76' cold start valve troubleshooting.. need help

[calling911]

Anyone with a 76' I'd appreciate some help.. I just got the haynes manual today and started to troubleshoot why my cold start valve is not working. According to the manual its connected to two points..
1) the thermal time switch.. I checked that switch and it appears ok.
2) Throttle valve switch (micro switch)

I can't find any microswitch on my throttle linkage.. none.. no full throttle, no idle.. is this correct?

[calling911]

Nevermind.. I figured out where it is.. its on the body of the intake "plate"

[Jim Sims]

I am unable to check my wiring diagrams but I don't recall there being a throttle valve switch (micro-switch) in the CSV circuit on a '76. Take note that the Haynes section you may be referencing has information on the '73.5 CIS; later systems were different. After '75 the hand throttle and micro-switch were not used. Note that the CSV only operates while the starter is cranking.

[calling911]

Originally Posted by Jim Sims

I am unable to check my wiring diagrams but I don't recall there being a throttle valve switch (micro-switch) in the CSV circuit on a '76. Take note that the Haynes section you may be referencing has information on the '73.5 CIS; later systems were different. After '75 the hand throttle and micro-switch were not used. Note that the CSV only operates while the starter is cranking.

Its there.... and I am looking at 75' on up. Not sure what to say cept.. its there, I found it. Its right on the housing. The throttle valve switch is what allows the pump to run and the CSV.

My connector was broken.. I crossed the wires and the damn csv still doesnt fire.. so I gotta keep looking.. kinda hard to start when the CSV doesnt fire.. I have to manually lift the plate so the injectors squirt a bit before I start.. looks kinda funny in parking lots

[Jim Sims]

I think you've found the "airflow" switch on the metering plate (under and up behind the air filter). That switch indeed controls the fuel pump while in running mode (ignition switch to on position); the fuel pump gets power through an alternative route during starting. I do recall the '76 CSV power runs from the starter through a thermal time switch mounted on the DS chain case cover. There is a '75-76 wiring diagram in the Haynes manual; does it also show this CSV circuit running through the "airflow switch"?

[Jim Sims]

One other piece of information: the CSV and airflow switch wiring electrical connectors are mechanically identical - they can be mistakenly swapped for each other. The connector going to the CSV should be blue or have a blue dot on it. The connector for the airflow switch should be green or have a green dot on it.

[calling911]

Originally Posted by Jim Sims

I think you've found the "airflow" switch on the metering plate (under and up behind the air filter). That switch indeed controls the fuel pump while in running mode (ignition switch to on position); the fuel pump gets power through an alternative route during starting. I do recall the '76 CSV power runs from the starter through a thermal time switch mounted on the DS chain case cover. There is a '75-76 wiring diagram in the Haynes manual; does it also show this CSV circuit running through the "airflow switch"?

Well; this is the connector I think they are refering too in the manual. My connector is damaged.. so I crossed the wires. Still no CSV start (my fuel pump has been moved to another fuse thats why it works).

[Jim Williams]

Here is a diagram which shows the CSV wiring. Although this is from a '78 diagram, the wiring is essentially the same. The '76 wiring has the starter wire (yellow) going directly to the CSV instead of first going though the starter and connecting to a set of relay contacts inside the starter. There is no throttle switch involved, only the thermotime switch mounted in the left side chain case cover. The thin solid black line is ground at the bottom of the photo.



The CSV operates only when the starter is energized and then only for 2-3 seconds until the internal heater in the thermotime switch opens the ground circuit (F26) and shuts off the CSV. That's the "time" part. The "thermo" part is the ground circuit also opening when the temperature rises above 45 Deg C, disabling the CSV altogether.

[boyt911sc]

Originally Posted by calling911

Well; this is the connector I think they are refering too in the manual. My connector is damaged.. so I crossed the wires. Still no CSV start (my fuel pump has been moved to another fuse thats why it works).

JP,

The switch shown in the above attached picture is the ground connector for the air sensor plate and it has no power just ground wires. That's is not the one that energizes the CSV. When you crossed the 2 brown wires from this connector, all you did was simply supply ground to terminal #85 of the FP relay.

The picture below shows the CSV (center) and the air sensor plate (upper left).



Perform basic test for CSV in conjunction with the TTS (thermotime switch). Verify for power (test light) and fuel flow (uniform mist). Stop guessing whether CSV works or not. Do a systematic diagnostic tests to save time and effort. Good luck.

Tony

[calling911]

Originally Posted by Jim Williams

Here is a diagram which shows the CSV wiring. Although this is from a '78 diagram, the wiring is essentially the same. The '76 wiring has the starter wire (yellow) going directly to the CSV instead of first going though the starter and connecting to a set of relay contacts inside the starter. There is no throttle switch involved, only the thermotime switch mounted in the left side chain case cover. The thin solid black line is ground at the bottom of the photo.



The CSV operates only when the starter is energized and then only for 2-3 seconds until the internal heater in the thermotime switch opens the ground circuit (F26) and shuts off the CSV. That's the "time" part. The "thermo" part is the ground circuit also opening when the temperature rises above 45 Deg C, disabling the CSV altogether.

