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97 Ranger, Wiring Fuel pump directly to battery


Big Aloe

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AM I damaging the fuel pump by running it directly from the battery, incl. a 20 Amp fuse and a switch installed inside the cabin?
I've been driving 50 miles so far, no problem, surprisingly the old Ranger is driving much faster.
 


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Mbrooks420

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If it's faster it was starving for fuel due to a wiring/relay issue most likely. Did you swap/replace relays first?

Is that a returnless fuel system? Have you checked the fuel pressure at the rail after direct wiring? Is the fuel pressure regulator cut out of the circuit?
 




Big Aloe

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If it's faster it was starving for fuel due to a wiring/relay issue most likely. Did you swap/replace relays first?

Is that a returnless fuel system? Have you checked the fuel pressure at the rail after direct wiring? Is the fuel pressure regulator cut out of the circuit?
Thanks for your reply. I have difficulty finding the the relays. But it is a fuel pump with a return pipe.
 




Turdle

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Google.
heck, even pinterest had a good result for you. 1997 ford ranger power distribution box

 




Big Aloe

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Google.
heck, even pinterest had a good result for you. 1997 ford ranger power distribution box

Wow that helps so much. Thanks for getting me going. Will check the relays.
 




Big Aloe

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Google.
heck, even pinterest had a good result for you. 1997 ford ranger power distribution box

But would it be ok to drive permanently with the direct battery connection to the fuel pump?
 




1998Exp

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But would it be ok to drive permanently with the direct battery connection to the fuel pump?
It will be bad for your health: 1) Bypassing the inertia switch increases the risk of fire in case of collision. 2) The system is designed to disable the pump if the engine doesn't run. That's another fire prevention mechanism.
 




fastpakr

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And outside of the safety factors, you certainly don't want or need the fuel pump running 24/7, burning it up and draining your battery.
 




Turdle

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But would it be ok to drive permanently with the direct battery connection to the fuel pump?
There is a reason for triple protection ( fuse-relay-inertia switch) , actually several reason I would say no. Definitely not OK.
 




Mbrooks420

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Does the FPR cut power to the pump?
 








J_C

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Heh, it seems that there is more than one thing that could be called an FPR, fuel pump relay or fuel pump return.

The fuel pump relay does not cut power in an accident, rather the inertia switch does, is the last thing in series right before the pump.

WHY would someone want to drive with it permanently wired to the battery? Doesn't seem to have any purpose except maybe save $10 by not buying a relay if that failed.

That distribution box diagram, as well as the fuse box diagram, should be in the owner's manual which you can get a copy of here:
https://owner.ford.com/tools/account/how-tos/owner-manuals.html
 




Big Aloe

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It will be bad for your health: 1) Bypassing the inertia switch increases the risk of fire in case of collision. 2) The system is designed to disable the pump if the engine doesn't run. That's another fire prevention mechanism.
Ok, didn't think about that. Where can I locate the inertia switch?
 




Big Aloe

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It will be bad for your health: 1) Bypassing the inertia switch increases the risk of fire in case of collision. 2) The system is designed to disable the pump if the engine doesn't run. That's another fire prevention mechanism.
Ok, didn't think about that. Where can I locate the inertia switch?
Heh, it seems that there is more than one thing that could be called an FPR, fuel pump relay or fuel pump return.

The fuel pump relay does not cut power in an accident, rather the inertia switch does, is the last thing in series right before the pump.

WHY would someone want to drive with it permanently wired to the battery? Doesn't seem to have any purpose except maybe save $10 by not buying a relay if that failed.

That distribution box diagram, as well as the fuse box diagram, should be in the owner's manual which you can get a copy of here:
https://owner.ford.com/tools/account/how-tos/owner-manuals.html
Thank you J_C,
this is not about saving money, so which relays should I replace?
 




J_C

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I would use a multimeter to trace where the power stops in the circuit, but if you want a quick relay test then on the diagram, swap the fuel pump relay with the Wide Open Throttle A/C Cutoff Relay, assuming they are the same type as shown on the diagram.

If the pump then works, just as a sanity check (in case the contacts were corroded or something and merely unplugging and replugging them got it working) swap them back and see if the pump works.

Also check fuse 12 in that same box, either with a multimeter, visually, or swapping it with the headlight fuse #11 right across from it.

The inertia switch is probably behind the trim panel on the right in the passenger side footwell.

While it could trip or fail completely, I'd sooner think it's a fuse, relay, or wiring/connector problem unless the vehicle was in an accident. With a multimeter you can tell whether power is getting to and past the fuse and relay, and whether that switch is conducting. If you measure 12V at the output from the inertia switch then there's a problem between it and the pump.

Where did you tap into the wiring to the pump to connect it to the battery?
 




Mbrooks420

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I was working under the vehicle and tripped my inertia switch while hammering before, it's worth a check.
 




Big Aloe

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I would use a multimeter to trace where the power stops in the circuit, but if you want a quick relay test then on the diagram, swap the fuel pump relay with the Wide Open Throttle A/C Cutoff Relay, assuming they are the same type as shown on the diagram.

If the pump then works, just as a sanity check (in case the contacts were corroded or something and merely unplugging and replugging them got it working) swap them back and see if the pump works.

Also check fuse 12 in that same box, either with a multimeter, visually, or swapping it with the headlight fuse #11 right across from it.

The inertia switch is probably behind the trim panel on the right in the passenger side footwell.

While it could trip or fail completely, I'd sooner think it's a fuse, relay, or wiring/connector problem unless the vehicle was in an accident. With a multimeter you can tell whether power is getting to and past the fuse and relay, and whether that switch is conducting. If you measure 12V at the output from the inertia switch then there's a problem between it and the pump.

Where did you tap into the wiring to the pump to connect it to the battery?
Thanks a lot J_C,
I'll try that today.
I installed a new cable, with a switch in the cabin and 20A fuse from the battery all the way to the fuel pump,
since the the old red cable only showed 7Volts open Voltage, which went down to zero Volts once connected
to the pump.
 




Big Aloe

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I was working under the vehicle and tripped my inertia switch while hammering before, it's worth a check.
I wouldn't know how to find that switch!!!
 




Mbrooks420

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Pull the carpet back in the passenger side footwell. I think it's red. Up near the glovebox.
 


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