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Testing.........

Quote:
Originally Posted by Walt Fricke View Post
Tony - do the standard fittings on the usual pressure gauge systems fit the connection on the return line? I didn't know that.

Since the return to the tank just dumps fuel to atmospheric pressure, shouldn't there be basically zero pressure with the valve open (return flowing)? Do you really need to try to connect up by the fuel tank, with the possibilities of fuel pouring out?

How often is the return line itself clogged? I'm hard put to see just how something big enough to obstruct a line could get into it.

The WUR has a filter on its exit side - a bunch of tiny drilled holes in the casting itself, it looked like. When that got obstructed on my WUR, control pressure equaled system pressure, which was a tip off for sure of a problem.

Easy enough to clean if you disassemble the WUR. Could that be a possible explanation for the quite high control pressure?


Walt,

The standard CIS pressure fitting is 12-mm x 1.5 and the fittings for the delivery and return lines have 14-mm x 1.5. So you will need an adaptor (12-mm x 1.5/14-mm x 1.5) to connect the CIS pressure gauge kit.

The normal return line will have very low pressure reading and could hardly register on the gauge. But a slightly restricted return line will register something on the gauge. Another restriction also occurs at the WURís micro screen filter when the screen gets clogged with dirt or debris.

You need to determine that return line is free flowing before blaming the WUR for excessive control pressure and vise versa.

Tony

Old 10-14-2019, 07:32 PM
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A quick test for the return line is attaching a new hose to metal line leaving engine bay and it should be easy to tell as gently blowing into it will prove line is clear.
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Old 10-14-2019, 07:49 PM
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Here are the specs for your car provided it is US market. Pressures are different for non-lambda cars.
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Old 10-14-2019, 08:01 PM
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Flow restriction........

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Originally Posted by manbridge 74 View Post
A quick test for the return line is attaching a new hose to metal line leaving engine bay and it should be easy to tell as gently blowing into it will prove line is clear.
What if the restriction is occurring some where between the gas tank and the connection to the metal line? You need to test the whole return line from start to end.

Tony
Old 10-14-2019, 08:06 PM
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Yes, I am talking about the line back to tank. Another guy watching through sending unit hole or even listening at gas fill hole should see/hear bubbles.
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I do not disbelieve in anything. I start from the premise that everything is true until proved false. Everything is possible.
Old 10-14-2019, 08:09 PM
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Quote:
Originally Posted by boyt911sc View Post
Blue,

The return line is bolted to intake runner #3. Or follow the drain line of the fuel accumulator in your motor to intake #3. See circle for reference.



Tony
If I understand correctly,
I disconnect the return line to the tank at the location you pointed to.
Attach, a hose to the return line and let the fuel drain into an external container.
Measure control pressures.

I really appreciate the patience of everyone. Forgive my silly questions that may be obvious to most. I am not very familiar with these cars.
Old 10-15-2019, 01:03 PM
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Pressure, pressure, whose got the pressure:

The fuel pump produces it - maybe 6 bar/90 PSI? If it is weak enough, you might not be able to hit the system pressure target. Yours is new.

System pressure: the line from the pump, after going through the filter and accumulator, has pump pressure reduced by a regulator in the fuel distributor. This can be adjusted by adding or removing shim washers. Your shop sounds like it did this, though I don't know which way they went. Maybe added one, because your system pressure is too high. Getting it back into spec would be a good idea. If this were mine, I'd remove a washer. I've had a FD apart, have a bunch of books, etc. But it sounds like this would be a challenge for you. Not for a shop with CIS experience, though. System pressure gets sent to the WUR, and also to the fuel injectors.

Control pressure: this is set by the misnamed warm up regulator, which really is the control pressure regulator. Control pressure affects the relationship between the amount of air flowing into the intake ports and the amount of fuel injected. More air needs more fuel, etc. It operates counter intuitively - more pressure means less fuel.

The warm up part of the WUR reduces the control pressure while the engine is cold. When the engine gets going, the WUR pretty quickly increases control pressure. This is why you see the two figures, one for a cold engine, one for a hot.

Cold engines like a richer mixture for starting. That's what this is all about. However, if too rich, there are problems, just like being too lean.

You have measured the cold control pressure and the system pressure. What is the warm/hot pressure? And what is the 10 and 20 minute residual pressure? Easy to measure - you've got the gauge set up. You should do those before moving your gauges to check for return line obstructions. I'd put those way down on the list - pretty hard to have anything partially block a return line.

