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fuel pump won't pump fuel

11K views 137 replies 4 participants last post by  flipit 
#1 ·
Alright,
so first off, I have been surfing the web quite a bit trying to find someone else who has answered the problem I am having, but I can't find one yet, unless it's the simple problem of the fuel pump I bought was shot from the factory, or something about it has to be either EFI or TFI? I didn't dig into that because I don't have a clue in what that means, and since i bought the unit from an auto parts store, I hope they were intelligent enough to give me a proper pump.

so, the problem I am experiencing... My gas tank is on hte floor right now, and the fuel sending unit is sitting on top of it. on the top of the unit, where the wiring harness comes in, on the under side, there are two prongs. hot and sensor.
the hot wire reads 12 volts (11.6 now as the battery is slowly draining) when plain, but when I connect the plug, it is significantly lower.( I'd have to go out and meter for an exact number if you need.) when put the ohms meter on the two plugs, there is no resistance through the circuit, the juice flows through the hot, into the pump, out of the pump, into the sensor, and out of the sensor out towards the gauge.
I really am at a loss here,
I'm hoping it was a very stupid, easily fixed mistake, If you need any pictures I can go out and take them-
Thanks in advance for any help anyone might have.
 
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#55 ·
So, if you turn the ignition switch to START or ON that green wire in the fuel pump plug at the gas tank should have 12 volts. If not and you have 12 volts at the terminal board feeding that green wire that green jeep fuel harness wire has a break in it.
 
#62 ·
can we reverse this?
i have 12 volts at START, and ON, and RUN, and OFF, and LOCK, and ACCESSORY, and at KEY OUT OF THE JEEP-

so, going with you (I) should not have 12v when the jeep is off, but only at start or on... and since that is not the case what you are saying is there is a break in the green/yellow wire?
 
#56 ·
Pin 19 should be relay ground. I am really confused why there is 12 on it. If the wiring is still there on the pdc we can use it to switch back in a relay to power the injector, coil.like the asd and another for the fuel pump. That is the way that controller should work. That terminal block on the firewall is hill jack. What you need to do is figure out what circuits are on the terminal strip and figure out how a ground line from pin 19 has power on it.
 
#57 ·
Maybe I am completely wet here but from what I can see the PNK/BK wire is a constant 12v source for fuel pump power BUT is also controlled by the position of the inertia switch. The fuel pump relay is powered by the YL wire BUT is controlled by the PCM power relay to close (turn on) power to close itself and the fuel pump relay also.

Is the LT BLU/OR wire do going to pin #22 the clutch pedal or NSS switch the the ground you want to see?
 
#58 ·
LOL Layback you rock. Looked at it and you are 100% right. I think I had too many Jamesons last night! Pin 19 still cannot be power. It must be a sense line because it would be hot all the time and give constant power to the pump. It isnt the control line, pin 22 definitely is. Why is there 12 volts on pin 19? Is it spliced somewhere? Layback you nailed it! Flipit, we need to make sure that the line is power going to the tank from that terminal block and the wire and if it is where is the wire it connects to on the terminal block getting power from.
You dont ever hear me admit to this and if you tell the GF I will deny itbut I was wrrr.....wrrrrr......wrong ok! LOL
 
#59 ·
You weren't wrong...you might have just temporarily veered away from absolute perfection!! :cheers: :cheers: :cheers: :cheers:
 
#67 ·
That is what we were talking about. I just got 19 confused with 22 and I still dont know where the pump power is coming from and what else is on the terminal strip. A fuel pump relay and an asd relay is a must. The pdc is there, the question is what to wire to what.
 
#70 ·
That is what we were talking about. I just got 19 confused with 22 and I still dont know where the pump power is coming from and what else is on the terminal strip. A fuel pump relay and an asd relay is a must. The pdc is there, the question is what to wire wo what.
"The pdc is there, the question is what to wire wo what"

And that is the $64,000.00 question!!!!!!

