problem with cis car

[godfather]

I recently bought A 1978 928 5SPD with 70k miles that has been sitting for 10-11 years. The fuel pumps were both dead and i replaced them and the fuel in the tank. now it starts and runs on what seems like 2 cyl. No fuel is getting to the other cyl. I completely disassembled the fuel dist. and cleaned it out and still the same. I'm leaning toward the injectors but would like to hear some opinions before i go ahead. any input is appreciated.

[Danglerb]

Your going to need some gauges sooner or later with a CIS car to measure fuel pressure.

My wild guess is that you might as well pull everything that has fuel go through it and clean and flush it out including the injectors and maybe the filters more than once.

You could also pull the plugs and check condition, color etc. Compression test might not hurt either.

[rhjames]

Here is my basic CIS fix.

CIS systems must be very, very, very clean.


you will need:

1. clean and flush the fuel tank.

2. replace fuel filter

3. replace fuel pumps (if not working or low output)

4. clean or replace fuel accumulator

5. flush the fuel lines (replace those which are collapsed, etc.)

6. clean or replace the warm up regulator

7. clean, adjust, replace the fuel distributor

8. clean or replace the fuel pressure regulator

9. injectors---see next


next:

injectors---- you can have them sonically cleaned, but not rebuilt.
CIS injectors can not be rebuilt, no matter what any injector shop tells you.

there are numerous places you can get new injectors, but prices vary widely anywhere from $40 + and up for the Porsche injectors.

I purchased a set of Mercedes Benz 047 injectors for my Euro and they have performed just fine. the injector is brass instead of steel, 1/2 inch shorter than the 928 OEM injector, but they were only $60 for the set of 8 (used but freshly cleaned). there is an on-line injector parts store in AZ that sell the 047 injector (new) for $27 each---best price I've found.

you can also purchase a pressure gauge kit for testing the system, which will give you a better idea of what's going on.

Another major issue you must take on is vacuum leaks---

There are silicone vacuum kits from several sources, and you may as well figure that (in your case) the hoses will need to be replaced. Do them all, but do them one at a time so as to not mix up the hose routings.

With my Dad's 79, he went through this entire process, and ended up spending about $2000 to have a Porsche repair shop get his car running after it was dormant for about 8 months. Not all of the above parts were replaced, but it does run fantastic now.

hope this helps---Russ

[Fabio421]

There are lots of little screens in the CIS system that get clogged with "gunk" over the years. Do a search here and at Rennlist and you will find a plethora of info. CIS is great when it works, but sometimes it doesn't like to work and you will want to slit your wrists. Once you get down to it and understand it its not too bad.

[rhjames]

Fab's right to remind us of the little screens under (ti seems) every fuel line connection.......I should have remembered this, but my Euro doesn't have any.

--Russ

[785sp]

I was in exactly your position. Exactly.

Spend a weekend taking the intake completely off, clean all the built-up gunk from every orfice you can find using any sort of degreaser, spray the same degreaser up into the injectors and down into the valve stems, replace every vacuum hose and rubber fuel line you see even if you don't know what it's for, and if any are missing make special note of them and cap them off for the time being. Pay special attention to the big rubber rings/tubes just under the octopus-thing (the "plenum," I think they call it) that have tightening rings around them, and also pay close attention to the gasket/interfaces between any hard-metal tubes and the plenum, especially the one that's hidden from view until you remove the plenum "legs" on that side. You will also have to replace the eight plenum-tube gaskets, a couple bucks each. If any of the old gaskets don't pull off, just sand off loose parts and double up (sorry purists!). Don't scrap them off with anything metal, or you'll gouge the aluminum in the same place you're trying to form an airtight seal.

Also, because you're already there, you can pull off the injectors and have then back-flushed at a shop or replaced if actually not working. I didn't do that, but wish I had. Be extremely careful unscrewing the fuel lines, or you'll be calling the salvage places for a replacement. (I ruined both of mine.) Incidentally, you'll need new, thin, copper crush washers for all of the fuel line connections, including those coming out of the fuel distributor. (Also sure to make purists cringe, I couldn't find one of the correct-sized copper crush washers, so I used a nylon or plastic washer that an auto-shop dude said was ok on fuel lines, and it's held for two years with no problems.)

After it's all back together, any further misfire symptoms, considering that you've already replaced the fuel pumps and cleaned the piston inside the fuel distributor (right?), might be caused by (i.e., in my case was caused by) a faulty Warm Up Regulator (a $200 part that you can replace in about fifteen minutes) and/or your double-disk clutch not releasing and mimicking a misfire symptom (yes, it really did sound exactly like a misfire).

Another tip I wish I'd known about on the first day was that Home Depot sells tiny rachet-wrenches in metric sizes for about 15 bucks a set, about five inches long each. Invaluable when you're trying to get the plenum tubes off.

Good luck bro!

[rhjames]

one last "tuning" item.....

the steel lines from fuel distributor to:

injectors

damper

warm up regulator

cold start injector


you should examine the openings on each end of these lines. if they are deformed, crushed, not uniform, not the same diameter as each other, etc..... you can drill open these holes.

Be damn careful doing this, starting with a bit that is small and work toward larger bits. don't go too big, just enough to clean up the openings and make them the same for all lines. the injector line openings are one size, the rest are another. use a slow speed drill and do not let the bit jam up in the line or puncture the line wall. it takes a gentle touch to do this, but in the end you'll have a fuel system that's right on target.

---Russ

[godfather]

thanks for the info guys im going to try a couple of things and get back to you.

[Danglerb]

I forget where I saw it, but somebody in the 928 community is making replacement CIS fuel lines, the ones that go to each injector.

[curt_924]

When my 79 cis beast instantaneously started running like s$%t tried to work down the problem.. turned out was both leaky cold start valve and a gunked up warmup regulator.. now she runs friggin sweet though a tad bit rich still I think. If it's running rich which can mimic 2 cylinders running via clogged mixture control.. you'll smell the gas at the rear tailpipe.. just a thought..
until then.. these guys have given great advice... it's exactly what I'd have done..

[curt_924]

btw.. I might have an extra injector lying around if you'd like to probe the theory of bad injectors..

[rhjames]

yep,

Carl Fausett has injector line kits in braided stainless steel for about $1000.

Brendan (Rennlist's San Diego know it ---) has claimed to put together a set for around $250 or so......

anyone can do this using flexible hose parts from your local hydraulics dealer.

steel lines are another issue.

---Russ