Back to the drawing board. 911SC won't start after rebuild
 

Aloha, My car will spin and backfire every once in a while. Number 1 cylinder checked at TDC using the stick in the spark plug hole with crank at Z1 and rotor pointing at the notch in the rotor. New battery, New rotor and cap. New hi torque starter. New plugs gapped to .7 mm. New engine harness from Dennis (Timmy2).


Here are some number I got:
1. Year of engine: 1981
2. US or RoW (Rest of World): US
3. WUR model number: 090
4. Ambient temperature at time of test (in degrees C): 26
5. WUR Resistance (in Ohms): 27.4
6. System Pressure (in bars): 4.5
7. Cold Control Pressure (in bars):1.95
8. Warm Control Pressure (in bars): Didn’t do yet
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds): Didn’t do yet
10. Residual Pressure @ 5 min (in bars): 2.2
11. Residual Pressure @ 15 min (in bars): 1.9
12. Residual Pressure @ 30 min (in bars): 1.7
13. Residual Pressure @ 60 min (in bars): 1.5

Coil resistance:
0.7 pole to pole
625 “A” to center

My next step is to take all the connections apart in the engine bay and clean all the contacts and assemble with dielectric grease.
Any other ideas?
Thanks.

Pull intake valve cover on 1 to 3. Z1 on the pulley. Check for loose rocker #1 intake so you know you're on TDC. Check rotor to see the rotor approaching the mark on the edge of the distributor.
The numbers on the WUR look decent for pressure. Maybe Tony will pipe in on injection numbers.

If you believe the injection is the problem then you're happy with spark and compression.

Bruce

have you checked for spark and fuel? My 73.5 rebuild was not getting fuel due to the CIS adjustment screw being off. Moving the air sensor plate a bit with your hand should start the fuel injectors squirting fuel. The problem with my no-start was the adjustment being so far out of whack the injectors were not being activated.

Bruce, ok, check loose rocker arm on #1 tomorrow.
rockreid, pulled #1 injector today and fuel squirted out of it. I'm going to do the fuel volume vs. time test tomorrow on all injectors.
Does my 3.0L have this adjustment and if so where? I'll do a search on here.

Thank you both.

Once you have determined your spark is right
With the key on and the fuel pump ready to run
Lift the airflow sensor and charge the fuel system for 4 or 5 seconds. Youll feel the system pressure with your lifting.
Now you have spark, fuel in cylinders, and should have compression,you should start and run for a couple seconds. If you lift the air flow sensor slightly with someone turning the key you might be able to sustain the engine running

Bruce

Bruce, what do you mean the spark is "right"? I have shorted #1 plug and got a spark but I am not convinced it is very good. It looked weak. It was during the daytime, so it might be subjective, but it looked very feeble. Is this caused from a weak coil?

Thanks, Mike

Plug wires going around the cap the correct way?

Counterclockwise looking down? Checked all the wires on cap for firing order and wires to correct cylinder.

Sounds like you are 180 off on the distributor. The stick method just tells you the piston is at the top, but not that it's on the compression cycle. You can confirm it with a compression tester or as Flat6pac suggested by removing the valve cover.

Aloha,
I'll do that. I had #1 at TDC with the crank at Z1 and the rotor pointing at the notch at about 12:30 on the dizzy. I'll check it the other way tomorrow. Might as well check the valves while the cover is off.

Rock, I found a diagram with the adjustment screw. 3 mm allen.

