need help with CIS
 

Ok, so I can get my 928 to idle durring warm-up and once the idle speed drops down after about 5 minutes or so, the thing starts to run rough until it eventually dies.

I cannot give it gas at all or it makes it worse. I apply slight pressure to the gas pedal and the thing spits and coughs and will die if I don't let off the pedal. (it's actually little backfires I think)

I put a pressure tester on the system and found the pressure to be around 80 psi and the control pressure without vacuum to be about 4.5 bar. (which is a little high..should be around 3.8....once again...i think)

One funny thing i noticed by pulling an injector to watch spray is that when I first start to push down on the plunger (I hope you know what that is...i don't know the correct term for it. The metal sensor plate under the air cleaner) i get gas through the injector but the farther i press the plunger down...the thinner the gas gets until it eventually shuts off completely. I don't think this is normal and would explain maybe why i push the gas pedal down and it dies...it might actually be shutting off the flow of gas.

I need help with this if anyone has any adeas.

#1 with CIS is have you cleaned the whole pathway of fuel? All the Filters in the Fuel Distributor and the one one the Inlet side of the WUR? Have you removed all your Injectors and verified they are actually any good. You can do a quick test with some Carb Cleaner in the Injector, then use a Compressor to push the fluid out. You should get a fairly decent fan spray out the tip. How is the condition of the AAV (Air Aux Valve)? have you tested it? There is a pretty good video on how to do that on Youtube.

Also, without actually taking the Fuel Distributor apart. Remove it and see if the plunger moves freely, which you will see on the bottom side of the Distributor.

Thanks MPDano for the advice. I have actually taken all of those steps and everything checks out ok. The nine filters are free of junk...never were really clogged to begin with, but I cleaned them all. I also tested the injectors and got a fairly nice spray out of all of them with carb cleaner and compressed air.

I hooked the AAV up to power and turned on a heat gun and carefully blew around the valve and got to watch as it closed...so I'm assuming that was a good test...and then it opened back up as it cooled.

The big mystery is why fuel would stop squirting out of the injector the farther i push down on the sensor plate (correct term)

It is working like a pump...lol...I can push down and fuel sprays out injector and then stops...so I let the sensor plate come back up and push down again...fuel sprays out the injector and then stops.

I really think this is my problem if I could figure out why it's doing it.

Did you make sure the A/F is set right? Use a jumper in place of the fuel pump relay, kick it on while you have your 3mm A/F adjusting tool and go rich until you hear the injectors start spraying (you'll actually hear it sing), then back off till it stops singing. I believe this get's you close to where you need to be (1/2 turn lean or rich). Have you done this one yet?

Yea, I have the A/F exactly as you have described. I jumpered the pump and from all the way counter clockwise, began to turn until I heard the fuel pass up through the distributer.

I also made sure the timing was on. I did a cold start...the only time I can rev up the engine and held it at 3000 rpm with the vacuum advance unplugged and had a friend make sure the timing was correct. Timing checks out.

check for vacume leaks. I had a similar problem years ago. I don't remember what hose it was or where it went but I put a golf t in a hose that was just loose and it ran perfect, i couldn't believe it

Does anyone have a user-friendly vacuum diagram for the 79? I remember seeing one on one of the posts, but can't seem to find it again and I don't have one on the hood.

Thanks

I put "vacuum diagram" and chose 928 in advanced search and came up with all sorts of posts.

Here is mine:

http://forums.pelicanparts.com/porsche-928-technical-forum/474551-need-some-help-here-82-a.html

Can be found on page 28 in the link below.

SharkSkin - 1978-80 Porsche 928 Tech Specs Booklet

Awesome, thanks guys....the search is on...can hopefully make it throught he entire system tomorrow. I bet that's my problem but i'll let you know.

Any thoughts on the fuel cutoff when i press the sensor plate all the way down? I can't see that being vacuum...

