fuel pump won't pump fuel - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > fuel pump won't pump fuel

XJ Rail Sale!The Ruffstuff NOT Universal 4 Link Kit!Vanco Big Brake Kit Promotion!

Reply
Unread 10-27-2013, 03:38 PM   #1
flipit
Registered User
1993 YJ Wrangler 
 
Join Date: Jan 2009
Location: East Bay, CA
Posts: 398
fuel pump won't pump fuel

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.

flipit is offline   Reply With Quote Quick reply to this message
Unread 10-27-2013, 07:46 PM   #2
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,211
Quote:
Originally Posted by flipit View Post
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.
Did you check for continuity on the ground side of the pump?
__________________
Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
laybackman is offline   Reply With Quote Quick reply to this message
Unread 10-27-2013, 07:52 PM   #3
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,211
Pump wiring that is. The ground is on the engine on the passengers side of the block
__________________
Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
laybackman is offline   Reply With Quote Quick reply to this message
Unread 10-27-2013, 08:14 PM   #4
flipit
Registered User
1993 YJ Wrangler 
 
Join Date: Jan 2009
Location: East Bay, CA
Posts: 398
Quote:
Originally Posted by laybackman View Post
Did you check for continuity on the ground side of the pump?
I did,
this afternoon I pretty much traced all the wires, because when I bought the fuel pump, it was new, so I plugged it in, and didn't have the chance to really test it til now, and of course the gas isn't pumping.
the ground grounds, the hot is hot, and the gauge wire goes to the gauge, It was off by 1/4 tank before the problem, but I'm sure it still functions quite properly.
my real hang up was the sending unit.
right before the sending unit is a "connector" (temrinal, plug something, insert correct nomenclature here) so I unhooked it and checked the three incoming wires. once those were all verified, I checked the ground to it's welded spot on top of the fuel sending unit, and that point, along with pretty much the whole unit, is properly grounded.
This is where it got tough for me, and my far from advanced knowledge.
on top of the underneath of the sending unit, there are two prongs, hot, and gauge. starting at the hot prong, the electrical circuit as I noted, is as follows-
Hot prong~left pump bolt^right pump bolt~sending unit ground point.
(~ is a small clip on wire, and the ^ is like, one is the positive bolt, one is negative, hope that makes sense)
attached to the sending unit ground point is the fuel level gauge, which has a wire coming off of it, going to the gauge prong on top.
so, when I plugged the hot wire into the hot prong, the circuit was completed.
for both-(i thought)
so i thought the gauge was pulling too much voltage, sending the pump down to only 1.6 volts (1.9 with good contact)
I'm kinda new to electrical, I've always enjoyed the mechanical aspect much more,
So,
closer to the evening I finally realized it wasn't the same circuit,
it's some kind of weird thing that i can only presume makes sense in the electrical world.
so i pulled off the fuel pump,
took the two cables, put one on the batterys ground terminal,
and one on the positive terminal.
and there was no pumping sound,
no smoke cloud-
nothing...
so i think either i bought a faulty pump,
or way more likely, I broke it along the way.
so I'll be picking a new one up Tuesday.
I dunno, maybe Monday If I have the time.
and we'll see if a new one fixes all my problems.
flipit is offline   Reply With Quote Quick reply to this message
Unread 10-27-2013, 09:30 PM   #5
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,211
There are three wires on your pump. One for power to the pump one for the gauge and one for ground. Test it at the battery with some jumper wires IF you know which wire is which.
__________________
Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
laybackman is offline   Reply With Quote Quick reply to this message
Unread 10-27-2013, 10:17 PM   #6
flipit
Registered User
1993 YJ Wrangler 
 
Join Date: Jan 2009
Location: East Bay, CA
Posts: 398
Quote:
Originally Posted by laybackman View Post
There are three wires on your pump. One for power to the pump one for the gauge and one for ground. Test it at the battery with some jumper wires IF you know which wire is which.
on the pump itself? my pump has two, the hot/power, and the ground. the sending unit has three- well three on top, the ground welds into the top and the other two go through as i mentioned.
flipit is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 07:30 AM   #7
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,211
Quote:
Originally Posted by flipit View Post
on the pump itself? my pump has two, the hot/power, and the ground. the sending unit has three- well three on top, the ground welds into the top and the other two go through as i mentioned.
I misread your answer but that is the three wires I mentioned. Do you know which contact is the hot lead to power the pump?
If you do, then you also know that the ground is the one welded to the pump body.

