# CIS Distributor and Pressure Regulator Seat



## DBabbitt (Dec 4, 2017)

I'm leaking fuel past the fuel distributor to the fuel tank after shutdown, a slow leak, but such that requires the car to be run 1/2 mile the next morning to fully reprime the distributor. 

Has anyone experienced that?

I've replaced O-rings on the two portions the regulator that drain to the tank, those being the warmup compensator end and the actual pressure regulator piston end. I suspect a deformed seat at the pressure regulator end within the cast iron fuel body. I have another distributor and I believe it has the same problem. Once I become more familiar of this site I'll attach photos showing the leak back to the tank at the distributor, but diverted through vinyl tubing into a container. 

Tha car is a 1978 VW Rabbit, 1.5L, gas, 4 cylinder, CIS, original as sold in Canada with no catalytic converter. Thanks.


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## Butcher (Jan 31, 2001)

I'm lost at what you are trying to say.

It is common that a CIS system looses it's pressure over a period of time. That is one of the reasons why the fuel pump is energized when you turn the key on. It should take seconds to build up fuel pressure again. The main reason to keep pressure is to help with vapor lock.


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## DBabbitt (Dec 4, 2017)

I know that pressure drops off, over maybe 1/2 hr as the accumulator piston unloads. The Bentley manual states the same. Why do you suppose it falls off, through the distributor to the fuel line to the tank? Fuel must move somewhere and so far per photos I have yet to upload, it is via the return to the tank. There are two possible routes through the fuel distributor to bleed off. When the car runs these routes are open to make the fuel pressure 70 psig, high enough to go through the fuel injectors as need be. If these regulating valves were to close, fuel pressure could exceed 100 psig? When the fuel pump is turned off, pressure drops to 30 psig which is less than the pop pressure to open the injectors. And then it slowly tapers off. No one has said why, where, whatever for that falloff in pressure as again, the accumulator bleeds off.

What has happened in the last 5 years of the car's 39 year life is that it not only bleeds to zero, air enters the distributor body. So getting air out is like priming a pump and that process, from starting the car to when it is completely filled, all air out, is the distance of 1/2 mile. It stumbles down the road if any torque is applied. Get past that 1/2 mile mark it is completely full, no air, good response.

Some web sits make it clear how to manage photos. How do you do it here?


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## Butcher (Jan 31, 2001)

I do not do pictures so I cannot help you there.

If air can get in, fuel can get out. I really do not believe you have air going in and that is the flaw of your diagnosis. As tight as the clearances are, the system only has seals that would prevent fuel to leak out into the atmosphere. As long as the sensor plate is closed, the fuel should be shut off to the fuel injectors. If the injector is leaking, then you would drop pressure and it would take some time for that pressure to build up again when you start it. I would remove the injectors to confirm none are leaking. 

If the fuel injector is not spraying well, the engine would do the same thing.

Again, it is common for the fuel pressure to drop. The fuel would go back into the tank [return line], out the injectors [leaking], on the ground, or leaking past the fuel pump [bad check valve]. Those are the only places. Even if the fuel drops, it does not mean there is air entering the system. I've been dealing with CIS issues since the system came out and I've never seen this. Of course, that does not mean it could not happen, it just means I've never seen it


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## DBabbitt (Dec 4, 2017)

I first thought the fuel was going back to the tank through the fuel pump check valve. I replaced it 3 times with new and also made a tool to test a check valve where air is injected in the output side and by putting the input into a vessel of water, look for air to leak in the check direction. I had no failures of any of the check valves.

I'm probably using the wrong term to say that air enters the system because as you say, fuel could them come out of it as evidenced by dripping gas.