There are several places where debris will occlude fuel flow. It might flow initially and tail off, though from the description I'm not sure what you are seeing at the injectors is a problem- is the system jumpered to sthe pump is running or are the injectors just bleeding off remnant system pressure?

I think you should chekc the system pressure and the regulator in the fuel distributor, and also the union at the fuel feed from the tank to the fuel distributor. The latter has avery fine screen and often gets plugged.

here are vac diag. I had terrible problems for a long time with my CIS on my 82 Euro S I rebuilt from trash. It turned out to be an unusable fuel distrib. My big thread-

http://forums.pelicanparts.com/porsche-928-technical-forum/540954-first-928-story-nightmare-begins.html has lots of info on CIS problems.


http://forums.pelicanparts.com/uploa...1335063012.jpg
http://forums.pelicanparts.com/uploa...1335063088.jpg
http://forums.pelicanparts.com/uploa...1335063109.jpg

K, let me try and explain it a little better in regards to the fuel shutting off-

I have jumpered the fuel pump so i can run it continuously via an on/off switch with enough wire so i can stand and look at the engine compartment when i turn it on.

On a normal (working) CIS I can take out an injector to watch spray...turn on the fuel pump and push down on the sensor plate, forcing gas to the injectors. I can hold the plate down for as long as i want and see a continuous mist of gas shooting out of the injectors and with the sensor plate fully depressed, the flow of gas is greater through the injector. This is a CIS funtioning properly.

On my 79, I can push down on the sensor plate and begin to see gas spraying from the injector but if i continue to press down on the plate, the gas stops flowing through the injector. I then let go of the pressure plate and let it float back up to it's nuetral position and press it down again to press fuel out of the injector again and then stop as i push the plate to the floor (so to speak)

It reminds me of an old water pump that you see in the old westerns. on each pump the water flows and then stops so you pump again...

I hope this is more descriptive of my problem. not sure how to describe it better than that.

Fuel flow is restricted with the pressure plate completely depressed.

It's making my brain hurt trying to figure this one out. ;)

That's a great picture of the inner workings of a WUR by the way. Thanks for that one.

I also need to point out that my fuel system is actually very clean. No varnished gas, no build-up or debris to speak of.

This will give you a good rundown on the inner workings of the WUR:

Porsche 928 Forums dot com - View topic - CIS Warm Up Regulator Made Simple

Sounds like the WUR is working ok cold then giving you a lean mixture when the engine warms up, kinda confirmed with the on the high side control pressure reading you took. Warm control pressure should be between 2.8 and 3.2 bar w/o vacuum and between 3.4 and 3.8 with vacuum.

Cold control pressure will vary and depend on the temperature, but will always be less than warm control pressure. There's a chart in the WSM that gives the info (page 25-6).

Verify your warm control pressures and go from there. Remember, the higher the control pressure the leaner the mixture.

I think i got ya. So what I think this all means is that my control pressure is high enough that it is beating out the vacuum and actually pushing the plunger back down in the distributor...cutting off the fuel.

Tomorrow, I will slowly tamp down on the WUR's plug as I read the pressure guage and see if i can't lower the pressure a little.

I'll let you know how it goes. This is extremely interesting to learn how it all works.

Note, tapping down on the plug will only reduce cold control pressure.

This video shows how to adjust warm control pressure and system pressure. Make sure the access hole for the allen adjuster is plugged once adjustments are made.

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

Yup, and tapping that plug too far, your taking the WUR apart.

After taking a look at vacuum this morning I noticed that the vacuum from the thermal valve is plugged and should go to the EGR...This is an American version btw by comparing the euro to the American vacuum system. The PO must have changed out the instrument cluster with a European version...(beside the point)

Is this an important part of the system? Could it create runnning issues or is it simply something for emissions?

