Archived Fuel Pump Problem

[robertyoke]

I'm hoping someone can help me out and point me in the right direction. For some background: This is on my 03 truck. I'm running 2 fuel tanks and a total of 3 fuel pumps. One pump is on all the time and it is mounted at the cross member. One pump for each tank runs to push fuel through a selector valve. I've been running this setup for well over one year. The other day, I lost all fuel pressure and the truck limped home; barely. At first I thought I had a bad selector valve or switch. But all of that seems to check out just fine.



All the power for both pumps comes off the original fuel pump lead. The fuel pump lead, when I check it, has 12 volts initially when the key is turned on then immediately drops to 8. 5 volts. The low voltage is causing a high amperage drain then causing the power source to shut off completely. The problem is that I don't know where the power comes from. I looked in the power distribution panel, and there is no fuse or relay for the fuel pump. I look in the service manual and it points me to the power control module, which looks like it is a sealed unit.



Can someone tell me where the fuel pump gets its power? It must have a circuit breaker of some sort and a relay of some sort. Does anybody know where they're located?



I'm hoping the low voltage is a bad connection/bad relay. But if anybody else has any other ideas, I'd love to hear them. All the wiring looks fine; no chafed wires or anything of the sort.



Thanks.

Robert

 

[lumberjack98]

If you are running 2 pumps off that wire it is too much draw for the small wire. I think most of us are installing a relay and triggering it with that wire so you get full power to the pumps and a relay takes little voltage to turn on. I would get it fixed before you drive it again if it is pulling voltage from the pcm it may be burning it out. any one else with a idea?

 

[ThrottleJockey]

What lumberjack said, your'e running a relay off the OEM trigger wire, right?



This IS the guy who fabbed up THE coolest towing twins on Earth, right?

Get to work on them fuel pumps man!!

 

[robertyoke]

I had it wired orignally with a relay. then back when I had a problem with no a/c with the tst box, I was talking with mark chapple of tst and he said that they run both pumps off the lead without a problem. so I simplified the wiring while I was looking for the a/c problem. It has been that way ever since, that was 35k miles ago.



the weird thing is the voltage I am reading is with the pumps disconnected.



after doing some more reading in the service manual, I see that the ecm controls the pump. No external timer, No external relay, and no separate current protection device. its is all internal, inside the ecm



I have wired in the relay back in the system and the current I have is strong enough to close the contacts and run the pumps. I hope it keeps working!



thanks

robert

 

[ThrottleJockey]

All right! Good deal!



Now get back to work on my set of twins!

 

[2-ND TIME]

Fuel pumps

Sorry for being daft but are you running the factory wire through the coil of a relay then to ground ? This is the best way to go for powering external ccts. This is then controled by the device but only adds coil current to the cct. Then take a fused cct to the contacts of the relay and then to the pumps #12 or 2 #14's would be good for this as well as good ground wire back to a good ground point by the batteries. Have you measured the voltage at the batteries? May have a resistance at one of the terminals or if not, too much current for the ECM to handle? Or do you have a bad battery? Hope this helps.

 

[robertyoke]

truck is up and running, well until it popped the fuse that I just put back in the system. the one fuel pump locked up today and was probably the cause of the whole problem, high current draw untill the pump locked and took out the fuse.

I guess I will find out how good speed world's warrentee is on that pump. see if it really lifetime!

-robert