Let me go through a startup/shutdown scenario.
1) before startup there is no fuel flow, fuel accumulator is completely discharged.
2) crank the engine, fuel pump turns on and starts filling the accumulator as well as pushing fuel up to the warm up compensator which is open, fuel pressure is low, plunger in the fuel distributor runs high, and the 5th injector is flowing fuel, and fuel returns to the fuel tank. No fuel is going through the pressure relief end of the pressure regulator.
3) release key from starter motor, 5th injector turns off, fuel still filling accumulator, through warmup regulator and returns to fuel tank.
4) warm up regulator is starting to warm up, cutting off fuel to the top of the distributor's plunger, fuel pressure rises, some flow through the pressure regulator end, both WUR and pressure regulator direct unused fuel to the tank as the 4 injectors spray it, still enrichened. Accumulator is finally filled up, piston depressing spring as far as it should.
5) engine is fully up to temperature, warm up compensator turns off, fuel pressure is finally at 70 psig, pressure regulator directs fuel to tank on the regulating end. 
6) shut off engine, fuel pump shuts down, accumulator wants to discharge through the regulator that is set for 70 psig, but pressure is back down to 30 psig so regulator shuts it off. Slowly the pressure decays over 1 hour or so as the accumulator pushes the fuel, somewhere, we just don't know where but I've proven it goes to the tank.
7) accumulator is now fully discharged, pressure at distributor is 0 psig, and there it is to stay that way, fully primed but no pressure.
8) on our car something continues to happen. Fuel drains from the fuel distributor. I wouldn't say air enters, but fuel vapors come from somewhere as the fuel drains away to the tank. This what I'm trying to find out. Why, where, how, what can be done to cure it.


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## Butcher (Jan 31, 2001)

I understand what you are saying.

The only thing I can say is that the only places that will cause fuel pressure to drop AND not leak on the ground is the fuel pressure and return line. 

I understand how CIS works on paper and I also understand how it works in real life. Many times the fuel system just does not maintain fuel pressure. I have rarely ever noticed it causing a customer complaint. If I spent my time on fixing a system that does not hold pressure, I would have wasted a lot of time and money and most importantly, not fix the customers complaint [which is my main focus/job].

When you first turn on the key, the fuel pump is cycled for a few seconds. That should build up pressure real quick [within a second]. If it does not, then I would try and find out why. 

The first place I would look at is the fuel pressure accumulator. That is the only place that can 'absorb' the fuel coming out of the pump and not cause a substantial pressure increase. My opinion is that you really do not need the accumulator to have an engine run. The reason for this part is to maintain fuel pressure when the pump is off and to smooth the pressure pulses of the fuel pump so the distributor works with a constant fuel pressure vs a pulsing pressure. 

If the fuel pressure is dropping fast when the pump is off, I would look at the pressure regulator at the distributor and the check valve in the fuel pump. The regulator is pretty simple, fuel should not leak out [but it can with age]. The fuel pump check valve is fairly easy but the pump needs to be removed. 

So, if the fuel pressure builds up within a second but the engine runs like crap for a few seconds/minutes, I would look for a fuel leak a the injectors which is pretty simple if you can get the injectors out of the holders as well as the cold start valve. Make certain the injectors have a fine mist at low flow [plate barely lifted]. They should not drip any fuel when the plate is at rest.

Then there is always the thought that maybe there is nothing wrong with the CIS system and you have an ignition issue.


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## DBabbitt (Dec 4, 2017)

The process began with replacing fuel pump check valves, accumulator, and fuel injectors tested (picked best 4 out of 12). Fuel pump starts immediately with key and the engine runs evenly so I have good spray pattern. Also, when shut down I removed all injectors from the head and placed into test tubes to look for leaks. There were none. 

What happened next is rocket science it seems, making the tool to check the check valves (only one is ever needed but had accumulated several new ones), inspect for fuel flow to the tank after shutdown, and replacing all O-rings (3) on the pressure regulator. I was measuring fuel pump pressure, the fuel gauge with its inherent shut off valve. I replaced the fuel distributor with a spare.

