Did I swap the FV & Air Flow Connections?

phocussed · 03-02-2011, 06:10 AM

After several weeks of rebuilding my 1980 3.0 engine I installed it and have not been able to get it to idle. This is my first 911 rebuild after doing several 356's, so I'm not a complete newbie.

Spark - confirmed
Timing - confirmed
Vacuum Leaks - none
Fire order - confirmed
TDC & Distributor Position Checked - confirmed
Ground Connections - confirmed
Relay Checks - Substituted and confirmed good for both Ignition and Fuel Pump.

What is not working is the fuel pump when I switch on the ignition.

With the ignition OFF and the fuel pump jumped to battery the injectors are spraying when I lift up the plate. When the ignition is on and I jump the fuel pump, it turns over the starter.... is this normal?

When I do turn over the car the engine fires on release of the key to the stop position for a moment.

In reading other posts regarding CIS issues, I came across a post from psalt in 2006. He asked a pointed question "If the engine was out, could you have swapped the FV and the Air Flow contact wire plugs?

Before I perform a partial engine drop to check this, would switching these two plugs cause the fuel pump to sit idle and keep the engine from firing?

Thanks in advance!

Flat6pac · 03-02-2011, 05:10 PM

What is not working is the fuel pump when I switch on the ignition.
fuel pump isnt suposed to run until the air flow sensor is lifted with the starter turning.

With the ignition OFF and the fuel pump jumped to battery the injectors are spraying when I lift up the plate. When the ignition is on and I jump the fuel pump, it turns over the starter.... is this normal?
You have the pump directly wired to the battery, there is no need for the key at this point.
I dont understand the starter turning. The starter has a yellow with blue stripe wire that activates off the relay for the cold start

When I do turn over the car the engine fires on release of the key to the stop position for a moment.
Sounds like a bad ignition switch

In reading other posts regarding CIS issues, I came across a post from psalt in 2006. He asked a pointed question "If the engine was out, could you have swapped the FV and the Air Flow contact wire plugs?

Before I perform a partial engine drop to check this, would switching these two plugs cause the fuel pump to sit idle and keep the engine from firing?

The 2 that get switched is usually the coldstart and the airflow sensor. Most other wires wont reach.

Bruce

Dan J · 03-02-2011, 05:50 PM

Are you sure that you plugged in the harness for the o2 sensor system? this is the 6 pin Koestal plug on the left side of the crossmember in front of the motor. I have seen many people leave this unplugged
with the symptons you describe

phocussed · 03-02-2011, 07:52 PM

Yes, the O2 harness is connected and thank you for the clarification of when the fuel pump should run.

To clarify the problem, I'm getting combustion but no idle and the engine only revs and runs for 2 seconds after I move key from start to run.

I have gas, spark and timing is correct.

Help!

psalt · 03-05-2011, 05:57 AM

phocussed,

I would first try to figure out if your wiring is correct. The fuel pump should not run with the Key in the "ON" position until you lift the air flow sensor . Try not to flood the engine. Next make sure the CDI ignition is getting power in the "ON" position, can you hear it whine ? It is not uncommon for a CIS lambda car to fire and stall before maintaining a cold idle. It is usually a lean condition which can be caused by several things. If it fires and stalls, the CSV is probably working, and the problem might be the cold control pressure, the mixture setting, the FV, ignition timing or a vacuum leak, which all need to be check separately. My advice would be to look for an obvious vacuum leak, disconnected hose, etc, then disconnect and plug both hoses from the distributor, listen for the CDI whine and try another start. The vacuum retard will often cause a cold engine to stall. How did you set the ignition timing ?Once you get the engine running, connect an analog dwell meter to the test connector under the plastic cover on the left side of the engine compartment. It will tell you if the lambda system is working properly and allow you to set the mixture.

phocussed · 03-05-2011, 01:40 PM

Thank you all for your help and advice.... as much as I hate to admit the fault, I will swallow my pride and admit my error. I had all 3 of the 2 prong plugs in the wrong place. Ok, quit laughing! It could have been the beer in celebration finishing the engine.

Anyway... got the car started... did my 20 minute run-in and changed the oil.

Thanks!