Feature request, custom control over fuel transfer pump relay

[twalterdmax]

Request to the EFILive guys (or anyone else who can suggest a better way). I just installed a lift pump on the truck. When I was figuring out my wiring I realized I had a "spare" relay in the stock underhood box labeled fuel pump. Turns out this is for the transfer pump if you have dual tanks. I don't so I figured I'd use the same relay. Already fused, even has "prime" contact in the box so you can manually jumper a wire to run the pump for priming.

It is factory wired to the ECU and from EFILive I can trigger a DVT to turn the pump on and off. I tried playing with the fuel settings but could not find a way to get the system to normally turn it on.

The custom digital output with the DSP will allow me to use that digital and swap pins but I'd rather directly use the one already wired (plus I have the other free for future playing). Also most of the input changes are not helpful. Ideal behavior would be:

Key-on, prime for 2 seconds and then turn off.
Engine running, pump on.
Engine stops, pump off.


Any mechanism to get this feature added or any suggestions on how to control the ECU pin another way? Would be handy for everyone adding a lift pump who does not have a dual tank setup (many of us). Really nice to have all the relays and fuses in stock locations if possible.

[GMPX]

Sorry, we won't be doing any modifications to the DSP OS's for this ECM.

[twalterdmax]

Thanks for the reply. If you guys ever decide to dust this OS off and add this (or help support a one off mod) let me know.

[GMPX]

Just so you don't sit there forever waiting, it will probably never happen, sorry.

[dansdieselp]

Fuse tap Ignition Fuse and close the hood.

[elcaminonut69]

What year and operating system is your truck

[THEFERMANATOR]

Sorry, we won't be doing any modifications to the DSP OS's for this ECM.

It's not a change to the DSP OS as ALL the DURAMAX ECM's have this capability. ALL DURAMAX's could have came with dual tanks, and have the circuitry and wiring there for a transfer pump. GM used this setup in the vans with a DURAMAX under the hood, so the architecture is there and proven to work. I know if we had this feature, MANY would use it to control there lift pumps. The DSP output is the one he was talking about that dealt with the DSP OS. Since mine is an early engine, I use the 3 wire GM oil pressure switch(but I don't have the prime feature).

[elcaminonut69]

After pulling up my fuel system the pid is there for the secondary sender. I wonder if you adjusted the total tank size and set the secondary sending unit up if it would control the transfer pump

[elcaminonut69]

Even though the fuel system segments show a different part number

[THEFERMANATOR]

After pulling up my fuel system the pid is there for the secondary sender. I wonder if you adjusted the total tank size and set the secondary sending unit up if it would control the transfer pump

No, the transfer pump will look for change in the primary and secondary level units. If it doesn't see the secondary level showing the level dropping, and the primary showing the same or increasing, it will most of the time default your fuel gauge to empty, or shut the transfer pump off thinking the transfer pump relay is stuck on. I ran into this on a DURABURB tune I wrote. On the economy tune he goes so far before the level really changes, it causes all kinds of issues. That and at first he had the stock Y to the 2 tanks which allowed fuel to slosh forward, and when it saw this, it would disable the transfer pump. it is a finicky system to say the least. That, and you have to have a cab and chassis fuel segment for the ECM to even enable the transfer pump.

[elcaminonut69]

No, the transfer pump will look for change in the primary and secondary level units. If it doesn't see the secondary level showing the level dropping, and the primary showing the same or increasing, it will most of the time default your fuel gauge to empty, or shut the transfer pump off thinking the transfer pump relay is stuck on. I ran into this on a DURABURB tune I wrote. On the economy tune he goes so far before the level really changes, it causes all kinds of issues. That and at first he had the stock Y to the 2 tanks which allowed fuel to slosh forward, and when it saw this, it would disable the transfer pump. it is a finicky system to say the least. That, and you have to have a cab and chassis fuel segment for the ECM to even enable the transfer pump.

Okay that answers my question Thanks TheFermanator

[twalterdmax]

The truck is a 2003. OS number: 15189044

As an update I ended up using the relay but hard wired the relay control to ignition switched power. I tried to use the DSP output but it would not sink enough current to switch the relay so I would have needed to install another relay/circuit. Works well though it is annoying to have the pump running when the ignition is powered and I'm doing an ECU flash and it would be nice to have the safety feature where the pump shuts off when the engine shuts off. Probably not as critical with diesel as with gasoline.

For anyone looking to do the same relay "reuse" you will need the fuse box pins to replace the existing ECU connection to the relay and will need to connect from the switched side to power the pump. The fuse box pins are Delphi Metri-Pack 280 series and the part number is: 12129061. I found them on Mouser part number 829-12129061. Ended up with a nice clean install. Once you pull the relay block you can get to all the pins and easily swap them around.

I also tried messing with the second tank values in EFI Live. I was never able to get the relay to switch on no matter what I set for tank sizes or fuel level calibrations. I suspect my OS does not have the second tank code enabled. Either way I gave up on that path.

[larski156]

Just so you don't sit there forever waiting, it will probably never happen, sorry.

too bad, really would be the right way to get it done.