Help with CIS test numbers (new guy)

[area man]

Hi folks, this is my first time posting here after a lot of lurking. I could use some help interpreting the results of a CIS pressure test on my 1980 Euro 911sc. (I bought the car last year from a former Pelicaner, so some people may recognize it - pic below). It runs pretty rough when it's cold - hesitating, low idle, and backfiring at times - and then it smooths out and runs really well when it's at full operating temperature. The gas mileage is not great (around 15), and after a long drive there's always a thin layer of soot on the back end. All this leads me to believe that the WUR is not functioning properly. I checked for vacuum leaks and didn't find anything, so I got the CIS pressure gauge from our host and tested it. Here are the numbers I got (in bar):

Control pressure cold 1.65
Control pressure warm (engine not running) 2.75
System pressure 4.8
Control pressure with engine running, warm 3.2

The right numbers for this car, according to Jim Williams' CIS primer site at Rennlist, are

Cold pressure 1.8
warm pressure 3.0
system pressure 4.5 - 5.2
warm pressure with vac connected 3.4

So, the long and short of it is the system pressure is within spec, but the cold and warm pressure numbers are low. I'm fudging it with temperatures as I don't have a thermometer.

My question is, before I go spending money on a new WUR, should I be looking at other possible sources for the problem? Do these numbers fit the pattern for malfunctioning WURs? I did give it a tune up recently - adjusted valves, set timing, changed the plugs, wires, rotor, cap, etc. Also a Porsche mechanic set the fuel mixture last spring, after a backfire blew out the pop-off valve. That helped with the idle but didn't solve the other issues. (I'm guessing that the mixture had been tweaked to compensate for the bad WUR). I'm working on the assumption that you have to get the CIS pressure sorted out before you can address any other issues. But on the other hand I don't want to get into a wild goose chase replacing this part and that.

Thanks a million for any help, Danny.

here she is:

[Joe Bob]

There is a test proceedure for the WUR in Bentley. The other item, cheap, is the check valve in the neck of the fuel pump.

Before you start screwing with the fuel mix you should have access to an exhaust analyzer.

[boyt911sc]

Danny,

You are on the right track for CIS troubleshooting. But before you start doing any alteration in your set-up, check for vacuum/air leak. Get the engine to reach operating temperature and let it idle for a few minutes and remove the oil filler cap. The idle speed should drop!!!! Next, have the exhaust gas checked using a gas analyzer and determine the current mixture reading.

The cold control and system pressures are OK but warm control fuel pressure is too LOW!!!! Check the WUR cold control fuel pressure from start to 3 minutes. There is another post today, where I suggested this simple test. Could you check the WUR ID number?

I could lend you one of my spare WUR's for your test in case you need one. Do you have the -072 or -089? Keep us posted.



Tony

[matstermag]

Originally Posted by boyt911sc

Danny,

You are on the right track for CIS troubleshooting. But before you start doing any alteration in your set-up, check for vacuum/air leak. Get the engine to reach operating temperature and let it idle for a few minutes and remove the oil filler cap. The idle speed should drop!!!! Next, have the exhaust gas checked using a gas analyzer and determine the current mixture reading.

The cold control and system pressures are OK but warm control fuel pressure is too LOW!!!! Check the WUR cold control fuel pressure from start to 3 minutes. There is another post today, where I suggested this simple test. Could you check the WUR ID number?

I could lend you one of my spare WUR's for your test in case you need one. Do you have the -072 or -089? Keep us posted.



Tony

That pictures is awesome! you want a used 008 for that collection?

Area man stick with Tony on K-jet pressures.

Cheers,
Matt

[area man]

Tony,

I checked for leaks before I did the pressure test, using a propane torch (not lit, ha ha). I didn't find anything. Also the idle drops off quite a bit when you remove the oil filler cap, so I don't think air leaks are the problem.

I can do the test with gauge hooked up for the first few minutes of warmup. What am I looking for there? I'll see if I can get an exhaust analyzer on it too.

Thank you for the offer of the loaner WUR. The one on my car is an -045. It's a Euro model and a lot of the parts are older or just different (no vac advance on the distributor for instance). Also it has SSI's, backdated heating, NO oxygen sensor. All pretty simple...

