CIS problem

[rhjames]

Here's one for the technicians----

CIS K-jet injection system, 4.5L 16V, 5-speed (Dad's 79 model).

Car idles as if not all injectors are firing. This continues off idle to approximately 2500 rpms. Gear selection makes no difference. Above 2500 rpms, there is a noticeable kick as if all 8 cylinders just started working. Pulls great above 2500 to redline. (fuel filter is new, fuel pump is OK, ignition system recently tuned up, nothing out of the ordinary----)

Care to take a stab at this one?

[Fabio421]

What have you checked?

The aux. air valve may not be opening up enough when cold. It is a very simple device. Just a bi-metalic strip with a heater coil attached. The Bi-metalic strip pushes a litte lever that rotates a disc with an odd shaped hole. As the car warms up the heater coil is warming the metal strip and causes the disc to rotate which closes off the valve. When its cold it is open and allows air to bypass the throttle plate in turn raising the idle. To take it apart you must drill out the 4 aluminum rivets. You can just replace them with some socket head capscrews when you finish testing it. You can hook it up to a 12v source to check the heater coil and see if the strip is moving enough when cold. If not you can carefully bend the bi-metalic strip to allow more air to bypass when cold. Its a pretty simple item.

Have you checked to see if the cold start injector is working? Its the one in the front of the plenum. There is an orange phenolic fitting that it is screwed into. These pieces crack easily when old. A small vacume leak could cause this problem to depending on where the leak is located. I bielieve you can disconnect that injector and still run the car. Try running the car and then disconnect the cold start inj. and see if the engine idle drops or not. If it is running as poorly as you say it should actually stall the engine when you disconnect it if its working. If you don't notice a difference in idle speed its not working. That inj is controlled by the temp II sensor I believe. I'll have to read up on it to verify but this should at least get you started.

Keep us posted.

[rhjames]

Fab,

I haven't checked into the air valve or the cold start injector as of yet. engine was running OK before intake and throttle body change, but I'm not sure that would have caused it to run idle to 2500 lacking a few cylinders. Above 2500, it runs great.

Maybe the fuel distributor is going south? (Or at the very least, needs to be adjusted?)

I wish I had a Bosch manual and a set of pressure gauges, but just haven't got that far into it.....

---rhj

[Fabio421]

I thought you were saying that it happens when its cold only. Is that not the case?

[rhjames]

Fab---

problem is not a cold start issue..... runs like one or two cylinders are not firing from idle to about 2500, above that it runs very smooth and pulls great all the way to redline.

it starts fine, a little bit up on the idle until is warms up, then rpms settle down, but runs like described above.



thanks--Russ

[rhjames]

went back to Dad's engine and checked a few things.

the aux air valve is working properly as far as I can tell. remove one hose from it, look into the port and the "plate" is half way into the closed position. once the engine is fully warmed up, hose off again and the plate has rotated to fully open.

checked the warm up regulator. disconnected fuel lines and found no trash in the inlet screens. I was not able to check the electrical side of things on the WUR, other than making sure the wiring connections were clean and attached properly.

I have another set of injectors that I am inclined to change to, but so far I'm not hitting a home run.....

----------

[785sp]

For what it's worth, I had identical symptoms on my CIS model. Turned out to be a combination of a vacuum leak in an unlikely place (recirculation tube leading back into the intack chamber) and, just as problematic, a slightly-dragging clutch that disengaged after about 2500 rpms. You have the double-disk clutch, I believe.

[Danglerb]

Just thinking a bit about what changes around 2500 rpm.

Airflow goes up, so effects of a small leak might go away.
Alternator starts making full output, so battery issues or grounds might be masked.

Maybe start the motor and run it just in the bad range below 2500 rpm for a bit, then stop and pull the plugs and see how they look?

Maybe use an IR thermometer and see if there are any temperature fluctuations in the exhaust manifold cylinder to cylinder.

Maybe do a compression test.

[Randy V]

I had the same problem with my '79. It was the fuel regulator.

Try cleaning it out. At each of the 8 outflow points is a small mesh screen that gets clogged up.

If that doesn't work, you may need to replace the fuel distributor. They are quite expensive and difficult to locate so hopefully a cleaning will do it.

Another possible culprit is the air metering plate. It may need to be slightly adjusted.

Search over on Rennlist for the procedure.