When you look at the fuel distributor from above, there are 3 ports facing the engine firewall. From right to left when looking from the rear is the fuel supply to the 5th injector, return to tank, and return from WUC. When you reach through the first of the 3 ports into the distributor you are very close to where the pressure regulator seat is. In fact through that port I insert a soft wire to push out the pressure regulator's piston if it doesn't come out with the springs. I'm thinking of inspecting the regulator's seat, somehow, though that port. 

Photos and sketch of all this is at the pelicanparts.com web site. I'll see if I can get a link to it and attach.

I could go on with fuel pump relays, how I've found cracks in the printed circuit board, how the relay itself is quite heavy and cantilevered so that the board is subject to cracking, how I've repaired and strengthened the bond of the relay to the PCB, etc., but that is distracting from this loss of fuel issue after shutdown through the distributor to the tank.


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## DBabbitt (Dec 4, 2017)

http://forums.pelicanparts.com/vw-a...ection-loses-pressure.html?highlight=dbabbitt

Butcher: I was able to provide the link above. Take a look and report what you think on it. Thanks.


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## Butcher (Jan 31, 2001)

I believe you are mixed up with the volume thing.

With any hydraulic system, liquid does not compress so when you have a leak, you will only leak that amount until the pressures equalize. How much volume? A drop would cause the pressure to equalize. Since you have the accumulator, that is where you can store the volume. So I think you are asking how much volume will leak out. My answer would be the amount of volume that the accumulator would have.

I have never dived into a CIS system that much. I have rarely replaced the fuel regulator but I have replaced my share of distributors. I have worked on many systems that dropped pressure. When you turn on the key, the pressure pumps up within a second and the car runs fine. That is why I do understand on paper that the system should hold pressure, but in reality, they do not. IF the system builds to the right pressure within a second or two, the CIS system will work fine.

The only time I found that the engine ran poorly for a few seconds [30 secs or less] was when the fuel pressure dropped in the injection line. The injectors were always the cause but it's always possible that the fuel distributor is causing the leak back. That would be something with the plunger and at the dealership, we would just replace the distributor. Due to the amount of flow out of the fuel distributor to injectors, it does take awhile for the injectors to finally open. Normally when I replace a distributor, I will lift/push down on the sensor plate to purge the air out of the injectors. Once I hear the fuel flowing, then I attempt to start the engine.

To wrap it up, if you are loosing fuel pressure in the system, it should build up during the cranking of the engine and certainly once it's started. I just cannot hang my hat on the idea that air has entered the system causing your running issue. 

I do not agree with the idea that while the accumulator is filling up, the system will not run right. The fuel distributor does not care what the accumulator is doing. The fuel pump should have enough delivery to fill up the accumulator AND operate the CIS system at the same time. The pumps are usually designed to deliver more than what the system needs.

I have a tendency of disagreeing with others diagnosis which causes people to get upset. That is not my purpose. I admire that someone will spend a lot of time to resolve an issue. At some point I believe you will and when you do, it will prove what theory was the right one. I'm waiting for you to come up with an answer.


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## cuppie (May 4, 2005)

First up, photos. Can't upload to the forum - need to host them elsewhere. Imgur and Flickr are used often. 
From the forum FAQ: http://forums.vwvortex.com/faq.php?faq=vb3_reading_posting#faq_vb3_attachments 

Now, I'll throw my hat in the ring on this... 
First off, dispel some things, and fix this:


> Let me go through a startup/shutdown scenario.
> 1) before startup there is no fuel flow, fuel accumulator is completely discharged.


 Not abnormal. 


> 2) crank the engine, fuel pump turns on and starts filling the accumulator


 Incorrect. It's a BIG pump - more than is required to feed the engine at full-load redline. And, it only has one speed. Key ON (don't crank, let the pump run its 3-second prime cycle), and the system is fully pressurized.


> as well as pushing fuel up to the warm up compensator which is open,


This is correct.


