1978/1979 911 SC COLD Control Pressure - Which Graph - 0438 140 045

[strictly]

I have two Porsche 911 Manuals, both showing different Graphs for Cold Control Pressure of a 1978/1979 SC?

Can i ask to anyone who has adjusted theres - which one they are using? I know it dosent matter that much, but might as well get it right, and hopefully help some others out at the same time!

I'm particculary interested in an ROW/Colder Climate info (i.e northern US states)

Warm Up Regulator : 911.606.105.05 (0438 140 045)

Known as a"045" Regulator

The three Graphs below are

LEFT Graph = Genuine Porsche Workshop Manual
RIGHT Graph = Genuine Porsche Workshop Manual
ABOVE Graph = Bentley Manual















So taking a temperature, say 20C, we see the

LEFT Porsche 045 Graph = 1.5 Bar
RIGHT Porsche 045 Graph = 2.0 Bar (this is the same graph as the bentley below, but note my comment in very end paragraph)
BENTLEY (TOP) 045 Graph = 2.0 Bar

All other pressures are the same (i.e Warm, no vac = 2.7 to 3.1 Bar)

BUT

Residual is

LEFT Porsche Spec = 1.5 Bar after 20 Minutes, 1.7(!) Bar after 20 Minutes (typo?)
RIGHT Porsche Spec = 1.3 Bar after 20 Minutes, 1.1 Bar after 20 Minutes
Bentley = 1.3 after 10 minutes, and 1.1 Bar after 30 minutes

A red herring, but i noticed on the Porsche Graph on the right it mentioned a test vacuum of 460 to 600 mBar, while we all know this is for the warm control side, why would it be mentioned ABOVE the diagram of the COLD control pressure. I'm guessing its not impossiable, the graph on the right, has been done under COLD vacuum? Hence the discrepancy between the two graphs...

[Steve F]

Good question, going through this myself tomorrow, same WUR, looking forward to the answer!

[T77911S]

tony is the man for this one

i have 2 charts that show the higher CCP.
I cant read your chart that shows the lower CCP but you do have a vacuum controlled WUR. does the chart with the lower CCP indicate that is WITHOUT vacuum. vacuum will drop the CP around .8bar. does one of the charts indicate a euro WUR

is the WUR adjustable?
what are the actual pressures. that might give you an idea.

this is just my opinion here, but how does it start? are you in a very cold climate?
if it starts good I would leave it alone. if it is adjustable I would drop the CCP and see if the cold starts get better and as long as it reaches full WCP I would not worry about it,.
the biggest concern is how does it start and will it reach WCP with a lower setting.

[strictly]

I trust Tony thats for sure, but i must say T77911S, ive read alot of your older posts/replies and they are really really good too! You two guys (and ossiblue) rock for CIS =)

No comment about VAC on the left porsche chart. Incidently there is a comment of VAC pressure just above the RIGHT Porsche chart, indicating that the chart was done with VAC applied to the WUR.

My WUR does have a VAC Port (it is also euro). My understaning of the VAC is that for normal cold control pressure testing, that is is not used, and that we only test VAC to see how it affect the Warm Control Pressure. At least that is how i understood it. PLEASE correct me, i'm all ears when it comes to learning about CIS and figuring out the problems!

My Current Cold Control Pressure is 1.5 bar @ 20 Deg C. I'm wondering if this is a little to rich. I'm chassing a hot start problem, which i know has no relation to cold control pressure, but i have decided to test and fix everything along the way!!

Luke

[914efi]

If your cold control pressure is too high it may be too high when hot also and will be hard[er] to start hot, they are related.

Vacuum leaks will also be a larger proportion of airflow when hot. When cold you have the AAV open [more air] and it is getting extra fuel through the cold start injector which can mask some of the finer tuning issues.

I like to tune for good running under load using a wide band 02 sensor. This is much more important and if correct it will usually start OK.