Two pieces of wire can be used to hot wire the fuel pump to test it. By momentarily touching the hot lead and ground lead using your battery and those wires I mentioned to the pump ground and hot lead contact.
__________________
Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
laybackman is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 10:11 AM   #8
flipit
Registered User
1993 YJ Wrangler 
 
Join Date: Jan 2009
Location: East Bay, CA
Posts: 398
Quote:
Originally Posted by laybackman View Post
I misread your answer but that is the three wires I mentioned. Do you know which contact is the hot lead to power the pump?
If you do, then you also know that the ground is the one welded to the pump body.

Two pieces of wire can be used to hot wire the fuel pump to test it. By momentarily touching the hot lead and ground lead using your battery and those wires I mentioned to the pump ground and hot lead contact.
This is the message You responded to, with the key parts in green and the other words omitted.
I used the two pieces of wire on the unit to test the fuel pump, and I got nothing. and both wires were in good working order, no resistance worth noting.

Quote:
Originally Posted by flipit View Post
I did... I checked the ground to it's welded spot on top of the fuel sending unit...there are two prongs, hot, and gauge. starting at the hot prong...so i pulled off the fuel pump,
took the two cables, put one on the batterys ground terminal,
and one on the positive terminal.
edit. Green was too light so i changed it to green
flipit is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 11:25 AM   #9
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,608
I think you are getting confused on what you are reading. Laybackman is trying to point it out. When you first turn the key to start the jeep, the ecu supplies power by pulling in the relay for a few seconds and then releases, the pump remains unpowered until you turn the key to start. If you are measuring voltage in the rear without the engine running or the key in the start position then you are measuring the voltage from the guage not the power to the fuel pump. You can jumper power at the relay from pin 30 to 87 in the relay socket with a short piece of wire to supply the pump with the key off.

Also if you are trying to measure any resistance the power to the circuit must be off. That means battery disconnected. If you are reading resistance through windings on a motor then the readings will be a short or very low resistance. The windings are just a long piece of wire.
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 11:26 AM   #10
vadslram
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2006
Location: VA Beach
Posts: 4,796
If it don't pump you can't call it a fuel pump now can you?
You seem to have issues with the wide spot in your fuel system
vadslram is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 11:53 AM   #11
flipit
Registered User
1993 YJ Wrangler 
 
Join Date: Jan 2009
Location: East Bay, CA
Posts: 398
Quote:
Originally Posted by Que89YJ View Post
I think you are getting confused on what you are reading.
what I am reading or what he is saying?

Quote:
Originally Posted by Que89YJ View Post
Laybackman is trying to point it out. When you first turn the key to start the jeep, the ecu supplies power by pulling in the relay for a few seconds and then releases, the pump remains unpowered until you turn the key to start.
my PO actually hotwired the fuse box, I'm trying to undo it, but I have more to learn before that- but... in all that, my relay does not click when I turn the key, the starter relay clicks, but the [org/blk -hot- wire] (Wrangler Chilton, pg 6-46) has the 12 volts running through it at all times.
so right now, If i go to the back of the jeep, and unplug the connector of the three wires, the hot currently has the 12v up to that point and beyond. the ground, well, is grounded, and the gauge shows continuity....

Quote:
Originally Posted by Que89YJ View Post
If you are measuring voltage in the rear without the engine running or the key in the start position then you are measuring the voltage from the guage not the power to the fuel pump. You can jumper power at the relay from pin 30 to 87 in the relay socket with a short piece of wire to supply the pump with the key off
if you are telling me that the 12 volts I am measuring is actually the gauge voltage... then I figured out the problem!
someone (possibly myself) (five years ago) attached that 12 volts to the fuel pump, and put the other cable onto the gauge...
if this is the problem that is really embarrassing.
what a dumb mistake to be made...

Quote:
Originally Posted by Que89YJ View Post
Also if you are trying to measure any resistance the power to the circuit must be off. That means battery disconnected. If you are reading resistance through windings on a motor then the readings will be a short or very low resistance. The windings are just a long piece of wire.
for the resistance, I unplugged the two points on the fuel sending unit,
and attached the red meter cable to the left one, and the black to the right.
obviously left and right don't matter, but yes, due to both circuits using the same ground, they in themselves made a full circuit.