If the fuel pump is getting constant power it won't live long and the OP
couldn't keep his battery charged!

flipit; Was this YJ a recent purchase??
 
#71 ·
He bought it before he went active duty and parked it for a few years! He's a Jar Head and damn proud of it.
 
#73 ·
okay, starting off, this is my engine compartment,
here is all the stuff



and this is the current condition of my interior-



please not, unless i say otherwise, during all testing,
this is the current position of the key



and in case there are any questions about the quality of this job,
this is under my battery...

 
#74 ·
okay, for this journey,
I'm going to start it off nice and easy-
these three wires connect to the fuel pump connector-



now, from bottom to top-
the ground wire,
note the color, black, with an orange stripe,
goes into the bay, and is screwed into the firewall here.
not the yellow crimp, kinda hard to see i know-



if there's a break in this wire, It touches another grounding point,
cause to the best of my knowledge this line works as advertised.

next up is the gauge,
most of the way up the line,
he cut the dark blue cable and spliced it,
then re spliced it at the end,
shown by the following pictures...




this line as well,
when the jeep started up, the tank was always 1/4 tank high, but it did work.

now for the painful wire,
dk grn/blk...

that cable makes a snug, straight shot here-



bottom right of terminal board-
then,
top right,
green/yellow, goes into here..



the excess is zipped tied,
and the end is add-a-spliced here.



if you follow the stock green/yellow, it is pinned on one side via the connector,
and the other goes into pin 19 of the ECU...



while undoing the wiring harness i found these two open wires...

and this guy is pin 22.

if i have the time, I can make a wiring diagram for all that,
but honestly i think that describes it well.
what else should i chase?
you want me to remove the ECU plug and see if 22 is coming in hot?
 
#75 ·
If that PDC harness is there you are in good shape. The pump failed because of continuous power. Figure out what is powered on that strip and from where. You should have auto shutdown relay power going to the injectors, coil and switch ignition power into the ecu and O2 heater. The fuel pump should be on a second relay. That wiring diagram Labackman posted is perfect. If you have that with the FSM In Morris4x4 you should be able to figure it out with his help. I am just confusing things so I am taking a back seat on the thread. Layback has it right and did all along.
 
#76 ·
alright, so just to see what happened,
I pulled the ECU,
it's off, and sitting on the bench momentarily.
I held up the ECU connector...
and...
pins 1 and 19 are hot. 22 is not hot.

I believe I chased wire 1,
back to this

so i think 1 is supposed to be hot at all times from the mustang diagram here,
but It's not right that the green/yellow is hot.
I'm going to chase that one arouind a bit...
 
#78 ·
I'm not sure I want to get any closer...
It's getting crazy.
Here's the latest scoop...
I pulled the battery,
opened the pdc.
decided I'd try to chase the Blk/grn and see where it dead ends, and maybe i could link back up to stock or something right?
haha, I'll show you some pictures of what i found...
it's awful,
I'm taking a lunch break, doing some math homework,
then maybe going back to it
This part I'm definitely going to need some help with,
I just don't even know where to start.
It's nuts!

oh i forgot, that last picture up there with all the red cables,
yeah, the two hot wires that go into my pdc,
one goes to the starter, and the other to the asd
 
#79 ·
the excess is zipped tied,
and the end is add-a-spliced here.



if you follow the stock green/yellow, it is pinned on one side via the connector,
and the other goes into pin 19 of the ECU...

QUOTE]

Whate is that green plug supposed to plug into? And, is that a relay hanging next to that green plug?
 
#80 ·
That is a relay socket. Look at the wire colors going into it and see what it goes to. It looks like the fuel pump relay.
 
#82 ·
that link shows these color wires; That is different from the one I posted. Which color wires does your ECU have flipit??