Thanks all so much for the help, Mike

Hey guys and girls, here's an update. I checked #1 at TDC by checking the rocker arm loose. I found this gasket on the mixture control unit, do I need to change this? Could this be a source of air?

http://forums.pelicanparts.com/uploa...1433208670.jpg

I also found this melted connector in the trunk. Does this go to an after market alarm or is the dome in the trunk standard? It says Behr on it.

http://forums.pelicanparts.com/uploa...1433208792.jpg

Still dumbfounded... :confused:

New coil will be here tomorrow. hmmm

The notch on the dizzy should at about 4 o'clock when standing behind the engine.

jbell, I don't understand what you mean. Can you elaborate please. Do you mean standing on the driver side looking down at it? :confused:

Can you post a picture looking down at your distributor without the cap on? Standing behind the car I thought the mark on the distributor for #1 TDC should be at about 4 o'clock but I could be mistaken. I don't have a 3.0 CCW dizzy here to check.

Here is a picture I found of a CCW SC distributor. The #1 TDC mark on the distributor is near 4 o'clock standing behind the car. It points toward the front lip of the fan shroud.

http://forums.pelicanparts.com/uploa...1433219027.jpg

Melted connector is for front AC fan.
Can't make out the gasket in the other photo.

jbell, yes, I see what you mean. That is what I have with the crank at Z1 and no. 1 at TDC.
Dennis, thank you. I will disconnect that and tape up each end as I took the AC compressor off for now.

I have an appointment to take my car in to a Porsche mechanic Monday. Bummed, I wanted to do this all on my own with y'all's help. :(

But if you turn the crank 360 degrees you will again be on Z1 and no. 1 on TDC but the rotor will point to the no. 4 connector on the rotor. At this point you should have no play at your no. 1 rocker because the valve will be partial open.
If you do have play on the rocker in this position the ignition setting is 180 degrees off. I a full ignition cycle the crankshaft turns twice (720 degrees) and the camsshafts once (360 degrees). That's why confirming the Z1 and the no. 1 TDC position is not enough to determine the right ignition timing.

Heinz, yes the rotor is pointing at the notch at no. 1 plug wire as in jbells pic. Thanks.

Yes, but that is only half of the check. You also need to check if the valves on the no. 1 cylinder are closed. You can only confirm this by taking of the left cover and check if the rocker has some play. If not then the ignition is 180 degrees of.

I agree, that is what I did last night. No. 1 rocker was loose. Cheers.

In the picture of the distributor your rotor @TDC Z1 needs to be approaching the line of the distributor, not past it.
I suggest that you're dist is one cog off. Pull distributor and rotate clockwise 1 cog on the bottom of the distributor.
Bruce

Double check your valve clearance.......
 

Speed,

Heinz has a very good suggestion and unless you have confirmed this condition, there is a likely hood your are 180 deg. off. I have read your initial post even before Bruce A. responded and kept following your saga. If you could check and confirm Heinz's suggestion and use an inductive timing light to test all six (6) ignition wires would give you a better picture of the situation.

I am about to do another SC start up very soon and the first thing I perform is to verify that I have a good source of ignition sparks for all injectors at the correct ignition timing followed by fuel pressures check and others. If I could not make the engine start on the first turn of the starter, I would be disappointed on my work. Let's say on the second try. Nine out of ten engine start ups, I was successful running the CIS engines on the first turn of the ignition switch.

Except for the low system fuel pressure @ 4.5 bar, the data you collected should be good for start up. One thing missing is your valve clearance/s @ Z1 compression (ignition rotor) pointing to the scribed mark on the dizzy.

Don't give up yet. I am taking a rest period after an eye yesterday morning and not allowed to go to the garage until Thursday and no lifting of weight more than 25 lbs. for a week. Let's tackle this together and get your motor running again.

If you could confirm Heinz's suggestion, presence of strong ignition signals for all six (6) ignition wires, fuel delivery during cranking, and it won't start, there is another last thing you need to test (will hold for the meantime). Keep us posted.

Tony

Thank you all. I will do the timing light test tonight. I'm at work so won't be for about 5 hours (unless I can bug out a little early). I'll post the results.
Thanks again. I wouldn't have even tried the trans rebuild without this board and now am close to an engine rebuild. Inconshevable....(Vizzini) :D

Ok, update. I put the new blaster coil on. BUT, when I checked for voltage across 31d and 7 on the CDI terminals I got no voltage. 12+ on terminal 15. Does this mean the CDI is shot??
5 ohms across rotor.

