Fuel pump not getting power
#1
Fuel pump not getting power
Hello all, Im new to the forum and trying to fix my 99 3.0 ranger that wont startup. I jumped the gun and put in a new fuel pump and its not getting power. I can hear the fuel pump relay clicking when the key is turned on.
When my fuel pump first started going i was having rough idle, difficulty starting etc, then i dropped the tank > rebuilt the old pump and the truck fired right up. Then a week later i was jumping a truck with the ranger and the rpms slowly dropped and it just sputtered out and it wouldnt start back up.
Im not super auto savvy but ive been trying to learn alot about the whole electricals involved in the fuel pump. The inertia switch isnt open, but I want to bypass it for testing purposes, thing is mine has 3 wires, two pinks and a green and im not sure how to bypass that since people say to just tie the two wires together and i dont know if one wire is just suppose to be left alone.
I pulled the PCM diode and it looked burnt on one side, ill try replacing that and see if i get any results.
A lot of people say check the ground connections but honestly i dont know where to look. Or to check the cabling under the power distributor, but its just a mass of wires, nothing seems loose but i dont know where to look specifically for corrosion or a ground thats gone bad
When my fuel pump first started going i was having rough idle, difficulty starting etc, then i dropped the tank > rebuilt the old pump and the truck fired right up. Then a week later i was jumping a truck with the ranger and the rpms slowly dropped and it just sputtered out and it wouldnt start back up.
Im not super auto savvy but ive been trying to learn alot about the whole electricals involved in the fuel pump. The inertia switch isnt open, but I want to bypass it for testing purposes, thing is mine has 3 wires, two pinks and a green and im not sure how to bypass that since people say to just tie the two wires together and i dont know if one wire is just suppose to be left alone.
I pulled the PCM diode and it looked burnt on one side, ill try replacing that and see if i get any results.
A lot of people say check the ground connections but honestly i dont know where to look. Or to check the cabling under the power distributor, but its just a mass of wires, nothing seems loose but i dont know where to look specifically for corrosion or a ground thats gone bad
#2
RF Veteran
iTrader: (1)
Welcome to the forum
You can just jump between the two terminals on the inertia switch, the 3rd wire goes to the computer, it monitors if fuel pump is getting the 12volts from fuel pump relay.
And just a heads up, that monitor wire has 5-7volts when computer is on.
When you turn on the key the EEC relay closes(1 click, this powers up computer), then computer closes the fuel pump relay(2nd click) but ONLY for 2 seconds then it opens.
So if you are testing for voltage at inertia switch, it should only show 12volts just after key is turned on, then it will drop to 5-7volts(monitor voltage)
You can turn key off and on as much as you want to test for the 12volts, won't hurt anything.
There is a 30amp fuel pump fuse in the engine fuse box.
Thats the power that is sent to the inertia switch when computer closes fuel pump relay.
EEC relay powers the computer(EEC), and also powers the coil in the fuel pump relay.
So coil has power with key on but no ground so stays open, computer Grounds the coil to closes it, but only for 2 seconds.
Once RPMs are about 400(engine started) the computer will ground the fuel pump relay again and leave it grounded until key off or engine stalls.
Fuel pump power
Battery------30amp fuse------fuel pump relay-------inertia switch----------------fuel pump
You can pull out the fuel pump relay and test it slots
Key off, only 1 slot should show 12volts, thats the power from the 30 amp fuse, 24/7 power
Key on, another slot should now show 12volts, thats power from the EEC relay
You can just jump between the two terminals on the inertia switch, the 3rd wire goes to the computer, it monitors if fuel pump is getting the 12volts from fuel pump relay.
And just a heads up, that monitor wire has 5-7volts when computer is on.
When you turn on the key the EEC relay closes(1 click, this powers up computer), then computer closes the fuel pump relay(2nd click) but ONLY for 2 seconds then it opens.
So if you are testing for voltage at inertia switch, it should only show 12volts just after key is turned on, then it will drop to 5-7volts(monitor voltage)
You can turn key off and on as much as you want to test for the 12volts, won't hurt anything.
There is a 30amp fuel pump fuse in the engine fuse box.
