fuel pump only getting 7 volts ?!?!?!? - JeepForum.com
 8Likes
Reply
 
LinkBack Thread Tools
post #1 of 42 Old 04-22-2004, 12:53 AM Thread Starter
tobrz
 
Join Date: Oct 2003
Posts: 63
fuel pump only getting 7 volts ?!?!?!?

1995 4 cyl stick
ok so the other day the thing quit running, everyone says its the fuel pump......after an hour of trying to pull the bolts off of the rusted sheild, i get the tank off......sure enough not pumping....so i put in the new one, plug in the harness to test to see if it works, and the new one doesnt work.....bring out the voltmeter.....test the connector, its only registering as 7 volts, so i take some wire and hook the old pump up to my battery, the thing works!!!! it says right on it that it is 12 volts......why would at the tank it only be 7 volts....i swapped relays, checked fuses, everything, doesnt work...HELP!!!!!!!!!!!!!!!!!

tobrz is offline  
Sponsored Links
Advertisement
 
post #2 of 42 Old 04-22-2004, 01:11 AM
Sarge37
 
Join Date: Oct 2001
Posts: 165
Have you checked your battery? Maybe you ran it down trying to start your jeep. Believe it or not. My Jeep died and I was convinced it was the fuel pump because it had been making a whining sound. Well I dropped the tank and was suprised when I found the fuel tank empty. Yea I know the gauge read 1/2 tank and I keep track of my mileage. Anyway sometimes in our anxiety to fix something we miss the obvious. Hook up your rig to another vehicle with jumper cables and then check the voltage.
BTW the whining sound was the sound of the pump without any fuel around it.
Hope this help.
Sarge37 is offline  
post #3 of 42 Old 04-22-2004, 01:16 AM Thread Starter
tobrz
 
Join Date: Oct 2003
Posts: 63
yup battery is good, it was just replaced, tested everywhere else all reads 12, fuel cell is half full....the pump in the tank doesnt do anything at all, but the old one, like i said, hooked up to a 12 volt source pumps, i just turn the jeep almost all the way on to see if the pump is pumping
tobrz is offline  
 
post #4 of 42 Old 04-22-2004, 01:24 AM
Sarge37
 
Join Date: Oct 2001
Posts: 165
Quote:
Originally Posted by tobrz
yup battery is good, it was just replaced, tested everywhere else all reads 12, fuel cell is half full....the pump in the tank doesnt do anything at all, but the old one, like i said, hooked up to a 12 volt source pumps, i just turn the jeep almost all the way on to see if the pump is pumping

If the fuel lines are connected the pump will energize and pump until it reaches a certain pressure then turn off. With the engine running you cannot hear the pump running unless its almost out of gas. Like I said you will hear the pump energize when you turn on the key. Once it pressurizes the system it cuts off until the engine is running. Maybe you have a bad fuel pressure relay.
Sarge37 is offline  
post #5 of 42 Old 04-22-2004, 06:20 AM Thread Starter
tobrz
 
Join Date: Oct 2003
Posts: 63
Quote:
Originally Posted by Sarge37
If the fuel lines are connected the pump will energize and pump until it reaches a certain pressure then turn off. With the engine running you cannot hear the pump running unless its almost out of gas. Like I said you will hear the pump energize when you turn on the key. Once it pressurizes the system it cuts off until the engine is running. Maybe you have a bad fuel pressure relay.
we were running it with no fuel lines attached to see if any gas would spurt out, none did, the relay i swapped out with each of the others that were the same part number to test, i am stumped
tobrz is offline  
post #6 of 42 Old 04-22-2004, 07:51 AM Thread Starter
tobrz
 
Join Date: Oct 2003
Posts: 63
the dealer says that there are no other electrical components between the relay and the pump, so it must be a wire
tobrz is offline  
post #7 of 42 Old 04-23-2004, 12:30 AM Thread Starter
tobrz
 
Join Date: Oct 2003
Posts: 63
Quote:
Originally Posted by tobrz
the dealer says that there are no other electrical components between the relay and the pump, so it must be a wire

i reran wires tonight, i have 12 volts in the rear by the pump, still, neither the old pump nor the new pump runs!!! as is before i can run it off the battery, i checked amperage, and its reading .09A, what the hell is the problem!!!! help me please!
tobrz is offline  
post #8 of 42 Old 04-23-2004, 01:04 AM
blackw
 
Join Date: Oct 2003
Posts: 99
Sorry dude, can't help you but I got a question if you don't mind me asking. Do you have to drop the fuel tank to get to the fuel pump? That sounds like a pain in the a$$. Is there any mods to get an external fuel pump?
blackw is offline  
post #9 of 42 Old 04-23-2004, 07:36 AM
MarathonScott
 
Join Date: Jan 2004
Posts: 11
I hate to get into something that i don't completely understand; my jeep doesn't have the electric pump, but I know a *little* about 12 volt systems. While you are checking the amp draw and you come up with a reading of .09A, turn your meter to volts and see if you still have your 12 volt reading. I'll bet that the voltage drops to near zero while under a load.

