard fittings at the parts store. If you search using Grady's name and fuel lines, You may just find a complete schematic.

MikeDL · 04-19-2009, 04:50 PM

I tried to plan this out today for my car and order the bits I'm missing. I have 9mm (-ish SAE) hard lines through the tunnel, but all the other barbed connections (MFI filter, fuel pump, fuel tank) seem to want an 8mm id hose. So I have to get from the 3/8" inch hose the hard lines want to a 5/16 hose the other places want.

I've looked around for both the VW line Grady mentioned and the hardware Milt mentioned. No luck finding a VW part like that, and nothing obvious in the fuel line hardware area at Summit Racing. Any suggestions?