Cold start issue CSV

[AUSTmike]

Hi guys...I hope everyone is well and good. I have a 1977 2.7 ltre CIS

I have a cold start issue. On crank I get a quick start then engine dies. If I put fuel down the throttle body (pop off cap in air box) the engine will start and runs perfect on idle. I don't have to rev or use throttle.

I did a test with the CSV by unbolting it from the back of the air-box with the fuel line still connected and pluged in for current and placed the CSV in a clear glass jar and cranked the engine on cold start.

There was only a small amount of fuel in the jar so there was some fuel but just a very small trickle of fuel!...not much.

Checked thermo time switch with only continuity and the beep on the multi-meter. and it beeped so there's a current going through it.

But haven't gone further in testing the switch.

Battery is good as its only 2 years old and on trickle when not in use.

checked CSV with multimeter off the car and not connected to a 12v battery and the CSV read 10 Oms

Could the issue be a faulty CSV?... I uninstalled the CSV and hooked it up to 12v to see if there was any volts going into it and there was clicking inside.

any ideas would be greatly appreciated.....

[Alan L]

Sounds like the CSV is working.
You need to check WUR pressures - esp cold pressure. Maybe too high.
I have the 2.7 pressures if you can't find.
Alan

[AUSTmike]

Thanks Alan...what pressures do I need to see if its the WUR?...cheers

also here a great video on maintance on your WUR...Thanks Alan you guys are always a big help!...God bless.

https://www.youtube.com/watch?v=VVsnF2RlEqw&t=17s

[spuggy]

Everyone with CIS always seems to fixate on the CSV. It's almost never the CSV, IME...

If your cold pressures are even vaguely correct, you often don't need the CSV at all - my 930 would start perfectly well with 1/2" of ice on the windshield and the TTS wire hanging off - so no CSV. For a while I would put the flag terminal back on every time I looked in the engine bay - but as it obviously made no difference to the ability to cold-start in freezing temperatures, I eventually just stopped bothering...

The CSV only operates when you're

1. cranking (circuit powered off the starter solenoid), and
2. ambient temperature is below the cutoff (which on some cars/TTS is quite high) and
3. the internal TTS heater hasn't yet raised its temperature enough (which it does after a few seconds) to disable the CSV circuit entirely (to prevent flooding the motor).

As the motor fires after cranking - and then dies immediately, this would seem to rule out the CSV, which seems to be working as designed. Instead, this would indicate mixture too lean to run when cold - eg CCP is too high. All as Alan says.


The "correct" control pressure is a band on the graph against temperature. So to quote numbers you'd need to know both your ambient temperature and the type of WUR. You'd probably find one of these useful:



I can't lay my hands on mine just now - so here's the corresponding page from the FSM:

[Alan L]

I agree, the CSV is unlikely to be the culprit. Mine is disconnected on the 930 - the TTS has failed - which means I get CSV on hot start and had hot start issues. It starts after about 2-3 secs of cranking when cold (without CSV). Before it would fire on the first compression stroke.
So here is the WUR chart I have for your car. But now it gets weird. It is the same Bosch# as the bottom rt chart posted above. But the graphs are different. Eg for 20 deg C the sweet spot on my chart is 2.0bar.
On the chart above it is 1.5.
I think first - ascertain what Bosch# you have, and what cold pressure you measure (you have to measure temp at same time).
Edit - the discrepancy may be with/without Vac.
Alan

[AUSTmike]

Thanks Alan and Spuggy....My climate is sub tropical simular to florida so by what your saying Alan and by the chart 20c at 2.5 bar and the car has been in this type of climate for over 20 years including the PO so I'll check the WUR an see how dirty it is inside. In the video that I linked up the heating strip inside the WUR needs to be around 36 OMS on the multimeter. Thanks again Guys for your help and I'll get back to the results of the WUR..cheers.

[Alan L]

Measuring the WUR pressures would be the best place to start. if it is crudded up, the pressures will be out of spec and tell you. Or they may just be out of spec.
Alan

[AUSTmike]

I've just taken the WUR out of the car and dismantled it. The filter screen is very dirty and the small pinhole that runs under to the screen may be blocked with crud. I'll clean it all out and give it a good service and put it back in the car to see if that was the problem...cheers

[PeteKz]

Yes, if the WUR is blocked with crud, then the CCP will rise to SP, which will make the mixture too lean.

Also see this thread. David was having a similar problem with a blocked WUR.
https://forums.pelicanparts.com/porsche-911-technical-forum/1159640-fuel-pressure-testing-system-pressure-cold-control-pressure-residual-press-0-a.html

[AUSTmike]

Finished cleaning out the WUR some crud in filter but easily cleaned out with brake cleaner. Put it all back together and installed in car and tried to start car but same as before no start.

so back to square one at lease I cleaned the WUR.

