CIS question - cold start valve test

[DAP231]

My 1979 911SC is reluctant to start when cold. I’ve found that the only way to get it started is to manually adjust the mixture control unit to run extra rich. The car will then start after a few cranks. I let it run for a minute, turn it off, adjust back to a regular A/F ratio, then restart without a problem. The car then runs perfectly - no backfires, good acceleration - and is easy to restart so long as the engine is warm.

I’m trying to establish whether the CSV is the culprit. With the engine cold, I’ve removed the CSV from the air box, disconnected the connector from the CDI, and put the CSV in a cup to test the spray. I have good fuel pressure to the CSV, and confirmed with a test light that the CSV is getting power when the engine is cranking. But no fuel comes out of the CSV when I crank the engine.

According to the Bentley manual, if the CSV has fuel and electricity but no spray during cranking on a cold engine, the CSV is faulty and needs to be replaced. But I’ve tried two other (used) CSVs and I can’t get either of those to spray either. I’m sceptical that all three are faulty.

Is there something that I’m missing here? Any suggestions gratefully received.

[47silver]

follow the wiring circuit
+12vdc goes to the valve when the key is turned to start,'
the negative side or the valve goes to the thermo time switch. If this is not working the solenoid will not work.
to test
if you can put 12vdc across the solenoid and you should hear it actuate. If it actuates then i think you have problem either with wire not connected or with the tts.

[DAP231]

Thanks for this response. I put a 12v test across one of my CSVs and didn’t hear anything, but it did get warm so I’m going to assume it is working.

I’ll look into testing the TTS next.

[boyt911sc]

Originally Posted by DAP231

My 1979 911SC is reluctant to start when cold. I’ve found that the only way to get it started is to manually adjust the mixture control unit to run extra rich. The car will then start after a few cranks. I let it run for a minute, turn it off, adjust back to a regular A/F ratio, then restart without a problem. The car then runs perfectly - no backfires, good acceleration - and is easy to restart so long as the engine is warm.

I’m trying to establish whether the CSV is the culprit. With the engine cold, I’ve removed the CSV from the air box, disconnected the connector from the CDI, and put the CSV in a cup to test the spray.I have good fuel pressure to the CSV, and confirmed with a test light that the CSV is getting power when the engine is cranking. But no fuel comes out of the CSV when I crank the engine.

According to the Bentley manual, if the CSV has fuel and electricity but no spray during cranking on a cold engine, the CSV is faulty and needs to be replaced. But I’ve tried two other (used) CSVs and I can’t get either of those to spray either. I’m sceptical that all three are faulty.

Is there something that I’m missing here? Any suggestions gratefully received.

DAP,

How did you confirm that you had good fuel pressure to the CSV? Just curious. The CSV’s seldom go bad and very robust. Thanks.

Tony

[don gilbert]

Check the wire going to the starter to. The spade that slides on the solenoid post could be loose.

[DAP231]

Hi Tony,

I’d previously checked the fuel pressures using the CIS pressure test gauge and, after recalibrating the WUR, everything was close to specification. I pulled the CSV to test it, and when it didn’t have any spray on cranking I tried to disconnect the fuel line to try a different CSV. The fuel started to spray out at the bolt end as soon as I loosened the line. I had to retighten it and wait a day for the pressure to dissipate. I suppose the pressure at the CSV could be below spec, but it seemed pretty fierce to me.

Thanks

D

[DAP231]

Don - will do. Thanks for this.

[boyt911sc]

Originally Posted by DAP231

Hi Tony,

I’d previously checked the fuel pressures using the CIS pressure test gauge and, after recalibrating the WUR, everything was close to specification. I pulled the CSV to test it, and when it didn’t have any spray on cranking I tried to disconnect the fuel line to try a different CSV. The fuel started to spray out at the bolt end as soon as I loosened the line. I had to retighten it and wait a day for the pressure to dissipate. I suppose the pressure at the CSV could be below spec, but it seemed pretty fierce to me.

