74 CIS Needs pumping on pedal to get started????????
 

I hoping someone can help out here. I am new to this CIS setup. My 74 2.7 will not start on its own when cold, even with the hand throttle pulled up. It will want to fire once while cranking and then nothing. If I catch that one time it wants to fire and I start pumping on the gas pedal, I can get it to start. She's not happy when I do this as its poping and sputtering. Once I get it going its no problem, runs great. I can even shut it down and its starts right up with just a turn of the key. But once it sits overnight its the same story again.

Does anyone know whats going on. Any help would be appreciated.

cold start
 

The cis system has a cold start injector as does most if not
all fuel injection systems. It sounds like your cold start injector
is not working. One way to check this although difficult to do
due to the location of the injector is to remove the cold start injector from the air box. (two allen screws)
Hold the cold start injector in one hand and point the injector into a container away from potential sparks. Have an assistant
start the engine after sitting for some time. It should spray
briefly. I've been told by several Porsche shops that cold start
injectors as a rule don't clog up like regular fuel injectors.
Additionally, look at the back of your airbox. Directly below
the fuel distributor ( firewall side) is a fuel hose leading from
the fuel distributor to the injector. There will be a small white
two prong plug ( 74 cis sysyems). Make sure that is connected.
On 74 cis they can easily come out for a variety of reasons.
If you do remove the cold start valve to check for spray make sure
you replace the rubber o-ring on the spray pintel. There is a
circuitry for the cold start system as well, auxillary air regulator
and timer If I am correct on the 74 cis.

Bfrenz,

Are you sure your hand throttle is functional? The plastic lever on mine deteriorated and I thought it was working correctly, but I replaced it this spring and the car starts much easier when cold now. The biggest problem I had was that my plugs were gapped too wide. Have you recently changed/regapped your plugs?

Could be your cold start injector-be careful not to loose the tiny rubber o-ring that seals it to the engine when you remove it to test. before I checked that...I would test to make sure that there is fuel in the accumulator when engine is cold. The fuel could be draining backweards leaving nothing but air in the lines. Could be a bad check valve in your fuel pump.

possibilities:

1. hand throttle lever connecting hand throttle to actual throttle cable in tunnel broken and deteriorated. have replaced two for friends with non-functioning hand throttles.

2. hand throttle simply out of adjustment. requires a small flathead screwdriver to be used in the tunnel under the hand brake assembly to move the position of the metal slider on the actual throttle cable. if this part isn't butting up against the adjacent lever, then the hand throttle won't work. it's a simple device. the 'hand throttle' movement actuates a lever that pushes against a part attached to the throttle cable. this will physically 'move' the accelerator pedal. it isn't a 'choke', it literally performs the function of your foot on the gas pedal until the car is warm enough to not need it, usually about 10 minutes until car reaches warm operating temps.

3. cold start valve not functioning as mentioned above or because thermotime switch (which signals the cold start valve to fire based upon engine block temp) is bad.

4. integral fuel pump check valve is really a hard 'warm start'.
issue. your warm starts bear out that the check valve is working properly.

probably not:

1. warm up regulator...because it runs fine when finally started.
2. mixture...same as #1...pull a plug or two to verify. oily plug, rich...whitish residue, lean...brownish reside, just right.
3. fuel filter...because car would start fine and gradually get worse as sediment which has settled overnight begins to get stirred up and enter the system.
4. air sensor plate...same as #1
5. fuel injectors...same as #1
ryan

I had the same problem and found my pop off valve was sucking air and needed to be reseated . The car starts fine now .
Jim

I have the same problem. mine is caused by one leaking injector which depressures the system after sitting for hours from what I can tell. I just leave the key on for a few seconds until pressure builds, apply a little throttle when cranking, and it starts. my sensor plate position switch is unplugged, so my pump runs when the key is on

John,

I think that is what my problem is. I happen to have a new set of injectors already and I am going to swap them out.

I have the same car 911 74' 2.7 L. I did a vacuum system check and guess what : Major vacuum leak (which is highlty needed when cold starting the car). Before starting to change parts, do the basics.
Good luck and bonne chance (same thing) !!!!!

I agree with filou, always check for vacuum leaks. I checked everything and the problem(s) I had with cold-starting were caused by:

- throttle lever broken and not functioning
- spark plugs were gapped at .060 and they should have been gapped to .030.
- bad plug wires


My car has been running and starting without a problem since fixing these...