2.3L ('83-'97) Fuel pump won't pump fuel

[photopaul]

I've been working on my 96 Ranger for 4 days now and I can't figure out why the fuel pump won't pump fuel.
I loaned it to my sister a while ago and she was responsible for the maintenance and when it died and wouldn't restart she took it to a garage for repair. They quoted $375 to replace the fuel pump.
I don't have a problem with the price (businesses need to make money) but on my old 96 Ranger with 200k on it I figured I would do it myself with Rock Auto parts ($50)
I removed the bed and accessed the fuel pump; removed the old one and installed the new one and no fuel would pump. It cranks fine, will run for a bit with starting fluid, I replaced the fuel pump relay though it didn't appear to be malfunctioning and verified the inertia switch was okay.
I get a brief 12 volts at the inertia switch and at the fuel pump connector then it drops to 6 volts like I have read it should and still no fuel. I removed the fuel lines to see if anything was coming out when I tried to start the truck and nothing. I removed the fuel pump and connected it to a 12v supply and the pump motor appeared to work. I re-installed the pump and left the fuel lines off and connected 12v to the pump directly and it pumped out fuel.
I jumped from the connector to the pins on the fuel pump with a wire to make sure there was a good connection between the connector and the pump and nothing.
Any suggestions??

 

[RonD]

Did the new pump come with a new filter(sock) on it?

If pump works hot wired and not in the tank then the 12volt wire or ground wire is bad at the tank connector
That's really all there is to it, those 2 wires
There are 4 wires on the connector
2 for fuel level sender, yellow for gauge, black/yellow for ground
and 2 for the fuel pump, pink/black is 12v and black is ground for pump

Yes, inertia switch should show 12v for just 2 seconds with key on and then 5-8volts after that from monitor circuit
The pink wire runs back to gas tank

 

[photopaul]

The pump did come with a new filter sock.
When I put the volt meter probes in the fuel pump connector I get 12v at the fuel level wires and 7.1v at the fuel pump wires

 

[RonD]

If possible cycle the key off then on and see it that 7v change to 12v for 2 seconds, like at inertial switch, and you are using the black wire as the ground for the meter correct?

And even better, check battery voltage FIRST
If its 12.4v than that's what you should see, if its like 11.8v with key on then connection is bad somewhere

A Volt meter(or test light) draws almost 0 amps, fuel pump draws 6amps
So if a wire has a corrode connection a volt meter might only show a .5v drop, but if fuel pump was connected the drop could be 7volts or more

 

[photopaul]

I will try that during daylight tmrw. One thing that did occur to me is that when I saw the 12v it really wasn't there for a 1001, 1002 count. Maybe just 1/2 second.
Could that be a diode or resister in the fuse box? I remember seeing something about that in one of the many youtube videos I saw.
Thanks for your help

 

[RonD]

No diode issue if its starts with 50/50 test
The diode is for the PCM relay, it powers up the PCM(computer) which runs the spark(in 1996), so if spark is working then diode is OK

You can put a jumper in the Fuel Pump relay socket so full time power to fuel pump

Ford used 2 different kinds of relays, mini and micro

Mini seen here: http://www.gtsparkplugs.com/images/mini-automotive-relay-wiring-840x.jpg

Micro here: http://www.gtsparkplugs.com/images/micro-automotive-relay-wiring.jpg

Put a jumper wire in slot 30 and then other end in 87 and fuel pump will get full time 12v power if the wires are OK

Relay pin numbers are all the same, just the layout changes

 

[photopaul]

Had a busy day at work yesterday,
I just tried the 30/87 jump and I have 12.5v at the battery terminals and 11.07 at the plug for the pump.
So i guess I have a bad wire/connection somewhere.
Any suggestions on where to start looking?

 

[photopaul]

The connection at the inertia switch looks clean

 

[RonD]

Whats the voltage at inertia switch?

If its the 11v then wire from relay to switch is the issue, if its 12.5v then wire from switch to tank is the issue

One other thing to test, test slot 30 (or 87) one will be 12.5v from the Fuel Pump Fuse, make sure you are starting with 12.5v there, because could be wire from fuse to FP relay slot, long shot but not a no shot
Under side of engine fuse box can get corrosion

Battery(positive)----FP fuse----FP Relay----------------inertia switch----------------------------gas tank

 

[photopaul]

Okay thanks! I'll try that now

 

[photopaul]

I'm getting about 12.4v at the battery and 12.01v at the fp relay
11.7v @ the inertial switch and variable 9v-11v at the plug for the fp
So I'm thinking I should get a new plug to make sure the wiring is good at that point.
Do you know if they sell them or is the original rebuildable?
Also there is a connection hanging on the front of the fuse box that has 2 pins in it. Is that of any concern?

 

[photopaul]

I found one at a local Advance auto parts
I'll get it and
install it to see if it helps

 

[photopaul]

I ended up not getting the part but I took the old connector apart so I could make sure I had a solid connection to the wires and I'm only getting around 8.2v
It's been raining on and off all day so tmrw I will crawl under the ruck and see if I can fine any connections that are bad
It seems to be worse between the inertia switch and the pump so I'll start tracing the wires between the 2
It seems like the pump has to have 12v to run is that correct?

 

[RonD]

It needs 6 amps at 12v, so its not voltage its the amps that it needs
Are you testing with the pump connected, try that, you should see a BIG voltage drop

 

[photopaul]

At this point I feel like I'm shouting at the wind. I can't keep consistent numbers on the volt meter so I'm not sure where to start.
Short of tearing out the interior I can't find any issues with any electrical connections.
While I was concentrating on finding some consistent numbers on the volt meter I forgot to check the 12v for 2 seconds at startup
I put the VM leads into the inertia switch and tried to start the truck and I definitely didn't 12v for 2 seconds. Now I don't even get the 1/2 sec @ 12v
Could it possibly be the computer in the passenger foot well?
What is "No diode issue if its starts with 50/50 test " What is the 50/50 start test?
At this point I may need to drag it to the local garage down the street