CIS Starting Point After Fixing Leaky System

[theFONZ]

I just got the engine/tranny back in after a tranny rebuild and an engine reseal/CIS refresh. I found a huge crack in the old airbox, and other possible leaks. The CIS ran OK before this, due to it being adjusted to get it to run with leaks. Well now that it has a new airbox, seals, o-rings, gaskets, and basically every replaceable part replaced, I can't get it to start.

Since the idle/mixture screws were set to run with a very leaky system, where do I start them at now that the system is sealed?

[tirwin]

edit: sorry. first pass I missed the you can't get it to start part. have you verified spark and fuel delivery?

what year? do you have an O2 sensor?

1. verify fuel pressures in spec (I'm assuming that was part of the refresh)

2. set timing

3. adjust basic mixture and idle

4. verify settings with exhaust gas analyzer and tweak as necessary

[stlrj]

Assuming it is running very rich now, the engine might be flooding. Try disconnecting the thermo-time switch next time you try starting. This will prevent the cold start valve from spraying extra fuel when you crank the engine and prevent/clear the flood mode.

If that gets it started, you then know it's running too rich. The next step would be to back off the CIS mixture screw to lean it out before reconnecting the TT switch.

By the way, did the new air box come with the cold start diffuser plumbing inside?


Cheers,

Joe
82 Targa

[theFONZ]

Car is a 78 SC.

The new airbox is a Webb stainless one, so it doesn't have a diffuser inside.

I have not checked the fuel pressures, but I will tonight. I was hoping to get it idling and go from there.

It sputters and backfires, but never gets itself going for more than a second or two.

[stlrj]

Was anything done to the ignition cables during the reseal?

[theFONZ]

Basically the motor was stripped of everything bolted to it. I'm going through now rechecking wiring and cables.

[ossiblue]

Originally Posted by theFONZ

Car is a 78 SC.

The new airbox is a Webb stainless one, so it doesn't have a diffuser inside.

I have not checked the fuel pressures, but I will tonight. I was hoping to get it idling and go from there.

It sputters and backfires, but never gets itself going for more than a second or two.

Did you pressurize the fuel system after everything was put back together?

[timmy2]

From my Porsche Manual Volume 3 Fuel injection Page 2.2-2/7
Injectors pulled and in jars.
1. Bleed fuel lines by lifting sensor plate many times. Ignition on
2. Use 3mm hex wrench to turn mixture screw 1-2 turns counterclockwise (should stop all flow)
3. Make pump run continuously by pulling air flow safety switch off. Ignition on.
4. Turn screw clockwise until the injectors just barely eject. From this point turn the mixture screw back 1/2 turn counterclockwise.
5. Run engine to operating temperature and adjust idle and CO to spec.

Personally I would jumper the fuel pump relay socket instead of pulling the air flow safety switch.

I think I will post this in the CIS for dummies thread too.

Here is a picture the text from the manual.

[boyt911sc]

Originally Posted by timmy2

From my Porsche Manual Volume 3 Fuel injection Page 2.2-2/7
Injectors pulled and in jars.
1. Bleed fuel lines by lifting sensor plate many times. Ignition on
2. Use 4mm hex wrench to turn mixture screw 1-2 turns counterclockwise (should stop all flow)
3. Make pump run continuously by pulling air flow safety switch off. Ignition on.
4. Turn screw clockwise until the injectors just barely eject. From this point turn the mixture screw back 1/2 turn counterclockwise.
5. Run engine to operating temperature and adjust idle and CO to spec.

Personally I would jumper the fuel pump relay socket instead of pulling the air flow safety switch.

I think I will post this in the CIS for dummies thread too.

Here is a picture the text from the manual.

Dennis,

I don't think the mixture screw for the metering units for 911 CIS use 4-mm allen wrench. But this information should indeed be added to Tim Irwin's CIS dummies thread. An excellent example of technical data for CIS troubleshooters.