Thanks

D

DAP,

Did you check the resistance (Ohms) of the CSV? On the average you will get between 4.6 ~ 5.0 values or simply test the continuity between the two (2) terminals of the CSV. Test and verify. Thanks.

Tony

[coomo]

Originally Posted by DAP231

Hi Tony,

I’d previously checked the fuel pressures using the CIS pressure test gauge and, after recalibrating the WUR, everything was close to specification. I pulled the CSV to test it, and when it didn’t have any spray on cranking I tried to disconnect the fuel line to try a different CSV. The fuel started to spray out at the bolt end as soon as I loosened the line. I had to retighten it and wait a day for the pressure to dissipate. I suppose the pressure at the CSV could be below spec, but it seemed pretty fierce to me.

Thanks

D

"Pretty fierce" doesnt actually mean its up to spec.You mention recalibrating the WUR.What did this entail.Did you strip & check the bi metal strip?

[DAP231]

I am still struggling to figure out my CSV problem.

Using Tony’s test advice [Thermo Time Switch 1978 SC 3.0 I confirmed that my TTS is functioning correctly. But I’m still not getting any spray out of my CSV.

I’m using three different CSV’s for testing. Each has a resistance in the range of 4.5 - 5.2 ohms.

I inserted my CIS pressure tester between the fuel line and the CSV. Fuel pressure to the CSV measures 4.8 bars, which is right in the middle of the range for the Bently manual’s recommended system pressure. So I’m confident fuel pressure is not the issue.

Next I disconnected the CSV from the engine loom. I then hooked up 12v directly from the fuse panel in the engine bay to the terminals of the CSV. I can see with a test light that 12v is going through the terminals, but when I turn on the fuel pressure, I’m still getting no spray coming out of the CSV. I’m not even hearing noise from the CSV to indicate that power is flowing through it.

All I want at this stage is to see one of my three CSVs spray, but it’s not happening. What am I doing wrong?

[boyt911sc]

Originally Posted by DAP231

I am still struggling to figure out my CSV problem.

Using Tony’s test advice [Thermo Time Switch 1978 SC 3.0 I confirmed that my TTS is functioning correctly. But I’m still not getting any spray out of my CSV.

I’m using three different CSV’s for testing. Each has a resistance in the range of 4.5 - 5.2 ohms.

I inserted my CIS pressure tester between the fuel line and the CSV. Fuel pressure to the CSV measures 4.8 bars, which is right in the middle of the range for the Bently manual’s recommended system pressure. So I’m confident fuel pressure is not the issue.

Next I disconnected the CSV from the engine loom. I then hooked up 12v directly from the fuse panel in the engine bay to the terminals of the CSV. I can see with a test light that 12v is going through the terminals, but when I turn on the fuel pressure, I’m still getting no spray coming out of the CSV. I’m not even hearing noise from the CSV to indicate that power is flowing through it.

All I want at this stage is to see one of my three CSVs spray, but it’s not happening. What am I doing wrong?

DAP,

First of all, I like to retract my previous declaration that CSV’s seldom go bad and very robust. I have a couple PP members sent their CIS components including their CSV’s for FREE testing and evaluations. Cold start valves I tested this morning:



The top row with X’s are the defective ones and the bottom row with OK are the good ones. The two (2) CSV’s at the lower right most belong to Don B. and Jeff B. both PP members. What surprised me more was the number of CSV’s that failed the test. Most of these defective CSV came from the CIS units I bought in this forum. No wonder the previous owners were having problems with their CIS resulting to ditching the system.

It takes a very short time to test and evaluate a CSV. But took me several hours to disassembled the CIS tester from my basement and assembled it in the garage because I was using gasoline to pressure test a few fuel distributors. Indoor, I utilize mineral spirits or kerosene for calibration and testing.

I rarely find a bad CSV. But the 50% failure rate from my recent tests is not a good statistical sampling because most of them came from units people were having problems. And I have another box of CSV in the basement.

Most people do not test the CSV because of its location and poor accessibility to it. Now that you are testing it, make sure that the CSV is working. And if you are interested, I could test it for you. PM me if you decide to send it for testing. Keep us posted.

