need help with CIS

[MPDano]

053 is what this WUR is.

[BoiseShark]

K, I'll cross-check in the morning. Thanks for the up-close pics

[BoiseShark]

I noticed in the 928 spec/parts book that there is a gas line that runs to the front of the plenum. If your looking at the engine, it is just above and to the left of the cold start injector. My car just has a bolt plugging the hole. Any ideas

[MPDano]

Originally Posted by BoiseShark

I noticed in the 928 spec/parts book that there is a gas line that runs to the front of the plenum. If your looking at the engine, it is just above and to the left of the cold start injector. My car just has a bolt plugging the hole. Any ideas

That's not a fuel line. That's a vacuum line for Automatic Trannys. If you have a Manual, then yours will have a bolt used as a plug.

That line controls hard and soft shifts.

[BoiseShark]

Thanks Dano. One less thing I have to worry about.

[BoiseShark]

K, one thing i noticed today and I don't know what to make of it is in this picture


below the distributor (where it would be) is a port that says "to vacuum source on intake plenum"

My car does not have this port. The vacuum that comes off the plenum on my car does the following;

1. lined tees off and goes to brake booster (this is correct from everything I've seen)
2. Main line then goes over and ties into the line going into the AAR. (could this be right?) The AAR opens and closes and blows air back into the plenum past the cold start injector.

I don't know why my system is missing this port. It has all other ports...just not that one

The port at the top of the picture that says "to throttle bypass circuit (incl Auxilliary Air Regulator)" has a hose coming up that runs directly into the AAR. This main line is T'd before it hits the AAR and the T runs into the vacuum port in the intake plenum which is T'd to the brake booster as I explained above.

I hope this makes sense.....it barely does to me...lol

[BoiseShark]

this is how mine is routed;

[MPDano]

That one pictured also has that electrical connector on the top right. The CIS went thru a lot of weird changes. Yours is probably original and fine. I am not at home but your booster routing sounds like mine and all others I've seen.

[Luis_M]

My 81 has the extra port. Your routing has the same effect, flow of metered air from before the throttle to after the throttle across a venturi tube, to provide a reliable vacuum for the brake booster. The hosing at the AAR changed when the new port was added, which makes for a slightly neater arrangement and less hose overall; on my car the hose goes straight down to the extra port instead around to the AAR hose. BTW, it shouldn't be a T to the brake booster; it should be more of a Y-shaped tube with the side port going to the brake booster.

[BoiseShark]

Thanks guys, can rule that one out as well then. You guys are fantastic. I hope to one day have the knowledge to help others and I have a feeling by the time i get this thing going I will be a wealth of it.

not sure whether to add a smile or a frown here...lol

[MPDano]

Here you can see some of my routing from the top. The "Y" that Luis mentions is kinda covered by the upper right two spider legs.

[MPDano]

Originally Posted by BoiseShark

I noticed in the 928 spec/parts book that there is a gas line that runs to the front of the plenum. If your looking at the engine, it is just above and to the left of the cold start injector. My car just has a bolt plugging the hole. Any ideas

Here is a pic of what is on mine which is an Auto

[BoiseShark]

Thanks for all the help Dano. I'm so frustrated at this point. I got it running today for the longest it has ever run and excepted throttle for about 15 minutes, but once again..once it warms up it starts having trouble running and will not except throttle. I actually took the WUR apart and cut about 1/32 of an inch off of the little rod to lower warm control pressure since the screw into the diaphragm was messed up. It did improve it and it ran for 15 minutes like I said...had such a smile on my face...but then back to the same old warm up stuff.

I can't keep this thing running. I fear i'm going to have to give up and take it to an expert (if there is one in Boise)

All vacuum lines are correct..thanks to all of you..and if there is still a vacuum leak...it will amaze me..although when i give it gas when it is starting to have problems I can hear a massive suction sound in place of the rev.

been working on this thing for a month...grrrr

It runs great when warming up. sounds mean and steady like i could go for a drive...but then the idle kicks down and it begins it's slow path to barely running again.