[boyt911sc]

Originally Posted by 914efi

If your cold control pressure is too high it may be too high when hot also and will be hard[er] to start hot, they are related.

Vacuum leaks will also be a larger proportion of airflow when hot. When cold you have the AAV open [more air] and it is getting extra fuel through the cold start injector which can mask some of the finer tuning issues.

I like to tune for good running under load using a wide band 02 sensor. This is much more important and if correct it will usually start OK.

914efi,

The cold and warm fuel pressures setting are independent from each other. They are not related. What made you think they are related? You may have a high cold control pressure and at the same time a low warm control fuel pressure. Or vice versa.

Maybe you meant AAR instead of AAV?

Tony

[914efi]

AAV, Aux Air Valve, maybe my term is different, same item.

Yes, you have higher control pressure when warm as the WUR valve closes when the bimetallic strip forces it closed as it warms up. When it is cold, the valve allowed to open. It is one setting that varies only with temperature. The system pressure obviously needs to be correct but we'll make that assumption.

In the units that have vacuum control CP is also responsive to manifold vacuum but that is a transient issue not related to the starting behavior.

My point was that you can get it started with a too-high CP when cold and have it not want to start when hot [especially after heat soak] due to the CP being too high [lean] and now having less start enrichment and no aux air coming in. If you add any vac leaks it gets even tougher.

[boyt911sc]

Originally Posted by T77911S

tony is the man for this one

i have 2 charts that show the higher CCP.
I cant read your chart that shows the lower CCP but you do have a vacuum controlled WUR. does the chart with the lower CCP indicate that is WITHOUT vacuum. vacuum will drop the CP around .8bar. does one of the charts indicate a euro WUR

is the WUR adjustable?
what are the actual pressures. that might give you an idea.

this is just my opinion here, but how does it start? are you in a very cold climate?
if it starts good I would leave it alone. if it is adjustable I would drop the CCP and see if the cold starts get better and as long as it reaches full WCP I would not worry about it,.
the biggest concern is how does it start and will it reach WCP with a lower setting.

Ty,

My good friend from the South, I hate to disagree with you but this for discussion purposes only. WUR-045 is a vac type assisted pressure regulator. And when you introduce vacuum to the WUR, the control fuel pressure reading increases. One good example is the table in the SC Bentley manual attached by Luke. Notice the difference in the control fuel pressure readings with and without vacuum applied?

Tony

[boyt911sc]

Luke,

I am back home and had some time today to look at the control fuel charts you have posted. Porsche shop manual and an SC technical bulletin issued by Porsche show two (2) different cold control fuel pressure charts. So the question is which is which? They both work as far I am concerned and tend to like the 'odd ball' chart data. Why? It's a trade secret (just kidding).

If I remember correctly you said your problem was only during a hot start and your WCP was 54 psi. Specification for WCP (WUR-045) is 46 ~ 53 psi. I prefer to set the WCP @ 51 ~52 psi. and the cold control fuel pressure slightly lower than the values from the chart. That's the reason I tend to use the 'odd ball' chart instead of the regular charts found in the reference manuals.

If I were doing the troubleshooting, I would do the following:
a). Adjust the WCP within the spec. (46 ~ 53 psi.) and use the mid point.
b). Test for vacuum leak. I suspect you might have unmetered air coming into the system(?). Test and verify.
c). Inspect your fuel injectors' spray pattern and for any fuel drips.
d). Measure the residual fuel pressure.
e). Have the exhaust gas analyzed only after confirming the absence of any significant vacuum leak in the system.

Keep us posted.

BTW, I also have a '78 SC where I began my introduction to CIS troubleshooting more than 25 years ago. Thanks.

Tony

[boyt911sc]

Originally Posted by 914efi

AAV, Aux Air Valve, maybe my term is different, same item.