Thats the power that is sent to the inertia switch when computer closes fuel pump relay.
EEC relay powers the computer(EEC), and also powers the coil in the fuel pump relay.
So coil has power with key on but no ground so stays open, computer Grounds the coil to closes it, but only for 2 seconds.
Once RPMs are about 400(engine started) the computer will ground the fuel pump relay again and leave it grounded until key off or engine stalls.
Fuel pump power
Battery------30amp fuse------fuel pump relay-------inertia switch----------------fuel pump
You can pull out the fuel pump relay and test it slots
Key off, only 1 slot should show 12volts, thats the power from the 30 amp fuse, 24/7 power
Key on, another slot should now show 12volts, thats power from the EEC relay
#3
Welcome to the forum
You can just jump between the two terminals on the inertia switch, the 3rd wire goes to the computer, it monitors if fuel pump is getting the 12volts from fuel pump relay.
And just a heads up, that monitor wire has 5-7volts when computer is on.
When you turn on the key the EEC relay closes(1 click, this powers up computer), then computer closes the fuel pump relay(2nd click) but ONLY for 2 seconds then it opens.
So if you are testing for voltage at inertia switch, it should only show 12volts just after key is turned on, then it will drop to 5-7volts(monitor voltage)
You can turn key off and on as much as you want to test for the 12volts, won't hurt anything.
There is a 30amp fuel pump fuse in the engine fuse box.
Thats the power that is sent to the inertia switch when computer closes fuel pump relay.
EEC relay powers the computer(EEC), and also powers the coil in the fuel pump relay.
So coil has power with key on but no ground so stays open, computer Grounds the coil to closes it, but only for 2 seconds.
Once RPMs are about 400(engine started) the computer will ground the fuel pump relay again and leave it grounded until key off or engine stalls.
Fuel pump power
Battery------30amp fuse------fuel pump relay-------inertia switch----------------fuel pump
You can pull out the fuel pump relay and test it slots
Key off, only 1 slot should show 12volts, thats the power from the 30 amp fuse, 24/7 power
Key on, another slot should now show 12volts, thats power from the EEC relay
You can just jump between the two terminals on the inertia switch, the 3rd wire goes to the computer, it monitors if fuel pump is getting the 12volts from fuel pump relay.
And just a heads up, that monitor wire has 5-7volts when computer is on.
When you turn on the key the EEC relay closes(1 click, this powers up computer), then computer closes the fuel pump relay(2nd click) but ONLY for 2 seconds then it opens.
So if you are testing for voltage at inertia switch, it should only show 12volts just after key is turned on, then it will drop to 5-7volts(monitor voltage)
You can turn key off and on as much as you want to test for the 12volts, won't hurt anything.
There is a 30amp fuel pump fuse in the engine fuse box.
Thats the power that is sent to the inertia switch when computer closes fuel pump relay.
EEC relay powers the computer(EEC), and also powers the coil in the fuel pump relay.
So coil has power with key on but no ground so stays open, computer Grounds the coil to closes it, but only for 2 seconds.
Once RPMs are about 400(engine started) the computer will ground the fuel pump relay again and leave it grounded until key off or engine stalls.
Fuel pump power
Battery------30amp fuse------fuel pump relay-------inertia switch----------------fuel pump
You can pull out the fuel pump relay and test it slots
Key off, only 1 slot should show 12volts, thats the power from the 30 amp fuse, 24/7 power
Key on, another slot should now show 12volts, thats power from the EEC relay
Thanks for the detailed response very helpful. Once I get a volt meter ill test voltage at inertia switch. Based on that logic if voltage at inertia switch is good, but still not getting proper voltage ati pump that should mean that everything prior, relays fuses grounds etc are good and the issue lies with or between the inertia switch and wiring/grounding at the pump, correct?
#4
RF Veteran
iTrader: (1)
Yes, if you have 12volts on both terminals of inertia switch then, either connector on the top of fuel tank is bad or new fuel pump is.
3rd partly fuel pumps, i.e. not motorcraft, can fail early even a few days, but they have 1 or 2 years warranties.
