CIS adjustment on 2L 924

[yundar]

Hey All, I am in the process of bringing a long parked 1980 924 back to life. I am currently having trouble with fuel. Specifically I am consistently flooding the engine. I have cleaned the fuel distributor and the metering piston. It seems to fit snug but move freely in the barrel. When I go to adjust the fuel I can turn the 3mm adjustment screw full counterclockwise but I can never get the fuel to stop flowing. I feel like I am following the procedure correctly where you turn the screw CCW until the fuel stops flowing and then you turn it back until it just starts. My problem is that I can turn it full CCW until it hits the stops but it just keeps pumping fuel? This is with the relay jumped out and the key on. Any help on why I can’t seem to adjust this or tips on massive flooding would be helpful. Thanks, Andy.

[jjeffries]

Andy, I don't know the answer to your question, although it would be good to know more about how you cleaned, then resealed the CIS fuel head/distributor.

I'd suggest you send a PM to Tony, whose Pelican forum name is below. He is a CIS/K-Jet guru and does component rebuilding and is generous with advice. Beware, however, that he can be very blunt in his communication style. He is a GREAT guy and knows his stuff. Please keep us posted. (I have an 82 911SC with CIS and think it's a great system. Some others disagree!)

Best of luck, John

Tony's PP handle:
boyt911sc

[yundar]

Thanks jjeffries. In response I didn’t disassemble the fuel distributor entirely. I took it off the air box and removed the metering piston which was sticky. I cleaned the piston and the barrel and reassembled them. There were no pits or corrosion and the assembly seemed to slide easily when I was done. I also removed the fuel pressure valve and cleaned it. The o ring is in good shape. In short no matter how I adjust the 3mm hex on the air flap lever I cannot shut off fuel from pumping through the fuel distributor. This is causing a massive flooding issue. I have a 74 911 that has been converted to carbs and I have always thought about reinstalling the CIS. I bought the 924 for cheap partially to try my hand at setting up the K Jet. Thanks again, Andy.

[jjeffries]

PROBABLY .... (caps for emphasis) .... that fuel head either needs more TLC (rebuild kit) or is spent due to internal corrosion. Again, you need someone more experienced than me to opine. I do know that piston is one of THE most precise bits in the car and easily ruined.

Do you know whether your injectors work?

The other question - once this leaking issue is resolved - will be your fuel system in general. Hopefully your tank’s innards are in good shape. My 87’s were not (see my thread), and I’m replacing all my fuel lines as a matter of principle, to protect all the F. I. components AND to mitigate fire risk ... a prime danger on all such cars. If yours is (as is typical) in bad shape, it’s possible that contamination is getting past the filtration and jamming the piston in the open position. Make sure you’re taking a broad view ... and thinking safety at each step.

Apologies if that sounds like I’m lecturing.

John

[yundar]

Fuel injectors are new and I have a Bosch pressurized bench tester and I tested them just to be sure. Tank was removed. I had it hot tanked and sealed at a local radiator shop just to be sure. I removed the non functional in tank fuel pump and replaced it with an early 944 sump screen. Fuel filter is new. I have not addressed the WUR or cold start valve yet as I can’t get past the fuel distributor flooding problem yet. I’m not completely inexperienced here just not understanding why the adjustment has no effect on the fuel distributor.

[jjeffries]

Glad to hear you have all the stuff (tank, injectors, etc) handled already. Hopefully you look up Tony on here and he can give you more specific guidance.

[kdjones2000]

If your piston is not moving freely you will get fuel all of the time.

Make sure it can essentially fall out of the disti by itself.

You also REALLY need a proper CIS fuel pressure gauge, set up to check WUR/disti differential pressure.

Go to 924Board.org :: Index and ask. Some of them are here, but they know all about this stuff and should be able to help you.

[yundar]

Thanks kdjones. I did disassemble the fuel distributor enough to remove the piston. I cleaned it as best I could without using abrasives. It does slide freely but maybe it is sticking at the top? I removed the nut holding the cylinder on but the cylinder did not come out. Is the cylinder supposed to slide out once the nut is removed? If not does anyone know the method of removal? I also looked at rebuild kits online and it just seems like they include the diaphragm and o-rings but not a new piston and cylinder. I guess at this point I need to disassemble the distributor further and see if the diaphragm is corroded or dirty. Without being able to remove the cylinder though I am not sure how far I’ll get. Does anyone know of a source for the piston and cylinder?

[kdjones2000]

Just saw this. I use a magnet to help pull the cylinder out. If you need to do that, it's sticking too much.

There are places who will rebuild the fuel disti for you, or if you are brave enough, just take is apart and clean everything up with carburetor cleaner and put it back together. If you are super clean, it should not leak. Dan (Ideola) has sources for this stuff on that site.

The "diaphragm" is actually a metal gasket. Some people recommend a shellac type sealer on it, but on the couple that I have done it wasn't needed.

The piston should fall out on its own. You can easily check for proper operation of the disti by bypassing your fuel pump relay and having it run all the time, then remove your air cleaner, pop the injectors out of your intake manifold and place them in cups, and manually move the air flow flapper with your hand and check for fuel delivery at the injectors. You can check for pattern and flow rate with this method without running your engine.

To diagnose this properly you really will need a proper CIS fuel pressure tester. You can make your own or buy the premium fuel pressure gauge at HF for this item.

You will eventually need to check / adjust your fuel distributor's control pressure, and check the pressure drop across the WUR and compare against factory specs.

The Haynes manual for the 924 actually has a really good writeup on CIS, if you can find one.

Good luck

[emoore924]

Did you drop the piston, even a little bit?

[yundar]

Hey All, I solved the problem and just thought I would post it here for future reference. Yes the fuel metering piston was sticking. I rebuilt the fuel distributor with a kit from Salvox. Not all of the o rings provided were correct but there was enough there to do the job. The main part is the stainless steel diaphragm that comes with the kit. I did use a sealant to reassemble the fuel distributor. When I reassembled the car I still had the flooding problem. The piston moved freely when the distributor was out of the car but it would stick inside the distributor when it was back on the engine. I disassembled it again an found some fine rusty grit in the top chamber. This I was able to trace back to the warm up regulator. I had to disassemble clean and rebuild the WUR. I did not use a kit for this as there is not much to them. One thing I did do was remove the tiny little screens from the WUR. There is a special tool made for this that looks all the world like a spot weld cutter. I think what was happening was the WUR was contaminating the control pressure side of the fuel distributor and causing the metering piston to stick. The lesson here is that if you are reviving a long dormant KJet system be sure and remove and clean all the components. I have been able to drive the car around the block a few times and now all the way to the gas station and back. Not bad for it being the first time it’s moved under its own power in 17 years! It even got a quizzical look and off hand complement while I put some fresh fuel in it. A few more steps to make it a decent driver! Thanks for the help, Andy

[jjeffries]

Andy, two great things here:
1. That you've solved the problem at hand,
2. You actually documented the fix. Many folks here ask for help then never close the loop.
Interesting how the upstream component was polluting the next one downstream, so to speak. Great job and please keep telling us what else you're working on.
Best regards, John