Anyone removed the Fuel Pump Inertia Switch out of circuit because it's faulty (and expensive)?

[cobrajocky]

I have a '97 B4000SE 4.0L V6, same a like Ranger XLT and I am having problem with the Fuel Pump Inertia switch, it's faulty, sometime completes the circuit and sometime fail even with the reset is down. It has made driving the truck completely unreliable, you never know when the switch is going to fail internally again.

After doing a bit of Google research, I've found that these switches are an age / mechanical fail limited weak link in the Ranger / B4000 series trucks and the damn things cost $108 retail at Advanced Auto. I'm thinking of just jumpering it out of the circuit.

Has anyone done this before and how is the best way to jumper the circuit? (please describe)?

Really appreciate the input and advice.

 

[RonD]

You just twist/jumper the 2 to 4 wires together to by-pass it
There is a 12v IN and a 12v OUT wire for fuel pump power
Then there may be a 3rd and 4th wire for the computer, it serves 2 purposes, it tells computer if the fuel pump relay worked, 12v IN has 12v when computer activated the relay, and in some years there is a inertia switch warning light on the dash, computer would activate that light if there was no 12v OUT

Not a Ranger thing, or even a Ford thing, all vehicles with electric fuel pumps have these, cars have them in the trunk

The point of an inertia switch is to stop electric fuel pump from continuing to pump out gasoline if there is a roll over or accident that breaks a fuel line
Ford computer also has a shut off of fuel pump relay if engine RPMs ever drop below 400
That's why fuel pump only runs for 2 seconds with Key ON, and then will only run full time after start up, engine RPMs above 400
Theory is if a fuel line breaks engine would stall, 0 RPMs, so fuel pump would be shut off, but on all Rangers there is a Return line that could break and engine would stay running if that was the case, long shot scenario but not a no shot
And that's why there is an inertia switch as well on all years

Yes, even the Returnless have a return line, but not in engine bay its on the fuel filter
Although I think there were 2 or 3 years, that were true returnless, 1998/1999 and maybe 2000

 

[snoranger]

I wouldn’t bypass a safety feature that shuts off the fuel pump when there’s a higher chance of a fire.

 

[racsan]

I bypassed mine when I thought I was having issues with it after a fuel pump replacement, not a 4.0 but a 2.3 It still had a intermittent fuel pressure problem so I guess I got a new pump that wasnt good. Put a inline electric pump in (well, back in-as I had put one in when original pump failed) and have never looked back. only issue ive had is a couple of times ive stalled it and it wouldnt restart for a long time. Im guessing it flooded somehow.

 

[cobrajocky]

Yeah I would agree that eliminating the Inertia switch is not safe, but everytime I save up enough money to have the truck repainted this sort of expensive "part" comes up. Frustrating on a 23 year old truck with only 99k miles.

RonD, thanks for the usual good info, you're better than a Chiltons Manual.

Has anyone used /found a alternate or generic CHEAPER Inertia Switch that works for the late 90's Rangers/B-4000's ?

I saw this one on Amazon. (https://www.amazon.com/Ford-5L2Z-9341-5L2z9341a-Inertia-Safety/dp/B000NTI03C)
It is for later model Rangers / Explorers / Merc Mountainers 2002 on. It is a heck of a lot cheaper than the original for 1996 - 1999 Ranger/B Series that are $108 bucks and up.

This is the later 2002 switch on Amazon

This is the OEM Switch for 1996 - 99 Rangers/B- Series.

 

[RonD]

You can use any "inertia switch", there is no assigned IN and OUT, it just a switch(on/off), two contacts

You may need to find a matching connector that fits

 

[Roert42]

Rockauto.com has two listed for your truck, one is a noname for $40 and an ACDelco for $70. Might be able to get a used one from a junk yard for just a couple of bucks.

 

[RonD]

Rockauto.com has two listed for your truck, one is a noname for $40 and an ACDelco for $70. Might be able to get a used one from a junk yard for just a couple of bucks.

Wrecking yard inertia switches are not great bets, they are usually "tripped" because vehicle ended up in a Wrecking yard, and once "tripped" they can never be fully reset
The reset button is there so vehicle can be moved, if its drive-able, after an accident, after being tripped once it will trip again even going off a curb or slamming a door, lol

 

[09fx4guy]

I am not exactly one for all of the newfangled safety features in modern cars, such as lane warning, etc. etc.