Que, I'm really hoping you're right about the circuits, and hopefully they were backward. I've been trying to remember putting the unit in but it's been so long and quick, I don't really remember what happened..
I remember buying the new pump, tossing it in,
and the battery was dead, so we charged it.
we tried to start it but it still didn't start, so we dropped the tank and then my trip was over so I cleaned up and haven't touched it sense.
but maybe, If those volts are only supposed to come in when I start it like your saying, maybe flipping them caused me to fry the pump?
$70 learning mistake if that's it. but i'll take that if it means I can get the engine running again. one step closer to getting back on the road.
flipit is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 12:41 PM   #12
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,608
He hotwired the fuse box? Not sure what you are dealing with!
Here is a link to the Factory manual at Morris:
http://www.jeep4x4center.com/knowledge-base/index.htm

Way better then the Chiltons. Especially in wiring.

Go to P112 on the wiring section:

Pin 1) Blk/Or Ground
Pin 2) DB? Fuel Guage
Pin 3) DG/BK Switched Power from pin 87 of the fuel pump relay
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 01:33 PM   #13
flipit
Registered User
1993 YJ Wrangler 
 
Join Date: Jan 2009
Location: East Bay, CA
Posts: 398
Quote:
Originally Posted by Que89YJ View Post
He hotwired the fuse box? Not sure what you are dealing with!
yeah, there are two random red wires going into the fuse box, I'm not sure where or what to,
so the plan is/was- to get the jeep to start, and make sure all the electrical components work (or well, the wiring anyways, cause most of it didn't work before anyways) and once I know it works before, I'll just kind of "undo" some things that he did, and redo them in a way that makes sense to me.


Quote:
Originally Posted by Que89YJ View Post
Here is a link to the Factory manual at Morris:
http://www.jeep4x4center.com/knowledge-base/index.htm

Way better then the Chiltons. Especially in wiring.

Go to P112 on the wiring section:

Pin 1) Blk/Or Ground
Pin 2) DB? Fuel Guage
Pin 3) DG/BK Switched Power from pin 87 of the fuel pump relay
I hadn't heard of these before, the Chilton works enough to get me by, but yes, I was having a hard time with the wiring,
I just assumed it was something the PO had rigged, cause the DG/BK changes to ORG/BLK right at the connection point i was talking about.
I actually think I am looking at a different manual than you, i went to the online, 93 yj, no wiring systems, so i went to fuel systems, and page 43/66 has a schematic, but i can't read it. i'm downloading the universal right now.
that was a parts manual. oh, haha, scroll down... found it!
okay, so on that schematic on that page, right there.
on that connection in my jeep,
with the key in the off position,
the black green has twelve volts.
the dark blue has 0
and the black orange has 0 (mine looks black pink, but i'll buy black orange.)

all three have continuity and run properly, I see no damage to any wires.
so again, the hot is hot. the ground goes to ground. and the sensor goes to the sensor....
on the bottom connection of that schematic, It doesnt list the colors,
but they change. orange, tan, black, something.......
the hot, stays hot, with all it's voltage, until it goes inside the sending unit,
inside the sending unit there are only two prongs- because the ground is welded on the top.
if I remove the clips from these prongs, they still meter exactly the same. my hot is at 12. my gauge is 0 and continuous.
If I attach the clip that goes to the the fuel pump, the volts drop down to just under two volts.

I feel like i keep reitterating the same thing, even with the manual here now.
all I'm saying is if you need a picture, I'll go out and grab as many as you'd like.

let me know if I'm poorly explaining any part at all.
I really think i just burnt out the fuel pump, but I'd like to avoid doing it again,
so I'm trying to make sure all the wiring is proper...
flipit is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 01:57 PM   #14
flipit
Registered User
1993 YJ Wrangler 
 
Join Date: Jan 2009
Location: East Bay, CA
Posts: 398
Quote:
Originally Posted by vadslram View Post
If it don't pump you can't call it a fuel pump now can you?
You seem to have issues with the wide spot in your fuel system
Sorry man, I get that this is a joke, but i haven't heard of a wide spot before, so the joke is lost on me.
flipit is offline   Reply With Quote Quick reply to this message
Unread 10-28-2013, 02:36 PM   #15
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,608
No, you are explaining it. There should be no voltage with the key off. It is wired wrong. The fact that you have 12 there doesn't tell you everything you need to know except that if that was left on the way it was wired you will kill the battery and or the pump. You need to pull the pdc and check the fuel pump wiring at the relay.

Check your fuel pump by jumping power direct to the pump. You have the pump out so take up front and put power right from the battery to it.
Que89YJ is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.