Yes, you have higher control pressure when warm as the WUR valve closes when the bimetallic strip forces it closed as it warms up. When it is cold, the valve allowed to open. It is one setting that varies only with temperature. The system pressure obviously needs to be correct but we'll make that assumption.

In the units that have vacuum control CP is also responsive to manifold vacuum but that is a transient issue not related to the starting behavior.

My point was that you can get it started with a too-high CP when cold and have it not want to start when hot [especially after heat soak] due to the CP being too high [lean] and now having less start enrichment and no aux air coming in. If you add any vac leaks it gets even tougher.

Art,

We are discussing WUR-045 in this thread and I agree with most of what you mentioned. But what has the system pressure to do with cold control fuel pressure. The system pressure is controlled by the primary pressure valve (PPV) located inside the FD. Maybe you meant warm pressure instead of system pressure. Please don't take this personal. This is the 911 Technical Forum and we are just discussing technical terms. Just like to know if we are on the same page. Otherwise, we could be comparing apples to oranges. Thanks.

Tony

[T77911S]

Originally Posted by boyt911sc

Ty,

My good friend from the South, I hate to disagree with you but this for discussion purposes only. WUR-045 is a vac type assisted pressure regulator. And when you introduce vacuum to the WUR, the control fuel pressure reading increases. One good example is the table in the SC Bentley manual attached by Luke. Notice the difference in the control fuel pressure readings with and without vacuum applied?

Tony

that's alright tony. just a typo. thanks for the correction.
don't be afraid to correct me, you know we have some good discussions when we don't agree.

[strictly]

Thanks for the help so far. Really appreciated. I will make up for it buy helping others on other posts where i can =)

Ok so on the 045, intresting they are both the same chart then, with the left one showing some vac. Good old Bentley missed that fact. Okay so for COLD control adjustment i therefore deduce i should use the LEFT chart, which is the odd ball one you like Tony. And if you like it, then I love it.

I will follow your troubleshooting steps. Can i ask how i test for the vacuum leak? I have done the smoke test on the CIS (pull and injector out, and blow smoke through the inlet manifold). It only has smoke coming out of the airflow plate. My entire CIS has new gaskets, seals, orings (recently rebuilt engine)

Since my last post, I have checked the CO on a meter (this is before i read your post). I set CO to 3%, it was much higher and i have brought it down.

I decided to re look at my fuel distributor/injectors. With the CO at 3% with engine warm (warm control pressures) and running, i have removed the injectors (engine off, fuel pump running) and YES my fuel distributor is dripping with no injectors fitted...oh dear!!

Before we conclude that my fuel distributor is no good, are there any other tests? Should i test the pressure between the fuel pump and the fuel distributor?

I will post my warm and cold pressures with residuals pressures. But all seam okay. Can i have a bad fuel distributor with good residual pressure? In any case i'll post them a little later because i know everyone likes to see them!! Myself included when i try and help others!

Thanks guys really appreciated =)

[ossiblue]

Originally Posted by 914efi

Yes, you have higher control pressure when warm as the WUR valve closes when the bimetallic strip forces it closed as it warms up. When it is cold, the valve allowed to open.

My point was that you can get it started with a too-high CP when cold and have it not want to start when hot [especially after heat soak] due to the CP being too high [lean] and now having less start enrichment and no aux air coming in. If you add any vac leaks it gets even tougher.

Just to clarify, again, the above is incorrect.

As Tony posted, Cold Control Pressure is independent of Warm Control Pressure.

The bimetallic arm does not "force the WUR valve to close" as it warms up. Technically, the control pressure is governed by the springs beneath the pin carrier, and those springs are influenced by the bimetallic arm only when the temp is cold.

When the WUR is warm, the bimetallic arm is completely free from pressure on the springs and the pin is controlled only by the springs. When cold, the bimetallic arm bends downward on the springs/pin carrier and moves the pin away from the diaphragm, lowering the pressure. The bimetallic arm only affects the pin when cold. Once warmed, either through the heating element or heat-sink, the bimetallic arm bends upward and removes all pressure from the springs. Warm pressure is thus controlled only by the pressure of the springs on the pin carrier and the pin's pressure on the diaphragm.