> fuel pressure is low,


Again, no. System pressure is fixed.


> plunger in the fuel distributor runs high


Yes,


> and the 5th injector is flowing fuel


Not necessarily for the entire crank time - max 8 seconds, less time with higher temperatures.


> and fuel returns to the fuel tank. No fuel is going through the pressure relief end of the pressure regulator.


 What? There are two return paths: the pressure regulator (which is the fast majority of it), and the Control Pressure Regulator (a very small amount.) All fuel that isn't injected (and, during engine start, would be about 99% of the pump output) returns to the tank - and, of that return flow, nearly all of it is vis the system pressure regulator.


> 3) release key from starter motor, 5th injector turns off, fuel still filling accumulator, through warmup regulator and returns to fuel tank.


 5th injector probably stopped before you released the key. And, the accumulator filled a long time ago.


> 4) warm up regulator is starting to warm up, cutting off fuel to the top of the distributor's plunger


 The opposite, actually. WUR is starting to close (restricting flow out of the 'top' of the distributor), control pressure is starting to rise,


> fuel pressure rises, some flow through the pressure regulator end,


Nope - system pressure is the same as it was at step 2, and there's a helluva lot of fuel going down the return line.


> both WUR and pressure regulator direct unused fuel to the tank as the 4 injectors spray it, still enrichened.


 Yes.


> Accumulator is finally filled up, piston depressing spring as far as it should.


 So many words, it feels like that happened an hour ago now. :lol: 


> 5) engine is fully up to temperature, warm up compensator turns off


Generally correct. But, more accurate if you call it what it is - Control Pressure Regulator.


> fuel pressure is finally at 70 psig, pressure regulator directs fuel to tank on the regulating end.


 Nope. System pressure is exactly what it was at step 2. If it's changed, something is very, very wrong.


> 6) shut off engine, fuel pump shuts down


Yes.


> accumulator wants to discharge through the regulator that is set for 70 psig


Not exactly. Imagine a spring pressing against a spring - that's the pressure dynamic that's happening here,


> but pressure is back down to 30 psig so regulator shuts it off.


Maybe. What does your pressure gauge say?


> Slowly the pressure decays over 1 hour or so as the accumulator pushes the fuel, somewhere, we just don't know where but I've proven it goes to the tank.


That isn't abnormal. The spec is "min 30psi after 20 minutes." 


> 7) accumulator is now fully discharged, pressure at distributor is 0 psig, and there it is to stay that way, fully primed but no pressure.


 Okay. This is not necessarily "broken."


> 8) on our car something continues to happen. Fuel drains from the fuel distributor. I wouldn't say air enters, but fuel vapors come from somewhere as the fuel drains away to the tank.


"Vapors" will only happen if you can't meet the residual pressure spec, on a hot engine - the fuel, literally, boils in the lines. And, air pressure has a hard time opening the injectors.


> This what I'm trying to find out. Why, where, how, what can be done to cure it.


 Re-run the residual pressure test, correctly. 

Read this. Save it to your computer. Print it if you want: 
http://tech.bentleypublishers.com/servlet/JiveServlet/download/47-29638-292583-4693/36-Bosch CIS.pdf 


Bentley Publishers said:


> REST PRESSURE & LEAK TEST
> 1) After correct warm engine control pressure has been
> obtained, stop fuel pump and note pressure drop. Pressure gauge valve
> should be in open position. Minimum pressure after 20 minutes must be
> ...


If you can pass the rest pressure check... Instead of going straight from OFF to START, turn key to RUN, and let the pump run first! Then start the engine. It's an old car. You can wait 4 seconds.  Run better now? 

And, CIS troubleshooting 101. 
System pressure correct? 
Control pressure correct? 
No injector leaks, spray patterns correct? 
NO VACUUM / INTAKE LEAKS (no matter how seemingly small)? They're very, very sensitive to these - especially when the engine is cold, and at lower engine speeds.