Motorcraft pumps have 60day warranty, lol, go figure
Lifting the bed of the truck is easiest way to get at connector and change the pump
You just need to slide the bed back a foot or two, or tilt it up and support it
$20 volt/ohm meter will save you hundreds of dollars in parts over the years, almost any sensor or control can be tested
And if you have a 1996 or newer vehicle, and a smartphone, you can get a Bluetooth OBD2 reader, $15-$25 and a free app for your phone, then you can see if inertia switch is getting the 12volts with key on, and watch any live data while driving, and of course get any "codes" if computer sets any.
This is not a Ford thing, it must work on any vehicle sold in the US or Canada from 1996 and up, it was/is the Law.
the $5 Torque app is a good software but the free apps are OK as well
3rd partly fuel pumps, i.e. not motorcraft, can fail early even a few days, but they have 1 or 2 years warranties.
Motorcraft pumps have 60day warranty, lol, go figure
Lifting the bed of the truck is easiest way to get at connector and change the pump
You just need to slide the bed back a foot or two, or tilt it up and support it
$20 volt/ohm meter will save you hundreds of dollars in parts over the years, almost any sensor or control can be tested
And if you have a 1996 or newer vehicle, and a smartphone, you can get a Bluetooth OBD2 reader, $15-$25 and a free app for your phone, then you can see if inertia switch is getting the 12volts with key on, and watch any live data while driving, and of course get any "codes" if computer sets any.
This is not a Ford thing, it must work on any vehicle sold in the US or Canada from 1996 and up, it was/is the Law.
the $5 Torque app is a good software but the free apps are OK as well
Last edited by RonD; 03-03-2017 at 12:52 PM.
#5
So ive checked the fuel relay, its getting 12 volts on two of the pins, one is on at all times and the second oen comes on when the key is turned, however the inertia switch is showing no power, i tried grounding 87 on the fuel relay and jumping between 87 and 30, when i do so i hear a soft whirring sound from the engine bay but its not the fuel pump, any idea what that is?
at this point i would guess the issue is a faulty ground or wire between the relay and the inertia switch. some people have found broken wires under the relay itself, i tried flipping over the power distrubition box but the cables restrict its movement, how do you access the wires underneath to check for integrity? any other ground locations i should check?
at this point i would guess the issue is a faulty ground or wire between the relay and the inertia switch. some people have found broken wires under the relay itself, i tried flipping over the power distrubition box but the cables restrict its movement, how do you access the wires underneath to check for integrity? any other ground locations i should check?
#6
also, i tried swapping out the ECM with a used one but that only triggered the factory passive theft system and theft would blink rapidly on the dash, i put the old one back in but if i try to crank the engine i get no response at all, prior the engine would crank but not fire since there was no fuel, now it does nothing like the battery is dead (which it isnt, all the lights work, they dont dim when attempting to start, battery shows 12.6V)
#7
RF Veteran
iTrader: (1)
Unhook both battery cables, then touch them together, that should drain all the memory capacitors in the system.
Hook battery back up and see if it cranks again, also if Theft Light is normal or still flashing rapidly.
There is a Starter Motor relay in the engine fuse box, it is for the PATS systems, Computer must Ground this relay so the 12volts from key in START can pass thru to the starter motor and activate it.
Your PATS system has a PATS Module(above glove box) that was "married" to the computer at the factory, when you turn on the key the two units exchange a 'handshake' that is unique so they know if either has been changed.
Ford Dealers can "remarry" new module or new computer if one goes bad.
So yes, new computer won't work with old PATS module, you can swap computer and PATS module set from one vehicle to another, you also need their PATS key(s) as each PATS key has unique number inside and that number is in PATS modules memory.
Newer models have PATS module built-in to the computer, so no separate module.
Fuel pump relay only powers the fuel pump, so any noise you heard when jumping 87/30 would only be the fuel pump.
Unless you are not testing fuel pump relay socket
Confirm correct socket by pulling Fuel Pump fuse, fuse #9 20amp), you should lose the 12volt key OFF power at the correct socket
Hook battery back up and see if it cranks again, also if Theft Light is normal or still flashing rapidly.
