Lift pump is not powering up in the on position

[dripley]

you will stilll be sending full pressure to the vp possibly causing hard starting. even when you bump the starter and start the engine during that cycle the ecm reduces the pressure for starting once the key is turned again. i believe it does this by cycling the pump on and off during starting. i have my AD connected to the alternator and plug into the wiring from the ecm to the old lift pump and when cranking i only see somewhere between 7 and 9 psi.

[I6FREAK]

you will stilll be sending full pressure to the vp possibly causing hard starting. even when you bump the starter and start the engine during that cycle the ecm reduces the pressure for starting once the key is turned again. i believe it does this by cycling the pump on and off during starting. i have my AD connected to the alternator and plug into the wiring from the ecm to the old lift pump and when cranking i only see somewhere between 7 and 9 psi.

Good point, I didn't plan it but isn't acc 12 volt power shut off during start up...like how the radio shuts off when you are cranking but it';s on in the start position?? I just paid attention to that today getting in and starting up..

[dripley]

you do have a point there. when you turn the switch on everything pretty much comes on, radio, heater fan, and so on. when you turn to start those things shut down while staring.They all come back on when you release the key. not sure what all shuts down but things do shut down, that might be a way around it, providing you dont overload any thing by putting the pump on one of those circuits that shuts down during starting. makes me wonder if there is a spare circuit on the accersory side of everything you could do that with.

[I6FREAK]

Will the ECM trip the CEL if I activate my fuel pump independent of the supply voltage from the ECM? In other words, if I leave the wiring harness that would normally plugged into the lift pump, unplugged. If so what is the safest way to complete the circuit so the ECM does not trigger a CEL?

[JAG1]

Will the ECM trip the CEL if I activate my fuel pump independent of the supply voltage from the ECM? In other words, if I leave the wiring harness that would normally plugged into the lift pump, unplugged. If so what is the safest way to complete the circuit so the ECM does not trigger a CEL?

I did this to my truck when Mike said I can do this w/o problems. I turned the key on only to get the FP gauge working to give a reading. IMHO it's better with the stock pump running off the batteries. So I'm going to wire it that way eventually. Like Mike says the best way is from inside the PDC cause the wiring is not corroding like it does close to the batteries. Hey Mike.....

[dripley]

Will the ECM trip the CEL if I activate my fuel pump independent of the supply voltage from the ECM? In other words, if I leave the wiring harness that would normally plugged into the lift pump, unplugged. If so what is the safest way to complete the circuit so the ECM does not trigger a CEL?

when i removed my intank pump i simply connected my new AD to the old lift pump plug that had just been hanging there for 4 years. never thru a code. the intank pump was working off a relay and i dont rember what power source it was connected to. so as far as i know you cna just leave the wire to the oe lift pump hanging like mine was.

[Mopar1973Man]

I see some people listen... :thumbup2:Now as the lift pump it should be power by the ECM because the crank signal to the pump is modulated at 50% duty cycle to lower fuel pressure to the VP44 during cranking to prevent hard starting issues cause by full fuel pressure. Hence why crank pressure minimum is 7 PSI and running minimum is 10 PSI...

[dripley]

i am connected to the old wiring harness for the oe lift pump, but that feeds power to operate a new relay i installed. my power source for the pump is connected to the altenator, also to eliminate corrosion from a straight batttery connection. i dont know that the connection is any better or worse than a PDC connection, it was the alternate method(i lieu of a straight battery connection)shown in the instructions. My intank pump was wired thru a relay and not connected to the oe lift pump harness. I was so happy to get all of that crap of my truck that i did not pay attention to how dodge had it all connected.

[I6FREAK]

I have fabricated the wiring harness using a weather resistant high rush amperage(up to 150 amp) relay(1 million cycle rating). I soldered the socket clips to all wires and shrunk 2 inch teflon sleeves over the beginning of all soldered joints. I machined an anodized aluminum switch panel that I will mount on my center console(homemade). I am using 16 gauge military grade teflon shielded electrical wire and an inline 15 amp fuse from power supply(Inline fuse harness has 14 gauge wire). Any one have preferences on a location to take power from? PDC of Alternator ?? or other??Thanks

[Dave3500]

How much do you want for it?

[JAG1]

I have fabricated the wiring harness using a weather resistant high rush amperage(up to 150 amp) relay(1 million cycle rating). I soldered the socket clips to all wires and shrunk 2 inch teflon sleeves over the beginning of all soldered joints. I machined an anodized aluminum switch panel that I will mount on my center console(homemade). I am using 16 gauge military grade teflon shielded electrical wire and an inline 15 amp fuse from power supply(Inline fuse harness has 14 gauge wire). Any one have preferences on a location to take power from? PDC of Alternator ?? or other?? Thanks

Where did you get the relay? I still can't remember if I should use a solid state relay or a solenoid type. I don't want it back feeding to the ECM if the pump goes bad and sends high amps:shrug:

[I6FREAK]

How much do you want for it?

Do you still need it?

Dave