Thanks! D

[boyt911sc]

Since the car has no lambda/OXS and your car is an EURO model, that's one less to worry. It would be easy to test run this one. Hook up the fuel pressure gauge and leave it there until you are done with the start-up. The fuel pressure readings alone, would give you information in case you are having difficulties getting it to start.

Observe the control fuel pressure go up over time (2 - 3 mins.) and that will give you a profile of the WUR's control pressure (from cold to warm).

Keep us posted.

Tony

[area man]

It'll take a day or two before I can get to it, but I'll let you know what happens with that test. Car starts up fine though. I can try the check valve too, as Joe Bob said, but since the system pressure is good, I doubt that's where the problem is.

Sounds to me like the WUR is bad, one way or another, given the warm control pressure numbers. I know there's a big thread on this, but... Leask vs. DWUR? Any opinions?
D

[ossiblue]

Originally Posted by area man

It'll take a day or two before I can get to it, but I'll let you know what happens with that test. Car starts up fine though. I can try the check valve too, as Joe Bob said, but since the system pressure is good, I doubt that's where the problem is.

Sounds to me like the WUR is bad, one way or another, given the warm control pressure numbers. I know there's a big thread on this, but... Leask vs. DWUR? Any opinions?
D

Don't jump to conclusions about the WUR being faulty. The WUR is a simple device with the most complex part being the heating element and the bimetallic arm--both of which appear to be working as the pressures do change over a period of time. The low warm control pressure can be adjusted and in your case, fairly easily because you wish to increase warm control pressure.

Once you know the engine and WUR are completely warmed and the fuel pressure is as high as it will go (pressure gauge set attached), you can gently tap down on the cylinder in the WUR body that holds the inlet/outlet for the fuel. With each tap, watch the pressure gauge and when it reaches spec, you're done. What you'll be doing is moving the diaphragm that regulates the pressure against the pin on the bimetallic arm--narrowing the gap and increasing fuel pressure. Do this slowly as if you tap too hard and the pressure goes too high, you will have to disassemble the WUR and press the cylinder upward in the housing and start over again. Not the end of the world, but something you should try to avoid. I've done this several times and used a long socket extension for a driver on the cylinder and a ball peen hammer for the tapping. Once you reset your warm control pressure, you will need to wait until the engine is completely cold and reset you cold control pressure by tapping down the round pin.

You're in good hands with Tony, and I don't foresee a major problem for you with your WUR.

[Bob Kontak]

Originally Posted by ossiblue

With each tap, watch the pressure gauge and when it reaches spec, you're done.

Great info.

I would not ditch the WUR even if you stay with the numbers you are getting now. But that is me. You are just running only a touch rich with the lower control pressure.

As Ossiblue says - gently. I would buy a nice quality drift and use a small ball peen hammer and tap ever so gently to bring it onto spec. If you whack it too hard you have to take the WUR apart and tap it back out which is a PITA - not hard - just tedious.

Keep it to the lower/rich side of the range as your system is 31 years old. I will see if I have the graph in the factory manual.

[area man]

Thanks everyone, this is really helpful information! I'm going to do the pressure test as per Tony's instructions in a little while, then try the adjustments. two questions though:

1. If you need to raise the cold pressure to get it up to spec, does that mean you have to bring the small pin up, rather than tap it down? And if so do you have take the WUR apart, or is there a simpler method?

2. Does the adjustment you make to the 'cold side' have an impact on the warm pressure adjustment? Looks like it would, just from looking at diagrams. If that's the case does it make sense to do the cold adjustment first? Pls correct me if I'm wrong. the diagram I'm thinking of is this one:

[area man]

Just to clarify, by 'small pin' I mean the thing that ossiblue called the 'round pin', which i'm assuming is this:



thanks

[Bob Kontak]

Originally Posted by area man

Thanks everyone, this is really helpful information! I'm going to do the pressure test as per Tony's instructions in a little while, then try the adjustments. two questions though:

1. If you need to raise the cold pressure to get it up to spec, does that mean you have to bring the small pin up, rather than tap it down? And if so do you have take the WUR apart, or is there a simpler method?

