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Fuel issue


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November 17, 2011
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I have been chasing a no fuel issue. I have gone and read many of the threads on fuel pumps etc. I am at a loss.

Here is what I have done.

I jumpered the inertia switch and checked with test light got my 1-2 sec light with key on. No pump priming.

I fought for 3 days after school and finally got my fuel tank down I thought before removing fuel pump test it. The dang fuel pump started humming.

Now I am at a loss. I checked relay by swapping out with other relays in power dist box.

I was always told to be very careful when in the power dist box so I cautiously checked fuses. I don't know which one is the 20amp blade fuse for fuel pump. In the center between relays and large blade fuses are four small ones two are 20 amps. Do I check these with key on?? I checked both 20 amp fuses and get nothing swap them out with new and still nothing all this with key off. I also checked where the relay plugs in and got -12v at a few of the connections but dont know really which to check.

I don't know where or how to check wiring under the brake booster. My dad is lost too.

This 93 Explorer 2dr has sat for 3 yrs in driveway and I am trying to get it running. It will start with staarting fluid sprayed into intake.

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well any fuses can be checked by just looking at them. and if your getting power at the fuel pump connector all the time (key on) then i would say replace the pump/ fuel filter and clean any gunk out of the tank.

I didn't check power at the connection at tank. I should have done that before dropping the tank. Dang! Tomorrow I will check power at the connector going to tank where I disconnected. My trouble is I don't know where to check under the brake booster. I assume that is where I need to check afterwards.

yeah if your not getting power at the pump you should follow the harness up to the power dist. box. its unlikely the in between wiring has an open but its possible i suppose

Make sure that when you swap relays that the one you stick into the slot for the FP has the same format (blades are in the same spots) or you are wasting your time.

If you check fuse position 18, 20 amp fuse (under hood power distribution box) that is the fuel pump fuse. It is one of the 8 small fuses and is furthermost to the right, closest to the larger fuses... yeah... I know. How about you PM me your email address and I send you a PDF of the Power Distribution Box?

If I swap a relay and the blades aren't in the right spot the relay wont go in. It looks like all the relays I was swapping out had the same 5 blades.

A side note when I looked into the connection from fuel pump to wiring on frame rail the pins looked like they were coated with a dielectric grease and they were diiirtty.

Also I am curious at the connection back at tank am I looking for the 1-2sec signal or can I get a constant reading with key on engine off?? Finding a 2nd pair of hands gets difficult. If I use my test light and move fast maybe I can see the pulse to prime fuel line. If I am understanding things correctly that is what I am going to be checking for is that 1-2 sec pulse sent from eec, and all the way along the wiring until I get to power dist box where I can check for 12V constant on at one of the locations where the relay plugs in.

When you turn the key to run the FP will run long enough to bring the pressure up then shut off. You will only get power to the pump when the relay is energized.

Get your wiring diagrams?

Reading your posts, it seems like you could troubleshoot this if only you could command the pump to stay on instead of running for 2 seconds. That's actually really easy to do.

(please fill out your vehicle specs when you have time. I'm assuming you have a 93 by your handle, but you could be 93 years old for all I know. thanks!)

This is your ODB-IV diagonostic port, if you have not found it already. It is either loose like this or it is attached to something in the general area.




(these images were absent for some time due to a website hosting error. I have now downloaded them to the forum for more permanence.)

Now, get some wire and ground the fuel pump connection. The hood has a nice handy grounding strap for you. Next, turn the key to ON. This will command the engine computer (ECM) to run the fuel pump continuously.

Now, connect and disconnect, listen for the relay to operate, listen for the pump. Tell us what you find!

My mom said she got a folder full of diagrams so yes.

A 93yr old Teen haha

yes I have a 93 2dr

I am going out to check this now I will reply back.

Ok so here is what I did.

Double checked inertia switch getting 1-2sec signal. Did the ground out at the OBD-1 relay clicks. checked power at the wiring connector back by fuel tank and got 11V (my battery is getting weak). When I put power to fuel pump connector (still haven't taken pump out of tank) I can hear it humming. The one place I cannot get 12V is at the #18 20amp fuse in power dist box. I then put another brand new one in and with key on and OBD-1 grounded if I check the exposed prongs on top of the fuse I get no volts. ?????? I was getting -0.00 can't remember but I know the (-) means something.