There is a Starter Motor relay in the engine fuse box, it is for the PATS systems, Computer must Ground this relay so the 12volts from key in START can pass thru to the starter motor and activate it.
Your PATS system has a PATS Module(above glove box) that was "married" to the computer at the factory, when you turn on the key the two units exchange a 'handshake' that is unique so they know if either has been changed.
Ford Dealers can "remarry" new module or new computer if one goes bad.
So yes, new computer won't work with old PATS module, you can swap computer and PATS module set from one vehicle to another, you also need their PATS key(s) as each PATS key has unique number inside and that number is in PATS modules memory.
Newer models have PATS module built-in to the computer, so no separate module.
Fuel pump relay only powers the fuel pump, so any noise you heard when jumping 87/30 would only be the fuel pump.
Unless you are not testing fuel pump relay socket
Confirm correct socket by pulling Fuel Pump fuse, fuse #9 20amp), you should lose the 12volt key OFF power at the correct socket
#8
I do appreciate everyones help, the issue is between the fuel relay and the inertia switch, I can't seem to find where the connection breaks so Ill have a shop do it hopefully i narrowed it down for them so its less cost for me.
Before I take it in though I was wondering if I can get the no crank situation fixed, I think by me swapping out the ECM it put the truck into security mode, PATS is blinking theft on the dash once a second (might be normal) but theres no cranking action by the starter motor since i swapped out the ecm, i put the original back but its like the system never reset
i touched the battery terminals together while the battery was unplugged to drain the capicators, but no dice
Before I take it in though I was wondering if I can get the no crank situation fixed, I think by me swapping out the ECM it put the truck into security mode, PATS is blinking theft on the dash once a second (might be normal) but theres no cranking action by the starter motor since i swapped out the ecm, i put the original back but its like the system never reset
i touched the battery terminals together while the battery was unplugged to drain the capicators, but no dice
#9
Same problem.
I'm not getting any power to my fuel pump either. I've traced the problem with a test light (all I have access to at the moment) and found that I'm not getting power to the relay post that's only hot when the key is on. I've checked the fuse, replaced the fuse, and flat out bypassed the fuse and still get nothing. haven't traced any wires at that point, but I did go on a replacement spree before getting here. I've replaced the fuel pump itself, the ignition switch, and the ecm. I'm at a loss and because it's 25 years old my local mechanic is calling it an antique and wants to charge me $150/hr to look at it. I'm a pretty decent mechanic as far as mechanical problems go, but I'm a terrible electrician. I've pretty much run out of ideas at this point. I finally traced all the wires and none of them are broken or not connected so idk what could be wrong.
#10
RF Veteran
iTrader: (1)
Welcome to the forum
So its a 1993 Ranger?
2018 - 25 = 1993
That would be EEC-IV computer correct, 1995 and newer used EEC-V
The Fuel pump relay Base has 4 working slots
12volt slot full time from FP Fuse, key on or off doesn't matter, if fuse is good then 12volt always here
Load slot, wire runs to Inertia switch in passenger side cab below glove box, inertia switch cuts power to fuel pump in a sudden STOP, accident, has RED reset button on the top
When these two slots are connected fuel pump gets 12volts, assuming inertia switch is OK
Relay's coil gets 12v only with key on, so key on and off 12v slot is not fuel pump power, it is to activate relay when it is Grounded
Relay coil's ground is controlled by the computer.
Computer Grounds this slot/wire for 2 seconds with Key on, then ungrounds it, its a safety thing, when engine RPMs are above 400(engine started), then computer grounds it full time.
So you need to cycle key on and off to test this Ground slot
But key on should have 12v full time on one the coil slot
OBD1 test port has a fuel pump relay Ground by pass for testing
Look at test port diagram here: https://www.therangerstation.com/how...ipped-engines/
Fuel pump slot is labelled, if you GROUND that slot and turn on the key then fuel pump relay should Close and fuel pump should come on, and stay on until key is turned off
That slots wire is spliced to computers Ground wire for fuel pump relay.
So its a 1993 Ranger?
