1980SC Starting Problem

[ajenks144]

Hey Everyone,

I am stuck and looking for help with my 1980 Euro SC. I took the engine out to reseal and replace a few things (oil pressure sensor, temp sensor, etc). I also rebuilt the CIS system with new fuel lines, vacuum hoses and injectors.

Now, with the engine back in, it won't start. It cranks well, fires and then dies right away. I "believe" the problem is in the air flow switch circuit.

Here is what I have checked:

1) I replaced the fuel pump relay because it is easy, but no change.

2) Early in my diagnosis, the fuel pump was running when the key was turned on, which it shouldn't. This didn't happen later, so it might have been a fuel priming thing.

3) Based on some great information I found from Tony (@boy911sc) I started testing the air flow switch circuit. I first put a test light on Pin 85 of the fuel pump relay socket and the battery to confirm ground, which I have. With the test light still on, I lifted the air flow plate and the test light did NOT go off. This is a problem I believe. The circuit should have been broken when the plate was lifted.

4) Next I started checking continuity. First I checked continuity from pin 85 to the connector in the engine bay on the left side (see picture). I confirmed continuity there. Next, I checked continuity from the engine harness side of that plug to the plug at the air flow switch. This is where things get interesting. I have continuity to BOTH pins on the air flow switch plug. I then checked both pins agains ground for continuity, and as expected, they both have continuity to ground. This would explain the no start because the circuit remains closed.

So that is where I am now. If I understand the circuit correctly, there should only be continuity between the plug on the left side of the engine bay to the LEFT pin of the air flow switch plug, not both pins. Am I correct?

If so, does that mean the wires are crossed somewhere in the harness? What am I missing? Could this be a ground issue somewhere else?

Thanks in advance everyone!!
Andy

[ajenks144]

Update:

I used a jumper wire on the connector on the left side of the engine bay to keep power to the CDI and take the wires to the air flow switch out of the equation. Car started right up. I "think" further evidence pointing to an issue in the harness.

[Walt Fricke]

The "air flow switch" (a safety feature, to be sure the fuel pump won't run if the engine stalls) can't be the source of start or run problems. If it is disconnected, the pump will run when you turn the key to run, as well as to start. And it will keep running after it starts.

An easy mistake to make is to plug the cold start valve plug into this switch, and vice versa. Offhand, I can't think of the symptoms of doing that, but guys have had that problem.