Pin # Wire Color Connections for a 88-93 5.0L HO Mustang Value at Idle
01 YEL +12 Battery Voltage 12-14 volts
03 DG/WHT VSS + / Vehicle Speed Sensor Positive 55MPH = 125hz
04 DG/Y IDM / Ignition Diagnostic Monitor (TFI) 20-31hz
06 ORG/YEL VSS – / Vehicle Speed Sensor Negitive 55MPH = 125hz
07 LG/RED ECT / Engine Coolant Temp Sensor 0.5 volts = 200*F
09 TAN/BLU MAF RTN / Mass Air Flow Return < 0.1volts
12 BRN/YEL Fuel Injector 3 4.9-5.2ms duty cycle
13 BRN/BLU Fuel Injector 4 4.9-5.2ms duty cycle
14 TAN/ORG Fuel Injector 5 4.9-5.2ms duty cycle
15 LG/ORG Fuel Injector 6 4.9-5.2ms duty cycle
16 BLK/ORG Ignition Ground (TFI) -
17 TAN MIL / Engine Light & STO / Self-Test Output ON = GND
19 DG/YEL FPM / Fuel Pump Monitor Pump on = 12-14volts
20 BLK Ground < 0.1volts
21 WHT/BLU IAB / Idle Air Bypass 3.0 – 12.0 volts
22 BLU/ORG FPR / Fuel Pump Relay ON = GND
25 GRAY ACT / Air Charge Temp Sensor 3 volts = 70*F
26 ORG/WHT Voltage Reference 4.9-5.1 volts
29 DK GRN Right HEGO 0.0-1.0 volts
30 BLU/YEL Transmission Neutral Interface 0.0 volts in neutral
36 YEL/LGRN SPOUT / Spark Output Signal (TFI) -
37 RED EEC Relay +12 volts 12-14 volts
40 BLK Ground < 0.1 volt
42 TAN/RED Fuel Injector 7 4.9-5.2ms duty cycle
43 DK BLU Left HEGO 0.0-1.0 volts
45 GRN/BLK BP / Barometric Pressure Sensor 159hz = sea level
46 GRY/RED Signal Return 0.1 volts
47 DK GRN TPS / Throttle Position Sensor 0.9 volts
48 TAN/RED STI / Self-Test Input GND = Self-Test
49 ORG Ground < 0.1 volt
50 BLU/RED MAF / Mass Air Flow Sensor 0.8 volts
52 LT BLU Fuel Injector 8 4.9-5.2ms duty cycle
56 DK BLU PIP / Profile Ignition Pickup (TFI) -
57 RED EEC Relay +12 volts 12-14 volts
58 TAN/RED Fuel Injector 1 4.9-5.2ms duty cycle
59 TAN/ORG Fuel Injector 2 4.9-5.2ms duty cycle
60 BLK Ground < 0.1volt
 
#83 ·
pin 3 is grey/black.

both of those are very similar, but you were right on the first one.

Right now I'm off to school, but tonight tomorrow I'll be trying to shoot some wires by the ignition and see what's sending the heat.
the green connecter has three green/yellow cables coming out, one goes to the ecu, one to fuel pump, and one goes into the wiring harness. that one is the hot line, so I'm going to try to find whatever it's connected to. but i also have to write an esay by 6pm tomorrow, so It's going to be a bit chopppy
 
#84 ·
the green plug doesn't plug, i believe it used to plug into the mustang dash- or a connector to route over there for that thing we were talking about before, so the OP removed it, cut the wire, and spliced it in himself.
 
#90 ·
and from a mustang forum in a place,
a member said
"If memory serves me correcly, the green connector goes off to the fuel pump relay."
not that that is really important at the moment, but it's an answer, and might help with the future clean up
 
#91 ·
It is important because the Ford product this harness and ECU you have in your YJ used a fuel pump relay originally. It was controlled by the ignition circuit.

I think the answer lies in that terminal board which seems to be the major point (possibly not the only point) where Mustang wiring meets YJ wiring.
 
