I have a problem with my harness that feeds power to the lift pump. The 4 pin harness that feeds into my tank, has no power on pin number 4 which is lift pump hot. How can I figure this out. I am an electrician so I know ectrical theory. I also know that power comes from the ecm. How can I figure out why I do not have 12v at the end of the harness????? any body
__________________

 

I'm wondering if it is a timing issue here. The pump only runs for so many seconds with the key on. Try bumping the engine, but not starting it, and keep the key in the 'on' position. Then go down and see how many volts you have. I don't remember how many seconds you have, 20-40 or so. Somebody will chime in with the correct answer.

 

no matter what I do with the key I do not get power and i am using my test light to confirm with a good ground

 

no matter what I do with the key I do not get power and i am using my test light to confirm with a good ground. even if I bump it

 

bump!! bump

 

First of all, Don't use a test light. It will light with 5 volts or 12 volts. Use your meter (VOM). Test lights will and can get you in trouble. Why are you testing the circuit? Yes, the ECM turns on the fuel pump but it goes through a relay circuit for proper current draw. Find the fuel pump relay and start there. You can jump it hot to eleminate that part of the circuit.

 

I understand that I could jump the relay but, Where is the thing. I thought it is integrated into the ecm. not a cube relay. I don't know where it is. Is there a fuse for said relay? ANd I'm checking this because my pump is not getting power and I installed the knew fass harness and the trigger wire for the pump on the truck's harness has no power and i'm also getting 0 volts dc
I do appreciate the help and give me suggestions if you have them.

 

I forgot this is a CAN Bus system. Without a book it is going to be tough to figure out. If it has a relay it will be under the hood in the fuse box by the driver battery.


Edited: The CAN Bus started in 06'.

 

Are you getting any codes from the ecm?

 

I Am Not Getting Any Codes

 

What color wire are you checking? How do you know which one is supposed to be hot. I just read that when you turn the key on the pump is engaged for 2 sec. then when you bump the starter it runs for 30 seconds or so consecutively.

 

I've been working with Diesel Dan on this for a while. The wire is pin number 4 and that is how fass structured there harness so that they can get a trigger wire for the relay to open and close.

 

Is the factory wire your checking orange with red?

 

You know I'm not sure what color it is? but I just went outside and tried to bump it after I had the key on and the pump won't run. I'll check the color tommorow. I know Dan said pin 4 is for lift pump power. I wish i had a for sure way of making lift pump turn on

 

Does the factory pump run hooked up? I hooked my fass up by hooking one wire to the ground and one wire to fuse #40. No problems yet.