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.