banquest

Hi all,

I'm a new 1979 porsche 928 porsche owner and a new rennlist member. Briefly, I purchased this car which was parked for about 4 years and I'm trying to fix it up. I've worked on old cars for years as a self learner only, but never had any experience with a porsche.

I will go straight to the question I have and hope to get some help from the experts on this forum. I apologize if this has been posted before, but I can't seem to find any posting with similar issues.

I rebuilt the fuel distributor with a new rebuilt kit bought on eBay. needless to say, it took 4 tries removing, redoing, and reinstalling before I was able to get the car started(this is with lots of reading on this forum). Here is where the problem is. the car now smokes a lot with what seems to be oil mixed with gas but it does not smell like gas. This did not happen prior to my rebuilding it. It idles fine with no problem, no knocks, no pings and starts right up on warm start. It does take a few tries on cold start though. Lots of people mentioned that I just need to run it for a while to clear out the oil from the exhaust so I'm fine with doing that. The problem is that it is using up gas REALLY fast, but there is not gas leaking anywhere that I can see, only what I mentioned what seems like gas mixed with oil in the exhaust. it is white smoke coming from the exhaust.

My question is, where does the gas go if it is not leaking anywhere? could it be that I messed up on the rebuilt of the FD and it is leaking from the FD control plunger in the center down to the bottom of the FD?

My concern is not so much with the white smoke, but really with the fuel consumption. I do not drive the car, but at idle for about 10 minutes (while clearing the smoke) it uses up approx 1.5 to 2 gallons of gas. Is that normal?

I know this is not very clear, but please let me know if I can clarify on any thing in order for the experts on this forum to help. once again I apologize if this issue is posted somewhere and I can't find it being a newbie.

1979 porsche 928 - 5 speed

hlee96

A set of fuel pressure gauges would be required to tune up a CIS engine.

dr bob

Sniff the oil. Guessing that's where your oil is going. If the smoke/fog is sweet smelling, of course that would steer you to coolant. And you'd sniff that too.


How are your fuel and control pressures doing? They determine how fuel is metered into the injectors. Hard to fathom how you could push 1.5 gals of fuel through at 10 minutes. Without making a huge mess anyway. That much fuel should be really obvious.

AirtekHVAC

Seems like I have typed this in multiple times in the last month or so. Traveling and On my phone, so can't really find to paste... anyway... I believe you are pumping raw fuel into the block. Stop what you are doing and look into taking the FD apart again. I went through this, and had to disassemble mine 5 times, and also had to replace the o-rings again...problem was small spacer/washers that are under each spring. They were not shown in the Bosch manual. Mine were so gummed up that I never saw them and lost some during cleaning. Search me, or look for my thread on my #30 car.!fo to the last page and start going backwards and you'll find it quicker, or do a thread search. If you need to chat about it, send me a pm and I'll call you sometime this weekend.

AirtekHVAC

BTW, I emptied my tank in minutes, car ran awful, smoked, and fuel poured out the tailpipe, while the car was idling...scared me sheetless....

banquest

Hi all, apologies for the late reply. Thank you so much for all the great advice.


hlee96, yes, definitely a great idea and that is the next item on my list to purchase. Wife hasn't been too happy with lost of things I have purchased thus far to get it to start so I have to take it slow.


dr bob, the smoke does not smell sweet and my coolant level has been the same for the past month. I have no idea about the fuel pressure yet so will purchase the fuel pressure gauge to perform more testing on it.


AirtekHVAC, it sounds like I'm having this issue you described in this post, that is fuel is pumping into the block, but I'll go dig up your previous post and read on it today. I will work on the FD again this weekend and will update.


Thanks again so much for everyone's input.

docmirror

1) You absolutely cannot fix, adjust, or repair/replace parts in a CIS system without the pressure gauges and hoses. You must have them, call Roger at 928sRus and get a set.

2) Remove all your spark plugs and look at them. My guess you will find more than one with very dark deposits of unburned fuel. Maybe all of them. Get new plugs.

3) Change your oil, even if it's new, change it. More than likely fuel diluted.

4) There is a 3mm mixture adjustment screw in the center of the CIS fuel dist head for setting the mixture. It may have a screw cap over the adjustment screw which is embedded in the housing. It may also have a anti-tamper ball-bearing(KE mostly) in the hole which needs to be removed to get at the adjustment screw.

http://ww2.justanswer.com/uploads/Ra...adjustment.jpg

http://landiss.com/mixture.htm

Righty = richer, lefty = leaner. Turn it 4 full turns to the left to begin. (start excessively lean)

5) Remove all 8 CIS injectors. Clean them, and see if you can find someone to test them for pressure and spray pattern, ask Sean/Roger. If not, you can buy a set from Roger, or maybe find on ebay. In either case get new injector seals to install in the injector base fitting.

6) Hook everything back up, and finally set your pressures by the book. If you haven't touched the warm up regulator, now you will find out if it's working as planned.

7) Only after you get the pressures in spec can you try to start the car again with fresh oil, clean or new injectors, and a correctly working warm up reg.

Notes;

Since you have been running excessively rich, there's a lot of fuel residue in the engine, and maybe in the cats. This is a problem. If the cats get hot enough and there's a lot of fuel sitting in them, it could easily cause a fire and carbeque your car. I would recommend removing the cats until you get the mixture set right. If you don't remove the cats, at a very minimum, take them out, tip on end, and leave them to dry out for a few days.

The CIS mixture adjustment is very sensitive. If the engine won't start after a few seconds of cranking, move it 1/4 turn right(CW) and try again. At some point between where it was when you started, and where it should be, the engine will begin to sputter. Turn it another 1/4 turn right(CW) and get the car to run. Always try to adjust from the lean side, toward the rich side, and not the other way, as it will go back to the problem you had before with flooded engine and white smoke. Stay lean until the car warms up. Don't leave the adjustment tool in the CIS head. Make the change then remove the tool.

