1971 Ford 3500 Backhoe Electrical (also fuel pump)

[todintexas]

I have a 1971 Ford 3500, it's a backhoe. Had a lot of great help from this site so here I am again, lol! I'm trying to rewire the tractor, not completely just clean up the mess and make it usable. Discovered two things, appears to have a one wire GM type alternator, there's a single wire comes from the key switch to it, but nothing off the post of the battery, I have not checked output yet but I'm going to. I assume this needs to have a charging circuit and it may be that small wire to the switch is a trigger wire? Unnecessary though I think on a one wire? We use these wires pretty regularly in our build, typically one post to the battery second from the switch for the charging signal.

Now here's a little bit odd encounter, is this machine supposed to have an electric fuel pump or lift pump? See the attached picture, on the right side of the tractor is a small 12 volt powered pump, feeds the filter housing and then the filter housing to the injection pump. At the moment this pump is hooked up through a switch screwed on the dash, but the switch doesn't work. Pump works when powered up but is this something that came factory or do I even need it?

Thank you!

 

[Sean in PA]

No, that tractor did not have an electric fuel/lift pump when it left the factory. A previous owner most likely installed it to overcome some issue that they were having without properly diagnosing and resolving the true problem.

 

[Jim.ME]

I have a 1971 Ford 3500, it's a backhoe. Had a lot of great help from this site so here I am again, lol! I'm trying to rewire the tractor, not completely just clean up the mess and make it usable. Discovered two things, appears to have a one wire GM type alternator, there's a single wire comes from the key switch to it, but nothing off the post of the battery, I have not checked output yet but I'm going to. I assume this needs to have a charging circuit and it may be that small wire to the switch is a trigger wire? Unnecessary though I think on a one wire? We use these wires pretty regularly in our build, typically one post to the battery second from the switch for the charging signal.

Now here's a little bit odd encounter, is this machine supposed to have an electric fuel pump or lift pump? See the attached picture, on the right side of the tractor is a small 12 volt powered pump, feeds the filter housing and then the filter housing to the injection pump. At the moment this pump is hooked up through a switch screwed on the dash, but the switch doesn't work. Pump works when powered up but is this something that came factory or do I even need it?

Thank you!View attachment 70155View attachment 70156

That is a three-wire alternator. It is missing the 10- or 12-gauge wire from the output post running back to the ammeter or starter solenoid to carry alternator output. The small wire from the switch should be on the #1 spade terminal to provide excitation for the alternator the #2 spade terminal should connect to the alternator output post (as it appears to be) to provide system feedback to the voltage regulator. The excitation wire should have a charge indicator light, diode, or resistor in it unless it is wired such that feedback from the alternator doesn't prevent shutting the engine down.

 

[todintexas]

That is a three-wire alternator. It is missing the 10- or 12-gauge wire from the output post running back to the ammeter or starter solenoid to carry alternator output. The small wire from the switch should be on the #1 spade terminal to provide excitation for the alternator the #2 spade terminal should connect to the alternator output post (as it appears to be) to provide system feedback to the voltage regulator. The excitation wire should have a charge indicator light, diode, or resistor in it unless it is wired such that feedback from the alternator doesn't prevent shutting the engine down.

Thank you! We use a lot of these in our car builds so I figured that was the case, im going to test the output today and see if it works. I don't think the feedback would be an issue, there's a manual fuel shutoff that kills the engine but I'll check it.