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## DBabbitt (Dec 4, 2017)

The fuel pump starts in the "run" switch position only if the ignition points are open or closed. I forget which. If it is retained in the run position, engine stopped, the pump stops shortly thereafter for safety reasons. When the points pulse, it constantly runs. If they stop, the pump stops shortly thereafter, not wanting to feed any fire by the pump.

What I called a warm up compensator is called a control pressure regulator/warm running compensation so I call it WUC for short. It is open when cold, closed when hot. When cold it allows the plunger to run high for enrichment, when hot it closes, controlled pressure is high, pushing down the plunger, leaning fuel.

My sketch at pelicanparts.com at the link I provided *had an error showing the 4 slits in relation to the plunger*. I've not corrected it, but it should be apparent from a sketch that the plunger rides high when cold, low when hot, restricting flow to the injectors.

No air enters the closed system. To keep from vapor lock or boiling of fuel in the injection lines, some pressure is always in the system while the engine is still hot or warm.

The fuel pump does have quite the capacity, enough to allow the engine to run under full load and yet bypass some fuel back to the tank. During startup fuel is used to fill the drained accumulator which I estimate to be 1/2 cup in capacity, maybe 2/3 cup. Yet there is still enough flow for the 5th injector to work and the 4 injectors and return to tank. The 5th injector operation is limited by a temperature device in the upper radiator hose area. Also dependent on cranking motor operation. I've actually interrupted the circuitry with a push button switch so that it won't inject when it thinks it should. If I want 5th injector operation, I depress the switch to allow flow through the normal control process.

I know the fuel bleeds back to the fuel tank after shutdown, else pressure would stay at 30 pisg, call it controlled or residual pressure. Where it is doing it is at the piston end of the pressure regulator. *Why,* is my question. I suspect a slightly deformed seat in the cast iron body.

By the way, if you're interested how I was able to get the split cast iron fuel distributor body to seal after several unsuccessful attempts, I'll share that information.


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## cuppie (May 4, 2005)

That relay should close (for 3-5 seconds) 100% of the time, when you turn the key to RUN - if it doesn't, it's faulty, and should be replaced. 

{bunch of rehash from earlier in the thread} 

Re-sealing the fuel distributor isn't a secret - that info is out there. Indian Head gasket shellac is the widely-accepted thing to use. 


Just like Butcher, I think that you're so focused on the long-term (overnight) pressure bleed-off from the system, that you're ignoring everything else. So, I'm going to ask: 
What is your system pressure, cold control pressure, and hot control pressure?


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## DBabbitt (Dec 4, 2017)

You're right, I'm focused on the bleed down phenomenon, 1/2 to 2/3 cup in quantity. Didn't know if there was perhaps a 3rd, unknown, undocumented, very small track for the fuel to bleed down to the tank after shutdown. I like this forum because people talk and give ideas and show experience I don't have. I like pelicanparts.com because that was the first forum I asked the question at and that I can add photos. Maybe someone with a Mercedes or 6 cylinder Bosch fuel distributor that can help. This site has had 750 views on this subject and pelicanparts has 1700. 

The system does vent vapors to air through the carbon canister above the left front wheel.

Pressures. I graph them on page 33 in the Bentley manual, bottom of page, where they show the pressure gauge with 3 way severe at positions A and B. If I could attach a photo of it I would. Cold, it slowly ramps up from 35 to 51 psig, regulated, for about 2 minutes. If the pressure is valved off (position B, flow blocked) it goes up to 70 psig. Open it up, back to 51 psig. By now it is warm, at 51 psig regulated, 70 psig if blocked off. Shut off the car, immediately drops to 40 psig and then over a course of 50 minutes drops to 29 psig. Data taken 20 years back and a few months back.

What is the pressure now? I need to take the numbers again because I was telling everyone 70 psig, regulated. That is too high. So I'll put the gauge back on in the next 2 weeks.

