Have you verified that the microswitch on the throttle body that energizes the CSV is closing and providing power to the CSV?

This is getting difficult.

Try this: after the engine has sat for one hour, turn on the ignition so that the fuel pump runs. Take off the air filter and reach up into the air plate and lift it until you hear the injectors squeak. They should squeak as soon as you lift the air plate. Then try to start it.

Two guys here (one of them was Phil) had a problem last year where the FD plunger was getting sucked up by some negative pressure in the fuel system, causing the FD to have to re-prime before it would restart. There is a small spring that fits on top of the plunger in later non-Porsche CIS systems that prevents the plunger from lifting, and that fixed their problem.

I don't know if this will fix your problem, I'm mentioning it to get Tony thinking about it again.

I would post the link too that thread, but I didn't find it in my forum search.

I see.

So, without a temperature controlled device, doesn't it necessarily mean then the driver needs to know when the engine's "cold" enough or not to require activating the CSV via the hand throttle ?

Yep, you just have to know. For me, the rule is "When in doubt, you use it."

Harry, it is a new filter too. I really thought I systematically checked all the usual suspects before reaching out to this team.

I have no reason to believe the battery is not holding enough charge, and not spinning the engine fast enough. It works fine when cold. But I'm going to check the voltage and give a full charge before my drive later today.

I did take the cold start injector out, put it in a jar, and cranked the engine. It did result in gas in the jar. I do not know any volume numbers.

Jay, I must say you are dedicated to your car. I've read quite a few of your threads over the years. You've put quite a bit into rebuilding and replacing parts. Loren even entertained you a bit in one of them.

While you seem to have moved past this question, has your rear console been modified? It looks like some wiring has been removed. Even though they are not used, the Aux start and single stage defrost socket would originally have been there.
http://forums.pelicanparts.com/uploa...1711668971.jpg
http://forums.pelicanparts.com/uploa...1711668971.jpg

Here is the 73.5 wiring diagram I made.
http://forums.pelicanparts.com/uploa...1711666199.jpg
The only fuse installed should be the red one in position 3 (top) for the rear defroster. Fuse 2 protects the Aux start relay and Fuse 1 is for Sportmatic, which are not used. Power from fuse position 2 to the WUR is from the non-fused side.
Anyway, the WUR relay picks up power from the regulator D+61 and WUR itself get power from the ignition switch pin 15 when the key is in the run/start position.

To answer a couple of your older Thread questions to the best of my knowledge, which others can correct:
The 002 fuel distributor was on a few of the very early '73.5's, and then the 004 was used. When they refer the the mixture control unit in '74 being recalibrated, that is basically the air flow plate. The 0 438 120 002 was for the '73.5, and the 0 438 120 004 had a different plate and venturi shape calibrated for the 2.7l, but still used the 004 fuel distributor.
You had asked if you could test the TPR by blowing through it. You would need a bit more pressure to test, and the ones I have only seem to flow in one direction with a fair amount of pressure. I use a syringe and rubber hose connected to the smaller inlet nipple. It would be hard to test with the hose and banjo fitting on. When testing the TPR, it specifies warm pressures. The engine does not have to be warm, but 12v should be supplied to the WUR and warmed up. Idle and full throttle should be about the same, with an increase of about .5 bar in the mid range position to slightly lean the mixture.
Just to get a baseline of where you CIS is now, what are the numbers for the mixture control unit, fuel distributor and WUR?

Great stuff.

I got his car 1988, with only 44k miles on it. It had sat for 10 years without use at that point. My first car was a Sunbeam Alpine in 1978, that I kept running over the years. My dad was a 50s rocket scientist and brought me up working on his '66 911, and other cars. So I always want to do what I can on my cars.

Yes, I have had problems with the CIS over the years, and kept tracking down the issues. And I truly appreciate the support I've received here.

I did end up buying a NEW TPS from Porsche. It solved a number of problems. I have gone through a number of WURs over the years. They simply have been problematic. I am now running a beautiful 001 which is in fact working very nicely, and seems to match the engine better than the 129 and 008 that I've used. I could never get the mixture right to work in all temp or driving conditions right, except now with the 001. I don't know why. But it's a fact.