Thanks.. I guess I need to get the boot off so I can reach behind and attach my multimeter and see if I have voltage.. I am not sure where I got the idea that the switch on the throttle body was in the path.

Sounds like if I do not have voltage it might be the starter.. how odd.. I have already checked the time switch and it is showing a path to ground when its cold.

[calling911]

Actually, my manual says 75' on up has a "throttle valve switch" in line. see the red arrow.

[calling911]

[boyt911sc]

JP,

The wiring diagram you attached for the '75 indeed has throttle valve switch. But your car is a '76. The '75 and '76 have different wiring diagrams for the this section.

Here are some of the differences you can find in the wiring diagrams:
'75 has no FP relay, '76 has one
'75 has Throttle valve switch, '76 has the air sensor plate switch
'75 has the FP running when ign sw @ ON, '76 FP not running
'75 CSV is energized via throttle valve switch, '76 energized directly from ign switch (not from starter like SC's).

Hope this information helps your troubleshooting. Good luck.

Tony

[calling911]

Originally Posted by boyt911sc

JP,

The wiring diagram you attached for the '75 indeed has throttle valve switch. But your car is a '76. The '75 and '76 have different wiring diagrams for the this section.

Here are some of the differences you can find in the wiring diagrams:
'75 has no FP relay, '76 has one
'75 has Throttle valve switch, '76 has the air sensor plate switch
'75 has the FP running when ign sw @ ON, '76 FP not running
'75 CSV is energized via throttle valve switch, '76 energized directly from ign switch (not from starter like SC's).

Hope this information helps your triubleshooting. Good luck.

Tony

My manual says 75 and onwards (note I said 75' on up and if you look closely at my diagram that is indeed what it says.. my manual (Haynes) jumps from 75' to 78' in the wireing diagrams). What manual are you using?

[calling911]

Originally Posted by boyt911sc

JP,

The switch shown in the above attached picture is the ground connector for the air sensor plate and it has no power just ground wires. That's is not the one that energizes the CSV. When you crossed the 2 brown wires from this connector, all you did was simply supply ground to terminal #85 of the FP relay.

The picture below shows the CSV (center) and the air sensor plate (upper left).



Perform basic test for CSV in conjunction with the TTS (thermotime switch). Verify for power (test light) and fuel flow (uniform mist). Stop guessing whether CSV works or not. Do a systematic diagnostic tests to save time and effort. Good luck.

Tony

Im not guessing whether its working or not. Its NOT working. I have to prime the system myself to start it. Its just a matter of why. My guess is that its not getting power but until I get my multimeter on it I dont know for sure.. I simply cant reach the darn thing to put probes in it at the moment. I think if I take off the boot I can.

[calling911]

Well, I found a diagram for a 76' specifically. Accoding to it the CSV gets power from the fuel pump relay.. so its all related. My fuel pump was moved to another fuse.. I know darn well that the circuit failed and thats why they moved it. Then the they couldn't start the car so they went SUPER rich to make it start.. as soon as I leaned it out it would not start. So this is really making sense now.

EDIT: Correction.. after rereading the 76' diagram 6 times it is indeed powered directly from the ignition.. So now I understand the whole circuit.. I should be able to get this fixed in 60 minutes or less now..

[boyt911sc]

JP,

The power supply to the CSV valve could be easily tested by using a simple test light/lamp. This is only half of the test. The other part is the flow test of the CSV.

If your car is a '76 as you mentioned earlier, your car does not have throttle valve switch as shown in a '75 wiring diagram. I'm no expert so why would you believe me? Look and peruse the Porsche shop manual for wiring diagrams. The '75 and '76 have so many differences. Now if you believe that Haynes manual is more reliable than the factory manual, I rest my case.

Tony

[calling911]

Originally Posted by boyt911sc

JP,

The power supply to the CSV valve could be easily tested by using a simple test light/lamp. This is only half of the test. The other part is the flow test of the CSV.

If your car is a '76 as you mentioned earlier, your car does not have throttle valve switch as shown in a '75 wiring diagram. I'm no expert so why would you believe me? Look and peruse the Porsche shop manual for wiring diagrams. The '75 and '76 have so many differences. Now if you believe that Haynes manual is more reliable than the factory manual, I rest my case.

Tony

I don't have a factory manual so I can't "peruse" it.

If I can't get my multimeter probes on it I'm guessing my test light probes wont go either so I am not sure what your idea is here.. Like I said, I need to pull the boot. Im not particulary excited about doing that but as I said its the next step.


BTW.. you never did answer my question as to what manual you were using.. I assume based on your response you have the factory manual. I think what I have online is also the factory manual.


And yes, you are correct, if power is there then flow would be the next part of determining why the CSV isn't letting the car start.

[g rad]

I love this site...... I'm trying to check for csv flow,,, all I see looking down the throttle body is the pipes and no mist..... should I see mist anyway? thanks, gerry rad