911 SC 1980 running bad after CIS rebuild - Page 2

pmax · pmax's Garage

I would remove the WUR and do a visual. The screen is visible in this pic from a 12 page WUR servicing guide someone wrote to assist all the amateurs like us.

http://b2resource.com/PDFs/wurservicing.pdf

Of course, you can send it to a rebuilder and have a warrantied WUR. But you still need to verify it's in fact a problem with the WUR and not an obstruction downstream otherwise the problem will remain.

Philipp1988 · 08-26-2019, 09:10 AM

Hey,

i cleaned the WUR, inspected the screen, but looked really good.

ok i think the WUR is defect.

I looked at the cold control pressure again (jumped fuel pump and disconected the heating element on the WUR):
startet at 3 Bar, then i closed the line and control pressure raised to 5 bar, opened, closed,...for about 5 times
so the cold control pressure slowly rised to about 4 bar...

seems there is something wrong.

Regards Philipp

boyt911sc · boyt911sc's Garage

Philipp,

Try this simple test to evaluate your WUR:
1). Removed the four (4) bolts holding the WUR upper and lower sections of the WUR together.
2). Separate the upper and lower sections. You will find a spring, a cup or “sombrero” and a pin. Remove and save them. You don’t need them for the test.
3). Assemble back the upper and lower sections together. Make sure you put them together the same way they were before. You will notice if they were put together differently. Install back the 4 screws and nuts.
4). Install the WUR back on the car and connect the fuel lines. Do not connect the electrical plug to the WUR. Test run the fuel pump and record the new cold control fuel pressure.

Do not worry about the WUR, I will show you a step by step procedures with pictures for the assembly in case you need them. This particular test will demonstrate the flow restriction if any in your system.

If you have any question or concern, let us know or PM me. Keep us posted. Thanks.

Tony

Philipp1988 · 08-27-2019, 09:31 AM

Quote:

Originally Posted by boyt911sc

Philipp,

Try this simple test to evaluate your WUR:
1). Removed the four (4) bolts holding the WUR upper and lower sections of the WUR together.
2). Separate the upper and lower sections. You will find a spring, a cup or “sombrero” and a pin. Remove and save them. You don’t need them for the test.
3). Assemble back the upper and lower sections together. Make sure you put them together the same way they were before. You will notice if they were put together differently. Install back the 4 screws and nuts.
4). Install the WUR back on the car and connect the fuel lines. Do not connect the electrical plug to the WUR. Test run the fuel pump and record the new cold control fuel pressure.

Do not worry about the WUR, I will show you a step by step procedures with pictures for the assembly in case you need them. This particular test will demonstrate the flow restriction if any in your system.

If you have any question or concern, let us know or PM me. Keep us posted. Thanks.

Tony

Hey Tony,

thanks for the good advice!!!! I'm really thankful to this forum.
I have send the WUR to checking ang calibration. I will build a connection to check the pressure if the fuel lines make any blocking...

I replaced all the fuel lines and build them myself by DIN 73378 polyamide tubes. cleaned them carfeully with air.. but yeah i know, everything can happen....

Regards Phil

Philipp1988 · 08-29-2019, 10:59 AM

Hey Tony,

ok i made the analysis. Pressure goes against zero, so there is nothing that restricst the flow to WUR. Do you think too?

Hope to get my WUR back soon. Can't wait too get it done

Thanks!

Regards Phil

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Philipp1988

Hey Tony,

ok i made the analysis. Pressure goes against zero, so there is nothing that restricst the flow to WUR. Do you think too?

Hope to get my WUR back soon. Can't wait too get it done

Thanks!

Regards Phil

Philipp,

How did you get zero pressure reading? Could you elaborate how you did the test? It is not obvious to us what was done to get your result. Thanks.

Tony

Philipp1988 · 08-29-2019, 08:40 PM

Quote:

Originally Posted by boyt911sc

Philipp,

How did you get zero pressure reading? Could you elaborate how you did the test? It is not obvious to us what was done to get your result. Thanks.

Tony

Hey,

i connected the both fuel lines wich are normally connected to the WUR (One comes from the fuel distributor to WUR, One goes from WUR to the fuel tank)
With the normal pressure gauge in line as to test the control pressure.

So the control pressure goes to zero. When i close the valve, Systempressure 4,9 bar...

Hope is was better explained now.

Regards Phil

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Philipp1988

Hey,

i connected the both fuel lines wich are normally connected to the WUR (One comes from the fuel distributor to WUR, One goes from WUR to the fuel tank)
With the normal pressure gauge in line as to test the control pressure.

So the control pressure goes to zero. When i close the valve, Systempressure 4,9 bar...

Hope is was better explained now.

Regards Phil

Philipp,

One more question. Was the pin inside the WUR removed when you did the above test as I requested earlier? Pin removed or pin installed? Please advise. Thanks.

Tony

Philipp1988 · 08-30-2019, 04:29 AM

Quote:

Originally Posted by boyt911sc

Philipp,

One more question. Was the pin inside the WUR removed when you did the above test as I requested earlier? Pin removed or pin installed? Please advise. Thanks.

Tony

Hey Tony,

the WUR as itself was removed. I connected both the lines witch are normaly attached at the WUR with a fitting.

Hope its explained better now?

Regards Phil

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Philipp1988

Hey Tony,

the WUR as itself was removed. I connected both the lines witch are normaly attached at the WUR with a fitting.

Hope its explained better now?

