CCP 3.6 Should be 2.7 Bar?

[Funracer]

Having trouble getting my mixture right. When I warm up the car and set the FV to 45% the car runs and starts fine.
The problem is next morning it will start perfectly on the first crank, then die in 2-3 seconds. I can richen the mixture a lot to overcome this but then of course it runs rich after it starts (FV is about 75-80%).

Checked several things finally needed fuel pressure gauges to check the WUR. Returned the first set back to Harbor Freight because of a bad leak at the shutoff valve. Got the next set, removed all the Scrader valves male and female, this one did not leak. got the following pressures:

System pressure 4.6 bar, within the range specified in Bentley
CCP pump on, engine not running: 3.6 bar, out of range in Bentley
CCP with engine cold and running: 3.6 bar, out of range in Bentley
CCP with engine warm and running: 3.6 bar, within range

It was not clear to me exactly how to measure CCP with or without engine running so I did it both ways and same result of 3.6 bar. The Bentley graph for a 1983 with lambda shows 2.7. It is 84F/29C here today.

The way I see it CCP is too high when engine is cold. Does this mean it is too rich when cold and stalling out until it warms up? WUR has a vacume line and ends in 090.

Thanks

[boyt911sc]

Funracer,

First of all, if your WUR is 0-438-140-090 (for ‘81~’83 SC USA), it is not vacuum assisted. Could you post a picture of the WUR? Measure the heater resistance (Ohms) of the WUR at room temp. and post the numbers.

Measure the cold control fuel pressure when the engine is COLD. Since you are having problem with your cold control fuel pressure based from recent tests, please do this:

• Place the WUR inside your freezer for 15 mins.
• Or place some ice in a zip lock bag and place the bag of ice over the WUR.

Either one of the above will be a good way to test your cold control fuel pressure.

• Pull the electric plug to the WUR.
• Test run the FP. Read the pressure gauge. This will be the starting point (0 min.)
• Plug the elec. connector to the WUR and start the count (timer) and read the pressure gauge at 1 min. intervals.
• Take the pressure readings every min. until the CCP maxed out and became WCP.
• Stop the test when pressure reading stopped increasing. Total test duration 7 mins. (Use a timer).

The data you will collect will be the baseline data for your WUR. Since your WUR is not vacuum assisted, all you need is CCP@ x°(for calibration) and WCP@max. (highest). You are not calibrating the WUR yet, you are just simply testing the WUR for control fuel pressures. You can do the calibration later.

The values you will collect will tell you how close the control fuel pressures to spec. If you have any question, let us know. Keep us posted.

Tony

[Funracer]

Hi Tony. Thanks so much for responding.

This is the only picture I have of my WUR. I took it this way because you can zoom and just see the 090 on it. If you want a different pic let me know.

Is that not a vacume line next to the 090 digits in the photo? The line runs to the throttle body so I thought it was a vacume line.

I will do the tests as you describe tomorrow and post the numbers here before lunch.

Regards

[boyt911sc]

Funracer,

The main objective of the test is to see the starting control fuel pressure from a cold state until it stabilizes (max.) to WCP. I did not see from your post how long (minutes) it took to get the CCP to 3.6 bar (52 psi).

Be aware that WUR will be heated (energized) as soon as the FP starts to run. So unplug the connector (electric) to measure the CCP. If the plug is left connected to the WUR, you got a few seconds to read the CCP. Otherwise, the CCP is gradually increasing or changing to go to WCP condition.

Tony

[Funracer]

Resistance is 9.0 ohms at ambient temp 85F

[Funracer]

Better WUR pic

Ice bags in place

[Funracer]

All done.

Ohms unplugged cold 9.0
Ohms after plugged in for 7 minutes to test fuel pressure also 9.0. No change
Voltage measured at the plug with ignition on is 11.85 VDC

After 25 minutes under ice CCP is 2.3 Bar. Near spec on the Bentley graph.
Plugged in CCP jumped to 3.7 bar in about 10-15 seconds
Took reading every minute 1-7 minutes no change. 3.7 bar

Planning to repeat these tests later today to confirm my findings.

Any ideas?
Thanks

[boyt911sc]

I forgot to ask you to check the resistance (Ohms) after you placed the bag of ice over the WUR. Please do this when you get a chance. Thanks.

Tony

[Funracer]

Ok interesting things here. Iced it down again. After about 15 minutes WUR ohms went to 25.6 ohms. After it made that jump I plugged in the WUR again and turned on the FP and got only 1.6 bar, then it rose slowly to 3.7 bar over the next 2 minutes or so. The 3.7 looks to be in spec but the 1.6 is low for 85F

[boyt911sc]

Originally Posted by Funracer

Ok interesting things here. Iced it down again. After about 15 minutes WUR ohms went to 25.6 ohms. After it made that jump I plugged in the WUR again and turned on the FP and got only 1.6 bar, then it rose slowly to 3.7 bar over the next 2 minutes or so. The 3.7 looks to be in spec but the 1.6 is low for 85F

Funracer,

The experiment you did simply demonstrated that the WUR is out of spec. Placing the bag of ice is my “exaggerated cold control condition version“ that showed the different transition phases from cold to warm. You need this WUR-090 rebuilt and calibrated to work properly. Otherwise, your motor will always have a cold idle problem if not corrected. Good job.

Tony

[Funracer]

So what is happening on my cold start? The CSV gives it a shot, it starts on first crank, after a couple of seconds the CSV is out of the picture and the WUR takes over for warm up, then it dies.

Is it dying because the WUR is making it too rich until it transitions to 3.7 bar when warm?

Just trying to get the current situation figured out in my mind before moving on.

[boyt911sc]

Originally Posted by Funracer

So what is happening on my cold start? The CSV gives it a shot, it starts on first crank, after a couple of seconds the CSV is out of the picture and the WUR takes over for warm up, then it dies.

Is it dying because the WUR is making it too rich until it transitions to 3.7 bar when warm?

Just trying to get the current situation figured out in my mind before moving on.

Funracer,

The CSV only works when the engine temp. is below 113° which is controlled by the TTS (thermotime switch). When you turned the ignition switch @ START and the TTS is closed or grounded (cold engine), the CSV sprays fuel and makes the motor run. The engine revolution creates vacuum to suck the air sensor up and move the FD plunger upward too causing the six (6) fuel injectors to deliver fuel into the combustion chambers and make the motor run and idle. This is the ideal condition. But you don’t have this condition now.

You artificially set the cold condition using “ice” and brought the cold condition closer to spec as you noticed it. Try this experiment, place a bag of ice over the WUR for about 10~15 mins. Removed the “ice” and start the motor. See if it will start and idle. Keep us posted. Thanks.

Tony

[Funracer]

Good idea. Like Arnold said, I’ll be back.

[Funracer]

Had to start the car and warm it up to reset FV to 45%. I’ll have to wait for tomorrow to get another truly cold start.

[Funracer]

Redid the ambient CCP again this morning for confirmation.
With WUR unplugged it went to 2.7 bar and held there for a couple of minutes.
Plugged in the WUR it quickly began a steady climb to 3.8 bar

Both in spec at 82F I think.

Got family plans today the ice tests will have to wait til this afternoon.