I am going to reconnect the fuel pump and see if I ground out the OBD-1 if the fuel pump will run post back afterwards

Ok so I hooked up the fuel pump grounded OBD-1 with key on and verified I was getting power (meter read only 9.4v I have a battery charger hooked up to battery) to fuel pump. But when I put the connectors together I didn't hear fuel pump kick on (disconnected and recconected several times stuck my ear to the hole where I disconnected the filler tube, quiet) but last night when I ran power to fuel pump using a battery charger it hummed.

The only hum I heard was from the rear storage area inside the little compartment I had to open the hatch to see where it was coming from. Fuel tank is sitting outside the truck next to wheel on trash can.

to summarize so I am straight:

Ground OBD-1 with key on result
1. relay clicks
2. constant power at inertia switch
3. 9.4v at harness connector at tank frame rail
4. no power at fuse #18 in power dist box when checking prongs on top of fuse (fuse changed out result same)

OBD-1 left alone results
1. inertia switch using test light got 1-2sec signal
2. wire harness at frame rail fuel tank rec'd 12v then dropped to 6v after 2sec (reconfirmed)
3. relay swapped out

Pulled fuel tank put power to fuel pump using a battery charger result
1. pump hummed (got another pair of hands and was reconfirming my results I used a brand new battery instead of the battery charger and wouldn't you know it I couldn't get the fuel pump to do jack maybe sticking brush motors. would a battery charger do anything different than a brand new battery?) I feel OCD I want to go use the battery charger now and see if it will run the pump.

The fuse should have power unless the diagram I have is incorrect. I will go to the shop tonight and check mine, that is where all my tools are. By grounding the test connector you are simply activating that circuit, same as though you were driving and the computer was commanding the fuel pump to run. Weird...

You get power at the connector at the frame, but not the fuse, puzzling.

Fuel pump's get bad spots in them, you can sometimes wack them and they will turn. Doesn't explain to me what you are experiencing...

Why not jump 12 volts to that fuse and see what happens. Use a fused jumper mind you. Are you testing pink/blk at the pump and not the yellow/white?


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I was checking pink/blk at the pump took some wire from pos batt term to pink/blk and wire from neg terminal to blk. I don't have a fusable jumper. can I use a test light? I am assuming it doesn't matter which metal prong I jumper on top of the fuse.

I was looking at the wiring diagram and I now understand it much better. If I read it correct I should have 12v constant at #18 fuse. I better go double check my method of testing. Yep stupid kid I was checking from post to post on the fuse like a continuity check. Dang well I ran through my power dist box and I am getting 12v at all fuses. So now I am back to fuel pump. I am going to yank it out of tank tonight and bench test it.

Oh I discovered another thing today. I was going to change the fuel filter and noticed the installed doesn't match the one I got. The one installed is wrong. The downside is that the ends are not as long as they should be and there is not enough room to get the pressure fitting tool in to remove the line. I think my only option is to cut the ends close to the fuel filter then use the needle nose plier method I read about on another fuel related post here.

Should always use fused jumper... as long as your fuse isn't bad it doesn't matter which blade you energize.

You haven't opened the fuel tank have you? If so be very careful of sparks from jumping wires testing the pump and static discharge.

Did you check the ground wire coming from the pump?

It is at G104.


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My fuel filter was like that too. I eventually fought the tool (white lisle plastic type) in and got it off. But, I was very close to grabbing my giant diagonal cutters and doing what you are thinking. I did have to do that to get the lines loose at the fuel pump once.

Er, I was a bit confused until I realized you were going back and editing your last post. Easier to follow if you just do a new post each time you come back to ask a question or make a comment.

Anyway, glad to hear you do have 12+ at the fuse, you had me wondering.

Check that ground.

I am off to the gym, then the shop. I will check back in a few hours.

yes I checked the ground at the fenderwell.

The fuel filter body is big and there is not even 1/4" to fuel line end I mean it is tight I am now worried if I cut it off whether I would have room to use needle nose and the fuel line tool......Dang

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