Fuel pump problem

[nibbes123]

Has anybody run into this problem? The car is a 1981 Spider with FI, the pump runs all the time when the key is turned to start position and engine not running.

Thanks
Nick

[76was124]

With the ignition on, the pump shouldn't run unless there is airflow through the AFM (during cranking and subsequently engine running) Either previous owner changed the wiring, or the AFM flap is sticking partly open

[RRoller123]

Very common that these cars were rewired so that the pump runs when the ignition is on, due to failure of the dual relay. They can be made safe by adding an inertial switch to shut off the pump in the event of an accident. Ford has an inertial switch that is suitable for the application, and I think there are a few threads on this general topic that can be found with the search engine.

[wizard124]

With the ignition on, the pump shouldn't run unless there is airflow through the AFM (during cranking and subsequently engine running) Either previous owner changed the wiring, or the AFM flap is sticking partly open

This statement is incorrect
In the start position, the fuel pump is hot through the ignition switch. When the key is released to the run position, the contact in the AFM ( air being drawn thru the flap by a running engine) energizes the double relay sending current to the fuel pump.

So, there is no problem

[76was124]

This statement is incorrect
In the start position,

Good catch Wizard, I was thinking he meant the 'run' position, not the true "start" position which requires holding the key in that spring loaded position to start the cranking.

[nibbes123]

Thanks everyone for the help , will check the AFM.

[RRoller123]

You can see in this pic from under the top cover of the AFM, that the arm in mine has been bent to the left so that it will NOT make contact with the brass piece, and thus the fuel pump is taken out of the equation. My FP was then hard wired, bypassing the dual relay, which is fine with me now that I have installed the inertial switch.



inertial switch (wired inline with power feed to FP):

[nibbes123]

Thanks RRoller123.

[ClarkTheShark]

You could also just fix the afm or find a used one.

[spider2081]

Rroller123
I may be miss reading your post.

You can see in this pic from under the top cover of the AFM, that the arm in mine has been bent to the left so that it will NOT make contact with the brass piece, and thus the fuel pump is taken out of the equation. My FP was then hard wired, bypassing the dual relay, which is fine with me now that I have installed the inertial switch.


With the arm bent away as you show. The contact in the AFM are always closed. This supplies voltage to energize the dual relay which in turn supplies power to the fuel pump. I think if you remove your dual relay your fuel pump will not run.
Were you saying in addition to the bent arm your dual relay was rewired so it is energized in the "run" position of ignition switch.
I am not trying to be picky just trying to better understand the circuit.

[RRoller123]

I think you are probably right and I have incorrectly described the circuit. I didn't do any of this mod on my car, just added the inertial switch. I guess it is more accurate to say that when the AFM flap moves, the arm opens the connection, somehow energizing the relay to power the pump. Bending the arm to the left keeps this from ever happening. My assumption is that the pump circuit needs to be rewired in someway for this to work, but maybe that is not true? I am happy to be educated on this, as it always appeared an overly complex design to me.

[courtenay]

Several years ago, I looked at a Spider that the owner had rewired the fuel pump such that it was controlled by a switch hidden under the dash. It was not connected through the ignition at all. Get in the car, activate the fuel pump with the switch, then hit the ignition. I think I would have wanted to add the inertia sensor into the equation, but the set up would have acted as a fairly effective anti theft device.

[RRoller123]

Man that is pretty extreme! It could be just wired directly to the hot "on" side of the ignition switch, which is I think what they did to mine. I haven't traced it out, and have no desire to do so, since it all works well.

[azruss]

when i rebuilt mine, the PO had wired past the dual relay. I dont know why since the dual relay worked fine and the line fuse was still good. I took it back to stock, change the pump ground to a chassis ground 3" away. The main issue with custom wiring is for the future owners of the car. In my case, its my grandson/granddaughter. I prefer to leave them with a system that is well documented and can be easily diagnosed even if i'm not around. I did the same thing when i relayed the entire electrical system. Designed it so all the wires out of the ignition switch performed their original function.