Another CIS thread

[schryvere]

Hi everyone,

Been reading on this forum for a long time. Last year I purchased a 1983 911 SC convert. It was a non runner... When I first got it, I figured out some bad electricals and fuel pump and bled the fuel system and it was 'running'. After tackling some vacuum leaks it run better and then I heard the distinct noise on accelaration indicating a very nice broken head stud... So instead of driving it last year, I spent the winter doing a partial rebuild of the engine and cleaned up, repaired/restored the engine bay when I was at it.
What was kind of strange at the time, it always needed a very long crank....


Now the engine is back in the car and I was not expecting it to be a pain to start up again..

After an initial false connection of the spark plug wires :s what is corected now... but still just the moment where you think it will get going and let go of the key, it shuts down, with a small backfire... As backfires can indicate lean condition, I probably did the worse change and just richened the mixture a bit. That still did not bring the car to life..

So I purchased a fuel pressure gauge set after a lot of reading on this forum, especially the dummy thread was very helpful.

So after some more reading, here are my findings, and I hope someone can confirm my suspect, I am not looking at throwing more parts at it than needed.

the pressure test set has e 2 point connection without valve and fast gauge connector that I put between the line just after the fuel filter.

it has a second 2 point connection with valve and fast gauge connector that i pu between the Warm Up Regulator and Fuel distributor, valve @ WUR side.

So system pressure measured between FD and WUR, valve closed maxes out at around 4.6Bar (ok, as to K-jet workshop manual) it builds very slowly, it's fast up to 3bar and then wait a minute...or 2(yess there is an air bleed valve on the gauge)

+-the same value was read when connecting after the fuel filter. (4,5)

So to test control pressure, I opened the valve (electrical connector off), it dropped to 3 bar, but then slowly rises to 3.9BAR... it seamed like maybe a blockage?

As I read a little on how WUR s work and how to make it adjustable, I as a small test tapped the top of the shaft thet you would drill to make it adjustable. Pressure went down to 3BAR again, slowly rising to 3.5. did it again and now if i repeatedly test opening closing the valve it drops to 2.8 which is in spec as well. (put it needs some time as well)
(Before this, I put some injector cleaner in the wur and left it for a couple of hours)

Now leakage test should be done when hot... Since I do not intend to start it up and risk blowing the airbox due to this backfires, I suspect related to fuel delivery. I did it cold, so it 's possibly not very valuable but might confirm my suspect:
The pressure (valve open) drops to 0 in 3 seconds to 0.

I also disconnected the bottom connector of the Fuel Accumulator and it is leaking. As some posts are contradictory, one saying it can leak another says it doesn't....
But it is still my suspect due to the pressure drop!(?)

I also measured pressure after filter with return line blocked(it 's now leaking... old stuff) and the pressure remained, so it's not leaking back through the Fuel pump.

So if anyone can confirm or point me in another test direction... advice is welcome.

Also, I have all injectors in a bowl and I don't see them leaking. Can I set an initial mixture this way as well? I found somewhere turn clockwise until they start spraying and then counter clockwise a half turn. I suppose this can be done @ 2.8BAR with WUR in the loop?

[tirwin]

Well, first of all, it sounds like you've sure done a lot. Sorry to hear that you had a broken head stud. Good on you for tackling all these issues.

There are a lot of issues you raised and I'm not sure I'm following everything you did, so let's start with the basics.

On cold start, as cold control pressure increases, the mixture leans. It should be richer than normal on a cold start and lean out to normal as the engine warms up. Is your '83 US model (it has K-Jetronic with lambda) or a Rest of World (RoW)?

What was the ambient temp when you tested the cold control pressure? It may be fine if you're in the Sahara but not if you live in Fairbanks, Alaska. It sounds like you're still lean but need to know the air temp to confirm.

Your system pressure value seems fine but odd that it is slowing building. How much time would you estimate it takes to build pressure? This seems suspect.

The fact that cold control pressure changed with time is unusual (assuming you did not plug in the WUR electrical connector or tried to start the car). Or maybe I misunderstood you. On a cold, non-running engine with the WUR electrical disconnected, the cold control pressure shouldn't change.