I tapped the plate down just enough on the WUR to bring cold pressure down within range and then removed the pressure regulator from the distributer to possibly lower it's pressure because my system pressure is almost 6 bar. Thought I would remove a washer to get it closer to 5 and noticed the bushing on the bolt head side of the regulator was blown out. This is the second time it had blown a bushing in two days from fuel pressure i guess..not sure...

waiting until the hardware store opens this morning to find the right metric bushing.

Question--Now if i create a hole in the bottom of the WUR to expose the allen bolt, will that adjust my control pressure at operating temperature "warm control pressure"?
Won't the pressure regulator that i just pulled out of the distributor do that by adding or removing washers?

And after making the hole, do I need to seal it off from gas leaking out or just debris getting in?

Good morning by the way ;)

I just realized that is a ton of questions in one posting...lol

Sorry about the terminology...i meant o-rings when i said bushings...too early in the morning I guess.

So, update...I adjusted the cold control pressure and the system pressure and got them spot on and the car started up and ran perfect under rev and at idle for about 10 minutes until the car warmed up and then it started to do it's lean backfire thing again with zero throttle control...no rev with a cough and a spit and a little backfire here and there.

I shut off the car and then checked control pressure again and it was about 4 bar so I'm heading back to drill a hole to access the allen screw on the bottom of the WUR.

I'm just not sure what i should seal the hole with once i make it. I'm assuming from watching the WUR video linked from this post that the hole will not let gas out because I think he was adjusting it with the car running.

I'm so excited! It is running better and longer than ever. Thanks to everyone for your help and I'll keep you undated when I get back.

Theres no need to seal it. There is no fuel where you are drilling open. If you find a pic of one (WUR) open, you will see that. Plus, my understanding is that the adjusting screw is mounted on the case anyways. Rjm65 did his last year.

If you are pushing down on the air flow metering plate by hand, you are overriding any effect of control pressure. Like you said, you should see more flow the farther down you push. Higher control pressure basically pushes back up harder on the plate against air flow, so it deflects down less for the same air flow, but this doesn't matter when you are using your hand to push down.

The fact that the fuel flow is falling off as you push farther down means that the WUR has nothing to do with your main problem. Something is wrong with your distributor or possibly fuel delivery by pump. While unlikely, the linkage between the plate and the control rod in the distributor could also be broken. The pressure regulator in the distributor could certainly be part of the problem.

I would start by checking fuel delivery rate with engine off and fuel pump relay jumpered, CIS gauge connected and set to check system pressure (to remove WUR from the loop). You can check fuel delivery at the return line and system pressure at the same time. If this looks good, and the linkage from the plate is properly pushing up on the control rod in the center of the distributor, then you probably have a bad distributor. You may also have a bad WUR, but this is a secondary issue.

There's no fuel there but that compartment is what the second vacuum hose on the WUR ties in to. A small dab of silicone or epoxy after adjustment is made seals it right back up.

Thanks again for all the imput guys. I drilled the hole and set warm control pressure. All pressures are perfect. Cold starts at 1.5 and works its way up to about 3.2 where the top control pressure levels out after warm. The system pressure is 5.2 and the car runs very nice and is able to rev up for about 15 minutes and then once again starts to stumble and slowly (4 to 5 minutes) dies.

I really suspect a vacuum leak that accurs when something opens at temperature.

Once it dies, I can start it right back up and it will go through the same process again only shorter interval from start up to die.

I am going to take the spider off tomorrow and make sure the main throttle body seal is free of leaks. I sprayed carb cleaner toward the front of the throttle body today and noticed a slight surge in the engine.

The other thing i noticed is that when it is running good and I rev it up, it takes longer than it should to return to idle...it kindov floats down slowly.

I'm getting there guys. hearing her run with that throaty growl if only for 15 minutes is worth all the time it's taken so far. I hope to soon put her in gear and see if the transmission works...DOH!

