troubleshoot this CIS problem please

[Sunroof]

Lets start with the engine being the 2.4 with the first CIS (1973.5T). Car ran great for a long run into the hills of North Georgia but on return, the engine died on me rather quickly at several lights. The first time I pulled over I figured the engine was not getting fuel. I had a spare fuel filter (existing filter has only 2-3K miles on it) so I decided to change it or start to change it. I relieved the pressure soaking a small towel and re-tightened one fitting. I decided to forego the change and try the start up again. The fuel pump is howling, the CDI is humming and the car starts right up! Vapor lock? Bad fuel filter (purged by opening)? Do I have a bad fuel distributor? I manage to get home okay, but as soon as I get into my driveway its dies again. No start up but I can feel the fuel line from the fuel pump flowing.

What are the signs of a failing fuel distributor? Anyone else have this problem with early CIS?

Thanks

Bob
73.5T

[47silver]

sounds electrical
remover you distributor, reset the points check all of the wiring.
i had a wire touching the distributor cam that caused me to shut off and intermittent starting/stalling.

[Lapkritis]

Pressure gauges on fuel distributor. A tired fuel pump will recover efficiency when it cools off. Lots of other possibilities too.

[ossiblue]

Two good suggestions have already been given and it would be best, IMO, to follow them to eliminate the most obvious possibilities. Be sure the electrical is sound, then check the fuel delivery system.

As to your OP, the possibilities you list are not as likely. Vapor lock? No, not likely on a CIS system. Bad fuel filter? Maybe, but it wouldn't be remedied by what you did. Bad fuel distributor? Maybe, but these typically don't have intermittent issues like you described. Your fuel pressure tests will let you know if there may be a problem with delivery and then you can test/check the filter and FD.

I'm suspecting an air leak may be causing the engine to die at idle, or a combination of a fuel delivery problem with an air leak that results in a killing of the engine. Let us know your results of checking the ignition and fuel pressures. If those tests don't show any issues, air leaks will be your next area to inspect.

[E Sully]

Have you changed the whirl pot filter in the bottom of the tank?

[T77911S]

classic symptoms of a bad CD/coil. dies when hot then after a cooling period it starts up.

start with spark. it is the easiest thing to check. but it must be checked when it will not start.
once that is verified THEN move on to fuel.
ossi is right, fuel filter, vapor lock, FD pretty much at the bottom of the list if even on the list, especially for a car that is running.

after ignition move on the fuel pump. make sure it runs and if you can check pressures.

[Targa4now]

To aid in CIS troubleshooting, you may want to start by familiarizing yourself with the system as a whole. Below is a very insightful video I stumbled upon a few months ago that I haven't seen posted before.

Bosch K-Jetronic (CIS) explained on YouTube: http://youtu.be/a4fJAfXYxWk

Good luck!

[Sunroof]

Thanks for the responses. You know, I have had many issues with this CIS, being the first to be installed in the Porsche 911 (1973.5T). Some say, the damn thing shouldn't even be working! No thermotime switch (yes), no independent fuse protection for the fuel pump (runs off fuse 7 or 8 at the fuse box but not solely for the fuel pump), the first WUR that cannot be adjusted unless you pound the pin in, etc, etc.

I believe Sully might be right in looking at the mesh tank filter, but I replaced it once before and noted that the mesh can be cleaned and the filter re-used. I had the tank boiled and coated with "redkote" (remember those long threads guys?) and the redkote according to the manufacturer does not adhere to backlite (swirlpot material). The shop had no idea what the inside of a 1973.5T looked like and neither did I. I never did change out the mesh filter; I only replace the fuel filter. I believe that is where my problem lies. The tank might be dirty again from the redkote coming off the plastic baffles and swirlpot.

I will change the filter and take a look at what is coming out of the tank and take it from their.

Thanks
Bob