Help! Fuel pump not turning on.

S

Steezin636

New Member
Dec 13, 2024
13
1
3
Florida
#1
Hey everyone!

First time post here. I inherited a 1989 foxbody 5.0 with 72k original miles a couple of years ago. Admittedly life has been busy and have not touched it since I parked it in the driveway. Did a fresh oil change, charged the battery, and went to go start it up and it’ll crank all day long but won’t fire up.

So I started doing some research and started trying to diagnose my issue. It’ll start for a split second with a spray of starter fluid so I know I’m getting spark.

I began going down the rabbit hole of figuring out fuel delivery issues. The relay under the driver seat clicks, inertia switch passed its test. I’m getting 12v at orange/blue wire, 12v at red/black, 12v at tan/green, and 1.46v at pink/black.

I know pink/black is the wire to supply power to the fuel pump. I tried to bypass the relay and connect the red/black to pink/black but had no luck.

Any ideas or help would be much appreciated.
 
#2
Is it getting fuel pressure? If it is, I'd say that the fuel in the tank is bad. Your best bet would be to siphon the old fuel out and replace it with fresh. You'll also want to clear the lines when you do that. The easiest way that I've found was to disconnect the lines at the engine and cycle the key a bunch of times until fresh fuel starts spitting out. You'll obviously need a couple tools to get this all accomplished, these are my recommendations:

www.harborfreight.com

Multi-Use Transfer Pump

Amazing deals on this Multi-Use Transfer Pump at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com

 
#3
Now, if you're not getting pressure and it sounds like everything else is checking out, you may need to drop the tank and replace the pump. If that's the case, you'll probably still want that siphon pump but I've been able to do everything else with basic hand tools.
 
#4
I tried to siphons the fuel out last night because I was anticipating it being a bad fuel pump but decided to do a deeper diagnosis first. The fuel gauge says full so I bought a similar pump to what you posted and put the hose in there to start siphoning and got nothing. So I grabbed a 5gallon fuel tank and added 5 gallons and it didn’t overflow… so obviously the fuel gauge is off.

As for checking fuel pressure I will do that… but I’m not hearing the fuel pump priming at all and I’m not getting correct voltage to the power wire for the fuel pump…
 
#5
Sounds like a new pump is in order from what I can gather. Maybe someone else will chime in and give you a different idea on what to look at. :shrug:

I let my 87 sit for a couple years and had to siphon the fuel to get it running again, but I can hear the pump prime.
 
#7
Well that did nothing. I don’t want to drop the money on a fuel pump if I don’t have to. If anyone has any other suggestions I’m open to try anything.

Even with 12v to the pink/black wire still didn’t hear the fuel pump. Everything that I can think of is pointing towards that being the issue.
 
#10
LILCBRA said:
Is it getting fuel pressure? If it is, I'd say that the fuel in the tank is bad. Your best bet would be to siphon the old fuel out and replace it with fresh. You'll also want to clear the lines when you do that. The easiest way that I've found was to disconnect the lines at the engine and cycle the key a bunch of times until fresh fuel starts spitting out. You'll obviously need a couple tools to get this all accomplished, these are my recommendations:

www.harborfreight.com

Multi-Use Transfer Pump

Amazing deals on this Multi-Use Transfer Pump at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com

Click to expand...
I’ve always had trouble with the hose on those pumps curling up, and then they’re not getting to the bottom of the tank. Anybody have any tricks that worked to get that hose all the way to the bottom?
 
#11
Have you checked the wiring harness connection just above the fuel tank?

AeroCoupe

Engine Post in thread 'Intermittent CEL with loss of power'

There is a connector between the body harness and the fuel tank harness. This connection is located under the car and behind the bumper. The fuel tank harness has a clip that hold it to the fuel tank on the fuel tank seam and just beyond this is the connector. This is a picture of the connector separated:

IMG_2982.webp


This is a picture of it connected. You can see the clip holding it to the tank in the top left and the connectors are top center.

