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With the oil pressure sensor bypassed, I get 12 volts at the blue wire at the connector in the trunk with the key in the ON position. I heard the pump run (it's a new pump), started the car and ran it for a minute. When I shut the car off and then tried to start it again, the pump did not run with the key in the ON position, and of course the car did not run. Can just I install a mechanical fuel pump? It's a 231 v6. Thanks, Dan.

Sounds like your ignition switch is intermittent or out of adjustment.

Thanks Chris. I didn't realize that ignition switches can be adjusted. Do you know how these are adjusted? Thanks, Dan.

The switch slides up and down the column about a half inch after loosening two small 5/16" head screws. Easier if you drop the column down.

Chris,

I decided to replace the ignition switch since I had to drop the column anyway. This is tonight's sequence of events.

1. Went out and before I did anything, checked again what would happen with the oil pressure sensor jumped. Sure enough in the ON position, I heard the pump run. Proceeded to start the car and it idled for a few minutes. Shut if off, turned the key back to the ON position and heard the pump run again.
2. DIs-connected the battery and replaced the ignition switch. Reconnected the battery and (with the oil pressure sensor still jumped) turned the key to the ON position and heard the pump run. Did that a couple of times and heard the pump run each time. Then after the 3rd or 4th time, went to turn the key to the ON position and THE PUMP DID NOT RUN! Checked and I was getting 11.75V at the pump. Turned the key to the START position and the starter engaged and the car idled on the gas still in the carb.

I'm stumped. Any ideas? Since the car able to run, that's why I was wondering if I can run a mechanical fuel pump (which FWIW, I think I can cause I looked and there is a block off plate on the driver's side of the block with enough room to fit a pump). Thanks in advance.

Dan

When you had no pump action but seen 11.75 volts at it, exactly how were you measuring? With ground of meter at sender terminal?

There's no reason you can't run a mechanical pump if you have one that clears the frame plate.

I inserted the red probe of my meter into the connector (blue wire) and touched the black probe to the pump's ground wire.

Could be that your new fuel pump is intermittent. Try hooking a test light to it and see if it lights up with every switch cycle?

Went out to the car this evening, turned the switch to the ON position and the pump ran. Did that for 5 cycles, and each time the pump ran. On the 6th attempt, nothing. I checked the connection with my test light and got a bright light. Is it possible that the pump is dead heading after so many cycles since the car is not running, and therefore stops operating? Maybe the pressure bleeds off over night to the point where it runs the next day?

I don't believe they work like that, they just keep running and have an internal bypass. Either pump is intermittent or it's losing connection from sender terminals to pump.

Thanks Chris. Is there a relay in the fuel pump circuit?

No fuel pump relay on H's.

Schematic and circuit description here: viewtopic.php?f=44&t=45520