Tony

[DAP231]

Thanks very much for this Tony. Seeing all those failed CSVs gives me some hope!

I'll send you a PM and figure out how to get my CSV to you for testing.

[boyt911sc]

Originally Posted by DAP231

Thanks very much for this Tony. Seeing all those failed CSVs gives me some hope!

I'll send you a PM and figure out how to get my CSV to you for testing.

Des,

If you are sending the CSV for testing, you might as well include the 6 fuel injectors. Don Becker sent me a box of Techron injector cleaner with 6 bottles (12 oz. per bottle) for testing and cleaning his CSV & 6 FI. Still has a lot of extra Techron available.

It’s amazing how the cleaning solution transformed Don’s injectors from 3 decent and 3 poor spray patterns to acceptable then to fair and finally to very nice mist-like spray patterns. The back-flow flushing technique was also important to clean and revive an old CIS fuel injector/s.

Tony

[tirwin]

Originally Posted by boyt911sc

The top row with X’s are the defective ones and the bottom row with OK are the good ones.

Tony,

Just a curiosity question... any idea what is exactly failing on those CSVs? Have you tried dissecting one to see if you can determine what is happening?

[boyt911sc]

Originally Posted by tirwin

Tony,

Just a curiosity question... any idea what is exactly failing on those CSVs? Have you tried dissecting one to see if you can determine what is happening?

Tim,

Inside the cold start valve are the electromagnet armature (valve) and solenoid winding that allow the compressed fuel to squirt out when energized. My guess is that the electrical portion has failed to open the valve. BTW, all the failed CSV still have resistance readings between 5~6 Ohms like the good ones.

Since the movement (opening/closing) of the valve is electrically controlled, it is safe to say that the CSV has an electrical problem. Maybe someone more familiar with the operation of the CSV would chime in.

Tony

[47silver]

Csv. We call them a solenoid valve. They consist of a n electrical coil, a stem inside the coil and a spring. On a csv without power the stem is pushed down by the spring and closes off flow. When the coil energizes it pulls the stem up compressing the spring and allows fuel to flow.
If you have the fuel pump running and have fuel pressure on the inlet side of the calve and energize the csv you should have flow.
If not either the stem is stuck from gas residue ir the soleniod coil is bad. If you apply power with a stuck stem the coil should get hot if not chances are your coil is bad. If it gets hot your stem is stuck. Soak the valve body only in carb cleaner.

[sunlion]

Sweet post. Currently going thru same exercise with a ‘78 that won’t start when cold unless primed by moving the flapper plate. Wondering if D got his car running and if Tony is still around. Last post by 47silver is crucial info to have. Tried a back up CSV and it got hot. Likely both are bad with stuck stems. Off to napa for carb cleaner. I ❤️ pelican.

[Alan L]

They can stick. If sitting too long. Rust and fuel crud. I have had this happen.
If it is not giving an audible click with 12 v (the right way round) then it is stuck or the coil has failed. That can be checked with ohm meter. If you have continuity and not opening - it is stuck. It may free with 12V and some gentle tapping. If not, you need a new one.
If you get the 12V the wrong way round it won';t hurt it, but it won't open either. The magnetic field is directional dependant on current flow direction.
Alan

[PeteKz]

Be sure to test the thermo time switch (TTS) on the back of the left chain case cover too.

I don't think you can effectively test the CSV without fuel pressure. A click isn't enough. It may click, but still be clogged. Either leave the CSV connected to its line, or rig up something from the fuel filter to the CSV to test it.

[930cabman]

Originally Posted by sunlion

Sweet post. Currently going thru same exercise with a ‘78 that won’t start when cold unless primed by moving the flapper plate. Wondering if D got his car running and if Tony is still around. Last post by 47silver is crucial info to have. Tried a back up CSV and it got hot. Likely both are bad with stuck stems. Off to napa for carb cleaner. I ❤️ pelican.

Yes, Tony is around, but was/is out of the country. Stay tuned I'll bet he will chime in