Tony

[stlrj]

Originally Posted by boyt911sc

Dennis,

I don't think the mixture screw for the metering units for 911 CIS use 4-mm allen wrench.
Tony

3mm allen works for me.

[timmy2]

Typo. Sorry...all fixed now. And on the CIS for dummies thread.

[theFONZ]

Thanks Timmy, thats exactly what I was looking for. Turned out I fiddled with the screws enough that I got it running, barely.

It runs but sounds pretty crappy, it backfires and idles rough. I checked timing and it was dead on. My pressure tester showed 59psi/4bar with the WUR plugged in and the engine off. I have an LM-2 on the way, but what else should I check in the meantime?

Does anyone know a starting point for the idle screw?

[snbush67]

Check and recheck the plug wires and firing order, then check to make sure the coil wire is connected properly.

When you say the timing is dead on is it set at 7 degrees advance at 950 rpms?

Check each plug wire for spark. Just use your timing lite lead on each wire to check.

You can turn the idle in a bit, or out a bit to see if the engine reacts, it is probably set too rich if you were having leaks before.

Check for leaks around the boots.

You can grab the whole CIS assembly and try to wiggle it when the car is running, sometimes you can discover leaks this way.

[theFONZ]

Well I found my possible problem, my plug wire were ordered clockwise around the distributor. I guess I had it in my head that the fan/crank goes clockwise so I applied that to the plug wires. What a dummy!

Sadly, I found this after I broke the fuel connector going into the fuel distributor while connecting the pressure gauge. I was able to remove it and still connect the gauge, but I'd given up on starting it for the night and rolled it back into the garage. Now the only way I can run it is with the gauge connected, but it's too late to roll it out and start it. I'll try to run it tomorrow.

For the connector, the only thing I can find in PET, although, it looks slightly different, is NLA everywhere. Is there another source, like maybe a non-porsche part? The number I have is 911 110 160 01 Screw Socket.

[theFONZ]

Oops, forgot pics. One of the (gold/brass) pressure gauge adaptors is connected in the pic.

And HEY it's post 911!!!

[snbush67]

Originally Posted by theFONZ

Well I found my possible problem, my plug wire were ordered clockwise around the distributor. I guess I had it in my head that the fan/crank goes clockwise so I applied that to the plug wires. What a dummy!

I've been there, glad you found your issues!

[porwolf]

Originally Posted by theFONZ

Well I found my possible problem, my plug wire were ordered clockwise around the distributor. I guess I had it in my head that the fan/crank goes clockwise so I applied that to the plug wires. What a dummy!

Sadly, I found this after I broke the fuel connector going into the fuel distributor while connecting the pressure gauge. I was able to remove it and still connect the gauge, but I'd given up on starting it for the night and rolled it back into the garage. Now the only way I can run it is with the gauge connected, but it's too late to roll it out and start it. I'll try to run it tomorrow.

For the connector, the only thing I can find in PET, although, it looks slightly different, is NLA everywhere. Is there another source, like maybe a non-porsche part? The number I have is 911 110 160 01 Screw Socket.

As I posted in your parts WTD thread try to get in touch with "BoxterGT". He seems to know all about fuel line fittings, makes fuel line assemblies and possibly source the part you are looking for. And if you know the thread sizes and the fitting cone inside the fuel line receiving end a machine shop should be able to reproduce the part rather easily. And it is worth checking with Porsche direct to see whether they can get it.

[boyt911sc]

Are these you need? BTW, your WCP (warm control pressure) at 59 psi. is out of spec. too high.

Tony

[theFONZ]

Thanks for the leads on the fitting!

Tony, after looking at it more last night, I think I may have been doing it wrong. I'll recheck tonight.

[theFONZ]

It's aliiiiive!

The plug wires were the culprit. I got it running fairly smooth, but I'll do a good adjustment with the LM2.

It's a pretty good feeling to do that much work and have it going, even if there was a hiccup. If I didn't break that fitting I could be driving it around right now, oh well, more time to fine tune and check things over.