CIS Experts! HELP!

[JagerPorsche]

Hello,

I dont post often but I have been having trouble lately with my 78 924's CIS unit. I tried to adjust the mixture myself, following the shop manual. Anyway, I did more harm than good really, but now I have an even larger problem.

The blue plug which connects to the CIS unit is giving me trouble. When it is plugged in, the fuel pump turns off. However, when it is not plugged in, the pump runs. Whether it is plugged in or not, I cannot get any fuel to spray out of the injectors when I lift the sensor plate. I cannot even get it to drip. I do have plenty of fuel pressure at the injector lines.

Any ideas would be greatly appreciated!

Thank you,
Ryan

[bholmes]

hmm, i don't know much about the old 924's....maybe check out 924.org or 924board.org or something like that. It's more 924 specific and maybe more people on there know about the CIS systems.

[924RACR]

Sounds like someone has miswired your car to get around that safety feature. You'd have to trace/check the wiring and relay, see what was changed. But I wouldn't lose sleep over it right now.

As for the no-fuel situation - sounds like maybe you leaned it out way too much? I'm guessing it won't start any more?

[JagerPorsche]

hey guys, thanks for the input. Im on 924.org already. I have tried to turn the mixture more rich (clockwise) but it doesnt seem to help. I will try again though.

Thanks,
Ryan

[JagerPorsche]

Had some time to mess with it today. The electrics are wokring just fine it according to the manual, I just didnt realize how it works exactly. (The pump runs when I lift the sensor plate)

Anyway, I noticed another thing- Fuel is getting into the injector lines, I loosened the banjo fittings at the injectors and fuel can out. With that said, could air in the lines cause the injectors to not fire or something?

Is there a special way to bleed the air out of the system?

Thanks,
Ryan

[rb101]

if fuel is getting into the lines going to each injector, then the injectors are clogged. Pull the injector straight out of the intake. Place in cup and lift the sensor plate, fuel should shoot out. If not clean or replace the injectors.

[JagerPorsche]

The injectors have been out while I have been working on this. They are not spraying. Im thinking maybe a fuel pressure issue

Thanks,
Ryan

[JagerPorsche]

Still having problems.

Could I have a faulty WUR? I just bought a brand new one, and after I installed it I had this issue a day or so afterwards.

Thanks,
Ryan

[RC924]

Originally Posted by JagerPorsche

Still having problems.

Could I have a faulty WUR? I just bought a brand new one, and after I installed it I had this issue a day or so afterwards.

Thanks,
Ryan

No. Neither low or high control pressure would cause lack of fuel at the injectors, if system pressure was OK.

You do not have to bleed the injectors, and it is highly unlikely that all 4 are blocked or faulty.

Check the main system pressure is around 70PSI. Sounds like it is very low, below the 30PSI or so that is needed to open the injectors. First check the O ring on the main pressure piston. Then pump pressure and possibly a fully obstructed filter.

The blue connector on the AFM breaks the circuit to ground, as does lifting the plate which triggers the relay.

Roger

[mgatlag]

I had some similar issues a while back with my NA also. Do as Roger said and check the pressure. If you've messed with the A/F mixture, it's easy to screw it it up if you're not sure how sensitive it is. IIRC the range of the screw is about 180 degrees. Once you do get it to fire, moving the adjusting screw very slowly is what you want to do because it is so sensitive. When I was messing with mine, 924RACR had me set mine at just la little past the halfway mark from lean to rich, seems great now. You may want to check over at the 924board for some more help though, great source of info from everyone there. Good luck!

[JagerPorsche]

thanks for the input guys. I havent been able to get on 924board lately. I think it is down or something. I will see about checking the pressure. I think you are right because there is pressure in the lines, but probably not enough

Thanks
Ryan

[JagerPorsche]

Originally Posted by RC924

Check the main system pressure is around 70PSI. Sounds like it is very low, below the 30PSI or so that is needed to open the injectors. First check the O ring on the main pressure piston. Then pump pressure and possibly a fully obstructed filter.



Roger

Roger, where exactly is the O ring you are talking about? Is it in the CIS unit or elsewhere? Sorry for all the questions, I have never had fuel delivery problems before

Thanks,
Ryan

[RC924]

The main system pressure valve is on the lower half of the fuel metering unit. IIRC there is a 17mm cap nut. Undoing this reveals 2 shims, a spring and the piston which may need to be removed with a chopstick, pencil or whatever. The O ring is on the end, and if faulty will allow the fuel to return to the tank without building much pressure.

Hopefully that may be the problem since its much cheaper than a pump and easier to check.

[JagerPorsche]

Thanks for the help. I think I am aware of what you are talking about now. Do you know of a good place to source this part? My favorite online parts store doesnt carry them.

Ryan

[RC924]

Only a $ or 2 at the dealer but they will likely have to get one in.
Special T auto have them.
Alternatively go to an industrial or hydraulic seal supplier, take the piston and old O ring, tell them its for fuel and its metric and let them measure it. Probably cost about 25c.

[JagerPorsche]

Hey thanks for the help guys! I just ordered two of them from my local porsche dealer. They were $3.50 each or something.. not really too bad. The part # is
911 110 936 00 if anyone happens to need it.

Ryan

[Rasta Monsta]

Don't forget the copper sealing ring and secondary o-ring.

[prebordao]

I have a WUR with bosch part number 0438 140 011, which I believe was used in older 924's.
Can anyone advise on the correct cold / warm control pressures for cars with this part (or for early 924's for the matter) ??