2018 - 25 = 1993
That would be EEC-IV computer correct, 1995 and newer used EEC-V
The Fuel pump relay Base has 4 working slots
12volt slot full time from FP Fuse, key on or off doesn't matter, if fuse is good then 12volt always here
Load slot, wire runs to Inertia switch in passenger side cab below glove box, inertia switch cuts power to fuel pump in a sudden STOP, accident, has RED reset button on the top
When these two slots are connected fuel pump gets 12volts, assuming inertia switch is OK
Relay's coil gets 12v only with key on, so key on and off 12v slot is not fuel pump power, it is to activate relay when it is Grounded
Relay coil's ground is controlled by the computer.
Computer Grounds this slot/wire for 2 seconds with Key on, then ungrounds it, its a safety thing, when engine RPMs are above 400(engine started), then computer grounds it full time.
So you need to cycle key on and off to test this Ground slot
But key on should have 12v full time on one the coil slot
OBD1 test port has a fuel pump relay Ground by pass for testing
Look at test port diagram here: https://www.therangerstation.com/how...ipped-engines/
Fuel pump slot is labelled, if you GROUND that slot and turn on the key then fuel pump relay should Close and fuel pump should come on, and stay on until key is turned off
That slots wire is spliced to computers Ground wire for fuel pump relay.
Last edited by RonD; 10-09-2018 at 01:07 PM.
#11
I have power at the relay on one pin only I know the other pin is only on for 2 seconds after key on and that's the one with no power. I've checked the inertia switch and it's good and I bypassed it just to be on the safe side and still get no power to that pin key on, off, or at all. The wires are all there, the fuse is good, and everything that should be connected is connected. I've even run a jumper wire in place of the fuse just to be sure I was getting current through the circuit and still get no power on that one pin.
#13
RF Veteran
iTrader: (1)
That key on power for FP Relay comes from the EEC(PCM) Relay not ignition switch, ignition switch, key on, causes EEC relay to close
EEC Relay's "power out" is usually on a Red wire, EEC Relay also powers EEC(computer), fuel injectors, MAF sensor(heater), IAC Valve, and a few solenoids also all red wires
EEC power OUT is a separate fuse, 30amp in engine fuse box
There is often a common splice where all these Red wires are connected to the one red wire coming out of EEC relay base, FP relays Red wire would be connected there
EEC Relay's "power out" is usually on a Red wire, EEC Relay also powers EEC(computer), fuel injectors, MAF sensor(heater), IAC Valve, and a few solenoids also all red wires
EEC power OUT is a separate fuse, 30amp in engine fuse box
There is often a common splice where all these Red wires are connected to the one red wire coming out of EEC relay base, FP relays Red wire would be connected there
Last edited by RonD; 10-09-2018 at 03:20 PM.
#14
Bypass Fuel Pump Relay!
If your Ranger died while driving, will not stay on after crank/roll-over, engine stalls, etc? And you have already: cleaned the MAS, replace the fuel pump, filter. Still no fuel pressure?
Check the fuses under the hood, maybe you did this first, but you are sniffing it out. The Fuel Pump Relay could be the issue and you have to direct/bypass. Google/Youtube: Bypass Bad Fuel Pump Relay
I cannot take credit, I had help from guys in West Texas. They used an electric wire, and ran it from the relay into where the wires plug into more wires (connector below the panel box), and spliced a line I assume going to the fuel pump, or from the battery? I believe my fuel pump now runs all the time, so I am going to check it out more before considering myself done but hopefully this helps you get it running to the next spot.
Check the fuses under the hood, maybe you did this first, but you are sniffing it out. The Fuel Pump Relay could be the issue and you have to direct/bypass. Google/Youtube: Bypass Bad Fuel Pump Relay
I cannot take credit, I had help from guys in West Texas. They used an electric wire, and ran it from the relay into where the wires plug into more wires (connector below the panel box), and spliced a line I assume going to the fuel pump, or from the battery? I believe my fuel pump now runs all the time, so I am going to check it out more before considering myself done but hopefully this helps you get it running to the next spot.
