Improving CIS reliability?
 

I want to do some PM on my C2T to avoid being left stranded by an engine related problem.

To this end I will replace the DME relay and fuel filter.

Which CIS components are known to fail that will leave the car seriously down on power or in a no-start situation?

Fuel pressure accumulator? Fuel pump(s)? WUR?

:confused:

Hi,

What I did in my 89 930 was to replaced the fuel accumulator and the fuel pump relays.

tdh888

The Lee Rice electrical upgrade is a good one. Takes the load off the already overloaded fuel
pump fuse.

Checking and cleaning all
your electrical connections
is another.

I installed an inertia switch to the grounds of the fuel pump relays. The pumps start when I turn the key on. No more wondering if all the needed items in the engine bay will work.

The CIS system is an incredibly reliable system. I have traveled four times cross-country with nothing more than a set of fuel pump relays in the glove box.
I would be more concerned about having the right tool to fix any nagging issue that may pop up in your journeys.

You'll be happy to know that your car does not have a DME relay.
You could have your WUR rebuilt by Brian Leask and replace all vacuum hoses. Otherwise, that's about it.

A ha that is good to know :p So is there just a fuse for the DME and pumps in a C2T?

Will do on the Brian Leask part and the vacuum hoses. I still think a new accumulator is a good bit of insurance.

When a fuel pump fails is it typically the front or rear? Does one do more work than the other?

I think that the fuel pumps are powered by the Turbo control unit under the drivers seat but I'd have to look at wiring diagrams to refresh my memory.
If I were you I wouldn't get too carried away replacing stuff like the accumulator and fuel pumps. IF that stuff failed it's a tow home at worst, as opposed to it failing on an airplane. Believe me, you will find plenty of other things that you will need to spend money on with these cars.

Agreed but sometimes a "tow home" can be 1000 miles which costs $$$ and is a major PITA, especially if the wife is riding shotgun!
I would rather spend $1000 up front to reduce the chances of needing a tow :) I appreciate all the suggestions thus far.

Mechanical components such as most CIS parts tend to fail slowly over time, electrical components fail immediately. Replace any aging relays, fuel accumulator/filter and give the engine a tune-up. Other than that spend good money on tools and books to educate yourself on how the car works. Once you understand that, and have the tools, you can fix most things that might pop up on a long journey.

install a new crank sensor
or at least
change the crank sensor connector, they have a habit of disintegrating and you lose crank signal = no spark = dead car

The K-Jetronic/CIS fuel system found, OEM, on 930s does NOT utilize a "crank sensor" (nor does the ignition system). . . you must be thinking of another car . . .

correct you are but

a C2T does have a crank sensor that talks to the EZ-69

WOW, I didn't know that - thanks !!

...but it's a solid state Hall Effect sensor and those fail fairly quick due to manufacturing issues. The EZ 69 is more likely to go bad first and when it does EFI conversion is the cheapest fix.

Found this:

Before you decide to replace your fuel pump, make sure that your fuel pump relay is functioning properly. Also be sure to check to that your DME relay is working properly.

Fuel Pump/DME Relay, 911 Carrera 2/4 (1989-98), 911 Turbo (1991-98), 993-615-227-00-M76 $25.00

Looks like you got some bad info.
There are no CIS applications that utilize a DME relay.
There is a single pole relay in the fuse box for the pumps (R61). The pumps are triggered through the Turbo control unit under the driver's seat when ignition is energized and a speed signal is received from the sensor at the flywheel.
On the normally aspirated cars this position would contain the DME relay, which is a dual pole relay and energizes the ECM, injectors and fuel pumps, among other things (source: Bentley "Technical Data Without Guesswork" and "Porsche 964 Enthusiasts Companion").

That year, "1991-1998" is incorrect. The 993tt part number is for the years 1995-1998.

We have handled a few C2T "backdates" of CIS to the 930 system. Unplug all the electronics/EZ69 and put in the 930 ignition. Delete the Lambda system / frequency valve on the fuel head. All that can be done for <$1000 and some time if you are a DIY guy.
No opinion as to if this is best for you personally, just another option ...

The green wire/sensor on the distributor!