Cold Start problem

[dano]

I'm having trouble starting my '79 SC; it does not seem to be getting its gas when it has been sitting and the engine is cold, it eventually starts after A LOT of pumping on the gas. Warm starts are fine so I was thinking it may be the cold start valve or the fuel accumulator. I started with the cold start valve; removed it and tried testing it by seeing if any gas came though when turning the engine over... no gas appeared.

Questions:

1. Should I ground the cold start valve to test it in the manner described above?

2. How can I test the electric circuit going to the cold start valve?

3. How can I test the accumulator, I tried removing a fuel line to see if had pressure but I couldn't get it off quick enough to see a "spurt" of pressure?

4. What should I look at next?

I appreciate any info you can provide, I'm not very experienced with the CIS system.

Thanks,

Dan

[tab tanner]

Get the Robert Bently manual on Bosch Injection systems. It's the best money spent.One other place you can get alot of help from is the Hanyes manual for the Porsche 924, it really covers the CIS system well. With alot of trouble shooting tips, the best part is you can get this from AutoZone for about $16.00 Good luck

[vash]

the main reason a cold start valve fails is the thermswitch. the CSV is not going to spray, unless the thermswitch is cooler than 95 degrees and the starter is turning. and i think the thermswitch only lets the CSV spray for around 10 secs.

ok here is what you need to do. with the car cold, disconnect the CSV, connect a test light across the terminals (or continuity meter?) and have someone crank the motor over. the light works, then the harness is good and the CSV is getting juice. loosen the fuel line to the CSV and have the same buddy crank the motor. fuel should spray, if not check the supply line coming from the fuel dist. IF the test light doesnt come up, then you need to put a multi meter on a 12v source and probe the either terminals that connect to the CSV. one should get a reading the other should not. if neither lights the meter, then you need to test the thermo time switch. good luck.

just for info the other causes of a cold start issue are, lack of fuel pressure, sticky airflow sensor, aux air valve not opening (you know this may be the issue, because if this is bad, the car will only start with the foot on the accelarator),CSV, sticking control plunger, restricted injectors.

[dano]

Thanks For the info from you both. Correct me if I'm wrong, the Termswitch is on the timing chain cover and can I test it with an OHM meter; closed circuit if it is working correctly when cold?

[vash]

my car doesnt have a thermo time switch, so i dont know where they would put it. sorry. but yes, your method is sound. (but i think the starter needs to be cranking)

[yelcab1]

Originally posted by dano
Thanks For the info from you both. Correct me if I'm wrong, the Termswitch is on the timing chain cover and can I test it with an OHM meter; closed circuit if it is working correctly when cold?

Driver side valve cover, two terminals, the resistance should be fairly low at cold temp.

[Pat S]

loosen the fuel line to the CSV

unfixed I think you worded this wrong. You want to pull the Cold Start Valve, not the line to it. There will always be fuel coming to the CSV, but it only squirts when power is applied. You can also just remove the valve and apply 12v to it. You'll feel it click and it squirts whatever fuel is sitting in it out if it is working. Just be careful as fuel and sparks don't mix.

I'd also reccomend the book "How to Tune and Modify Bosche Fuel Injection" by Ben Watson. Very good book with lots of info on how to tune each component of CIS. Doesn't cover decel valve but gets almost everything else.

Pat

[vash]

you are right pat. maybe i was think of checking for obstructions in the line? i typically always move systematically upstream from a suspected problem. i think your method may get two birds with one stone.

[dano]

I finally made it back out to the garage to take another look.. I was not getting any fuel from the cold start valve when the engine was cranking, I applied 12v directly to it and it sprayed fine. I'm now trying to test the current to the CSV. How much voltage should be coming to the CSV? I am getting a very small reading on the continuity meter but I'm not sure if it is enough to open the CSV. Thanks.

[Pat S]

You should be getting 12V to the CSV. I assume you mean that you have good continuity on the thermoswitch?

[targa80]

With the positive lead of a volt meter make contact with one side of the wires to the CSV. Then connect the negative lead of the meter to ground and try starting the car. The meter should read ~12 Volts(battery voltage). If you have 12volts then apply a ground wire to the other lead on the CSV and try starting the car. If it starts then you do have a problem with the thermal switch being open.

[dano]

Thanks, you both answered my question, I should see 12 volts on both contacts going to the CSV.. I'm only getting a very small reading, less than 1v, on both contacts and the same reading on both sides of the thermotime switch. I guess is the next step is to trace this back to the starter? Any input on the best way to approach it?

[targa80]

On the schematic for the 1978 the 12volts for the CSV comes from the starter terminal 16. When you start the car and the starter solenoid closes its contacts it supplies the 12 volts from terminal 16 to the CSV. I would check your connections on the starter.

[Hladun]

CIS Cold Starting Solution

[Lorenfb]

The thermo-time switch is located on the chain housing covers. It provides
a ground to one side of the CSV. The other side gets +12 volts from the
starter as mentioned. use a test light when checking for proper voltage,
since the light will load the voltage source and provide a better indicator
for proper voltage than a meter (high impedence load).

[dano]

Problem solved... Finally! Thanks to your suggestions I located the problem, it was a loose wire on the starter. Crazy, a 30 second fix, it only took me 3 weeks to find it! At least I learned a lot in the process.

[vash]

right on. thanks for closing the loop.