I wish some of you lived near me...i'm thinking of buying someone a round trip ticket to boise and a twelve pack of coronas if anyone is interested...hint hint

[DPW928]

Concerning the suction sound when trying to accelerate, the sound could be normal if you have the filter assembly removed. If not removed, there could be a vacuum leak between the top and bottom section of the lower intake plenum. The gasket will often blow out if there is backfiring into the intake. Also, make sure the Y adapter on the vacuum line going to the brake booster is oriented correctly. If oriented incorrectly, it can cause a large vacuum leak as it is fed by lines before and after the throttle plate.

[BoiseShark]

The filter assembly is removed, but I am beginning to suspect the gasket on the lower intake plenum as well.

I have decided to make a good video of it running its course and also all the vacuum lines and where they go to currently.

I hope to make it a good enough video that you guys might be able to get an idea of what is going on. I will also show control and system pressures.

Last time it ran is after I cut the rod down in the WUR and i noticed the warm control pressure was actually lower now than it should be...woops...but car actually ran longer and then had the same symptoms as if control was still too high.

I'll just make a video of everything i have done so far and we'll go from there.

[JK McDonald]

Hey BoiseShark, One question that also may help to diagnose your fuel control problem is to know if your car has ever run correctly since you’ve owned it or did you inherit the issue with the car ?

It looks like you have chased down and followed up on most of the suggestions provided so far but it sounds like your warm-up-regulator is still questionable. One test that I’ve used to eliminate a potentially erroneous WUR is to substitute a manually adjustable shut off valve in it’s place. I have found that a brass shut off valve with coupler nuts and a pair of 3/8” in/out copper lines worked fine. With a bunch of hose clamps and a few feet of rubber fuel line you can plumb in your fuel system pressure gauge in series with the added shut off valve. This contraption looks crude, rude and socially unacceptable but now you can manually adjust the reduced fuel pressure that controls one side of the sensing plate in the fuel distributor assembly.

You will probably need an assistant in the driver's seat to help initially get the engine started but by tweaking the pressure normally controlled by the WUR while monitoring the results – you will know if this is where your problem is located. Set your (cold) start up pressure and then gradually increase it per the spec chart as your engine warms up. Carefully check all your connections and of course smoking during this test is not recommended......

Good Luck Michael

[JK McDonald]

Hey MPDano, Man the photos you posted of your engine compartment look really great. I wish mine was that clean. Excellenteeeee -

Michael

[BoiseShark]

Yeah Dano, those pictures were awesome. Thanks so much for doing that for me. I can't believe you disassembled your car to show me what was going on.

Update--I know this sounds crazy, but I found an '80 mercedez in a junk yard and pulled the fuel distributor for the hell of it because it was an aluminium one with adjustable ports and they asked $24.00 for it...figured i couldn't loose. With a day of soaking and a little bolt swapping and plugging, I hooked it up and my car runs great....well, at least it starts and runs and accepts throttle after it warms up. (still never drivin it...lol)

Now I've developed a whistle..probably some vacuum issue that I messed with earlier.

I'm so happy that I not only own a 928 but that I am also..with this forums help...becoming a novice expert on the working of such a beast.

I stopped today at the good running. I'll track down the whistle on another lucky day.

I'm so smiling right now!

[AirtekHVAC]

Boise....Where did this end up? I noticed that your issues are very similar to my issues....what has been done in between this last post and now? You may have gone to another thread, but my head is swimming with all the info. As my car has sat the last 20 years...I feel my problem could also be in the WUR or the fuel distributor...my symptoms are near EXACT to yours.....I'm at this stage now...

Thanks!

[MPDano]

In short, you'll see another one of our members here did the exact same thing using a MB Fuel Disty that was adjustable. He fought it for months trying to get it running right until he finally listened to us to get a stock one. Guess what? He got a stock Disty and it actually ran as it should. Who woulda known?