[rhjames]

I was really hoping it wasn't a bad fuel distributor, but the symptoms are steering me that way.....injector nozzles are not symptom cylinder specific---in other words, if I swap injectors from one cylinder to the next, the problem doesn't change.

good tip on the mesh screens in the fuel distributor, hadn't got that far into it----

thanks--rhj

[rhjames]

well, after reading up on the CIS system, plus all of the helpful tips here and on Rennlist, I'm headed towards taking apart the fuel distributor.

all of the vacuum lines and intake connections are good and tight, and a light dose of ether (yeah, starting fluid---don't attempt this at home, or on a hot engine, for that matter) sprayed around the intake didn't turn up any vacuum leaks. (if there were any leaks, the ether spraying would have resulted in the engine speed coming up.)

hopefully cleaning the screens as RandyV suggests will take care of the problem.....

thanks for the help-------

[785sp]

If you're going to tackle the fuel distributor, doing it half-way might solve the problem and a lot of time. The unit can be unbolted from the eight lines, unbolted from the intake, and then mostly cleaned out without having to dismantle it completely. This will be obvious once it's out of the car and in your hands; basically, there's a fastener underneath that keeps a sliding piston from falling out. Undo the fastner, drop out the piston, and spray that and everything else out with carb cleaner, including the fuel-line ports in both directions. It only took me a couple of hours, which means it's very easy.

[rhjames]

thanks for the cleaning tips---that appears to be where I'm headed this week.

swapping for a rebuilt unit is not on the table at the moment, but cleaning is.

This all seems to have started after Dad and I swapped out the fuel tank (it had a crack in the bottom of it) for a used one that I got in the hoard of parts I bought. I thought we did a pretty good job of cleaning the tank before installation, replaced the fuel filter too, but now we've got this rough idle deal going on.....Glad my Euro hasn't developed something like this, as I have no idea what it would take to get a fuel distributor for it

And yes, everything I have recently read up on regarding CIS states that it is very finicky when any dirt gets into the system.

Thanks again for the tips---will keep you posted.

---rhj

[Danglerb]

Russ as far as I can tell all of the CIS cars, US, Euro, and Euro S used the same 928 110 906 00 fuel distributor.

[rhjames]

update:

decided to tackle the fuel system today.

unplugged the spark plug cables (one by one) to determine which cylinder was firing and which ones were not. (#5 and #8 were the likely suspects)

next removed the injector lines and injectors (kept the injectors in order for further diagnosis).

removed banjo fittings from fuel distributor, and found no screens under them. sprayed brake cleaner in the hole to remove and possible dirt.

injector line end flares were in really bad shape---almost closed off on some, deformed on others. Resurfaced the flares with emory cloth, and drilled the holes out to uniform size (all of them, including the other lines such as the WUR line-cold start injector line, fuel pressure regulator line, etc---both ends). Flushed all lines vigorously to remove any debris. You have to be damn careful doing this, as breaking off a drill bit or drilling through a line wall is bad, bad, bad.....Did this same repair to my Euro while I was at it (working on Dad's). My lines were in horrible shape as well.

checked injector spray patterns using spray can break cleaner (with the little tube stuck up in the upside down injector). Could not believe how little pressure it took to make the injectors pop. Also checked my Euro injectors, and found only 2 good injectors between my Dad's car and my Euro. Spray patterns were any where from just barely dribbling, to one or two streams, to the two "good ones" with cone shaped fine mist sprays (buzzzing away).

Reinstalled lines and injectors, still had misfire issues but not as bad----moved injectors to different cylinders and the problem moved with the injectors......

I think I've found the source of our troubles........maybe.

Looks like we'll be ordering two new sets of injectors this week.

More later-------rhj

[rhjames]

more CIS info:

in my search for injectors, I have found that the 0437 502 012 injectors are selling for around $45 each in most places.

I did find a Mercedes Benz injector, 0437 502 047 that is similar (but made of brass---supposedly and upgrade) that a place in AZ sells for $27 each.

Witchhunter in WA does injector service (cleaning, not rebuilding) for about $17 per unit, but their website states they do not service CIS injectors.

has anyone had any experience with the MB 047 injector?

----rhj

[Randy V]

This place seems to carry reconditioned OEM ones for $29 -

http://www.fuelinjector.citymaker.com/page/page/5132845.htm

Might be worth a shot.

[rhjames]

bought a set of 047's for less than $60. just freshened. will be here nest week

didn't figure I could go too wrong for the price---we'll see......

-rhj

[rhjames]

update:

MB injectors arrived yesterday.

they are the same as the Porsche CIS injectors, except that they are approx 1/2 inch shorter and are made of brass.

these injectors were reportedly cleaned and ready to go.

I installed the removed the Porsche injectors, installed new injector seals on the MB units, installed them, and fired up the car.

WELL, what a difference they made. The idle is smooth, the throttle response is very crisp.

the engine has never run this good......

thanks to all who suggested their "help" ideas.

life's good again........

---Russ

[Randy V]

Nice!