#93 ·
If you wanted to get this running you could wire in that relay with 4 wires and have it controlled through a relay by the ECU the way it should be.
 
#95 ·
very true.
The problem there is-
that's a quick fix.
There is a lot of dangerous wiring in this rig,
and as I know you are well aware,
that could come with some very negative repercussions.

I have a hot wire that isn't supposed to be hot-
well i haven't started the car since that wire became hot.
what else is hot?
I can't just leave a loose hot wire,
that's just begging for more problems.

I'd love to get this engine fired up,
but even so,
this jeep won't leave the garage before 2014.
 
#102 ·
Going by the diagram LBM posted sinse the wiring colors seem to match, you have 4 power lines, none of which you have located a fuse for. These are the circuits that need to be wired in to make it run and IMO the 4 that need to be rewired.

Fuel pump pink/black
PCM power relay Yellow
O2 sensors Grey Yellow
Ign coil Red/Lt Green

You are missing 2 key relays
1) Fuel pump
2) Pcm power

And you currently have a constant power from some unknown circuit powering back through to feed the fuel pump.
Add on top of this you have a terminal strip just screwed into the bulkhead with live power.

You are fighting hard to trace down 1 circuit but look at the big picture here. Even if you got the fuel pump taken care of I would not drive this jeep around the block until you get the other stuff taken care of but its your call. I had you look over on the bulkhead connector and the ignition switch to try and chase down which circuits are wired into those 4. Did you narrow it down? You are going to have to keep pulling circuit to figure out which one he tapped into to wire it up. If it is unfused it wouldnt surprise me at this point!
 
#103 ·
Going by the diagram LBM posted sinse the wiring colors seem to match, you have 4 power lines, none of which you have located a fuse for. These are the circuits that need to be wired in to make it run and IMO the 4 that need to be rewired.

Fuel pump pink/black
PCM power relay Yellow
O2 sensors Grey Yellow
Ign coil Red/Lt Green

You are missing 2 key relays
1) Fuel pump
2) Pcm power

And you currently have a constant power from some unknown circuit powering back through to feed the fuel pump.
Add on top of this you have a terminal strip just screwed into the bulkhead with live power.

You are fighting hard to trace down 1 circuit but look at the big picture here. Even if you got the fuel pump taken care of I would not drive this jeep around the block until you get the other stuff taken care of but its your call. I had you look over on the bulkhead connector and the ignition switch to try and chase down which circuits are wired into those 4. Did you narrow it down? You are going to have to keep pulling circuit to figure out which one he tapped into to wire it up. If it is unfused it wouldnt surprise me at this point!
I agree with you Que, BUT this supposedly ran at one time. Then he went away then it wouldn't start when he came back.

Then he tore out the interior. Change can cause problems. Flipit tore out the interior. IF this YJ ran at one time and he could get it running again would be nice just to see what the PO did. Then this YJ needs a whole rewire....FOR SURE!!

What is left of the YJ harness? How much of the Mustang wiring is there? (relays seem to be removed OR bypassed) was used are the two $64,000.00 questions.
I need to know what the wiring in the Mustang ECU does.
Looking at any wiring schematic power always come from the top when possible.

On the stock Mustang wiring diagram, the wiring for the fuel pump constant power to the relay for the fuel pump is the PNK/BLK wire which is a fusible link. Power to the PCM and then the Fuel pump relay is the Yel wire that also has a fusible link. That makes sense. RD wire.

The Lt BLU ORG wire has to be ground. That closes the PC relay allowing voltage to flow through the PCM relay via the RD wire and close fuel pump relay allowing the both relays to close and and allows power to go through the FP relay to the fuel pump...or I am completely stumped! Maybe I better hit the bottle of jameisons :cheers::cheers:
 
#104 ·
:) Jamesons

Yeah, I had him hook his meter up to the fuel pump circuit so he could see the 12 volts and start pulling the circuits like the ignition switch and the bulkhead connector to see if we could narrow the circuit down. Fuses were next if the bulhead worked.
 