#15
#16
RF Veteran
iTrader: (1)
Welcome to the forum
No, this is a message forum
In a 1986 Ranger you will have 2 fuel pumps, but both share the same 12volt wire from inertia switch
One pump is inside the gas tank
The other is in the drivers side frame rail under drivers seat area
First thing to know is that the fuel pumps ONLY run for 2 seconds with key on, but will run for that 2 seconds EACH TIME key is turned from off to on
Fuel pumps will not get power(12v) full time until engine is started and above 400rpms
There is a Fuel pump Fusible link(fuse wire) in the engine bay connected to the starter relay(solenoid) battery post and then connected to fuel pump(FP) relay
FP relay will be on passenger side inner fender and has a GREEN base(pug-in for relay)
Can look like this: https://www.therangerstation.com/for...228-jpg.34656/
Brown base is EEC relay, it powers up the EEC(computer) and injectors, and FP relay power, NOT fuel pump power, just FP relay power
The computer GROUNDS the FP Relay for 2 seconds with key on, then computer waits until it sees RPMs above 400 to activate relay full time
You can activate FP relay manually using the OBD1 test port, its on the passenger side main wiring harness in engine bay
Find the OBD1 connector
Look at 2nd drawing here: https://www.therangerstation.com/tec...ry/OBD_I.shtml
Fuel Pump slot is labelled
Use a Jumper wire and GROUND that slot, this will activate FP relay full time while key is ON, over rides the 400rpm thing
You can also test that slot for 12v with key ON, if you see 12v then FP relay is getting power from EEC relay and FPR relay should "click" closed when you GROUND that slot
From the engine bay the fuel pumps 12v power runs into the cab, passenger side footwell, to the inertia switch
Inertia switch should be mounted to firewall behind glove box area, looks like this: https://www.explorerforum.com/forums...tch.13002/full
Has a RED button that will pop up to cut power to fuel pumps in the event of a crash, but can pop up if it gets old enough or was damaged
You can push button back down to reset, but it may pop up again if a door is slammed or you go off a curb driving
Power path
Battery positive post on starter relay---fusible link----------------FP Relay-------------inertia switch-----------------------------fuel pumps
No, this is a message forum
In a 1986 Ranger you will have 2 fuel pumps, but both share the same 12volt wire from inertia switch
One pump is inside the gas tank
The other is in the drivers side frame rail under drivers seat area
First thing to know is that the fuel pumps ONLY run for 2 seconds with key on, but will run for that 2 seconds EACH TIME key is turned from off to on
Fuel pumps will not get power(12v) full time until engine is started and above 400rpms
There is a Fuel pump Fusible link(fuse wire) in the engine bay connected to the starter relay(solenoid) battery post and then connected to fuel pump(FP) relay
FP relay will be on passenger side inner fender and has a GREEN base(pug-in for relay)
Can look like this: https://www.therangerstation.com/for...228-jpg.34656/
Brown base is EEC relay, it powers up the EEC(computer) and injectors, and FP relay power, NOT fuel pump power, just FP relay power
The computer GROUNDS the FP Relay for 2 seconds with key on, then computer waits until it sees RPMs above 400 to activate relay full time
You can activate FP relay manually using the OBD1 test port, its on the passenger side main wiring harness in engine bay
Find the OBD1 connector
Look at 2nd drawing here: https://www.therangerstation.com/tec...ry/OBD_I.shtml
Fuel Pump slot is labelled
Use a Jumper wire and GROUND that slot, this will activate FP relay full time while key is ON, over rides the 400rpm thing
You can also test that slot for 12v with key ON, if you see 12v then FP relay is getting power from EEC relay and FPR relay should "click" closed when you GROUND that slot
From the engine bay the fuel pumps 12v power runs into the cab, passenger side footwell, to the inertia switch
Inertia switch should be mounted to firewall behind glove box area, looks like this: https://www.explorerforum.com/forums...tch.13002/full
Has a RED button that will pop up to cut power to fuel pumps in the event of a crash, but can pop up if it gets old enough or was damaged
You can push button back down to reset, but it may pop up again if a door is slammed or you go off a curb driving
Power path
Battery positive post on starter relay---fusible link----------------FP Relay-------------inertia switch-----------------------------fuel pumps
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