You don't have to start the car to test the warm control pressure. Just plug in the WUR electrical connector and measure how long it takes to transition from the cold control pressure to it's max. Should be around 3 minutes, give or take.

[tirwin]

Can you confirm that you have 12V at the WUR electrical connection?

Also thinking you need to make sure the cold start injector (or cold start valve, CSV) is firing but let's come back to this later.

[gazzerr]

After the rebuild and installing back the CIS did you set the mixture baseline, i.e. 2 full turns ccw then cw until the injectors start to eject then back off cw half a turn? Experts will chime in but I'm thinking you would need to reset the CIS so you know that you are in the ballpark.

I'd smoke test it first to make sure you don't have a vacuum leak after the CIS reassembly too.

[schryvere]

ok, great to see replies

My car is a US with lambda (new relay)..

I see what you mean with sahara, I checked it against the warm control temp, and the temp at test must have been around 15-20C.

I also tested and received voltage at WUR (9,5V) -> made me think that maybe this voltage drop is caused by the test setup jumper cables so I did the test again with AFS disconnected and 12V...
Something else I did was measure ohm's again (thought I did that hen I opened the wur) and at the pins I have 11ohms.

So today I did the test again with AFS disconnected (No cranck/ Injectors out CSV disconnected)
System pressure went up to 4,9Bar.

Cold control pressure after some gentle taps and wur disconnected 1,8
Warm control pressure With the wur connected 2.6 (prob the 10Ohm plays part in that). If I were to do the test again tomorrow, I wonder if the wur would need some help again...

The pressure this way went up a lot faster as well: 30 seconds instead of 2minutes.

It still dropped to 0 within 5seconds when I turned the key off (WUR open and connected).

Anyway, while the system was pressurized with wur open and warm (electrical plugged in) I did set the mixture ... I started at the point where the 1st one starts to open, turned back 180°.

Put them back in, connected the CSV and AFS and tried to start. pressure reading valve open when crancking.... 2 - long cranck 3Bar with valve closed.

So I guess the wur will need changing or rebuild,
Still not sure about accumulator (Pressure drop)

I will try crancking it again tomorrow, but will put in another fully charged battery first.

[schryvere]

ok, great to see replies

My car is a US with lambda (new relay)..

I see what you mean with sahara, I checked it against the warm control temp, and the temp at test must have been around 15-20C.

I also tested and received voltage at WUR (9,5V) -> made me think that maybe this voltage drop is caused by the test setup jumper cables so I did the test again with AFS disconnected and 12V...
Something else I did was measure ohm's again (thought I did that hen I opened the wur) and at the pins I have 11ohms.

So today I did the test again with AFS disconnected (No cranck/ Injectors out CSV disconnected)
System pressure went up to 4,9Bar.

Cold control pressure after some gentle taps and wur disconnected 1,8
Warm control pressure With the wur connected 2.6 (prob the 10Ohm plays part in that). If I were to do the test again tomorrow, I wonder if the wur would need some help again...

The pressure this way went up a lot faster as well: 30 seconds instead of 2minutes.

It still dropped to 0 within 5seconds when I turned the key off (WUR open and connected).

Anyway, while the system was pressurized with wur open and warm (electrical plugged in) I did set the mixture ... I started at the point where the 1st one starts to open, turned back 180°.

Put them back in, connected the CSV and AFS and tried to start. pressure reading valve open when crancking.... 2 - long cranck 3Bar with valve closed.

So I guess the wur will need changing or rebuild,
Still not sure about accumulator (Pressure drop)

I will try crancking it again tomorrow, but will put in another fully charged battery first.

[boyt911sc]

Originally Posted by schryvere

ok, great to see replies

My car is a US with lambda (new relay)..

I see what you mean with sahara, I checked it against the warm control temp, and the temp at test must have been around 15-20C.

I also tested and received voltage at WUR (9,5V) -> made me think that maybe this voltage drop is caused by the test setup jumper cables so I did the test again with AFS disconnected and 12V...
Something else I did was measure ohm's again (thought I did that hen I opened the wur) and at the pins I have 11ohms.

