Final word on electric fuel pump for carbs

[jefflit]

I've done a fair about of searching/reading but am unclear on how I should proceed with replacing my janky electric fuel pump situation (I have dual Webers and an external electric mounted under the car near tank by PO, with wiring zip-tied to hard lines under the chassis).

From the posts it is clear that I want low pressure (0-3 psi) and high volume. Also clear that putting a filter prior to the pump is ideal and that best location is low and near the tank. The question I have is external (i.e. Carter P4070) or internal (i.e. 1984 633CSi)?

An in-tank solution seems ideal if it picks up all the fuel and keeps the fuel gauge accurate. Does the 633CSi pump fit that bill? If not, is there a different in-tank solution?

Finally, if the in-tank option proves too complicated, I'm unclear on the actual pressure output of the 4070. Some say you can run it without a regulator, others measured it at 6 psi?

 

[bavbob]

Leslie Wong has a nice DIY for the Bavaria which may help.
http://www.lesliewong.us/tag/bmw-bavaria/

 

[Stevehose]

the low pressure/high volume thing is more for Weber side drafts vs down drafts. Stock fuel pump is about 3.5psi at 4k rpm so I'd run a regulator set at 5 or so but I doubt 6 would blow past the float needles.

My 4070 mounted to the diff with a regulator and filter in the spare tire well has proven to be reliable, no vapor lock or uptake issues, also no need to mess with the sending unit area.

 

[Nicad]

the low pressure/high volume thing is more for Weber side drafts vs down drafts. Stock fuel pump is about 3.5psi at 4k rpm so I'd run a regulator set at 5 or so but I doubt 6 would blow past the float needles.

My 4070 mounted to the diff with a regulator and filter in the spare tire well has proven to be reliable, no vapor lock or uptake issues.

Hi Steve, I think we discussed it years ago, but what safety shut off system did you go with? I rigged a switch off my oil filter housing, but I would also like an impact cutoff. I know I bought a Ford one on Ebay, but have misplaced it.

Also, if you have a photo of the pump mounted in it's location I would like to see it. My pump was mounted in the trunk initially, but that was out of necessity because I had no access to the underside at the time.

 

[Mike Goble]

I use the pre-supply pump from an E24, same as the ones from the E28. It installs in the original hole in the tank, the level indicator and switch wire right up, and it supplies a pair of Webers quite nicely.

I also have a Chevy Vega pump as a spare, as recommended by sfdon.

http://www.e9coupe.com/forum/showthread.php?t=22239

 

[Markos]

Watching this thread closely. I’m new to carbs so I never considered an inertia switch for the fuel. It looks like they are typically under $25. I'm switching to sidedrafts so I have an electric pump in my future. I feel like the mechanical fuel pump is the only reason why my project car runs. All the electric stuff is on the fritz and I have a short somewhere to boot. The old fuel pump works flawlessly though.

 

[Stevehose]

The impact switch is still on the to do list, I do have the rpm sensor which also acts a primer:

http://revolutionelectronics.com/Fuel_Pump.html

Pump (there is a dense foam pad cut to the shape of the bracket between it and the diff to give more sound insulation, plus the 3 rubber bushes it hangs from). I also put a dab of epoxy on the rubber connector boots to keep them from pulling off:

Hi Steve, I think we discussed it years ago, but what safety shut off system did you go with? I rigged a switch off my oil filter housing, but I would also like an impact cutoff. I know I bought a Ford one on Ebay, but have misplaced it.

Also, if you have a photo of the pump mounted in it's location I would like to see it. My pump was mounted in the trunk initially, but that was out of necessity because I had no access to the underside at the time.

 

[Ohmess]

I am running a pierburg pump just like this one - http://www.piercemanifolds.com/product_p/99009.131.htm - along with a Bosch (VW I think) inline filter installed in the trunk just like Stevehose's install.

My pump is attached to the subframe using the rubber isolation mounts, near where Steve has his, but my location was dictated by the desire to remove some damaged fuel line.

I've also installed the revolution electronics relay, which will kill the pump if it does not get a signal from the coil that the car is running. I also have a switch in the car to kill the coil signal manually, so if I crash, and am hanging upside down with gasoline spilling all over and the engine still running and flames starting to shoot up around me, I can kill the pump manually.

 

[Mike Goble]

If you are upside down the engine will stop running ( an automotive carburetor does not work inverted ), the floats will be at the top of their travel and fuel flow will be minimum. The gas in the tank will be at the top of the tank with the pick-up hanging out in the air, and the pump will be starved for gas.

 

[Ohmess]

To be clear, I only replaced the mechanical pump to make room for my setup. The stock mechanical pump was fine.

 

[NilsH]

@Mike Goble
Mike, you wrote in another thread:

I use the pre-supply pump from an E24, same as the ones from the E28. It installs in the original hole in the tank, the level indicator and switch wire right up, and it supplies a pair of Webers quite nicely.

Does your Bav tank have a single hole for a twist in unit or one with nuts and bolts? From the pictures of the E24/E28 assembly it looks like the pre-supply pump and level indicator assembly is mounted with nuts and bolts in a single hole. My CS have a twist in mounting so then it won't fit without modifying the fuel tank. Am I right here?

If you have any picture of your setup it would be great!

 

[Mike Goble]

@Mike Goble
Mike, you wrote in another thread:


Does your Bav tank have a single hole for a twist in unit or one with nuts and bolts? From the pictures of the E24/E28 assembly it looks like the pre-supply pump and level indicator assembly is mounted with nuts and bolts in a single hole. My CS have a twist in mounting so then it won't fit without modifying the fuel tank. Am I right here?

If you have any picture of your setup it would be great!

I drilled six small holes in the top of the tank and use sheet metal screws and the E28 gasket. I'll get some pics and put them in this thread.

 

[Mike Goble]

This is the setup I have. It's the in-tank pump from an E28/E24/E12 listed as 16141179425 in the RealOEM catalog, along with the sender 16121153050. I JB Welded a short length of copper tube into the outlet tube to adapt it to the existing fuel hose. I plugged the return line with a short length of tubing and some JB Weld. I adapted the sender wiring to match the new sender and plug. I ran some wire from a relay to power the pump, and the relay is actuated by a N/O oil pressure switch. It's been in my car for about 10 years and works very well. You will also notice I have a spare pump with a quick disconnect on it so I can change the pump in about 15 minutes, depending on how full my trunk is.

 

[mr bump]

This is the setup I have. It's the in-tank pump from an E28/E24/E12 listed as 16141179425 in the RealOEM catalog, along with the sender 16121153050. I JB Welded a short length of copper tube into the outlet tube to adapt it to the existing fuel hose. I plugged the return line with a short length of tubing and some JB Weld. I adapted the sender wiring to match the new sender and plug. I ran some wire from a relay to power the pump, and the relay is actuated by a N/O oil pressure switch. It's been in my car for about 10 years and works very well. You will also notice I have a spare pump with a quick disconnect on it so I can change the pump in about 15 minutes, depending on how full my trunk is.

Brilliant idea and set up!