82 308 GTSi - Fuel pump runs when key turned to position 2

Using the search function on FerrariChat and the Mondial 8 WSM I have been troubleshooting the cause of the fuel pump running when ignition is turned to position 2 but car is not running or being started.

I believe I have confirmed that the airflow sensor safety switch is not working. Steps I have taken:

1. Remove fuel pump fuse and verify that fuel pump does not run. Fuel pump did not run but does run with fuse in place.

2. Visually verify that airflow sensor plate is closed when engine not running by removing the air box. It is closed.

3. Unplug cable to airflow sensor safety switch and verify that fuel pump still runs in ignition position 2. It still runs.

4. Jumper cable to simulate a closed airflow sensor switch. Fuel pump no longer runs when ignition turned to position 2. Pulled out jumper and fuel pump starts running.

Conclusion, I believe the safety switch is not going to a closed state when airflow sensor plate is in full closed position.

Some questions for the group:

1. Do you agree with my conclusion?

2. What are possible causes for this failure?
a. mechanical geometry changed
b. dirty contacts inside assembly
c. other

3. What are possible fixes?
a. replace just the switch?
b. clean contacts with carb cleaner/other without disassembling unit
c. clean contacts with disassembly required
c. send unit for rebuild
d. other

Since the airflow sensor plate is fully closed and the engine runs fine throughout all revs/conditions it would seem that the only thing wrong is the safety switch mechanism. If this is the case, fuel will not go to engine until airflow sensor moves out of closed position even though pump is running when ignition turned to position 2. If I am correct about this, I have a couple more questions:

4. Would pressure just keep building until something gives or is there a flow back to the tank?

5. What would be the safety risk of operating in this state?

Disclaimer: I am brand new to Ferrari and the 308, but I have a fair amount of background working on Porsche and BMW cars from the 80s. I'm a self trained "mechanic" and do this stuff as a hobby. I apologize if I am missing some steps and I did look for answers to these questions first but haven't been able to find them after a reasonable amount of time.

Thank you for any assistance.

 

Thank you for the replies.

I read that about the QV but I couldn't find a similar statement regarding the 2v KJet cars.

 

The connector sits next to the fuel distributer toward the back right corner of the car just to the left of the air box/airflow sensor plate. I believe it connects to some type of contact points that measure the height of the airflow sensor arm. It is hard to tell from the diagram exactly how it works.
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That is my understanding.

 

I have now confirmed via the book, Bosch Fuel Injection & Engine Management: How to Understand, Service, and Modify by Probst that the fuel distributer in all K-Basic and K-Lambda systems includes a pressure regulator that sends fuel back to the tank when maximum pressure fuel pressure is reached.

I could not find any description of the actual mechanism of the safety switch or photos of the inside of the downdraft AFM assembly used in the 1982 Ferrari 308 GTSi application.

So the big questions for me at this point are:

Can I attempt to clean it in place with some carb cleaner without causing any other damage?

Should I just leave it as is until the need to have the AFM rebuilt due to operational issues?

Should I have the AFM rebuilt and recalibrated and fix the safety now even though the AFM is otherwise functioning correctly?

 

Thank you Steve. I had looked at the diagram in the WSM you mentioned but I wasn't "seeing" how it worked. The photograph you just posted filled in the gap for me. I am going to try some air intake cleaner and see if I can get a clean contact area.

 

I resolved the problem with air intake cleaner spray and a 3mm allen wrench wrapped with white cloth. Holding the plate down I pointed the red tube on the spray into the area where the contact should be made to close the circuit. I then used the cloth on the allen wrench to gently rub around on the surfaces. It came out with lots of black "dirt" on the cloth. I did this until I was no longer getting any "dirt" on the cloth. The switch is now working, keeping the fuel pump off when in ignition position 2.

 

Glad to hear. I think it works that way for ease of troubleshooting fuel injection problems. Since for many checks you need the fuel pump working to pressurize the system but without the engine running. By disconnecting the connector at this safety switch a technician has a very easy way of getting the pump to run without turning over or running the motor.

 

Sorry Steve, I missed this question. Yes the plate mechanism appears to be correctly adjusted.