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no power to fuel pump 98 ram pickup
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skydver
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Mar 14, 2008, 9:08 PM
Post #1 of 7
(2024 views)
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no power to fuel pump 98 ram pickup
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First I will preface this fact, I am an A&P mechanic. I work on airplanes not trucks. I have tinkered with cars all my life but only as a hobby not proffesionally. I do as much stuff as I can when I can read the directions.
the manual I have is a Haynes repair manual. Last night my truck quit. it ran out of fuel with a full tank. I just filled it so I know the gauge wasn't lying.
when trying to start it would fire but not continue to run. I did not hear the usual sound of the fuel pump running. I got out my manual and started checking what it told me.
1st I checked the relays, fuel pump and asd relays. The slots they plug into have power where and when they are supposed to. I checked the relays they have continuity and the coils ohm out as prescribed in the manual. I unplugged the line from the tank module and checked for power. I found none. I did confirm that I had a good ground and that I had continuity throughout the entire wire both power and ground from the power distribution center to the pump. I did not try putting 12 volts directly the fuel pump. didnt know if that would hurt anything. According to the wiring diagram the power comes from the start switch thur the fuse to the fuel pump relay. I pulled the cover off the top of the relay visually inspected it and tried manually closing the contacts and still the pump will not come on. all the relays are the same. I have switched some around and used the ones that I know worked to test but know luck.
What do I do next? any suggestion from any of you experts out there?
sorry for the lengthy post but I wanted to give you as much info as possible.
(This post was edited by skydver on Mar 14, 2008, 9:10 PM)
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DanD
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/ Moderator
Mar 15, 2008, 6:13 AM
Post #2 of 7
(2020 views)
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Re: no power to fuel pump 98 ram pickup
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Don’t apologize for the length of your post the more you can tell us the better.
For some reason I can’t seem to access my repair manuals that are NET based and can’t get to the wiring diagrams.
So how much help I’ll be right now I’m not sure? But yes you can jumper power to the pump and not hurt anything as long as you are confident you’re jumpering the proper circuit.
When you initially turn the ignition on or during a crank of the engine do you feel or hear the relay tripping?
Chrysler is known for adding short jumper harnesses between the main wiring harness and the different devices. Any time there are extra connectors, there is a potential for connection problems. So follow the harness and have a look for any jumpers and if you find any don’t be shy at taking them apart, confirming that there is continuity through them.
Dan.
Canadian "EH"
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skydver
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Mar 15, 2008, 6:47 AM
Post #3 of 7
(2018 views)
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Re: no power to fuel pump 98 ram pickup
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No I don't feel or hear the relay kicking in. The asd relay will click every time I turn the key. In the wiring diagram I have (very poor in my opinion, more of a block digram than a schmatic) the ground side (?) of the relay coil goes into the power train control module at a conection marked fuel pump relay control. What is the "powertrain control module"? is that a fancy word for computer?
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DanD
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/ Moderator
Mar 15, 2008, 6:55 AM
Post #4 of 7
(2017 views)
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Re: no power to fuel pump 98 ram pickup
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Yes that’s the computer and yes I bet 90% of the computer’s functions are achieved by supplying grounds to the different working devices. This function at times is call a driver; ie: fuel pump relay driver.
Dan
Canadian "EH"
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way2old
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/ Moderator
Mar 15, 2008, 8:27 AM
Post #5 of 7
(2014 views)
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Re: no power to fuel pump 98 ram pickup
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As you seemed to have checked up front and can not see a problem, I suggest going to the fuel pump wiring to see if there is current at the pump itself. If there is current to the pump, either a ground for pump is bad, or the pump has quit.
Being way2old is why I need help from younger minds
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skydver
User
Mar 15, 2008, 9:03 AM
Post #6 of 7
(2012 views)
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Re: no power to fuel pump 98 ram pickup
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Already did that in fact I did it first. My original thought was the fuel pump. After 225000 miles its about time for it to die. when I found that I would have to drop the tank(just after I filled it of course) I decided to check voltage first. thats when I realized it was at least an electrical problem. I have no pwoer to the pump. I have checked every connector between the pump and the relay.
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skydver
User
Mar 15, 2008, 11:21 AM
Post #7 of 7
(2010 views)
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Re: no power to fuel pump 98 ram pickup
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Well its off to the dealership we go. Ouch I know its gonna hurt. Looks like the computer is bad. Parts houses can order me a computer but the dealership has to program it before the engine will even start. So maybe they can download updates to make it work. So anyway you slice it; this is gonna hurt. .
thanks for the help but its now over my head. I think I'll stick to fixing airplanes.......they are alot simpler.
(This post was edited by skydver on Mar 15, 2008, 11:23 AM)
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