There are other adjustments here. There is an idle speed screw. If the cold idle is too low, you can increase or decrease the throttle bypass air to lean the mixture - or richen it. That isn't likely to help with the starting problem, where you have to put the pedal down a bit. But could with the idle. Of course, it might mess up the warm engine idle.

There is a screw which affects the relationship of intake air to fuel. When you take the air filter off, and reach into the air box and up on the right side, you can feel a lever. More air flow, the sensor plate moves the lever up, and this increases the fuel flow. A screw semi-buried down inside this side of things, reached from on top between the FD and the rubber boot through a small hole, adjusts the relationship. A shop sets this by using a CO meter, or nowadays more often an air fuel meter. There are techniques to do this at home, so to speak, also. Probably not where your starting problem is, but could be. It is used to get the emissions where they should be, but can be adjusted a bit rich for more power. Too much either way, and you get various problems.

Two additional checks have been mentioned.

--You can check for air leaks by having a smoke test done. If a shop asks what is that, try another shop. If you have air leaks, fix those. If you don't have leaks, one less thing to worry about.

==The frequency valve system, which works with the oxygen sensor to fine tune the mixture so your air/fuel ratio is very close to 14.7 for complete combustion, is part of the equation. If it is disconnected you can experience hard starting. I learned this when putting a 3.0 into my 2.7. The 2.7 CIS didn't have this feature, and I figured I didn't need it, so didn't put it in. Once I hooked it all up, even though I didn't have an oxygen sensor yet, the car started much better.

The white circle is the frequency valve.



You can reach back there to make sure it is plugged in. With the engine running, you can reach it to feel with your fingers if it is vibrating or not. It should vibrate. You could remove the connector with the engine running to see if it feels different, and again when you reconnect it. If it vibrates, one less thing to worry about fixing your starting problems. If it doesn't vibrate, well that's a whole different line of troubleshooting.

Since the car runs great when warmed up, I don't think anything especially bad is going on that would be quite expensive to fix.

But give us the hot control pressures, and the residual pressure figures.

Tony knows these systems almost by heart, and differential diagnosis should work with enough pertinent information. He's a methodical engineer numbers guy, so give him the numbers.
Old 10-15-2019, 03:00 PM
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Pressure, pressure, whose got the pressure:

The fuel pump produces it - maybe 6 bar/90 PSI? If it is weak enough, you might not be able to hit the system pressure target. Yours is new.

System pressure: the line from the pump, after going through the filter and accumulator, has pump pressure reduced by a regulator in the fuel distributor. This can be adjusted by adding or removing shim washers. Your shop sounds like it did this, though I don't know which way they went. Maybe added one, because your system pressure is too high. Getting it back into spec would be a good idea. If this were mine, I'd remove a washer. I've had a FD apart, have a bunch of books, etc. But it sounds like this would be a challenge for you. Not for a shop with CIS experience, though. System pressure gets sent to the WUR, and also to the fuel injectors.

Control pressure: this is set by the misnamed warm up regulator, which really is the control pressure regulator. Control pressure affects the relationship between the amount of air flowing into the intake ports and the amount of fuel injected. More air needs more fuel, etc. It operates counter intuitively - more pressure means less fuel.

The warm up part of the WUR reduces the control pressure while the engine is cold. When the engine gets going, the WUR pretty quickly increases control pressure. This is why you see the two figures, one for a cold engine, one for a hot.

Cold engines like a richer mixture for starting. That's what this is all about. However, if too rich, there are problems, just like being too lean.

You have measured the cold control pressure and the system pressure. What is the warm/hot pressure? And what is the 10 and 20 minute residual pressure? Easy to measure - you've got the gauge set up. You should do those before moving your gauges to check for return line obstructions. I'd put those way down on the list - pretty hard to have anything partially block a return line.

There are other adjustments here. There is an idle speed screw. If the cold idle is too low, you can increase or decrease the throttle bypass air to lean the mixture - or richen it. That isn't likely to help with the starting problem, where you have to put the pedal down a bit. But could with the idle. Of course, it might mess up the warm engine idle.

