MFI Fuel Pump Replacement

Eric Lintner · 05-05-2007, 10:31 AM

Good Morning
I have a '70 914-6 with '72 2.4S and mechanical injection. A few weeks ago, I was driving home on the freeway after a little Sunday afternoon drive. The car started losing power and finally died at the off ramp. It had not been run much over the winter, so I suspected moisture in the fuel. After 30 minutes, I added fuel and some stabilizer and it started. I drove to the local Chevron and filled it up. It then died again 2 miles later. I let it sit a couple of hours, then it started and I drove it home. Suspecting the fuel filter, I replaced that, after which I've not been able to get it to run. I then ordered a "tested good" fuel pump which I connected to the battery, but it would not even spin the fuel pump motor. I returned that one and got a remanufactured pump. I primed it with gasoline, but it won't spin the motor, either. The old fuel pump I took out of the car was getting noisy, but it spins the motor. I guess my options are to return it, too, or assume I'm doing something wrong. Any ideas?

Thanks much!
Eric Lintner

Zeke · 05-05-2007, 11:22 AM

MFI fuel pumps are much different than the carb version. You have the right part to start with? They cost well north of $400.

BTW, welcome!

Eric Lintner · 05-05-2007, 04:36 PM

Yep, same part as listed for a 911 of that vintage with MFI (Bosch 0 580 970 001 or Porsche 901 608 105 00) and looks same as the one I removed originally.

Thanks,

Eric

Grady Clay · 05-05-2007, 05:57 PM

Eric,
Welcome to the Forum

You will find a lot of help here.

These are the usual symptoms of the screen filter in the fuel tank clogged with contamination/rust. A 914-6 (and four) tank has similar issues as a 911.

What is happening is the recirculation of the fuel puts debris and rust at the electric pump inlet filter screen in the tank. When enough is present, it blocks the fuel flow and eventually there isn’t enough fuel to run the engine. When you turn off the pump the circulation flow stops. Some of the debris then falls off the screen and you can re-start the car.

The fix is to remove the tank for cleaning. Most important is to remove and clean the filter screen integral with the fuel outlet fitting to the pump. Typically 914-4 screen fittings were plastic. The better part is the brass OE 911/914-6 part.

With any 914 conversion to MFI, the fuel filter console needs to be plumbed correctly. There is a bit written about this as Porsche published published an incorrect fuel plumbing diagram. Occasionally conversions follow the incorrect diagram. All is posted here on Pelican.

OE, a 914-6 had the pump just aft of the rear bulkhead. A very important mod is to move the pump to the front cross member as ’69-’70 911 and later 914-4s.

I too have an original ’70 914-6 - - with a 2.8S MFI for the street. You have the best-of-the-best hot-rod. The classic “Wolf in sheep’s clothing.”

Best,
Grady

Howard Taylor · 05-09-2007, 09:17 PM

Grady,

I have been waiting for you to give me some info on inspecting the plastic fuel lines in the tunnel. You asked me what year the car was and I responded with '72 and haven't heard from you since.
I also want to relocate my fuel pump to the front but I could use a sketch or a photo that shows the electrical details.