Loosing power and some times engine will stop.

[Fritz Peyerl]

1972 911T with MFI


Few days ago I went on a drive with our local club. We stopped for 2 hr and than went on, the car started acting up and coming down a hill I had lots of miss firering and I lost power on and off.
Engine lost RPM and than picked up again. I decided to get a ride home on top of a flat bed. I was 60 km from home.
The tow truck managed to slide the car onto my hoist.
First thing, I did was checking the Pelican forum for any help. After reading all the threads, I am totally confused.
Car has all new fuel lines 1500 miles ago, new fuel filter canister, new distributor and rotor. New plugs and ign. Wires. Fuel tank was steam cleaned 1 year ago
Car was running strong and never gave any problems.
Following checks I did,
#1 remove fuel line from tank to pump and checked fuel flow.
Fuel run freely
#2 compression test all cylinders where at 120 to 125 psi
#3 just for the hell of it, done a leak down test results where under 10 %
#4 checked plugs -bit black, but not fouled
#5 checked for spark and all Cylinders are firering
#6 installed plugs and checked timing and dwell – both ore in factory specs
#7 installed a pressure gauge between fuel filter and MFI input

When starting up and idling pressure builds up to 15 psi, pressure stays same when revving up to 3000 rpm.

I felt safe enough to take the car out for a spin. Outside temp was 10degr. Celsius or for you Americans it was 50degr. F. the car run well for aprox 10 miles and than started to act up again. Operating temp was less than 180 degree.
The pressure from the pump to the MFI input went down to 5psi and less (fluctuating)
I stopped for a few minutes and tried to start the car again, it run for 2 or 3 minutes and got me closer to home again. When it started up the pressure was 15psi and when it started to act up again, the pressure went down.
I had a few down hill sections on my way home, so I turned off the ignition and coasted down hill, on the bottom of the hills I popped the clutch and the car started up strong and got me up the hill again.
It looks like that the fuel pump get’s warm and starts acting up.

Since I have a full tank I did not want to drain the tank, but this will be my next step, to make sure there is nothing floating around and obstructing the strainer.

My self, I lean towards a defective fuel pump.

My question is if I can’t find a used fuel pump with the ending numbers 0001, than who would you recommend to rebuild my pump or what is the consent about using a Walpro rotary fuel pump and a fuel bypass regulator.
I rather get my pump rebuilt, buying a used one, you never know what you get.

[Eddyvdw]

I had exactly the same symptoms with my car.
Turned out to be the in tank filter.
Also pulling the tank vacuum was not smart...
Sure your breather line is clear and tank filter not dirty?
If not, then it must be the fuel pump :-(

Ed

[Fritz Peyerl]

Hi Ed

Never thought about the vent line, will do that when it get's light out.
Love your City, Praque is such a beautiful City, I cam from Vienna and we have similar architecture.

[john walker's workshop]

restricted fuel flow to the electric pump would be my guess.

[Eddyvdw]

Vienna, Budapest and Prague were once part of the same empire so quite alike.

Greetings from Prague!

Also a picture of the breathing system and my dirty filter ;-)

Gruss,
Ed