IMG_2983.webp


This connector can corrode and cause loss of connection for the fuel pump and/or the fuel gauge sending unit.

The other thing...
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If that checks out then drop the tank. Nothing else to do but that to further figuring this out. While you have the tank dropped you should probably install a new fuel neck seal and look the vent over as the seal around them tend to leak as they age.
 
#12
Yes , I separated that connection and am getting the same voltage on there that I’m getting at the fuel pump relay… unless the post you referenced is talking about deterioration at the connection where it makes its way to the pump. I’ll have to drop the tank and check the wires at the pump to see if it’s making it that far I guess.
 
#13
Rdub I believe mine was twisting in the tank also. I tried to siphon out the 5 gallons I added last night and nothing came out. I will just use a piece of 2x4 and a jack to assist in lowering the tank I suppose.
 
#14
AeroCoupe said:
Have you checked the wiring harness connection just above the fuel tank?

AeroCoupe

Engine Post in thread 'Intermittent CEL with loss of power'

There is a connector between the body harness and the fuel tank harness. This connection is located under the car and behind the bumper. The fuel tank harness has a clip that hold it to the fuel tank on the fuel tank seam and just beyond this is the connector. This is a picture of the connector separated:

IMG_2982.webp


This is a picture of it connected. You can see the clip holding it to the tank in the top left and the connectors are top center.

IMG_2983.webp


This connector can corrode and cause loss of connection for the fuel pump and/or the fuel gauge sending unit.

The other thing...
  • Like

If that checks out then drop the tank. Nothing else to do but that to further figuring this out. While you have the tank dropped you should probably install a new fuel neck seal and look the vent over as the seal around them tend to leak as they age.
Click to expand...
I got codes 95 and 96 on my CEL, from my research it seems like those codes reference a failure for the voltage for the circuitry for the fuel pump
 
#15
I’m not 100% sure, but I suspect these pump have a low torque capacity. So, any particle could jam or clog the pump vanes. And the priming noise is just the pump building pressure, so it’s running. If it’s clogged or jammed, it can’t do that. But as others have said, it all starts with dropping the tank. Good luck.
 
#17
Code 95, Post #2:

R

Thread 'Code 95. What is considered the Secondary fuel pump circuit'

So I have the legendary stumble, hiccup, misfire... what ever you wanna call it issue. Comes up with code 95. So what is considered the "secondary fuel pump circuit" vs primary. The only other codes are egr.
93 LX 5.0 T5

Code 96, Post #4:

FoMoCo17

Thread 'Code 96 Repair:'

Got a code 96 on a 1990 Mustang GT. Replaced the fuel pump relay and got the pump from running on continuously. But, for some reason, I keep getting the Code 96 after wiping the memory. Checked wires on secondary circuit. In the process of replacing the EEC relay. All wires on relay read battery/alternator voltage as they should and Pin 19 reads the same so I am unsure what is causing the problem. The tan/green wire that goes to Pin 22 is reading 1.40 volts at the fuel pump relay and 1.15 volts at ECU Pin number 22 ... this doesn't seem right from what I have read. Also, the car...

Referenced these as jrichker always had the goods on this stuff.
 
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Reactions: Shakerhood
#18
Rdub6 said:
I’ve always had trouble with the hose on those pumps curling up, and then they’re not getting to the bottom of the tank. Anybody have any tricks that worked to get that hose all the way to the bottom?
Click to expand...

Not really - I just tried to make sure that the natural curl of the hose ended up pointing down as best I could before I tried using the pump.
 
#20
Could it be the switch got triggered like if you got rear ended? The one on the inside up behind the taillights? I remember I was parallel parked overnight once and tried to start my mustang the next morning and it just kept cranking and cranking, finally figured out the car behind me must’ve bumped me trying to get out and triggered that switch.
 
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Reactions: Shakerhood, Mcmahst and LILCBRA
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