2nd Gen Non-Engine/Transmission Ecm / lift pump relay install

[STUMPY]

I have read several post about installing a relay for the lift pump when having voltage problems from the ecm. My question is how long does this fix the problem or should i expect to have more issues down the road. Also i have not seen any post about voltage readings at the lift pump connector, if my info is correct it should be 8 volts momentarily when the key is turned on and 12 volts for 25 sec when the starter is bumped. This is a 2000, 2500 with the pump located on the block, drivers side.

 

[hcole]

This has been covered several times in the 2nd generation engine forum. You can install a relay like I have done like this. Install a relay near drivers side battery. Come off the relay that powers the VP44 injection pump and take this wire to power up the relay coil. Put an inline fuse direct from the battery thru a NO contact on the relay that you installed and on to the lift pump. Now you have taken the lift pump off the ECM and now it will turn on when you turn the key on and run until you shut the truck off. This is how I have set mine up app. 2 years and 50,00 miles ago. I expect this to last forever on my truck. This gives you a reliable source of power and the pump will run when the switch is on without switch bumping or timers. The original design off the ECM to power up the lift pump is NOT fused and the lift pump has been known to drag down the voltage to the ECM. If you use the search forums you will find lots of info on this mod. Also, you should have 12 volts all the time on the lift pump in the factory wiring, not 8 volts. The power when you first turn on the switch is only there app. 1/4-1/2 second so your meter can't pick up 12 volts fast enough before it's back off.

 

[Bill Stockard]

I have read several post about installing a relay for the lift pump when having voltage problems from the ecm. My question is how long does this fix the problem or should i expect to have more issues down the road. Also i have not seen any post about voltage readings at the lift pump connector, if my info is correct it should be 8 volts momentarily when the key is turned on and 12 volts for 25 sec when the starter is bumped. This is a 2000, 2500 with the pump located on the block, drivers side.

See TDR Issue 67, page21 for a wiring diagram and instructions.

Bill

 

[STUMPY]

this has been covered several times in the 2nd generation engine forum. You can install a relay like i have done like this. Install a relay near drivers side battery. Come off the relay that powers the vp44 injection pump and take this wire to power up the relay coil. Put an inline fuse direct from the battery thru a no contact on the relay that you installed and on to the lift pump. Now you have taken the lift pump off the ecm and now it will turn on when you turn the key on and run until you shut the truck off. This is how i have set mine up app. 2 years and 50,00 miles ago. I expect this to last forever on my truck. This gives you a reliable source of power and the pump will run when the switch is on without switch bumping or timers. The original design off the ecm to power up the lift pump is not fused and the lift pump has been known to drag down the voltage to the ecm. If you use the search forums you will find lots of info on this mod. Also, you should have 12 volts all the time on the lift pump in the factory wiring, not 8 volts. The power when you first turn on the switch is only there app. 1/4-1/2 second so your meter can't pick up 12 volts fast enough before it's back off.

just finished installing the relay, i am new to tdr and did find the thread & print on here be for i posted my question. Thank you for answering, 50k sounds good to me! I have owned this truck since new and up until now she is 100% stock. This problem just came out of the blue. I have had pumps go out before, both lift & vp-44. Will be installing a "drp" as soon as it gets here. Thanks again, sure is cheaper than a ecm.

 

[cerberusiam]

Just keep in mind the VP-44 does not like that constant pressure when starting. It can and will cause hard starts and issues with the IP. Eventually it can cause IP failure.

 

[Bob4x4]

interesting notes
With the engine running, the pump has 2 modes of operation: Mode 1: 100 percent duty-cycle with a minimum pressure of 10 psi except when the engine is cranking. Mode 2: 15 percent duty-cycle with maximum pressure of 7 psi with the engine cranking

The 15 percent duty-cycle is used to limit injection pump inlet pressure until the engine is running.

The transfer pump is self-priming: When the key is first turned on (without cranking engine), the pump will operate for approximately 1/4 second and then shut off. The pump will also operate for up to 25 seconds after the starter is engaged, and then disengaged and the engine is not running. The pump shuts off immediately if the key is on and the engine stops running.Also the pre-start operation has been modified by ecm software updates
Of course with the retrofit in tank kit this is changed.The ecm triggers the newly added fuel pump relay that will power the in-tank lift pump