Originally Posted by smokinlmm

There was tuning involved. Truck made 630 tire with fast injectors and stock pump.

Originally Posted by smokinlmm

Yes it was my truck. The hellcat pump is almost drop in, will supposedly support 800 or more tire on 93. Stock flex pump is about equal to a 255 Walbro if I remember correctly.

Originally Posted by infiniticrypto

I'm sorta pumped.....pun unintended! I think I found my out....in the cleanest way. I"ll just copy and paste from a post I just made elsewhere.

I've scoured the edges of the inner webz and have seen lots of solutions that entail ditching the FCSM and running hoses and going return style. Also the option of stuffing a Walbro 450 in the factory bucket with some rigging. My tuner mentioned the Hellcat pump (Walbro 525) I'm not certain on how the FSCM reacts to higher current draw. Poking around for a few minutes it looks like some GM vehicles with FSCM use a 20 amp fuse, I'm assuming that's the circuit that powers the pump. So you'd be limited. Another vehicle (CTS-V) possibly uses a 30 amp fuse, I went out and checked this truck and it uses a 25 amp fuse. I think I've found what I'm looking for though. I went to the TI Automotive website and found that they offer a replacement module (could very well be the GM source) but they also offer a High Performance version. If the factory one is going to end up being close....I think the High Performance version gets me there with not having to hack anything up on the truck. The truck has 110k miles, so I wanted to drop a new pump/module in it anyway so I'm going to give the High Performance version a shot. Here is a flow graph I found on TI Auto site, I'm quite sure it's for the module I'm referring to. TU4005HV High-Performance-GM-Truck-Module.pdf

So if as you say the stock pump is close and it's 255lph, according to my math the High Performance TI Automotive module is 340lph. Of course there are nuances like a pump rating gets reduced once in the module because some pumping get allotted to the venturi. So is a 255lph the rating of just the pump.....and it's actually a little lower once in the module.....but the High Performance version seems to be rated including the module. If that makes any sense. I'm probably clueless and splitting hairs.

Originally Posted by jclark10

When you say "module" you are talking about TI's fuel pump and bucket assemblies right? and not a aftermarket FPCM?

Yes, I'm that's correct, when I say module I'm referring to the bucket/pump assembly. I talked to TI Auto and was told the performance version of the module uses the F0000285 pump (older Hellcat) which I was a little suspicious of since they rate the module current draw at a relatively low amperage compared to what you'd see when looking at the "285" pump on it's own. I don't know if that's because pump alone ratings are tested at higher pressure because they never know what application/pressure they'll be run in......and in the case of the module the pump is installed in a specific application/configuration. Anyway I'm having a hard time getting my hands on the performance module from TI Auto part # TU4005HX (you just add HX suffix to the factory equivalent module part number from TI Auto.) My luck they were closed the entire week last week for the 4th so I'm hoping to hear about availability/wait time today through one of of not their largest distributor.

As far as I know no one makes any aftermarket or "modded" FPCM. Also as far as I know, HP Tuners will not help you do anything with the FPCM, you may get a very small gain by raising the system voltage boost threshold, but if I remember correctly I think that is in the ECM anyway. All the other tables in the FPCM have zero effect, at least in my operating system. I know there are some stand-alone PWM controllers for fuel pumps, but of course they wouldn't run all the other functions of the FPCM.

I'm new to this so I can only tell you what I've been lead to assume about the FPCM (I'll call it FSCM from here on out as that's what I believe it's called my GM) I believe the truck FSCM has a less aggressive tune compared to a CTSV and that you can take a CTSV tune for the FSCM and stuff it in the truck one. I have heard about the trailer brake thing and I don't believe this truck has that. (FSCM 20964304)
Just as a quick reference it's talked about here: https://www.performancetrucks.net/fo...-549140/page2/

I need to go try and find my old logs to see how much my fuel pressure was dropping on my 6.2 L9H with a GT45 at around 10 psi, but if I remember correctly it was enough for it to go lean and sputter. I put a TI/Walbro 535 in the stock bucket (the 09+ GMT-900 Bosch buckets ("modules")) are harder to deal with and upgrade pumps and there is less room in them. Even with the 535 in the stock bucket with the GT45 at around 10 psi on a stock L9H it was dropping to about 38-45 psi from 65 psi commanded. Like I was saying above, you can lower the system voltage boost threshold and it will go to about 14.7-14.9 volts at WOT/high fuel flow, but even then there is something in the FPCM looking at the duty cycle and voltage combination and limiting it. You can run it at about 14 V at 90-100% duty cycle, and then try to boost system voltage to almost 15 V, but then the FPCM will then limit duty cycle to around 80% or so to where the end result is about the same pump output.

Looks like you should have plenty of pump even without JMS. I wonder if FSCM tuning would have helped you get there. That pump you're using seems pretty stout while having lowered current draw due to having no check valve. Have you experienced longer than factory engine start-up crank time?

I was just like you and was very reluctant to hack and chop up everything and have to put in a manual regulator and run new lines and I really wanted to avoid that and be able to have the stock nice and clean setup. I wanted to avoid buying a boost a pump too just because its kind of a hack and gimmicky itself, but that is just what I ended up doing.

Now with the JMS set on 100% I think I am holding full fuel pressure. However, it did drop again here recently and I fixed it and that was just because the fuel filter sock on the end of the pump was getting clogged up, so its very sensitive if you drop dirt in taking the pump out of the tank or any other trash getting in the tank. It will make it clog up and drop pressure very easily. The JMS boost a pump is extremely and unnecessarily expensive for being such a simple amplifier in series with the FPCM and pump.

Also one more thing to note, if you have the trailer brake controller (I think JL1 option?), there is a threshold in the FPCM on system voltage which triggers some logic in the trailer brake control and will throw a "Service Trailer Brake Message". There is a GM TSB about it somewhere, so if you end up boosting voltage, through HP Tuners on the FPCM or with a boost a pump, be prepared to have that message pop up on the DIC when you go WOT. It won't however cause any MIL from what I can tell, just the message. I also could never even find any freeze frames or history if its even telling the ECM to illuminate the MIL either. I have been looking to try to find the TSB on it to see if I could fix it, but I can't find the TSB anymore.