To properly set a WUR, the warm pressure is set first with the bimetallic arm pressure completely off of the pin carrier--either by ensuring the arm is fully bent upward or by pressing the plug upward to remove all pressure. Once warm pressure is set, the plug is pressed downward until the cold pressure is in spec. This process ensures that the cold bimetallic arm only moves the pin from its warm setting to its cold position, and that when the arm heats up, it will bend upward far enough to release all pressure from the pin carrier.

[strictly]

Originally Posted by ossiblue

Just to clarify, again, the above is incorrect.


To properly set a WUR, the warm pressure is set first with the bimetallic arm pressure completely off of the pin carrier--either by ensuring the arm is fully bent upward or by pressing the plug upward to remove all pressure. Once warm pressure is set, the plug is pressed downward until the cold pressure is in spec. This process ensures that the cold bimetallic arm only moves the pin from its warm setting to its cold position, and that when the arm heats up, it will bend upward far enough to release all pressure from the pin carrier.

That's exactly how i understand it too. Last time i set my WUR up for warm (my old 78) i took the heater and arm out completely, with the pin and the springs still in place, in that particular case, i then set the WUR up for warm, no vac, then drove the cold pin in to set the cold pressure

----------------------------- HOT START PROBLEM & PRESSURES --------------------------

Ok so moving on to my Hot start problem. I have found that with the mixture set on a gas analyzer (see previous post),and the air flow plate at rest (and the correct height to the upper edge of the venturi), then my fuel distributor is leaking or dripping fuel (FP running, and injectors removed). The same test with the injectors fitted results in either one injector spraying, or them dripping.

Is it posisable to have a faulty fuel distributor with a good residual pressures?

I tested my pressure after the fuel accumulator (see end paragraph) and it gets a bit weird.

Here are my pressures

CONTROL

COLD 1.5 Bar (22 PSI)
WARM 2.8 Bar (41 PSI) this took 5 minutes with the heater

RESIDUAL (FROM WARM CONTROL)

0 Minutes 2.8 Bar (41 PSI)
10 Minutes 2.6 Bar (38 PSI)
20 Minutes 2.4 Bar (34 PSI)
30 Minutes 2.2 Bar (33 PSI)

SYSTEM

COLD 4.8 Bar (69 PSI)
WARM 4.8 Bar (69 PSI)

RESIDUAL (FROM SYSTEM)

0 Minutes 4.8 Bar (69 PSI)
10 Minutes 4.6 Bar (66 PSI)
20 Minutes 4.4 Bar (64 PSI)
30 Minutes 4.2 Bar (58 PSI)
60 Minutes 3.6 Bar (54 PSI)

Is it possible to have residual pressures which are too good?

---- FUEL ACCUMULATOR ---

One thing i noticed was in some later tests, if i reconnected the fuel pump, while the system was under pressure (i.e holding rest pressure). I would get a spray of fuel instantly from all of the injectors (therefore giving me a too rich mixture??? Hence problems with the hot start?

That got me thinking, about fuel surge, its a new fuel accumulator (which of course could be bad, but system rest pressure is good...) So ive tested the fuel pressure after the fuel accumulator and fuel pump but dead heading the pump.

I dead headed the pump by connecting a pressure gauge, and switching the valve closed. It went to 8.3 bar then rapidly fell to 3 bar. A good accumulator, should hold it at 7 bar right (above system pressure).

My resisdual pressures are good, it is possiable to have a faulty accumulator/fuel pump check valve but still have good residual system pressure at the FD? Maybe i did the above test wrong, and i will recheck it. I'm worried about blowing some the main fuel pump to fuel accumulator line/connection, as pressure is over 10 bar.

