Just to recall, wur from a 911 SC euro version

I repeated the readings today, after trying to set both pressures (cold and warm).
Cold control pressure: fuel pump relay jumped, wur plug disconnected, key on, valve on gauge open, 1,1 bar - car not running.

Connected the wur plug, fitted fuel pump relay, Drove it up to the running temperature and when stoped, gauge was showing 3.6 bar with both upper and lower vacuum hoses connected.

When I disconnect the lower vacuum hose on the warm control pressure drops to 3 bar.

Waited for another 25 min and...
Car struggles to fire when hot and now also when cold...
... and always with same symptoms... after starting it is not lean, it sounds there is not enough fuel but after pressing the gas pedal, it stabilizes...

WCP is primarily created by plugging the power source to the wur. The engine does not have to be running, or even present, as Tony’s setup shows. You can test for CCP with that plug disconnected. You then plug it in to get to WCP. Do this with the fuel pump jumpered so no engine start is needed.

Can you post a picture on the vacuum line from the wur (lower line on side of wur) to the ttv showing the connection points on the ttv?

WUR test and calibration.........
 

Alex,

Since you are using the FP and relay socket to test your cold control fuel pressure, you could do the same with the WCP (warm control pressure) and avoid driving the car. You are wasting your valuable time and fuel unnecessarily.

Your understanding of CIS is somewhat flawed but could easily be corrected by practicing the correct test procedures. SKIVT (Stuart) has given you a hint and he’s a sharp troubleshooter including Walt F. and other guys in this forum. The reason it is taking this long to solve your CIS problem/s is the way you communicated and your feedback. Instead of giving numbers for your fuel pressures, you tend to use words like they are in spec, they are new, they are good and OK.

Forget the past. This is what I would do if I were in your shoes:

• Measure your control fuel pressures (CCP & WCP) just using the FP. No need to drive the car.
• Measure the WCP again and apply 16” Hg vacuum. You would need a hand held vacuum pump.
• Measure the system pressure (valve close).
• Test your residual fuel pressure after 20 mins.
• Test your fuel injector’s spray patterns. They should have mist-like v-pattern shape. Not jet like spray patterns.
• Check for unmetered air. This is probably the reason you are having difficulties re-starting a warm motor.
• Post a picture of your throttle body and decel valve.
• What is the Bosch ID # for your fuel distributor? Last 3 digits?

Your WCP with and without vacuum are good. So what is preventing it from re-starting?

• Residual fuel pressure
• Test your fuel injectors for drips and spray pattern.
• I bet you have unmetered air.

You need to test and confirm the absence of unmetered air going into the system. Keep us posted.

Tony

First of all, I would like to thank you all for your insights.
I will try to be more specific next time and also improve my english...
I will check everything following Tony’s suggestion and post the results.

Sure! I will post more photos next time I do readings... soon...

Just for clarification: If I run the test the way you suggested, after some time I will get the same WCP as if I take the car for a ride for some time?

Here is a photo showing the mentioned hose (1):

http://forums.pelicanparts.com/uploa...1613731631.jpg

I think I found already a mistake...
http://forums.pelicanparts.com/uploa...1613732473.jpg

It looks like you are missing number 4 in this diagram, the TTV. It holds off vacuum for a short time when the engine is started. It heats up from power and opens to vacuum in about 45 seconds. I am not certain at what temperature it closes when the engine is shut off. In any case, your measurements while the engine is running are always with vacuum unless you plug the vacuum line. At cold or cool start, your pressure could thus be higher/leaner than optimal. After following Tony’s instructions, you could test this as a problem by duplicating your “hot starts” with the vacuum line at the WUR plugged with a golf tee or similar. I dont think the TTV is a problem for a restart 5 min after turning off a hot engine. It may or does become a problem the longer the engine cools before a restart.

http://forums.pelicanparts.com/uploa...1613732374.jpg

Our posts crossed!!!!

Found another strange thing (it was not me who assembled the engine)...
Found this valve behind the air pump...
Wasn’t it supposed to be on the other side, next to the auxiliary air valve?
http://forums.pelicanparts.com/uploa...1613733088.jpg
http://forums.pelicanparts.com/uploa...1613733088.jpg

One of the vacuum hoses comes from the throttle body and the second one goes to the air pump next to it.

The hose connected to the top of the wur by the electrical connection is not vacuum. It just vents to atmosphere.

Make sure the vacuum line from the wur to the TTV you just found connects to the outer connection on the TTV exactly as shown in the diagram.

On my 83 euro, the TTV is mounted to the bracket to the left of the decel valve that you circled in your picture using the welded nut on the L bracket. So it sits higher not touching the engine which may or may not matter.

I dont have an air pump so have no idea how that may or may not be interacting.

In your spare time watch the pressure change on a cold start about 35 seconds in when the TTV opens. Again, this may or may not matter and is secondary to first being sure the ccp/wcp are correct, no unmetered air, etc.

https://youtu.be/x3HXhqlwFMM

Better communication...........
 

Alex,

You and Stuart have the same engine and should be able to sort all your CIS problems. See how good communication makes the troubleshooting much easier and faster. Anyway, you are in good hands. Both Stuart and Walt, etc. have incredible ways to look at things. And they have the patience to compose detailed explanations that reminds me of Ossiblue (Larry). They are good teachers and their knowledge is very reliable.

Tony

Stuart and Tony, thanks for your good will! Has been very helpful and helping me modifying my approach.

One question: when I have my vacuum connections corrected, will the pressures be affected?

Vacuum happens when your lines are connected AND your engine is running. Your wur changes pressure in the presence or absence of vacuum, in addition to as it warms up. So as your engine idles, you have vacuum and it increases your pressure versus having no vacuum. When you drive at full acceleration, vacuum drops and your pressure drops, enriching your fuel mixture and putting a smile on your face. For testing, you can introduce vacuum using a hand held vacuum pump, as Tony mentioned, without ever starting your engine. You can match your pressure readings with and without vacuum to the specs for both CCP and WCP.

http://forums.pelicanparts.com/uploa...1613751108.jpg

So, I have been testing CCP with the vacuum line connected... but with the engine off...
meaning I have to do it again with the vacuum pump applied (if I remember, Tony mentioned the value). That is why I found the value under specs...