Here are the current numbers (all are to spec):

System pressure: 4.55
Cold Control Pressure: 1.85 at 66 degrees. Right to spec.
Warm Control Pressure:
Idle 3
Part load: 3.7
WOT: 3.1
Leak down after 20 min: 1- 1.3 (did it multiple times)

Oh, and I have no reason to believe that the wiring there has been modified. It all looks sound there. I haven't owned it since new. But given the condition I got it, and the condition it's still in, it seems pretty unlikely. I will see if those sockets have perhaps been pushed down inside. But I know there is definitely not that many wires down in there.

FWIW, my 1973.5 can be cantankerous to start hot or cold. I have noticed it is most cooperative when I place the key in the run position, let the pump run for 20-30 seconds (like lighting a joint and taking a few puffs :eek:) before cranking. Since it seems to mostly work, I leave well enough alone.

I will try that. I will say that I normally wait until I hear the injectors all sound like they have filled and the fuel pump changes its tune. I don't think that is usually 20-30 sec. Usually less. And the problem I'm having is that I have to crank and crank many times before it wants to even give any sense of ignition.

I'll first get a little burble of ignition trying. If I can stop the starter spinning at that moment, it tends to catch. But that may be coincidence as well.

Hmmm. New fact. I just had my 12v tester light hooked up to the CSV switch. As I understand it, that should have power when the starter is cranking. My light showed nothing.

I'm going to have trace that.

Indeed.

A few years ago, I was having a hard start issue both hot and cold. I discovered that when I was chasing an oil leak, I had inadvertently pulled the power connector to the CSV.

Any suggestions where the starter powered hot line come from to go to the CSV micro switch?

It doesn't show in the CIS wiring diagram above, or in Ed's picture above.

Now that I think about it, I recall a post by someone somewhere about hard start problems and they may have mentioned the wiring from the starter with this wire can be a problem.

Separately, I'm looking at a 1972-3 wiring diagram. It shows a #14 Temperature Time Switch, with the same color wires, and that goes to #52 Auxiliary Starting Relay. First, as indicated above the 73.5 did not have a TTS. But then neither did any other 72 or 73, right? So what is that? And if it is the TCV micro switch, where is that relay?

Jay:

It is in the Part 2 of the 1973 Wiring Diagram on the lower left side. Here is a blowup of that part.

http://forums.pelicanparts.com/uploa...1711749450.JPG

http://forums.pelicanparts.com/uploa...1711749450.jpg

Thanks!

I just recently bought the Porsche Service Manual for mine, I was tired of searching and saving bits and pieces.
Harry posted while I was scanning, but I'll toss mine in anyway.
12 Cold Start Solenoid, 13 Control Pressure Regulator (WUR), 14 Micro Switch.
http://forums.pelicanparts.com/uploa...1711750791.jpg

Jay, that last bit of info may be a coincidence, or it may indicate some electrical involvement.

Remind me, did you try starter fluid spray to help start it? Did that make a difference? If not, then it's most likely related to spark, which would also point to electrical issues.

I would make damn sure all the grounds to the CDI, dizzy and other igntiion parts are clean and secure, and the ground strap to the transmission is clean and tight. Then I would pull all the connectors apart, espeically the engine 14-pin connector, and make sure there isn't any corrosion. Pull them apart and plug them together several times to clean the contacts.

Am I misunderstanding how this works? I confirmed that when I take off the lead from the CSV to the microswitch (taking off the microswitch side), and I attach my test light to that wire, when I crank the starter, the light goes on. So power is getting there (from the starter through the CSV to the switch).

But when I put that lead back on the microswitch, and crank the engine with the test light attached to that post (and the switch "on"), the light does not go on. I would have thought if the switch went on, that would have lit the light too. When I put the multimeter up to it, it's not showing 12V while cranking either.

So I'm thinking the switch is broken or intermittent.