It sounds to me that you have a connection that is just barely working someplace. Most often I find that it is the ground lug, by wiggling the wire you might find that it is about to break. But if it is a bad connection in the wiring, it could be anywhere at any of the connections. To pinpoint the problem you will probably have to test the circuit while under a load. If you don't want to use the pump as a 'test load', use a tail light bulb or some other light that will draw a few amps to give yourself an honest test. Using the light bulb would get around the question of how long the pump would run.
MarathonScott is offline  
post #10 of 42 Old 04-23-2004, 07:58 AM Thread Starter
tobrz
 
Join Date: Oct 2003
Posts: 63
Quote:
Originally Posted by blackw
Sorry dude, can't help you but I got a question if you don't mind me asking. Do you have to drop the fuel tank to get to the fuel pump? That sounds like a pain in the a$$. Is there any mods to get an external fuel pump?

u can run the pump dry, i did it right off the battery in my hand, i found the problem i THINK, im at work so i cant try it.

i made 654964 phone calls, to all my friends,and finally one to a good buddy who owns a shop....he tells me that if i set the key on run, the computer will only engauge the relay for 2 seconds to pressurize, and after that it will kill it, i am assuming this is my problem, as i just left it on run all night when i was testing
tobrz is offline  
post #11 of 42 Old 06-05-2019, 10:22 PM
Louie4
Injanir
 
Louie4's Avatar
1993 YJ Wrangler 
 
Join Date: Aug 2008
Location: Phoenix
Posts: 11,816
I’m brining this up again because I now have the same problem. I believe my pump is toast but I’m getting 7 volts to the plug. With a battery charger I get 8 volts.

Doesn’t seem right to me. The pump is the larger Bosch and the original OEM from the factory.

What should I check next?
Louie4 is offline  
post #12 of 42 Old 06-06-2019, 05:51 AM
Siva283
Registered User
 
Siva283's Avatar
1993 YJ Wrangler 
 
Join Date: May 2011
Location: Baltimore
Posts: 4,490
Quote:
Originally Posted by Louie4 View Post
I’m brining this up again because I now have the same problem. I believe my pump is toast but I’m getting 7 volts to the plug. With a battery charger I get 8 volts.

Doesn’t seem right to me. The pump is the larger Bosch and the original OEM from the factory.

What should I check next?
Check your pump ground. YOu can cut it and ground it to the frame right by the tank. Thats one of the things Que89yj will tell you to do. You should also check the power wire to see if corrosion is causing resistance or save your self the trouble and run a new power wire. Usually that voltage drop is from the ground or corrosion on the power wire.
Awesome and Stitch586 like this.

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

Quote:
Originally Posted by Magnum View Post
I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim
Quote:
Originally Posted by ldso View Post
. It started with a $200 axle, and a few thousand dollars later I was done :)
Quote:
Originally Posted by Luuca View Post
diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...
Quote:
Originally Posted by Overhead View Post
this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
Siva283 is offline  
post #13 of 42 Old 06-06-2019, 05:52 AM
Siva283
Registered User
 
Siva283's Avatar
1993 YJ Wrangler 
 
Join Date: May 2011
Location: Baltimore
Posts: 4,490
An even quicker test run a test wire from battery to pump and another on from ground to a ground right there on the frame.

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

Quote:
Originally Posted by Magnum View Post
I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim
Quote:
Originally Posted by ldso View Post
. It started with a $200 axle, and a few thousand dollars later I was done :)
Quote:
Originally Posted by Luuca View Post
diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...
Quote:
Originally Posted by Overhead View Post
this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
Siva283 is offline  
post #14 of 42 Old 06-06-2019, 06:05 AM
1project2many
Registered User
1995 YJ Wrangler 
 
Join Date: Oct 2018
Location: Lakes Region
Posts: 305
My first question is where are you connecting the ground for the meter? If you are using a ground wire in the harness or touching it to the tank it would be better imo to clean a spot on the frame and connect the meter ground lead there while checking for 12V. I would also remove the relay and jumper between terminals 30 and 87 to provide a source of constant power during testing. If your meter shows 12V with a good ground but less than 12V using the harness connection, that's an indication you have a problem in ground connection in the harness.
1project2many is offline  
post #15 of 42 Old 06-06-2019, 07:58 AM
jtec
Registered User
2014 JK Wrangler 
 
Join Date: Oct 2017
Posts: 6,300
there are 3 wires at fuel pump,
with KOEO - what voltages are you seeing on which wire? tell us color

GTG
Attached Images
 

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
jtec is offline  
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.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
Replace Fuel Pump or Fuel Pump/Sending Unit assembly? Muratus TJ Wrangler Technical Forum 10 02-09-2012 09:08 AM
inline fuel pump or new tank with pump in it? cubbybear YJ Wrangler Technical Forum 2 12-25-2008 05:13 PM
Fuel pump assembly vs. fuel pump? eclipse27 TJ Wrangler Technical Forum 11 11-11-2008 09:18 AM
Why Only 2 volts going to the fuel pump harness... rgs112 YJ Wrangler Technical Forum 6 08-18-2008 07:31 PM
Electric Fuel Pump Issue, NOT pump 1995yj1978cj YJ Wrangler Technical Forum 4 05-28-2005 12:12 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome