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Discussion Starter #1
So, my '03 dually quit the other day. Acted up a bit then up and quit. Turn the key on and the lift pump (in the tank) would not run so i replaced the pump and still no go. Turn the key on, and or bump the starter and the lift pump does not do anything. I have 11.55 Volts on the two outside wires at the pump but no pump action. No codes. Seems to me that with 11.55 volts the pump should run. Thoughts??.
 

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Discussion Starter #2
Did some more tests. The pump runs when hooked to a battery. Multimeter reads 11.55 volts with the key on but test light shows no power. The ground wire has contact. So, is there any reason that I can't just run a new wire from the power terminal from the pump to keyed power and call it done??.
 

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How many volts does the battery have, the one you used to test the pump? Maybe you need new batteries. I believe you need 12.6v or the finicky electrical systems in these pickups can give you issues.
 

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12.2-12.6 is OK for battery voltage
 

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Discussion Starter #5
Testing just the drivers side battery I get 11.7 volts. Likely because i have been trying the starter many times. The engine spins over extremely well (batteries are both near new) si I don't think the problem lies with them. The truck was running then stumbled a few times then quit. Pump hasn't worked in the truck since. I don't know if the lift pump is in any way controlled by, or wired through the ECM. If not, I don't see any reason I can't just run a new power wire to keyed power
 

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Put your batteries on a charger and see if the lift pump will come on.
 

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IIRC, it is triggered by the ECM.
You could use a key-on wire to trigger a relay to send power to the LP.

Multimeter reads 11.55 volts with the key on but test light shows no power.
Are you sure you had good ground on the test light or if the test light even works?
 

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Discussion Starter #8
Found the problem. Did some more research and found that the relay for the pump is the one hanging on the firewall by the brake booster. Removed the relay and jumped it with a jumper wire and the pump came on and the truck started. Will go to town today for a new relay. Thanks to all that responded. Much appreciated.
 

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Good simple easy fix. Thanks for the update.
 

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TY for posting the fix.
 
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