Why do we continue running this old car? My wife bought it new in 1978, we were married in 1979, and I've done all the maintenance. When it starts using a quart of oil every 600 miles I replace the valve guide seals just like VW did on the first recall, same issue, 1980. We go back to 3000 miles per quart of oil. It has 360k kilometers on it now, it is the car we use daily. I've had the engine out once to rebuild it, the head off 4 times in 2 months looking for the coolant or oil leak kind of thing. I also like the VW recall where they pulled the fuel pump relay off of the black fuse block assembly and mounted it just above. That allowed the heat from the fuse on the relay to dissipate somewhere else.

Thanks for the comments.


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## cuppie (May 4, 2005)

DBabbitt said:


> You're right, I'm focused on the bleed down phenomenon, 1/2 to 2/3 cup in quantity. Didn't know if there was perhaps a 3rd, unknown, undocumented, very small track for the fuel to bleed down to the tank after shutdown.


There is a third bleed path - the warmup regulator. That's why the rest pressure check is performed twice - it's detailed in the pdf that I posted a link for earlier. Frist check tests the pressure loss (in total), second check tests the WUR. 



> The system does vent vapors to air through the carbon canister above the left front wheel.


And, that has nothing to do with liquid fuel in the lines, or any of the fuel system parts in the engine bay. It's for vapor storage and recovery (from the gas tank). Works the same on a MY2018 vehicle as it did on your MY1978 Bunny. 



> Pressures. I graph them on page 33 in the Bentley manual, bottom of page, where they show the pressure gauge with 3 way severe at positions A and B. If I could attach a photo of it I would. Cold, it slowly ramps up from 35 to 51 psig, regulated, for about 2 minutes. If the pressure is valved off (position B, flow blocked) it goes up to 70 psig. Open it up, back to 51 psig. By now it is warm, at 51 psig regulated, 70 psig if blocked off. Shut off the car, immediately drops to 40 psig and then over a course of 50 minutes drops to 29 psig. Data taken 20 years back and a few months back.


 You're actually measuring two different things there. Position B measures the system pressure; Position A measures the control pressure. System pressure should be a constant 70psi (and, yours is - that's good); control pressure will start low, and rise as the engine temperature increases. 
From memory, your control pressure looks correct. 



> What is the pressure now? I need to take the numbers again because I was telling everyone 70 psig, regulated. That is too high. So I'll put the gauge back on in the next 2 weeks.


No, that's absolutely correct. If it's lower, the car won't run correctly, if at all. 



> Why do we continue running this old car? My wife bought it new in 1978, we were married in 1979, and I've done all the maintenance. When it starts using a quart of oil every 600 miles I replace the valve guide seals just like VW did on the first recall, same issue, 1980. We go back to 3000 miles per quart of oil. It has 360k kilometers on it now, it is the car we use daily. I've had the engine out once to rebuild it, the head off 4 times in 2 months looking for the coolant or oil leak kind of thing. I also like the VW recall where they pulled the fuel pump relay off of the black fuse block assembly and mounted it just above. That allowed the heat from the fuse on the relay to dissipate somewhere else.


 No need to explain love of the car. My current summer daily is an '88 Scirocco. Had her almost 8 years now, absolutely love the car - even if she can be a bit needy sometimes (and, she was very needy this year.) 
When my son was born (summer 2014), I was asked "so, you have a kid now. Are you going to sell the Scirocco?" Answer: "Absolutely not!" And, of the three cars here, that car is the boy's favorite to ride in. 

And, pictures on the forum: 
Covered that earlier.


Cuppie said:


> First up, photos. Can't upload to the forum - need to host them elsewhere. Imgur and Flickr are used often.
> From the forum FAQ: http://forums.vwvortex.com/faq.php?f...b3_attachments


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## DBabbitt (Dec 4, 2017)

I mentioned earlier my mistake in sketches at pelicanparts.com with the slits in relation to the plunger.