There is supposed to be a high wining sound from the cd.
Unplug the 12 volt feed to see if the wine is detectable.
Put stock coil back in if its a 001
Bruce

I get the whine with both. The old coil is 0221121001, is this the one you want me to put back on? Thank you for your time.

Edit: Stock coil back on

That's the coil,, back stock til you get it running
Bruce

K thanks. What's next?

I have back fire when it cranks. Is it possible, as some have said, my dizzy is a tooth off? I can get it to point right at the notch with the play in the hold down groove. The
Rotor has a lot of plat in it. I would call it 5 degrees. Is this too much?

I have to have something hooked up wrong. As Tony said he cranks 'em right up. This is taking too long. What could I have done that would cause this no start condition?
What about the no voltage situation between 7 and 31d in Bentley?

I hope you haven't broken your airbox with all this backfiring :(

Me too!

Feedback.........
 

Speed,

You are doing things left and right. You have no definite course of action and your feed back is not too good. If you think you are frustrated, imagine the people wanting to help you. The reason I was not getting involve earlier was your failure to communicate (timely feed back). You are here simply because you needed help and plenty of help is available.

Let's slow down and get to the basic questions:
1). Are you getting strong ignition signals using an inductive timing light? Are all the six ignition wires getting strong signal?
2). Do you have consistent and strong cranking of the starter?
3). Are you sure you have the correct valve clearances for all six cylinders?
4). Are you getting spray mist from all 7 injectors? Yes, seven!
5). Did you pressure test the air box before installation?

Let us know your answers to these five (5) questions and I will give you more to answer. I have not encountered a CIS engine I could not make to run. I would even offer to pay you if I could not make it run! That's how easy to get a Porsche CIS engine to run. Stop guessing and you will be successful. BTW, did you tinker the fuel mixture screw setting? Keep us posted.

Tony

Tony,
1, no I have not done that yet.
2, yes
3, yes, .004 on all valves
4, no getting baby bottles tonight, test tomorrow
5, no sir
BTW, yes. Idle fuel mixture screw turned it counter clockwise yesterday.
Got it. I'll not post again till I do those things.
Thank you.

CIS troubleshooting assitance.......
 

speed,

Since you are doing all the work in locating and identifying possible culprit/s, we (the readers) have no idea what's going on. Unless you reply to a specific question that was asked, it would be difficult for us to know what have you done so far. You asked a question we give you a reply and vise versa.

Why did you adjust the mixture setting? That's the last thing you touch or tinker when doing a fuel injection troubleshooting. The mixture calibration is for fine tuning to minimize CO pollutant in the exhaust. Your main goal is to get the engine to start and idle during a start up. Ignore your mixture at this point if you could not even make the engine to start. Once you are able to consistently get the engine to start and run, go to the next level and tune it up. You can not tune a non-running engine!

Could you pull out all the spark plugs and take pictures of the electrode? Like to see the color of the electrodes at this stage. Keep us posted.

Tony

I adjusted the mixture setting because rockreid said his no start condition was because of the adjustment being far out of adjustment. Pics of plugs tomorrow. Thank you.

I hope I am not coming across as unappreciative. I am very appreciative of all the help I am getting. I am following directions from the posters and am not doing things on my own. Maybe my posts are answering questions from others and it seems disjointed and for that I apologise. Thank you all for the help.

You turned the 3 mm Allen CCW you leaned the system.
Force start the engine turn the key to on. Lift the airflow sensor charging the fuel into cylinders
Turn key to start. You have fuel and compression, if your spark is correct it will fire.
Bruce

double check firing order , don't ask why ;)

I have done that. I'm to the point of taking all the wires off and rerunning them. They are numbered. I'll do that first and then check fire on each wire as Tony has told me to with the stock coil.