Christian J

Working on a C 3.0 that has sat for many years and it starts but is running on 5 cylinders. Verified spark to all cylinders and pulled the injectors- surprise! Can you mix 'n match like this? The skinny ones look like Bosch but I can't verify the other type. Is either style oem? Can they simply be cleaned and popped back in or do they all need to match? Thanks

Droops83

Well, the obvious difference is the injector sleeves came out along with the # 1, 5, and 6 injectors. Before you do anything else, make sure that the remaining sleeves are intact in the heads. When pulling old injectors you run the risk of the sleeve breaking, and the pieces can then fall into the intake port.

It is hard to tell from the photo, but the tips of the injectors with the sleeves attached DO look slightly thicker than the others. Verify they are all the same, and that the Bosch part #s are all the same (should be 0 437 502 004 on a 911SC.

The opening pressure and spray pattern of the injectors needs to be tested, which normally requires the use of a special testing fixture that measures injector opening pressure.

DISCLAIMER: WORKING WITH OPEN FUEL LINES IS DANGEROUS! Have a fire extinguisher handy and work in a well-ventilated area!!!!
You can perform a rough approximation of this test by reattaching each of the injectors to their lines, tightening the fittings and placing each injector in a large transparent jar. Disconnect the airflow plate sensor connector from the rear of the sensor plate unit and turn on the key. You should hear the fuel pump running. Slowly lift the airflow sensor plate arm and observe the spray patterns of each injector. They should be uniform, and each should be a finely atomized mist. Any dribbling injectors are no good and should be replaced.

Whether you reinstall these injectors or replace them, first install new injector sleeves, seals, and O-rings.

Of course, on any CIS car that has been sitting, a fuel delivery problem to an individual cylinder could also be the result of a fuel distributor issue (they can form varnish inside, causing flow issues). You can carefully crack each fuel distributor banjo bolt loose one at a time while the engine is running (once again, have a buddy with a fire extinguisher present!!!). Fuel should come out and the engine RPM should drop. The cylinder where the RPM doesn't drop is your problem. If fuel doesn't come out from under the banjo bolt, then the fuel distributor is likely the issue. If it does, then your problem could be the injector.

Be sure to check basics like valve adjustment and compression/leakdown. TRIPLE CHECK that the ignition is disabled before performing a compression check, especially since you have had open fuel lines!!!!

Amber Gramps

^^^^ That is exactly what it looked like to me when I first looked.

Here are all the parts:

http://www.pelicanparts.com/catalog/...FULcis_pg5.htm

Peter Zimmermann

You need 6 injector sleeves, 6 sleeve o-rings, and 6 injector o-rings. Everything will fit tighter because the sleeve design changed slightly.

Pull your plugs; do you have one dark one? If yes, that will probably be the bad injector. As Chris posted, it's possible that you have a fuel distributor problem, dirt in the system, etc. Do the easy stuff first!


BTW; HI, CHRIS!!!

greg1990964

sounds just like my 80 sc that has been sitting for a few yrs. How much is a injector set? And were is this banjo? On the fuel block?

Droops83

Hello, Pete!

Hope all is well with you. Last I checked Santa Barbara is not that far and is not too bad of a place to visit! Would love to meet you in person someday.

This thread is an interesting coincidence, I am going through an old '73.5 CIS system for a customer who is restoring the car and converting it back to stock (was carb'd long ago apparently). We happened to have a NOS set of '73.5 injectors on the shelf, so I dusted off the old Bosch MFI/CIS injector tester (the thing is older than I am!) and tested them out. I forgot to snap a pic but I'll post one tomorrow. The original cold start injector actually tests OK and doesn't drip!

Charles Freeborn

When I pulled all my sleeves and injectors only one was shot. The rest I soaked in Acetone and re-used. Removing sleeves is tricky - you have to plug the hole and then grind off the detent that traps it in the intake runner. Then clean thoroughly and carefully with a long handled q-tip. Install new sleeve and o-ring, peen a new detent with a punch and hammer. Next install cleaned or new injector with it's new o-ring, bleed the air out by putting all the injectors into catch containers, turn on fuel pump and manually lift air valve inside airbox until you hear them "sing". Push the injectors into the new sleeves and you're good to go. As I recall the one injector I replaced was around $45. Whole job took 3 or so hours. Be careful with the plastic fuel lines as they can be brittle from old age.

Droops83

The banjo bolts that I refer to are on the fuel distributor. They are the six bolts around the perimeter of the fuel distributor, one for each cylinder. If you decide to perform the quick power balance test described above, BE CAREFUL!!! Helper with a fire extinguisher, well ventilated area, no smoking/sparks, etc.

You don't need to loosen each bolt that much, use a 12MM box-end wrench and loosen it just enough so that a bit of fuel runs out. The RPM should drop when the bolt is loosened. If the RPM does not drop, or not as much as on the other cylinders, you have found your problem cylinder. If fuel comes out from under the banjo bolt same as all of the other cylinders, the fuel distributor is likely not the problem. If nothing comes out, or not as much (you will likely need to go around the fuel distributor a few times for consistency), then the fuel distributor itself could be the culprit.

But, like Pete said, check the basics first! If one cylinder is a dead miss, spark plugs can tell a story. Check em out, and make sure there is spark at each plug connector, and that all of the connectors are tight (check for spark BEFORE you attempt to check anything in the fuel system for obvious reasons!!!!).

Check compression if you can if the above tests are inconclusive, and if you are in doubt or uneasy about opening up the fuel system, defer to a competent professional Porsche specialist.