Luis M is correct about the air sensor plate and control pressure. If you initially get fuel to the injectors then it drops off, there is a problem with the system pressure. The air sensor plate is a mechanical link to the control system piston so moving the piston up exposes more of the metering slits which allows more system pressure to feed the injectors.

Might want to look for blockage at the port between the relief valve and fuel distributor body.

K, I can't adjust the warm control pressure through the hole i drilled in the bottom of the WUR. The allen bolt is there and I can turn it, but it has no effect on the control pressure and I think mine is way too high at about 4.5 bar.

I hate throwing parts at this thing and the WUR is a spendy one. Is there someone out there that has a confirmed working one they are willing to send me so I can varify if this is the problem or not? I'll take great care of it and send it back after testing....or will buy it from you at that point if you want to sell.

I'm pretty sure this is where my problem lies.

It seems like your not grasping how this piece works. Here is a link to make your WUR adjustable, rjm65 did this so he could make adjustments from the top of the wur. Sorry the write up has no pics but it does explain how to do it. The post also has the correct pressures you'll need as well.

Porsche 928 Forums dot com - View topic - Making a WUR (Warm Up Regulator) Adjustable

The mods to make the WUR externally adjustable are only for cold control pressure. The allen he's turning on the bottom of the WUR is for adjusting warm control pressure, and somethings up since he says turning it has no effect.

Might as well pop open the WUR at this point, I think someone had previously mentioned this writeup but no link provided :

http://www.landsharkoz.com/images/pdf/wurfix.pdf

turning the screw with care if turned down to low when trying to adjust as theres finicky adjustments to be made by machine really only. its nearly impossible to adjust if gone to low/out. turn it back up just doesnt bring it the other way unfortunately.

make sure all contacts and switch testing for thermotime, cold start valve, idle,. the switches that switch cold/to warm up. carbon isnt clogging any valves, regulators. any gaskets , hoses, orings arent sucking air.

enough fuel cis doesnt like low low fuel tank.

backfire through exhaust? exhaust/gasket air leaks.

Run ok for 15 min even after a hot start makes me think something slow unrelated to temp is happening, like a fuel leak in one of the vacuum control diaphragms.

Make sure the timing is ok under all conditions, good running and bad.

Is the good run time the same if you just let it idle vs run at 2k rpm?

I took the WUR apart today to see what was up with the adjustment screw for warm control. Cold control is exactly where it needs to be.

The diaphragm was stuck to the threads of the screw and the center metal ring would turn with the adjustment...so in short...no adjustment could be made.

The car will idle for about 15 minutes if you leave it alone. If I get in and start revving the engine it sputters and dies quicker than 15 min to answer your question Danglerb and the link Rjm65 sent me said the correct warm control pressure should be 41 to 46 psi. Danglerb and Rjm is right about the externally adjustable modification is only for cold pressure.

I kept a close eye on pressure guage today and saw that the car ran good until the control pressure climbed above 4 bar which is about 58 psi or so and kept climbing up to 4.5 bar (65 psi) and I can't figure out what other component would be allowing pressures that high at operating temperature.

In my silly mind, it has to be the WUR. A leak or anything else...even the distributor would not be creeping the pressure up to operating pressure (which is set on my car at 5.2 bar (75 psi)

Even though I've convinced myself, I still don't want to waste money on a part I don't need...but I guess I should just bite the bullet and rule out the WUR...new (or rebuild on my budget) couldn't hurt in the long run.

P.S. I had to separate the WUR into three parts actually to get to the diaphragm and see what was happening at the thread level of the warm control adjustment.

I can think of two possible reasons for the high control pressure when warm. One, is the wrong vacuum line attached to the diaphram at the bottom of the WUR? It should only have vacuum during deceleration which increases control pressure and leans the mixture. If it has constant vacuum it will incorrectly keep high control pressure all the time. Two, if there is a blockage in the housing for the FD relief valve, it is possible that residual fuel can not bleed off the WUR thus causing high control pressure.

