No volts to the fuel pump - JeepForum.com

Reply
 
LinkBack Thread Tools
post #1 of 42 Old 11-19-2012, 07:50 PM Thread Starter
JeepComanche89
Registered User
1989 MJ Comanche 
 
Join Date: Jan 2012
Posts: 3,101
No volts to the fuel pump

Well i went to try to start my comanche today after my engine swap (88 4.0 to 89 4.0). The engine will crank great, but no voltage is being sent from the fuel pump. Were thinking that it might be the fuel pump relay, but it looked fine. Any other ideas before i go replacing stuff. Thanks in advance.

JeepComanche89 is offline  
Sponsored Links
Advertisement
 
post #2 of 42 Old 11-19-2012, 09:04 PM
DeejayZeejay
Registered User
1994 ZJ 
 
Join Date: Mar 2012
Location: Macomb
Posts: 325
Check the wiring where it goes through the grommet to the inside of the tank. That was my problem. Pump was still good.

Jeeps 4 Life!
DeejayZeejay is offline  
post #3 of 42 Old 11-19-2012, 09:18 PM
cruiser54
Web Wheeler
 
cruiser54's Avatar
1990 MJ Comanche 
 
Join Date: Oct 2009
Location: Prescott
Posts: 11,229
Do you for sure have spark?

If you own a Renix Jeep, you'll want to check this out.

An index to over 30 write-ups can be found in the link below


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


My Jeep Technical Photos


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
cruiser54 is offline  
post #4 of 42 Old 11-20-2012, 05:52 AM Thread Starter
JeepComanche89
Registered User
1989 MJ Comanche 
 
Join Date: Jan 2012
Posts: 3,101
Quote:
Originally Posted by DeejayZeejay
Check the wiring where it goes through the grommet to the inside of the tank. That was my problem. Pump was still good.
I have a brand new pump, so i know the pumps good. And I checked the plug that comes out of the cab with a meter and nothing was being sent.
JeepComanche89 is offline  
post #5 of 42 Old 11-20-2012, 05:52 AM Thread Starter
JeepComanche89
Registered User
1989 MJ Comanche 
 
Join Date: Jan 2012
Posts: 3,101
Quote:
Originally Posted by cruiser54
Do you for sure have spark?
Starting is not the issue just yet because i know for sure the pump is not running.
JeepComanche89 is offline  
post #6 of 42 Old 11-20-2012, 05:57 AM
cruiser54
Web Wheeler
 
cruiser54's Avatar
1990 MJ Comanche 
 
Join Date: Oct 2009
Location: Prescott
Posts: 11,229
Quote:
Originally Posted by JeepComanche89 View Post
Starting is not the issue just yet because i know for sure the pump is not running.
Do you have power at the ballast resistor on the driver's side inner fender?

How about to terminal #30 in the fuel pump relay receptacle?
Power to terminal #86 when key turned to Start?
Attached Thumbnails
Ballast Resistor.jpg   renix relay center.jpg  

If you own a Renix Jeep, you'll want to check this out.

An index to over 30 write-ups can be found in the link below


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


My Jeep Technical Photos


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
cruiser54 is offline  
post #7 of 42 Old 11-20-2012, 08:19 AM Thread Starter
JeepComanche89
Registered User
1989 MJ Comanche 
 
Join Date: Jan 2012
Posts: 3,101
Thanks, that helped alot. I will check today when i get home.
JeepComanche89 is offline  
post #8 of 42 Old 11-20-2012, 08:35 AM
97_4popper
Registered User
1990 MJ Comanche 
 
Join Date: Jan 2005
Location: Guston
Posts: 469
Ground for the whole back of the truck is a small wire behind one of the taillights. I just put a ground strap on mine from the cab to the bed and solved all of my problems.

90 MJ 4.0 4X4 5sp LB Pioneer Big Ton.
Truck contains parts from 3 MJs, 2 XJs, 1 TJ and a dishwasher.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Check out comancheclub.com...
My build thread:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Wifes: 97 TJ 2.5 4X4 5sp 31's stock. . . Slow but; reliable.
97_4popper is offline  
post #9 of 42 Old 11-20-2012, 10:25 AM
DeejayZeejay
Registered User
1994 ZJ 
 
Join Date: Mar 2012
Location: Macomb
Posts: 325
Just a strap by itself? Or did you connect anything with it?

