Fuel lift pump positive lead hook up

[Jcrilly1]

Where do I hook up the OEM fuel lift pump positive terminal ? Mechanic omitted on engine install.
universal M-25XP on Ericson 32-3 .

 

[JohnW]

On my M-25, the fuel pump positive is spliced into the purple wire that goes from the key switch to the alternator (exciter wire?), so when the key is turned, the fuel pump activates and I can hear it clicking.

 

[Jcrilly1]

Thank you for your great photo and wire markings. Believe it or not, I have done many avionics and wiring of aircraft jobs over the years your photo is going to be a great help.
This one has really had me scratching my head because the mechanic disconnected everything, marked nothing then dropped the engine on the mounts bolted it in and scrammed.

 

[Kenneth K]

On my M-25, the fuel pump positive is spliced into the purple wire that goes from the key switch to the alternator (exciter wire?), so when the key is turned, the fuel pump activates and I can hear it clicking.

Yeah, that's correct. On many Ericsons the fuel pump (+) was spliced into the alternator excitation (purple) wire. You can reinstall things up this way just to get the motor going, but over the long-term it's worth re-doing.

For one, an unsealed mid-wire splice leaves the purple wire subject to moisture and corrosion (though I suppose you could side-step this with proper heat-shrink terminals and liquid electrical tape) but check the current condition of the purple wire in the vicinity of the old splice.

For two, the Universal M-25 manual shows the purple wire as 14 gauge. The facet gold-flo fuel pumps use 1.5-1.6A. A quick internet search shows that the excitation circuit on a 50A alternator varies between about 1.5 and 5.0A depending on load. You'd need to consult ampacity/wire gauge charts for the specific lengths of your wiring runs, but you'll likely find that 14 ga wire is too small to small to power both devices (aside from the fact that it's been working fine for the last 40 years!). The alternator grounds itself to the engine block so you can ignore the length of the ground wire on the ampacity chart. If the fuel pump is grounded to the engine block, then the ground path only adds 2-4 feet (versus grounding at the engine panel, which requires likely 12-18 feet length).

My solution was run a new, 10ga wire from the engine panel down to the engine compartment. The wire connects to a 4-terminal fuse block. Any time the engine panel is powered, so is the fuse block in the engine compartment. Each of the four terminals (used for alternator excitation, fuel pump, and two engine monitoring circuits) has it's own fuse protection, which greatly aids troubleshooting when any one device fails. A remote block like this would also be a likely place to power the Hobbs meter.

 

[Loren Beach]

Speaking of having a Hobbs meter, here is a picture or two our changes, and a circuit diagram.

O34 - New Hour Meter & Halon Status light (part 1)

After removing the old (crumbling lens) Halon status light in its escutcheon plate, I needed to install a new one. The purpose of that light is to see if the Halon extinguisher has discharged, without opening the hatch to the engine compartment...

ericsonyachts.org

 

[Jcrilly1]

Yeah, that's correct. On many Ericsons the fuel pump (+) was spliced into the alternator excitation (purple) wire. You can reinstall things up this way just to get the motor going, but over the long-term it's worth re-doing.

For one, an unsealed mid-wire splice leaves the purple wire subject to moisture and corrosion (though I suppose you could side-step this with proper heat-shrink terminals and liquid electrical tape) but check the current condition of the purple wire in the vicinity of the old splice.

For two, the Universal M-25 manual shows the purple wire as 14 gauge. The facet gold-flo fuel pumps use 1.5-1.6A. A quick internet search shows that the excitation circuit on a 50A alternator varies between about 1.5 and 5.0A depending on load. You'd need to consult ampacity/wire gauge charts for the specific lengths of your wiring runs, but you'll likely find that 14 ga wire is too small to small to power both devices (aside from the fact that it's been working fine for the last 40 years!). The alternator grounds itself to the engine block so you can ignore the length of the ground wire on the ampacity chart. If the fuel pump is grounded to the engine block, then the ground path only adds 2-4 feet (versus grounding at the engine panel, which requires likely 12-18 feet length).

My solution was run a new, 10ga wire from the engine panel down to the engine compartment. The wire connects to a 4-terminal fuse block. Any time the engine panel is powered, so is the fuse block in the engine compartment. Each of the four terminals (used for alternator excitation, fuel pump, and two engine monitoring circuits) has it's own fuse protection, which greatly aids troubleshooting when any one device fails. A remote block like this would also be a likely place to power the Hobbs meter.

Kenneth, Thanks for taking the time to offer this information. J

 

[Jcrilly1]

Speaking of having a Hobbs meter, here is a picture or two our changes, and a circuit diagram.

