400 lph pump pressure issues

[Kalatrax]

I picked up the 400 lph walbro drop in unit from late model restoration a few weeks back. I put it in a cleared the Kam as stated was the only requirement for it to work properly. Initial data logging showed 75 fuel pressure and 75 fpdc with no fluctuation between idle or wot. I pulled the negative off for an hour and tried a different tune. Same thing. I swapped the pump back and called late model. Their in house tuner said it requires a little bit of driving to kick in. Put it back in yesterday and have put 100 miles of mixed driving on it so far. Same thing and it's throwing a p0191 code as well. Do you guys think the pump is just defective?

 

[s8v4o]

It's known that the 400+ LPH pumps don't play nicely with the returnless fuel system. That being said it's usually an issue with pressure spikes, seemingly not the same issues you are having.

Did you leave the PRVV installed or did you delete it? SO let me get this straight, your fuel pressure is always 75 PSI no matter what?

 

[JeremyH]

Why the upgrade based on your sig stock fuel pump is more than capable? FYI those pump assemblies only flows around 300lph and is not the 400lph version of the pump like advertised. I would not plan to drive it without a revised tune. And you are going to want to upgrade your fuel system wiring if you haven't.

Swap the stock hat back in and see if it fixes it.

 

[Kalatrax]

It's known that the 400+ LPH pumps don't play nicely with the returnless fuel system. That being said it's usually an issue with pressure spikes, seemingly not the same issues you are having.

Did you leave the PRVV installed or did you delete it? SO let me get this straight, your fuel pressure is always 75 PSI no matter what?

Yes it reads 75 at all times but it doesn't fluctuate at all which makes me think it's not communicating properly. I believe the valve was deleted on this unit. I didn't see one in line.

Why the upgrade based on your sig stock fuel pump is more than capable? FYI those pump assemblies only flows around 300lph and is not the 400lph version of the pump like advertised. I would not plan to drive it without a revised tune. And you are going to want to upgrade your fuel system wiring if you haven't.

Swap the stock hat back in and see if it fixes it.

The upgrade is for the turbo I bought from you. I also bought the wire upgrade from you a few weeks ago. I did swap the stock hat back and it did fix it as stated in OP.

 

[JeremyH]

Yeah something up with the pump then. Most guys end up maxing them out as well. Did you get the wiring installed?

 

[Kalatrax]

Yeah something up with the pump then. Most guys end up maxing them out as well. Did you get the wiring installed?

No I wanted to sort this out before installing anything else. I put the stock pump back in again today after talking to latemodel's customer service again. So last time I was told to put it back in and give it a hundred miles, this time I was told that the same tuner said it either works or doesn't and that he never said to put it back in. I was also told that my pressure sensor is probably bad even after stating multiple times that it works just fine with the stock pump. I asked if they would send me a replacement and was told no only a refund. In his words "this part just won't work with your car". So after 4 fuel pump replacements and 2 weeks of bullshit from latemodel and their "tuner" I'm sending this POS back and doubt I will shop from them again.

 

[07graygt]

Not trying to be a dick. But did you get the right one for you year. I just put one in my 07 gt. And it works great.

 

[07graygt]

I also had American muscle write a tune with the new pump.

 

[Kalatrax]

I got the correct year range and tried multiple tunes. By their statement it does not require a tune modification.

 

[s8v4o]

The purpose of the PRVV is to be a check-valve AND to bleed off fuel pressure that gets to high. I think it bleeds are around 80psi. It's very possible that by removing the PRVV that you could have damaged the pressure sensor in the engine bay from the excessive fuel pressure spike that those pumps generate.

 

[JimIII@JDM]

the only way to go... http://www.teamjdm.com/2005-2009-mustang-gt-dual-fuel-pump-upgrade-kit/

 

[Kalatrax]

The purpose of the PRVV is to be a check-valve AND to bleed off fuel pressure that gets to high. I think it bleeds are around 80psi. It's very possible that by removing the PRVV that you could have damaged the pressure sensor in the engine bay from the excessive fuel pressure spike that those pumps generate.

I didn't remove it. I'm thinking they might have because I didn't see an inline valve on this one like the stock one has. That may not be the PRVV valve though. In any event I put the stock pump back in again and it's at 39 psi reading fine again. Pump is the issue here.

 

[JeremyH]

Not trying to be a dick. But did you get the right one for you year. I just put one in my 07 gt. And it works great.

Year makes no difference for the pump itself. Only change is the fuel level sender resistance reading for your fuel gauge.

I also had American muscle write a tune with the new pump.

Boom. These pumps will not run write on stock fuel trims from my experience so always good to get it tuned.

I didn't remove it. I'm thinking they might have because I didn't see an inline valve on this one like the stock one has. That may not be the PRVV valve though. In any event I put the stock pump back in again and it's at 39 psi reading fine again. Pump is the issue here.

Yup. As far as I know those walbro hats retain pprv function, but I have not had one in front of me to examine.



In this case something is up with the pump/assembly for the pcm not to be able to lower pressure delta.

 

[s8v4o]

Boom. These pumps will not run write on stock fuel trims from my experience so always good to get it tuned.

From the little bit of research I've done on tuning the fuel pumps is that the computer should relearn the tables all by itself. That being said a tune for the pump/s is a good thing though because sometimes you might not have enough time for the computer to do a relearn process so getting the tables correct from the beginning is a good thing. A perfect example of this is if you're at the track and load a tune. You don't have the luxury of putting some miles on it for the relearn to happen.

If this is wrong someone please correct me.

 

[JeremyH]

I'm not a tuner, but have a lot of experience with the pumps. You can usually drive it but runs rich and dumps fuel and pegs the wideband coming off throttle, part throttle stumbling etc. Have not seen it not need to be adjusted for in the tune. That pump flows over double the stock pump.

 

[Kalatrax]

I wouldn't doubt that a tune would dial it in perfect but the fact that it showed the readings it did and made no adjustment to lower pressure is what is ridiculous.