GB26

Hey Guys: I really appreciate the dialogue. I am getting the picture of what I need to do. I live in Bethesda, Maryland.

Getting back to the issue, yes I replaced the fuel distributor. The car was sitting a long time and I could not get the car to run at all. With the fuel in the tank smelling as bas as it did, I figured that I needed to start back there at the tank and work forward -which I did.

So now having had the injectors cleaned, and the car running "okay" for a couple of minutes before the rpm drops to zero, I am left with how to keep the engine running.

I know that the engine is running rich because the plugs are black. They are not wet-just black. The car does not burn oil.

Before I purchased a fuel distributor, I took apart the warm up regulator. It was gunked up with varnish and using acetone, I got all of the ports pretty clean. I tested the electrical connection inside the warm up regulator and I know that the metal rod heats up because I could feel it heating up. However, I did not readjust the WUR.

I have not adjusted the a/f mixture. I have also not checked for vacuum leaks but I also k

I am also confused about something else. My car is definitely a 1979 with a 5 speed transmission. Looking at the diagram under the front hood shows that there is a PCV valve and a catalyst. If there is a catalyst then you would think that there would be an O2 sensor. In addition, 1979's supposedly did not have PCV valves.

I took out the cold start valve and checked to see that it was working okay. It provides a quick spray for a couple of seconds as soon as I start the car and then stops. It does not drip gasoline.

Any thoughts.

Gary

Dennis Wilson

Gary,

The WUR will need to be adjusted since it was disassembled. For that you will need the CIS test gauges. The 928's do have positive crankcase ventilation (PCV) but it isn't a valve. The crankcase is vented through the fill cannister. Your 79 should have a catalytic convertor but no Lambda (O2 sensors) were available on this model.

Dennis

docmirror

Dennis, you implied in post 12 that I advised the throttle bypass valve(it is NOT an aux air valve, that is something different) bypassed the metering plate. It doesn't, it bypasses the throttle plate, just as I stated in the first line of my first post.

Now, having this "throttle bypass valve" open will indeed reduce the movement significantly of the air metering plate, because air is being supplied from a different source via Solenoid, booster and blowoff valves in a complex vacuum operated affair. The air supplied to the cold start injector during COLD operation makes the metering plate stay nearly closed, until there is sufficient manifold vacuum to pull the booster valve shut, thus reducing, then eliminating the air source to the throttle bypass valve. If you remove the air cleaner and visually watch this process on a COLD engine you will see it quite clearly.

Right the THERMO - time valve is only operated by low (cold) temperature. Note the first sentence of my second paragraph which I will quote: "Once the temperature sense reaches a certain value, the cold start injector is closed". Does this need repeating? Maybe so; One the temperature sense(I'll help you out here, the sense is the thermo-time switch) reaches a certain value(I don't know what the temp is) the cold start injector is closed. Is this incorrect in any way? I don't think so, and the OP has verified this in his last post.

Finally, carb cleaner. Would you have us believe that an aerosol that is putatively designed and used to spray on carburetors is actually detrimental to said devices? That's fairly crazy. I've used carb cleaner on carbs for 35 years and have never seen affects like you're talking about. The percent of aeromatic solvents in carb cleaner is very low, much lower than 20 years ago and although they are indeed in the mix, they evaporate so quickly and leave such little residue that to have any affect on gaskets, or seals you would have to soak the unit in a vat of carb cleaner with a lid on for days. But you are correct that it may, in some cases of cheap automotive paint damage a painted surface. As for damage to a carb, seal, gasket, or rubber component by aerosol use, I say prove it, cause it just don't happen. Here's a shock for ya, I use carb cleaner on painted surfaces that have temp embedded grease stains! All you do is have carb cleaner in one hand, and a dry rag in the other. Spritz, rub, wipe - job done.

If you don't like carb cleaner that's fine but don't spread rumors about problems that just aren't there. I like it when people correct me, as I've made plenty of mistakes in the past, but when you correct me, at least make your corrections correct.

<edited for grammar>

Dennis Wilson

Doc,

Check the CIS diagrams out in the WSM. The only throttle bypass valve (solenoid) is for the AC system, not the cold start system. The AAV only bypasses the throttleplate, not the air sensor plate. Again, if you check the diagram you will see that it connects the lower plenum (after the air sensor plate) to the upper plenum on the 928. The air sensor plate measures ALL air going into the engines, unless there is a vacuum leak.

Concerning the thermotime switch, you asked a question and I answered it. If you don't like my answer, check it out yourself. It's on the first page of the electrical in the WSM.

Concerning the carb cleaner. Many contain actetone or methylene chloride. Throttlebody cleaner is safe, but carb cleaner is going to be a toss up as to the contents and any harm they can do. Are you confusing the two?

Recommend you buy a Bosch manual on the CIS systems, work on them for 20+ years, rebuild a fuel distributor or two then get back with me and we'll compare notes.

Dennis

docmirror

Dennis, once again, you're mixing terms. The throttle bypass valve is not the solenoid valve. They are two separate items. Solenoid valve is only for AC ramp up, it uses the same air path(around the throttle plate) as the throttle bypass valve, but is a different part. I suggest you see WSM pg 20-6 items C and D respectively. I know where the thermotime switch is, and what it does. I do not know it's temp coefficient. My question to you was to let you know that I know what job it does, to refer back to my first post which you incorrectly corrected. Let me summarize. Cold engine = cold start injector operation. Warm engine = no cold start injector operation. This may be why the OP has dark plugs, but he may have a lean situation during non cold ops. As you said, the WUR is prolly now out of adjustment, and will need to be set. Or, the fuel pressure relief valve on the side of the distributor may need adjustment as well.