Jeeps 4 Life!
DeejayZeejay is offline  
post #10 of 42 Old 11-20-2012, 10:53 AM Thread Starter
JeepComanche89
Registered User
1989 MJ Comanche 
 
Join Date: Jan 2012
Posts: 3,101
Quote:
Originally Posted by 97_4popper
Ground for the whole back of the truck is a small wire behind one of the taillights. I just put a ground strap on mine from the cab to the bed and solved all of my problems.
Hmm, ill take a look because my bed is off right now and i just have the tank on the floor. But i dont think a ground could be the whole problem
JeepComanche89 is offline  
post #11 of 42 Old 11-20-2012, 11:44 AM
97_4popper
Registered User
1990 MJ Comanche 
 
Join Date: Jan 2005
Location: Guston
Posts: 469
Nothing else. Just a ground strap from the cab to the bed. The bed has a hard time with grounds sometimes so this is another place to be grounded from.
The cab has a good ground already so this just makes another connection.

90 MJ 4.0 4X4 5sp LB Pioneer Big Ton.
Truck contains parts from 3 MJs, 2 XJs, 1 TJ and a dishwasher.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Check out comancheclub.com...
My build thread:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Wifes: 97 TJ 2.5 4X4 5sp 31's stock. . . Slow but; reliable.
97_4popper is offline  
post #12 of 42 Old 11-20-2012, 11:47 AM
97_4popper
Registered User
1990 MJ Comanche 
 
Join Date: Jan 2005
Location: Guston
Posts: 469
Quote:
Originally Posted by JeepComanche89 View Post
Hmm, ill take a look because my bed is off right now and i just have the tank on the floor. But i dont think a ground could be the whole problem

It may not be the whole problem, but it is a known issue with these trucks. I found out about it when I replaced the bed when my son still owned the truck. He had an accident and we put a new bed on it. The fuel pump wouldn't fire. I found about the little wire behind the tail light. Then I added the ground strap.
I haven't had any electrical weirdness on the fuel pump or tail lights since I added this strap.

90 MJ 4.0 4X4 5sp LB Pioneer Big Ton.
Truck contains parts from 3 MJs, 2 XJs, 1 TJ and a dishwasher.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Check out comancheclub.com...
My build thread:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Wifes: 97 TJ 2.5 4X4 5sp 31's stock. . . Slow but; reliable.
97_4popper is offline  
post #13 of 42 Old 11-20-2012, 11:48 AM
97_4popper
Registered User
1990 MJ Comanche 
 
Join Date: Jan 2005
Location: Guston
Posts: 469
If your fuel pump is on the floor, then it could be your problem.
Run a ground wire from the tank to the chassis and see if the fuel pump fires.

90 MJ 4.0 4X4 5sp LB Pioneer Big Ton.
Truck contains parts from 3 MJs, 2 XJs, 1 TJ and a dishwasher.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Check out comancheclub.com...
My build thread:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Wifes: 97 TJ 2.5 4X4 5sp 31's stock. . . Slow but; reliable.
97_4popper is offline  
post #14 of 42 Old 11-20-2012, 12:33 PM Thread Starter
JeepComanche89
Registered User
1989 MJ Comanche 
 
Join Date: Jan 2012
Posts: 3,101
I will definatly look into the ground. However im not getting any volts at the plug that comes from the grommet in the passengers floor pan. Im pretty sure its the resistor mentioned earlier is the problem. Im going to figure it out tonight
JeepComanche89 is offline  
post #15 of 42 Old 11-20-2012, 03:08 PM Thread Starter
JeepComanche89
Registered User
1989 MJ Comanche 
 
Join Date: Jan 2012
Posts: 3,101
Is it possible that my comanche, 88 does not jave a ballast resistor tht was mentioned above? I cannot find any wires that would go to it.
JeepComanche89 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









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.




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



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