Luke

[boyt911sc]

Luke,

The WCP @ 41 psi. is too low probably because you have not applied vacuum to the WUR. Did you do the test with the engine off and the FP running with no applied vacuum?

Second, rebuilding a FD is quite different from rebuilding a WUR. I have confident in your ability to do almost anything you put your mind on it. Salvox is a good rebuild kit but not cheap at all. The challenge you will have is how to rebuild the FD that does not leak fuel. Try to rebuild a FD and keep us posted. Thanks.

Tony

[strictly]

Originally Posted by boyt911sc

Luke,

The WCP @ 41 psi. is too low probably because you have not applied vacuum to the WUR. Did you do the test with the engine off and the FP running with no applied vacuum?

Second, rebuilding a FD is quite different from rebuilding a WUR. I have confident in your ability to do almost anything you put your mind on it. Salvox is a good rebuild kit but not cheap at all. The challenge you will have is how to rebuild the FD that does not leak fuel. Try to rebuild a FD and keep us posted. Thanks.

Tony

Thanks for the confidence boost =) I'll have a go at the FD (and will fix the WUR after). Good to know the Salvox kits are considered good, that gives me some confidence in it too.

Besides the FD and the WUR, have you ever tested the pressure before and after the fuel accumulator?

I did the test after the accumulator, and it sent my gauge to 8.3 bar then rapidly fell to 3 bar.... It is a new accumulator, but is it not supposed to hold the pressure at say 7 bar, to proect the FD from a pressure surge? Also i dont understand if its possiable to have a bad accumultor of fuel pump check valve and still have good system pressure

I'm wondering if I am chasing multiple problems (not surprising)!

Can i test the fuel pump check valve by dead heading the pump (i.e connecting a pressure gauage with valve, and then turning the valve closed) like for testing system pressure?

Luke

[strictly]

P.S (see above first)

yes on the WARM Control, sorry i did not test with vaccum. Presumably it needs to pass both tests, as bentley says, the pressure with no vac (39 to 45 PSI) and then the pressure with VAC (46 to 53). What Vac pressure should i use?

[boyt911sc]

Luke,

You could test the FP, FA, and FD individually. First, install the pressure gauge after the FP and run it for a couple of seconds and close the valve and immediately shut off the FP from running. Record the pressure reading and observe the pressure drop during the next 20 or 30 mins.

Repeat the same test for the FA and install the gauge after the FA. Record the pressure the next 20 or 30 mins.

For the FD test, install the gauge after the fuel filter or before the FD to measure the residual pressure. Or between the WUR and FD (normal installation location). As you have demonstrated, a defective FD could easily pass the residual pressure test if the PPV is good and working. But would fail in the flow test. In summary, a FD has to pass the flow test to be considered a good working unit.

Now that you have discovered that FD is prematurely delivering fuel with the FD plunger down, this is a major problem you have to fix. There should be no fuel coming out from the FD when the FP is running and the plunger at rest. And if you get some fuel flow from any of the six (6) ports or lines, either the plunger is set too high (RICH) or one of the several o-rings inside the FD has failed or broken or defective (whatever you want to call it). This has to be fixed or corrected.

Tony

[strictly]

Hi Tony,

thank you for the explanation. That helps me understand it better.

Ok so either way, my FD needs to be rebuilt. I understand now that if it has a good PRV then it can pass the residual test, but it means i can still have problems with pressure loss from the FA or FP. Thank you, thats what i needed to understand.

So i will order the salvox kit, and I will continue to test the rest of the system, as it sounds like i probably have mutilple problems, which i would like to fix all at the same time.

I really like learning how to test things, rather than just throwing parts at something. Thanks to all for helping me with learning that. Problem solving is great when you have help =)

I will post my FP and FA results. And i will keep all posted on the FD rebuild, and the overall outcome.

Luke

[T77911S]

you have to keep it VERY clean between the top and the bottom.