#109 ·
it seems under further testing, that both "broken fuel pumps" still spin when hotwired to the battery. I know i said before they didn't. I am a bit embarassed to say they both are spinning now.

I went out to test the old one, and it came on decently easily, and so pump number two, i kind of tapped on the battery, it wasn't sparking or anything... all of a sudden it sparks, and after a couple more taps, it spins. but these pictures here will really get you... or at least, they got me

this is a circuit here,
You'll see the pump is plugged in as it's supposed to be, with the ground wire and ground point seperated by multimeter. the meter has 12 volts going through it, but i can't get the pump...to....pump!




 
#110 ·
That is good news! I had to know that the pump(s) were NG before moving on. If the pump is installed and it gets 12 volts and ground it should run.

There was/is a crankshaft position sensor mounted into the top of your bell housing. On a YJ the wiring from the crank sensor comes up to the main YJ harness just to the left of the MC and brake booster. Is it still there and is it connected?

Mustangs use a crank sensor also. If the crank sensor sees no movement you get no spark or fuel after an extended period of cranking with a no start situation

If ones battery is not fully charged the electronics often prevents the car from starting by disabling the spark and fuel.

I think the fuel pump and fuel tank aren't the problem. Did you change the inline fuel filter at some time recently? If not I would change it.

I just went through my Son's Mustang FSM and there is no detailed section for wiring diagrams and connector pin outs like a Wrangle FSM has. It seems that the Ford turd have yet a second manual for that.

Time for bed
 
#111 ·
That is good news! I had to know that the pump(s) were NG before moving on. If the pump is installed and it gets 12 volts and ground it should run.
what?! the pump only runs sometimes, straight on battery power, it's like twelve volts is not enough or something, cause only hotwired makes it spin,
but when i install and ground it it has he same voltage, but will not turn... Im missing the good news...

There was/is a crankshaft position sensor mounted into the top of your bell housing. On a YJ the wiring from the crank sensor comes up to the main YJ harness just to the left of the MC and brake booster. Is it still there and is it connected?
I really doubt it, but will check tomorrow, remind me if i forget-

Mustangs use a crank sensor also. If the crank sensor sees no movement you get no spark or fuel after an extended period of cranking with a no start situation
if both use it i should have one... should...
so, how do i reset that?
If ones battery is not fully charged the electronics often prevents the car from starting by disabling the spark and fuel.
i mean, I can trickle charge it all the way up, cause it's down to what, 12.25 now? think that's waht it was with those pictures, either way, yeah, I'll max it out again, wouldn't be the first time though so dont get any hopes up

I think the fuel pump and fuel tank aren't the problem. Did you change the inline fuel filter at some time recently? If not I would change it.
the fuel filter has not been changed, but if i remove it, then i should be able to pump fuel through the hose and out ont othe floor correct? it won't do that, I have removed the filter then reinstalled.

I just went through my Son's Mustang FSM and there is no detailed section for wiring diagrams and connector pin outs like a Wrangle FSM has. It seems that the Ford turd have yet a second manual for that.
I have never been a huge fan of ford. I know- I'm practically wheeling a ford, but, I just, i mean i like the other companies better, but Ford does have some things i like.

Time for bed
 
#113 ·
so look there, the green yellow is supposed to be hot at all times... wow... that seems weird to me, but okay, I'll take that i guess.
so... as far as we can tell...
everything works like advertised.. except, when i put it together-
so the plan is, to clean every connection?
 
#115 ·
In the stock configuration the DK GRN/YEL wire is supposed to be hot ONLY when the relay that controls the power to the fuel pump is closed by the ignition which first closed the PCM relay switch. The feed for that side of the fuel pump relay was the fused PNK/BLK wire.
 
#114 ·
That is back to what I was saying in my post. You need to find puree to those 4 wires. See how they are wired in. I am betting the ignition switch or the bulkhead.
 
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