2. Does the adjustment you make to the 'cold side' have an impact on the warm pressure adjustment? Looks like it would, just from looking at diagrams. If that's the case does it make sense to do the cold adjustment first? Pls correct me if I'm wrong. the diagram I'm thinking of is this one:

#1 See post number 2 in this thread. I think you are correct. Bumping the plug in will decrease control pressure and make your mixture more rich. It also intuitively makes sense from looking at the diagram. Pushing down on the plug levers the pin into the base of the diaphragm squeezing off system pressure.

WUR malfunction repair?

#2 Moving the plug will impact both cold and warm pressure. I want to say in a linear fashion but that would be outside my knowledge base.

Let me get you that pressure graph now.

Edit - Here is ossiblue's comment - "What you'll be doing is moving the diaphragm that regulates the pressure against the pin on the bimetallic arm--narrowing the gap and increasing fuel pressure." He may be right but I (the accountant) think that narrowing the gap would decrease the pressure as it restricts. Need clarity on this.

[boyt911sc]

Areaman,

#1. Yes. Pin down, control pressure goes down. And reverse.

#2. No. The warm control pressure is adjusted by moving the circular disc where the two (2) fuel lines are connected (see your pic). And is not affected by adjusting the pin for control pressure adjustment. Move it (disc) up, warm pressure goes down and reverse.

Lastly, that's the pin we are talking about. The pin is pulled up by the nut/bolt attached to it (see your diagram).

Tony

[Bob Kontak]

Originally Posted by boyt911sc

Areaman,
#2. No. The warm control pressure is adjusted by moving the circular disc where the two (2) fuel lines are connected

Hi Tony - are you saying the entire disc that the two fuel lines mount into is turned for warm pressure adjustment?

Is that what the two little holes are for - to put a spanner in there for turning?

[Bob Kontak]

Here is the factory pressure graph for the 78-79 Bosch "-045" regulator. I have the US manuals and the 80 has a different part number - must be O2 sensor related for the US version.

[Bob Kontak]

Oops - forgot jpg

[Bob Kontak]

Originally Posted by Bob Kontak

Hi Tony - are you saying the entire disc that the two fuel lines mount into is turned for warm pressure adjustment?

Did some searches - That is correct.

Edit - But information on this is sparse and not well documented. I am all ears.

[boyt911sc]

Originally Posted by Bob Kontak

Hi Tony - are you saying the entire disc that the two fuel lines mount into is turned for warm pressure adjustment?

Is that what the two little holes are for - to put a spanner in there for turning?

Bob,

That circular disc is pressed hard for mounting. You could not turn it with a spanner!!!! It is pulled up or pressed down to make the adjustment. I have a picture that someone had posted in the forum on how the adjustment is made (mechanical method).




Be aware that these discs do not have threaded holes as shown in the pictures. The guy fabricated these threaded holes to pull up the disc. I use a different method than what is shown above. HTH.

Tony

[Bob Kontak]

Great info. Thank you, Tony.

This runs contrary to the "standard" information. I offer the Jay Pineau / Bob Tindel article in PP's tech forums. See the 7th paragraph - quote from "The Bruce" no less.

Pelican Technical Article: 911 Warm-Up Regulator Adjustability

So I do some more sniffing on Google and find this tasty treat - I bet this is your method.

See video at 1:30 in:

k-jetronic adjusting warm-up valve, system & control pressure on golf mk2 gti - YouTube

Not arguing but I have to believe that bumping the plug has to impact warm C pressure to a degree? Or is it absolutely stand alone for cold control pressure?

[ossiblue]

Just to clarify a bit, I have adjusted the warm control pressure several times and, as Tony noted also, it is done by moving the entire cylinder with the inlet/outlet ports either up (lower pressure) or down (increase pressure)--no turning involved. I did not use the method shown in the diagram but rather used the tapping method with a drift and hammer--something you can do because you wish to raise your pressure and that can be done without disassembling anything, if you're careful and work slowly!