However, if it were me, I would replace it ASAP. If it was a plow truck that plowed one lot, that never saw the actual road, different story. But the chances of an accident are not exactly low when driving on the road today. And I take comfort knowing that in case of an accident, my fuel pump won't be pumping gas into an engine bay where a fire could start and render me a piece of KFC extra crispy chicken.

 

[snoranger]

I am not exactly one for all of the newfangled safety features in modern cars, such as lane warning, etc. etc.

However, if it were me, I would replace it ASAP. If it was a plow truck that plowed one lot, that never saw the actual road, different story. But the chances of an accident are not exactly low when driving on the road today. And I take comfort knowing that in case of an accident, my fuel pump won't be pumping gas into an engine bay where a fire could start and render me a piece of KFC extra crispy chicken.

Also... that $100 is dirt cheap compared to the lawsuit if someone else got burned.

 

[cobrajocky]

You just twist/jumper the 2 to 4 wires together to by-pass it
There is a 12v IN and a 12v OUT wire for fuel pump power
Then there may be a 3rd and 4th wire for the computer, it serves 2 purposes, it tells computer if the fuel pump relay worked, 12v IN has 12v when computer activated the relay, and in some years there is a inertia switch warning light on the dash, computer would activate that light if there was no 12v OUT

Not a Ranger thing, or even a Ford thing, all vehicles with electric fuel pumps have these, cars have them in the trunk

Hey RonD, here is a closeup picture of the Ford OEM Inertia Switch mounted and the disconnected plug.

How would I temporarily jumper this plug for testing, including driving it a bit to see if this is the reason the truck refuses to start after driving it. I was planning to use so 14 or 16ga solid core wire to do the jumping into the plug, just big enough to hold but not spread the female connectors much (not wreck the plug connection to a new Switch). There are 3 female connectors in this plug and the 3 wires are shown - Green/Yellow (left wire), Pink/Black (center wire) and Orange/Gray (right wire).

Thanks much.

 

[RonD]

Just put a jumper wire between the two contact slots, jumper wire needs to be at least the size of the Green/yellow stripe, that's the IN from fuel pump relay

The Pink/white wire is the OUT to fuel pump

The tan/orange wire goes to the computer to monitor voltage
Just FYI, this wire will show 5-8volts with key on/engine off, no AMPs just volts, from the computer's monitor circuit, this monitor voltage can be confusing when testing these wires, lol
Green wire will only have 12volts for 2 seconds with key on, tan wire will show 5-8v after that until key is off

 

[cobrajocky]

Just put a jumper wire between the two contact slots, jumper wire needs to be at least the size of the Green/yellow stripe, that's the IN from fuel pump relay

The Pink/white wire is the OUT to fuel pump

The tan/orange wire goes to the computer to monitor voltage
Just FYI, this wire will show 5-8volts with key on/engine off, no AMPs just volts, from the computer's monitor circuit, this monitor voltage can be confusing when testing these wires, lol
Green wire will only have 12volts for 2 seconds with key on, tan wire will show 5-8v after that until key is off

So jumper between the Green/yellow and the Pink/white connector slots and ignore the 3rd slot which is the computer feed?

What happens if the computer doesn't get a voltage signal (when jumping only 1 and 2 connectors) that the pump is running or activated?

Thanks Ron.

Guys, first thing I need to do is make sure this IS the reason the truck isn't starting. Then, because I'm on a tight Social Security budget, got to find it cheap. Thanks for all the input guys.
BTW - this same F5AB-9341-AA was also used on car like the 96 - 99 Taurus.
Thanks all!

 

[RonD]

You would get a code but engine would still start, I though pink and tan were in the same slot?

You can jumper all 3 if there are 3 separate slots, then no code

 

[cobrajocky]

You would get a code but engine would still start, I though pink and tan were in the same slot?

You can jumper all 3 if there are 3 separate slots, then no code

It's a 3 connector plug, that Orange/Gray wire, which is the smallest gauge (maybe 14 gauge) is the last to the right on the connector in the picture above. The Green/Yellow (left wire) and Pink/Black (center wire) are larger gauge wire, easily 12 or 14 gauge. According to the schematic I have which only shows the harness, not individual wires, the cable goes from the Inertia switch to the Fuel Pump Relay and branches on to the computer. So I assume the smaller gauge never carries any appreciable amperage to the computer. I'll skip jumping that connector for now, I can always reset that thrown code with my code reader later, besides that code will give me more diagnostic info.

BTW, I agree with you about not trusting a junkyard used unit, my truck only has 100,000 on the nose and my switch is already sketchy.

Thanks Ron.