928 Intl has Rebuilt ones for $195, I may have a good used one for 1/2 that. I ended up buying a new one from 928 Motorsports thinking that was my issue (which it wasn't). If you are interested, I would need to install it back on my Euro to make sure it's functioning as it should. I would shoot a video of it of course to prove it's worthiness. If you don't want it, I'll throw it up for grabs for $100 plus shipping fees (after I test it of course).

You may have a badly tuned WUR, but I don't think this is your main problem.
The business with the "push air metering plate down by hand = less fuel at injectors" that you described earlier points to a serious problem somewhere else, probably the distributor or fuel delivery. I cannot think of a way that the WUR could directly cause this behavior. Have you checked the fuel delivery rate? Has the fuel filter been changed recently. Is the bottom of the fuel tank clean? Debris in the tank could slowly plug the filter at the tank outlet during operation, slowly starving the fuel pump. Shutting the engine off would then let this junk fall off the filter screen until the next operation. This could be worse when the tank is near empty, with fuel sloshing around and stirring up junk.

The return from the WUR goes back through the pressure regulator valve apparatus in the distributor and this could also be a problem, as DPW has pointed out.

If you want to get the WUR set up, you have to do it in stages. You have to get the warm pressure right first, because the heated rod is supposed to deflect up as it heats up and put less and less downward pressure on the spring plate until it puts no pressure at all. So basically, if you take the control rod out completely, you can tweak the warm pressure. Setting the cold pressure first with an incorrect warm pressure does you no good.

DPW is right about the vacuum lines. But this should only make pressure about a 0.6 bar higher if the springs are set up correctly and it sounds like you are even farther off. The test values in the workshop manual are specific about whether they should be measured with or without vacuum. Vacuum is applied at the side port, not the top port.

Be careful with the screw at the bottom of the WUR so as not to tear the vacuum diaphragm. It sounds like your warm pressure is too high. Are you sure the filter at the inlet is clear? If so, you can try this test: Put a few thin shims in between the edges of the two WUR body parts at the regulator end while screwing the two halves back together. Does this lower your warm control pressure? It should. If this works and turning the screw is not having any effect, you can take out the shims and try making a new control rod to go between the regulator and the spring plate. Use a nail about the same diamter and make one that is just a tiny bit shorter than the original rod (I'd keep the original unmodified for reference). Round the ends. Then file off a tiny bit at a time if it's still too high until you get where you want to be. If it gets too low, you will have to start over.

If you want more help, consider posting the following pressure values:

1. control pressure with heated rod and all springs removed.

2. control pressure with only heated rod removed, springs in place, vacuum lines detached

3. same as #2 with vaccum at side port of WUR

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Great info guys. Now I have something to do tomorrow morning before work.

I would be interested absolutely MPDano if this is my problem. Let me take a day or two to check out all the new theories that just came in and I'll post it here If I still need one.

The vacuum is interesting. I did notice continual vacuum from the base WUR hose and I just assumed that was what should be happening.

I will also get the readings that you are asking about Luis. As for blockage, all is clear. I'm constantly checking the screen at the WUR and the filters inside the distributor injector bolts and have not yet found one blocked.

Here are a couple of pictures of my lawn art by the way. I hope to one day get it on my lawn.http://forums.pelicanparts.com/uploa...1335474891.jpg

MPDano, was that WUR out of a manual or automatic. I've noticed some parts houses make a distinction between the two. I can't imagine why, but then again...I am far from a Porsche/Bosche engineer.

http://forums.pelicanparts.com/uploa...1335475296.jpg

I don't think it matters but it was off an Automatic CIS Car. I will pull up the numbers on top since that will tell you something. I can't remember what, but it does.

I found pics of my WUR installed in my car.

http://forums.pelicanparts.com/uploa...1335482002.jpg

http://forums.pelicanparts.com/uploa...1335482011.jpg

http://forums.pelicanparts.com/uploa...1335482012.jpg