Regards Phil

Phil,

Thanks for explanation and now I fully understand what you did. Keep us posted after you received the WUR back. The WUR needs some work to reduce the flow restriction.

Tony

Philipp1988 · 09-02-2019, 09:55 AM

Hey,

ok i can continue, the WUR is here after rebuild. Put it back in the car.

Cold Control pressure at 15°C: 2.1 bar

warm control pressure 3,8-3,9 bar

seems to be good

Car starts fine now. Adjusted the CO at 950 rpm idle to about 0,4- 0,8 % (with the gunson gas tester, engine was hot, Lambda connector off).

Problems:
Duty Cycle at idle is not constant and skips fast from about 10% to 30 %

when i open the throttle just a few degree, rpm jumps to 2000 rpm and don't goes back to 950...

To do: Vacuum measure of CIS

Any ideas?

Regards and thank you
Phil

pmax · pmax's Garage

Quote:

Originally Posted by Philipp1988

warm control pressure 3,8-3,9 bar

seems to be good

WCP seems at the high side according to factory spec chart.

timmy2 · timmy2's Garage

Did you set your idle with engine fully warmed up?
Maybe the decal valve is sticking.
You can test it with a vacuum pump for proper function.
A quick test to see if it is the culprit is to disconnect the small vacuum line to it and plug the line it to see if the idle drops back down normally.

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Philipp1988

Hey,

ok i can continue, the WUR is here after rebuild. Put it back in the car.

Cold Control pressure at 15°C: 2.1 bar

warm control pressure 3,8-3,9 bar

seems to be good

Car starts fine now. Adjusted the CO at 950 rpm idle to about 0,4- 0,8 % (with the gunson gas tester, engine was hot, Lambda connector off).

Problems:
Duty Cycle at idle is not constant and skips fast from about 10% to 30 %

when i open the throttle just a few degree, rpm jumps to 2000 rpm and don't goes back to 950...

To do: Vacuum measure of CIS

Any ideas?

Regards and thank you
Phil

Philipp,

Contact your WUR rebuilder and have the WCP set @ 52 psi. Second, if your WUR reads 10 Ohms when cold, this is another problem you need to address. There could be more problems with your other CIS components (?).

But let us start one step at a time. Your newly rebuilt or calibrated WUR-072 will always give you an erratic cold idle.

Tony

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by pmax

Phillip,

The resistance doesn't affect the cold control pressure which is a tad high (lean) in your case.

The CCP can be made adjustable using a simple well known mod to the WUR (Search for adjustable WUR). That's what I did to the 072 unit in my 80. Bring the CCP to spec and it will start better.

PMax,

Why do you say and post something like the above highlighted information? I guess you still don’t understand how WUR-072 & -090 work. The cold control fuel pressures for these types of WUR’s are directly affected by the amount of the heater resistance. You could not achieve a good calibration for both WUR-072 & -090 if you don’t understand the correlation of control fuel pressures with heater resistance values.

The OP has only 10 Ohms reading for his WUR-072 when cold as posted earlier in this thread. Unless this WUR is correctly calibrated, the engine would always experience erratic cold idle. Specially at this time of the year when the ambient temperature is getting colder each day and the problem will be more noticeable.

Tony

pmax · pmax's Garage

Quote:

Originally Posted by boyt911sc

PMax,

Why do you say and post something like the above highlighted information? I guess you still don’t understand how WUR-072 & -090 work. The cold control fuel pressures for these types of WUR’s are directly affected by the amount of the heater resistance. You could not achieve a good calibration for both WUR-072 & -090 if you don’t understand the correlation of control fuel pressures with heater resistance values.

The OP has only 10 Ohms reading for his WUR-072 when cold as posted earlier in this thread. Unless this WUR is correctly calibrated, the engine would always experience erratic cold idle. Specially at this time of the year when the ambient temperature is getting colder each day and the problem will be more noticeable.

Tony

There's no causation from the resistance value to the cold control pressure.

Cold control pressure is measured at time 0 from a cold start where resistance does not play any role.

That's what I said and I think we are in agreement there from one engineer to another.

Philipp1988 · 09-04-2019, 12:43 AM

Hi guys,

ok so just to verify: i often read that 10 Ohm for the .072 WUR is correct?
For my thinking the resistance of the heating element of the WUR just leading to a faster heat up of the bimetal.

Ambient Temperatur at every test i did was at around 25°C (Good weather these days

)

Ok did some more analysis:

Jumped 87a and 30 of Fuel pump relay, fuel pump runs. Don't hear and feel the frequency valve buzzling... It should right? in this test case i normaly should measure 50% duty cycle nor?
Edit: I can feel the oxygen relay under passenger seat switching

Next: I will change the oxygen relay under the passenger seat

i think the problem i in the area of the frequency valve...

regards Phil

juanbenae · juanbenae's Garage

Quote:

Originally Posted by boyt911sc

PMax,

Why do you say and post something like the above highlighted information? I guess you still don’t understand how WUR-072 & -090 work. The cold control fuel pressures for these types of WUR’s are directly affected by the amount of the heater resistance. You could not achieve a good calibration for both WUR-072 & -090 if you don’t understand the correlation of control fuel pressures with heater resistance values.

The OP has only 10 Ohms reading for his WUR-072 when cold as posted earlier in this thread. Unless this WUR is correctly calibrated, the engine would always experience erratic cold idle. Specially at this time of the year when the ambient temperature is getting colder each day and the problem will be more noticeable.

Tony

that's gunna leave a mark.