There is a screw which affects the relationship of intake air to fuel. When you take the air filter off, and reach into the air box and up on the right side, you can feel a lever. More air flow, the sensor plate moves the lever up, and this increases the fuel flow. A screw semi-buried down inside this side of things, reached from on top between the FD and the rubber boot through a small hole, adjusts the relationship. A shop sets this by using a CO meter, or nowadays more often an air fuel meter. There are techniques to do this at home, so to speak, also. Probably not where your starting problem is, but could be. It is used to get the emissions where they should be, but can be adjusted a bit rich for more power. Too much either way, and you get various problems.

Two additional checks have been mentioned.

--You can check for air leaks by having a smoke test done. If a shop asks what is that, try another shop. If you have air leaks, fix those. If you don't have leaks, one less thing to worry about. Air leaking in past where the air flow is measured messes up the air fuel ratio.

==The frequency valve system, which works with the oxygen sensor to fine tune the mixture so your air/fuel ratio is very close to 14.7 for complete combustion, is part of the equation. If it is disconnected you can experience hard starting. I learned this when putting a 3.0 into my 2.7. The 2.7 CIS didn't have this feature, and I figured I didn't need it, so didn't put it in. Once I hooked it all up, even though I didn't have an oxygen sensor yet, the car started much better.

The white circle is the frequency valve.



You can reach back there to make sure it is plugged in. With the engine running, you can reach it to feel with your fingers if it is vibrating or not. It should vibrate. You could remove the connector with the engine running to see if it feels different, and again when you reconnect it. If it vibrates, one less thing to worry about fixing your starting problems. If it doesn't vibrate, well that's a whole different line of troubleshooting.

Since the car runs great when warmed up, I don't think anything especially bad is going on that would be quite expensive to fix.

But give us the hot control pressures, and the residual pressure figures.

Tony knows these systems almost by heart, and differential diagnosis should work with enough pertinent information. He's a methodical engineer numbers guy, so give him the numbers.
Old 10-15-2019, 03:08 PM
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"I am completely lost and do not know what the problem is or how to solve it. Have an appointment with another well known Porsche shop here. Not sure how good these guys are but I am not sure what I can do at this point."

When it comes to CIS injection, I find that most shops do not seem to know much more than we do and the they seem to make the most simple problems more complicated and expensive too.

Cheers,
Joe
87 Carrera
Old 10-16-2019, 06:23 AM
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"The standard CIS pressure fitting is 12-mm x 1.5 and the fittings for the delivery and return lines have 14-mm x 1.5. So you will need an adaptor (12-mm x 1.5/14-mm x 1.5) to connect the CIS pressure gauge kit."

FYI - I have this adapter fitting in stock if anyone needs one.

Len.Cummings @ verizon.net

Old 10-16-2019, 07:15 AM
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Hey, nice marmot.
 
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Quote:
Originally Posted by stlrj View Post
"I am completely lost and do not know what the problem is or how to solve it. Have an appointment with another well known Porsche shop here. Not sure how good these guys are but I am not sure what I can do at this point."

When it comes to CIS injection, I find that most shops do not seem to know much more than we do and the they seem to make the most simple problems more complicated and expensive too.

Cheers,
Joe
87 Carrera
Exactly. Not saying there aren't good shops out there but the only sure-fire way to figure it out is by the size of the check you write.
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Old 10-16-2019, 10:30 AM
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Quote:
Originally Posted by tirwin View Post
Exactly. Not saying there aren't good shops out there but the only sure-fire way to figure it out is by the size of the check you write.
If not for CIS most shops would be out of business. Almost seems like a $cam.

Last edited by stlrj; 10-16-2019 at 11:43 AM..
Old 10-16-2019, 11:40 AM
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Hey, nice marmot.
 
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Quote:
Originally Posted by stlrj View Post
If not for CIS most shops would be out of business. Almost seems like a $cam.
Huh. Interesting. That's not been my experience. I do think where you live and the size of the market makes a big difference. Some people may not have a lot of choices. Some places here would turn away an old aircooled car. But it is always changing as some of the guys who cut their teeth on these cars are retiring. I see blank stares from the younger guys. Or they are looking stuff up on the Internet like the rest of us.

There's no substitute for experience.
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Old 10-16-2019, 12:40 PM
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I disconnected the fuel return line and connected it to an external container for recycling the gas.
System pressure 78psi, about the same as the previous test with the return line connected to the carsís tank. This tell me the return line is not blocked.