I see that the tee from the cold start valve does indeed go through a fitting to the low pressure side of the metering plate. When I watch a cold start on a CIS engine, the metering plate is deflected less than when the cold start valve is closed. I stand corrected, the air is drawn from the low side of the metering plate. This is somewhat different in other Porsches, VWs, Ferraris, and MB cars. My apologies, I've only done three actual distributors, but have now worked on a few dozen different cars with CIS. Some of them have different routing for the cold start circuit.

BTW, I have the Bosch book, and it is loaned out right now. If you want to find a buy throttle body cleaner(good luck), fine with me, but it's the same stuff - just check the contents on the can. Other useful CIS info:

http://forums.vwvortex.com/zerothread?id=3261252

http://www.pelicanparts.com/catalog/...ULcis_pg19.htm (Weber book is good)

http://www.books4cars.com/viewcart.a...s&BookID=11142

my experience with the Mondial CIS was a real eye-opener. It took me a while to decipher all the quirks.

guidon112

How come you guys didn't have this debate when I was having these problems? This discussion has been very enlightening to me after the fact, having solved the same issues on my 79. And just a note to GB26 If your control pressure is too high (WUR), your engine will starve for air regardless of what you do to the A/F screw, my pressure was strong enough that the intake vacuum could not pull the sensor plate open, effectively "choking" the engine. I am not a pro but I learned allot. It’s said many times, get a test gauge.

Dennis Wilson

Doc,

You used the term "throttle bypass valve". I have always refered to the auxillary air valve (AAV) except in response to your use of the term. You also mentioned a solenoid and I responded that the only solenoid for the 928 CIS cars is the AC solenoid. The Porsche 928 CIS cold start systems have never used a throttle bypass valve or a solenoid. There are solenoids on other CIS systems such a the warm start solenoids on earlier CIS or the control pressure solenoids on Lambda equipped CIS but these were not a fixture on the 78 or 79 928's.

Mondial CIS? What cars had this system?

Dennis

Dennis Wilson

Sorry that I missed yours. I've been on and off as my business allows. One correction on your advise. If the control pressure is too high it will cause a lean condition. i.e. the plunger/piston is pushed down and restricts the fuel passages.

Dennis

guidon112

Right also, unless he richens the A/F too much then he will get fuel seeping in but still possibly have too much down force on the plunger for the sensor plate to move and allow enough air in, resulting in a flooding condition, but still starved for air, I had both happen to me, but its all mash as this might not be GB26's issue, my point I guess was gauge=easy solve, you guys told me I listened, (should have listened sooner before I split my dizzy, but Ohwell replacement is on the way) I got all mine working now but as soon as the dizzy starts leaking the pressures drop and he sputters and dies, so I have great hopes for this replacement that is coming.

Dennis Wilson

Matthew,

I always try to remember it as system pressure less control pressure equals the pressure to the injectors. Actually that is over simplified since the control pressure is adjusted by the counter balance of the air sensor plate.

GB26,

Did the new distributor come with literature stating the system pressure had been preset? If not, your test gauges (when you get them ) should be used to test and adjust that if needed.

Dennis

GB26

Okay, the advice as follows is to get a set of gauges to test the pressures on the WUR. Simultaneously (excuse the spelling), I should also be looking for vacuum leaks.

BTW, the fuel distributor was practically brand new (but not new). The guy had just finished rebuilding his engine when he blew the engine (literally 600 miles after rebuild). He decided that he was done working on the car and began parting it out. Consequently, I did not get any literature.

So the next question is that I test the WUR and find that I need to reset the system pressure on it. There is no way to adjust the pressure on the WUR except maybe by taking it apart. Is that the idea?

Thank you for the dialogue.

Gary

curt_928

Gary,

Having taken my WUR apart and put it back together again and had a perfectly fine working car w/o adjustment.. please let me know how you adjust it... besides adjusting the main bolt inside (you know the one I mean.. holding down the warm up element and the plunger that pushes down on the membrane).. I'm wondering myself how you do this...? At the fuel distributor? Strikes me that the height of the bolt in the WUR should be a constant and the heating of the element just closes off the line into and out of the unit...

hmmm..

Curt
------------
79 5sp blk/silver
02 Boxster blk/blk

Dennis Wilson

The pressure is adjusted by moving the circular metal plate up or down in the tower. Moving it lower reduces the control pressure (richens mixture) and raising it increases the control pressure. I can remember a thread where someone had fitted a bolt in the top to adjust the plate externally. The only problem was that the bolt could be screwed in to reduce the pressure but unscrewing the bolt didn't raise the plate to increase the pressure.

Dennis

guidon112

http://forums.pelicanparts.com/showthread.php?t=272502

Not from our forum but here is a good bit on the WUR/CPR

docmirror

I didn't, Porsche did. Those are the terms that they used. The 928 uses both a throttle bypass valve and a solenoid(AC run-up).

Ferrari from 1980 through 1986 used CIS, later models added the Lambda circuit. I have an 83 without closed loop, so the solution to a hot cat was a red warning light actuated by a thermocouple on the console that says "bank 1-4(5-8) temp - slow down". Jeez.....