So today I did the test again with AFS disconnected (No cranck/ Injectors out CSV disconnected)
System pressure went up to 4,9Bar.

Cold control pressure after some gentle taps and wur disconnected 1,8
Warm control pressure With the wur connected 2.6 (prob the 10Ohm plays part in that). If I were to do the test again tomorrow, I wonder if the wur would need some help again...

The pressure this way went up a lot faster as well: 30 seconds instead of 2minutes.

It still dropped to 0 within 5seconds when I turned the key off (WUR open and connected).

Anyway, while the system was pressurized with wur open and warm (electrical plugged in) I did set the mixture ... I started at the point where the 1st one starts to open, turned back 180°.

Put them back in, connected the CSV and AFS and tried to start. pressure reading valve open when crancking.... 2 - long cranck 3Bar with valve closed.

So I guess the wur will need changing or rebuild,
Still not sure about accumulator (Pressure drop)

I will try crancking it again tomorrow, but will put in another fully charged battery first.

These are my comments to the highlighted sections of your above post:

• The heater resistance value (11 Ohms) for the WUR is too low and out of spec. Did you take measurement before running the FP or after?

• What was your WCP? Did you get 3.6 bar?

• Test the FA (fuel accumulator). Disconnect the bottom port of the FA, small amount of fuel coming out from the disconnected line is NORMAL. What is not normal is fuel flow from the bottom port. Place the end of the disconnect fuel line in a bottle or container or piece of rag. Do the same to the FA. Test run the FP for 1 or 2 seconds (max.).
  
  If fuel starts to flow out from the bottom of the FA, the diaphragm is broken or ruptured. And will cause to lose the residual fuel pressure?

• Why do you keep tinkering the fuel mixture setting?

• What did you mean by “2 long cranks 3 bar with the valve closed”? What valve was closed? The the valve for the pressure gauge?

• You need a good working and calibrated WUR.

Keep us posted. Thanks.

Tony

[schryvere]

11 ohms could be correct depending on the outside temperature, apparently these have 2bi-metalic strips, for cold and colder start... so the resistance might be ok, i ll take it out test in a 'hotter' environment.

The FA disconnect on the bottom, did not need 2 seconds to get a great spray out of that port. So I suppose that one is shot!

I'll order the FA, test the WUR and post later.

[boyt911sc]

Originally Posted by schryvere

11 ohms could be correct depending on the outside temperature, apparently these have 2bi-metalic strips, for cold and colder start... so the resistance might be ok, i ll take it out test in a 'hotter' environment.

The FA disconnect on the bottom, did not need 2 seconds to get a great spray out of that port. So I suppose that one is shot!

I'll order the FA, test the WUR and post later.

Schryvere,

The fuel accumulator is confirmed defective. Replace it and check your control (CCP & WCP), residual, and system fuel pressure.

The WUR will not cause any problem starting the engine but you will always have an erratic cold idle until the engine starts to warm up. This annoying behavior will not go away unless you fix it or ignore the symptom or get used to it. Keep us posted.

Tony

[schryvere]

Hi,

I want to thank you for the help. I have replaced the fuel accumulator and it started right up. I also bought a revision set for the WUR and played around with it a bit.
WUR has 2 resistors. The 11 ohms you get by having the 2 resistors in parallel in the WUR. 1 is 16 ohms, the other 26 as printed on them -> (1/16 +1/26)^-1 =9.9

As I found somewhere the switching of the bimetal is at around 15° I adjusted it in my basement where it is around 15

Checked the cold and hot pressure values, they are ok.

Just need to set the CO value to 2% I suppose to have it completely set up....

Anyone experimented with the lambda Voltage when disconnected? It starts at around 0,38V when cold and fals back when warming up, so lean. As a result it dies. When I connect the idle is stable havent tried to read the voltage delivered to the OX box. I know It's not conclusive, and as most I don't have a CO tester at home, but want to get to a shop without killing it.