Now here is the twist.
The cold control is 0.5 bar or 7 psi. The cold control pressure was 3.9 bar or 57 psi. I donít understand how the control pressure can change so much. I will do additional test again tomorrow with the return line connected back to the tank.
Old 10-16-2019, 09:47 PM
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Locating where flow restriction..........

Quote:
Originally Posted by bluelectron View Post
I disconnected the fuel return line and connected it to an external container for recycling the gas.
System pressure 78psi, about the same as the previous test with the return line connected to the cars’s tank. This tell me the return line is not blocked.

Now here is the twist.
The cold control is 0.5 bar or 7 psi. The cold control pressure was 3.9 bar or 57 psi. I don’t understand how the control pressure can change so much. I will do additional test again tomorrow with the return line connected back to the tank.


Blue,

The cold control is 7 psi. with the return line disconnected and goes up to 57 psi. when connected, as per your test. This simply indicates flow restriction some where along the fuel return line going back to the gas tank. This is the reason why you need to test the complete return line to locate the culprit. There are several connections in the return line, either test the line/s using compressed air or fluid to locate it.

You have a partially blocked return line. To demonstrate how the restriction affects your old control fuel pressure is gradually closing the valve to 70%~80% closed and you will replicate your problem.

Tony
Old 10-17-2019, 02:10 PM
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Update with new pressures

I remeasured all the pressures again after blowing the return line with compressed air.

Temperature in the garage was 13.5 C (Its already cold in Calgary )

Here are the pressures.

First disconnected WUR Electrical connection.

System Pressure: 5.4 Bar
Cold Control Pressure with WUR electrical disconnected: 0.6 Bar

After about 30s, reconnected the WUR electrical connection and watched the pressure rise

Time (min) Pressure (Bar)
0.0 0.6
0.5 0.6
1.0 0.9
1.5 1.2
2.0 1.5
2.5 1.7
3.0 2.2
3.5 2.9
4.0 3.4
4.5 3.6
5.0 3.6

So my cold control pressure is very low, from the charts should be between 1.6 and 2.0 Bar.

Here are the residual pressures.
Time (min) Pressure (Bar)
0.0 3.2
0.5 3.0
1.0 2.8
1.5 2.7
2.0 2.5
3.0 2.2
4.0 2.0
5.0 1.9
10.0 1.7
15.0 1.7
20.0 1.65

I think my first control pressure test posted before was incorrect. I had the electrical connection to the WUR connected and I was measuring hot control pressure instead.

I first plan on removing one shim from the fuel distributor and recheck all the pressures. If I understand the system correctly this should not affect the cold control pressure. But it should drop the system pressure.

Next, remove the WUR and try to push the pin outward. I am not sure if I want to drill and tap a screw into it or open the WUR and push it out.

Am I going in the right direction or is there anything else I should check first.
Old 10-19-2019, 08:39 AM
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DO NOT push out the pin on WUR.You will just upset factory specs,and maybe introduce other issues once this is solved.Take WUR apart, and clean,making sure not to drop top hat.Clean screen.This maybe a cause.
Old 10-19-2019, 09:37 AM
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Quote:
Originally Posted by coomo View Post
DO NOT push out the pin on WUR.You will just upset factory specs,and maybe introduce other issues once this is solved.Take WUR apart, and clean,making sure not to drop top hat.Clean screen.This maybe a cause.
I saw a few posts where drilled and tapped to make an adjustable WUR. I thought I could use a C-clamp to push the pin out a little bit, re-assemble the WUR and use c-clamp to put the pin in to get the desired settings.

I removed two shims from the fuel distributor and the system pressure has dropped to 4.9 Bar. Right where it should be. There was no change in control pressure.
Old 10-19-2019, 10:03 AM
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if you do this your simply masking a problem elsewhere.The system is finely balanced.Same goes for people chasing pressures, when they havent even done a smoke test.
Personally,Id get the WUR off and clean it.Dont forget to use new copper washers, or aneall the old ones.
Old 10-19-2019, 11:16 AM
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I managed to remove the WUR and check but in the process this happened.

The return line was twisted and in my stupid attempt to straighten it, the line broke. Also found that one of the bolts holding the WUR was sheared. Whoever removed the WUR before clearly didnít know their way around.

Just looking for something positive here. The inside of the WUR looks extremely clean. Maybe the mechanic I took the car to, cleaned the WUR.


I could not find the part number for the WUR return line. Looks like I am stuck till I replace this line.

Old 10-19-2019, 08:08 PM
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