O34 - New Hour Meter & Halon Status light (part 1)

After removing the old (crumbling lens) Halon status light in its escutcheon plate, I needed to install a new one. The purpose of that light is to see if the Halon extinguisher has discharged, without opening the hatch to the engine compartment...

ericsonyachts.org

Speaking of having a Hobbs meter, here is a picture or two our changes, and a circuit diagram.

O34 - New Hour Meter & Halon Status light (part 1)

After removing the old (crumbling lens) Halon status light in its escutcheon plate, I needed to install a new one. The purpose of that light is to see if the Halon extinguisher has discharged, without opening the hatch to the engine compartment...

ericsonyachts.org

Kenneth, Thanks for taking the time to offer this information. J

Loren,
I'll use this for future upgrades. Thanks

 

[Jcrilly1]

Yeah, that's correct. On many Ericsons the fuel pump (+) was spliced into the alternator excitation (purple) wire. You can reinstall things up this way just to get the motor going, but over the long-term it's worth re-doing.

For one, an unsealed mid-wire splice leaves the purple wire subject to moisture and corrosion (though I suppose you could side-step this with proper heat-shrink terminals and liquid electrical tape) but check the current condition of the purple wire in the vicinity of the old splice.

For two, the Universal M-25 manual shows the purple wire as 14 gauge. The facet gold-flo fuel pumps use 1.5-1.6A. A quick internet search shows that the excitation circuit on a 50A alternator varies between about 1.5 and 5.0A depending on load. You'd need to consult ampacity/wire gauge charts for the specific lengths of your wiring runs, but you'll likely find that 14 ga wire is too small to small to power both devices (aside from the fact that it's been working fine for the last 40 years!). The alternator grounds itself to the engine block so you can ignore the length of the ground wire on the ampacity chart. If the fuel pump is grounded to the engine block, then the ground path only adds 2-4 feet (versus grounding at the engine panel, which requires likely 12-18 feet length).

My solution was run a new, 10ga wire from the engine panel down to the engine compartment. The wire connects to a 4-terminal fuse block. Any time the engine panel is powered, so is the fuse block in the engine compartment. Each of the four terminals (used for alternator excitation, fuel pump, and two engine monitoring circuits) has it's own fuse protection, which greatly aids troubleshooting when any one device fails. A remote block like this would also be a likely place to power the Hobbs meter.

Kenneth,
Thanks for the information.

 

[JohnW]

Yeah, that's correct. On many Ericsons the fuel pump (+) was spliced into the alternator excitation (purple) wire. You can reinstall things up this way just to get the motor going, but over the long-term it's worth re-doing.

For one, an unsealed mid-wire splice leaves the purple wire subject to moisture and corrosion (though I suppose you could side-step this with proper heat-shrink terminals and liquid electrical tape) but check the current condition of the purple wire in the vicinity of the old splice.

For two, the Universal M-25 manual shows the purple wire as 14 gauge. The facet gold-flo fuel pumps use 1.5-1.6A. A quick internet search shows that the excitation circuit on a 50A alternator varies between about 1.5 and 5.0A depending on load. You'd need to consult ampacity/wire gauge charts for the specific lengths of your wiring runs, but you'll likely find that 14 ga wire is too small to small to power both devices (aside from the fact that it's been working fine for the last 40 years!). The alternator grounds itself to the engine block so you can ignore the length of the ground wire on the ampacity chart. If the fuel pump is grounded to the engine block, then the ground path only adds 2-4 feet (versus grounding at the engine panel, which requires likely 12-18 feet length).

My solution was run a new, 10ga wire from the engine panel down to the engine compartment. The wire connects to a 4-terminal fuse block. Any time the engine panel is powered, so is the fuse block in the engine compartment. Each of the four terminals (used for alternator excitation, fuel pump, and two engine monitoring circuits) has it's own fuse protection, which greatly aids troubleshooting when any one device fails. A remote block like this would also be a likely place to power the Hobbs meter.

Thanks for the heads up. Over last 40+ years and 4 owners, my E32-3 has various wiring, some with capped ends, throughout the boat. I am contemplating running a 10wire 10awg harness with terminal blocks at both ends from the engine compartment to the cockpit instrumentation area.

 

[Kenneth K]

I am contemplating running a 10wire 10awg harness with terminal blocks at both ends from the engine compartment to the cockpit instrumentation area.

Yeah, here are the blog entries about what I did (3 parts). https://ericsonyachts.org/ie/ubs/another-engine-panel-upgrade-pt-1.701/