Let me explain a mistake or how one can be misled viewing the Bentley manual Figure 1-2, schematic view of CIS fuel injection. This is per my disassembly of the control pressure regulator and replacement of 3 O-rings where 1 was for the entire body, one at the WUC end, and one at the 70 psig piston end. It is also shown at pelicanparts.com in one of their free references on CIS (there are 10 or so of them) on a certain page showing the same poppet valve as I discovered and sketched with Paintbrush.

The WUC doesn't direct the returned fuel directly to the fuel tank unimpeded as Figure 1-2 shows. Instead, it goes through the end of the pressure regular at the rectangular nut end where there is a poppet valve , rod and spring along the central core of it. The poppet has a small, O-ring with 1/8" hole that fits it snugly. When the car is running pressure opens the poppet valve so that the second of two return paths to fuel fuel tank is open. There aren't three paths, just two to the tank within the distributor body. When the fuel pump is turned off, this poppet immediately shuts so that no fuel leaking past the WUC can go to the tank. There is no pressure keeping it open. The fuel is held captive that had been WUC controlled. 

How I could tell I wasn't leaking fuel past this O-ring assembly after shutdown was by inserting the pressure gauge with shutoff valve on the distributor as it is supposed to be connected. Run the car, shut it down. Immediately close the shutoff valve to isolate the WUC from the fuel distributor. Remove the return fuel line and insert a custom banjo union with clear PVC line directed into a glass test tube. Then wait. Slowly, fuel starts to go up (or down) the PVC line at a rate of around 1/4 cup per hour. See my photo at pelicanparts.com. It leaks at the same rate as if the shutoff valve were open. That means the sole leak down or return to the tank is via the piston end of the pressure regulator.

Does this make sense, leading to my inquiry?


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## DBabbitt (Dec 4, 2017)

Thanks go to Butcher and cuppie for pushing me to get fuel distributor pressures, not from the past but from the current situation. I did this morning, below freezing temperatures, and cold/hot/regulated pressures were all 72 psig. With the test valve open or closed, always 72 psig.

That told me the warm-up regulator or control pressure regulator was stuck closed. Driving the first half mile with it stumbling was because the engine was running lean. Didn't need the rocket science I was putting into the situation. Rather than try to remove and repair (I've seen many posts on making them adjustable) and chance failure, I got a used one and between the two, I should have one working. Thanks again. I'll post this on pelicanparts.com, too.


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## Butcher (Jan 31, 2001)

You can buy me a beer and drink it. Tell me how good it was. You're welcome.

I can assure you, you learned a lot so it was not a waste of time what so ever.


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## DBabbitt (Dec 4, 2017)

http://forums.pelicanparts.com/vw-audi-technical-forum/971977-cis-injection-loses-pressure.html

At the link back above I wrote at the very end that the new, used control pressure regulator I installed works great and how I took the original one and got it repaired to be used as a backup. I can see the value of a clean fuel filter as there was, unbeknownst to me, a screen at the inlet of the control pressure regulator. Behind it was a small passage that had was completely closed off with debris. Ultrasonically cleaned it when completely disassembled in hot soapy water.


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## DBabbitt (Dec 4, 2017)

Our Rabbit still stumbles after working through throttle body shaft leaks. I used customized 1mm thick o-rings, thread, and string and grease to replace the worn original ones on either ends of both shafts. Intake manifold vacuum, idle, 11" Hg which is the best ever. Again, vehicle is a MK1 Rabbit with CIS, no EGR, 1.5L, gas. Ignition distributor has new parts and I'm back to the first fuel distributor. Wish it wasn't stumbling/hesitating/jerking.


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## DBabbitt (Dec 4, 2017)

See my other thread, CIS and Control Pressure Variants, to read how I got the jerky riding resolved. Replace/cleaned the control pressure regulator/warm running compensator (CPR/WRC).


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