Once you get it to run, even if its sputtering a little bit, let it run a while and clear out the exhaust, and vapor left behind. Allow the warm up regulator to do it's job and change the air/fuel ratio. You may have to make SLIGHT adjustment richer as the regulator warms. Always go back to lean as possible. Let the car warm up normally and get the exhaust system and engine dried out.

Only now can you set the mixture properly. If it still gives white smoke, you have something wrong with the dist head, WUR, or fuel pressures. Don't continue to burn all the gas, find out what's wrong and stop dumping gas into the engine and exhaust. It's a fire hazard. I would see if you have a smog shop nearby that will hook up to your exhaust and run a CO monitor test. Some will, some won't. If you can get it hooked up to their machine, you can set the mixture properly by the target value for this model. Every CIS is a bit different.

http://www.pelicanparts.com/techarti..._Injection.htm

When you have the CIS system adjusted close to best value, you may notice that the injectors will 'sing' or 'whine'. If you have the mufflers on and cats, in most cars you can start to hear this high pitched sound coming from the top of the engine. This is actually correct operation of the CIS injectors. It's an indication that they are working in the mode they were designed. Although this link is for the 911, it also applies to the 928, however the pressures on the tester will be different.

http://jimsbasementworkshop.com/CIS/...roduction.html

banquest

docmirror, and all,


I don't know how to thank everyone for taking the time to post replies. This forum is great and I'm so glad to have found it.


I've bought numerous 928 parts from Roger in the past few months so the fuel pressure gauge will be ordered today as well.


just a quick list of things I've already done in the past 2 months prior to my posting, and some coincides with your suggestion:


1. new spark plugs
2. new set of drive belts
3. oil changed twice (just because it has been sitting for years so I thought it would help to clean it out)
4. all 8 New fuel injectors


I will go over all things suggested but it will probably take all weekend or longer and will update. will also have to wait for the fuel pressure set to arrive.


Thanks again everyone. your are great!!

docmirror

Put your location in your signature block. There may be someone nearby with a set of pressure gauges that you can use.

banquest

docmirror, Learning how to add the signature block now and trying it out, hope it works.


I'm in Dallas, TX.

docmirror

You are in 928 mecca. I have a set of gauges, Sean has a few sets, Curry has a set. If you don't want to buy them, we'll get them to you. Sorry Rog, just cost you a sale!

I'm way out west in the country, but there are sets of gauges near you I'm sure.

hlee96

doc you're the best! I am saving your cis troubleshooting paragraph.

dr bob

With your DFW location, you have the amazing good fortune to be near several of the best 928 resources in the world. You know Roger already, and you've met Doc Mirror on line. You'll want to visit with Sean Ratts (SeanR here on RL), who offers pretty top-notch services on the cars. You may be able to coax him into a house call if you don't get things handled promptly. It will be money saved in the long run. Trust Me.

Perhaps the second-biggest danger (after !!fire!!) of spilling all that fuel into the cylinders is the loos of cylinder wall lubrication. The block is aluminum with embedded silicon particles in the bores. To survive with aluminum pistons, the piston skirts have an iron coating. Both that coating and the rings depend on oil for lubrication. Lose that, and the iron coating is quickly scuffed off. The pistons are then suitable for recycling, perhaps as ashtrays or paperweights. There is no recovery method available. Doc's advice to get the fuel system sorted before you even crank the engine again is absolutely spot-on.

I'd leave the plugs out during all CIS testing, so you can immediately smell when there's fuel going into cylinders. That will give you a clue before fuel ends up in the exhaust too.

As others have stated, "rebuilding" a CIS fuel metering unit includes keeping exact track of every shim, washer, spring, and piston, so that each goes back in exactly the spot from which it was removed. At original assembly at Bosch, the flows are balanced by swapping shims/washers and springs. Fuel pressure adjustments rely on a spring and shim/washer set, There are small brass screens at critical points in the system too, that rot if left dry for very long; then they disintegrate into the systems they are intended to protect.

The "warm-up regulator" is the other critical piece of the CIS puzzle. It adjusts mixture based on coolant temp, and includes a small electric heating element to help it through the period immediately following a cold start.

Cold-start injection valves that leak are also known sources of unintended fuel flow, if you have one.

------

Consider investing in Rennlist membership. There are some instant benefits, like way fewer ads, and other convenient features enabled like the ability to put your car information in a signature block. Else you get to type it into every post. Lots of other benefits too, like the ability to offer and solicit parts and pieces in your posts.

Click on "Membership" in the banner at the top of this page and you'll be able to quickly get started.


Welcome to the group!

docmirror

When I was working on the Mondial, I had this kind of issue as well. I was drooling gas into the engine and worried about hydrolock, so I pulled all the plugs just in case. After fiddling and getting the pressures set, and the mixture close, I decided to crank the engine a couple times. Well, the Mondial has transverse engine, with a little access hatch for the forward bank leading to the firewall behind the rear seats. With the little back seats folded down, it's easy to access that bank.

Anyway, I was getting in a rush, and reached in to crank the engine around, and fresh gas literally GUSHED out of a couple of front jugs! GAK! The back of my head, the seats, the rear carpet were drenched in fuel. They filled with fuel as I ran the pump. It would have surely hydrolocked, so this is pretty important, and thanks for bringing it up as well.

soontobered84

Doc,
I do not have a set of fuel pressure gauges. The one I used was Roger's and at the time I used it I added the adapters I needed for the Jalapeno. I then returned the whole kit and caboodle back to Roger since I knew I would never own another CIS car again.