I did notice the o-ring on the pressure plate where the fuel goes through the small holes on the fuel lines connected to the WUR was a bit flattered. I'll try and find another 0-ring tomorrow and replace the old one.

when testing the heat plate on the multi-meter it went to 28 Oms i think the range is 18-22 oms according to the Pelican parts maintenance on this website.

The guy in the video that I posted earlier says 36 oms not sure why it that high but would like to know the range to clarify. Thanks guys for all your help I learning so much from you.cheers.

[PeteKz]

What are your SP, CCP and WCP now that you have cleaned out the WUR? You might not have it clean yet. Disconnect the return line from the WUR, run the fuel pump, and make sure fuel flows out the return line.

The heating element not working, or being off spec will not cause cold start problems. Its purpose is to make the WUR lean out as the engine warms up. If you had some running problems between a cold start, and say, 5 minutes of engine warmup, then I would consider the heating element as a cause. I've seen at least one car with the heating element connector disconnected, and it didn't seem to bother the running of the engine during the 5 minutes of warmup.

[Alan L]

Yes - need the WUR pressures.
Start at the beginning rather than shooting for the end.
Alan

[AUSTmike]

i'm going to have to buy a fuel pressure gauge and test these pressures. I did what you said Pete in your previous post by disconnect the fuel line from the WUR that connects to the FD and return line and placed them in glass jars and on crank the FD line had great volume of fuel coming out the return line didn't have much just a tiny amount in the bottom of the jar simply because its separate from the main fuel line.

I also disconnected the fuel line to the CSV and that had a great amount come into jar.

I also replaced the 0-ring in the WUR for the pressure fuel.

The heater element in the WUR is 28 oms.

The csv has 10 oms but I also connected the CSV and tested but no fuel came out in the jar.

[boyt911sc]

Originally Posted by AUSTmike

i'm going to have to buy a fuel pressure gauge and test these pressures. I did what you said Pete in your previous post by disconnect the fuel line from the WUR that connects to the FD and return line and placed them in glass jars and on crank the FD line had great volume of fuel coming out the return line didn't have much just a tiny amount in the bottom of the jar simply because its separate from the main fuel line.

I also disconnected the fuel line to the CSV and that had a great amount come into jar.

I also replaced the 0-ring in the WUR for the pressure fuel.

The heater element in the WUR is 28 oms.

The csv has 10 oms but I also connected the CSV and tested but no fuel came out in the jar.

Mike,

You are not doing this investigation correctly. Get hold of a CIS pressure gauge kit and pressurize the system by running the FP (engine off). Measure the fuel pressures (CCP, WCP, SP, & RP) and perform your investigation. You need to know your fuel pressures first and foremost before making your troubleshooting diagnostic tests. Without knowing your fuel pressures, you are working blind. Some of your tests depend on residual pressure so breaking the fuel lines and cranking the engine could lead to misinterpretation. Just be aware of the test condition when you perform the investigation. They are simple and straight forward. And take your time, you will be OK.

Tony

[AUSTmike]

tony I understand I've got to get a fuel pressure kit and your right about braking the fuel lines as it loses the pressure each time. I just have to wait unto till I get the kit.I was thinking that today so I am on it. I also checked that the AAR was half way open in the opening when I removed the clap of the pipe.

[boyt911sc]

Originally Posted by AUSTmike

tony I understand I've got to get a fuel pressure kit and your right about braking the fuel lines as it loses the pressure each time. I just have to wait unto till I get the kit.I was thinking that today so I am on it. I also checked that the AAR was half way open in the opening when I removed the clap of the pipe.

Mike,

The AAR’s that we use in 911 CIS should not have a large aperture. They are usually at quarter-moon shape or less and closes between 3~4 mins. from a cold start and stay close after the warm up. As they get older, the bi-metallic spring gets lethargic and takes longer time to fully deflect to close the valve. Test the duration it takes to close from a cold start. Do the test at room condition.

Tony

[AUSTmike]

Thanks Tony much appreciated on the info you guys are a BIG help!...If the fuel pressures are ok what would be some of the issues that would cause the CSV to not spray.I realize that at that point of trying to fix an issue you would think its a faulty CSV even if the oms are right and the CSV passes the 12v test with the clicks. I've even installed over 5 different CSV's but with ALL the same result.

Another thought I have today after spending time working on the car. would it help if I started the car with some fuel down the throttle body warm up the car to temp or run for 20-30 mins them turn off the car and try again the next day stone cold as normal start. This may reset the WUR and what ever in fuel pressures to get back to normal.

[AUSTmike]

I forget to mention my WUR is 0438 140 033 do I have the right WUR for the 1977 2.7 ltre magnesium engine. sorry I don't have the bently manual.

[E Sully]

The 033 is the original WUR for a '77.

[AUSTmike]

Thanks E Sully much appreciated.