LTG LPFP Upgrade - Before you Start
By: Dennis Phelps
So, I have yet to see any sort of reference for the VAST amount of fueling options available for the Alpha platform vehicles, whose engine management systems are referred to as Gen 5 ECM systems. Because of this I did a deep dive into the various options that have been offered for the Camaro, CTS, and ATS platforms. Given the sheer number of powertrains available, there is also a large number of fueling solutions. It would seem as if there is almost a concerted effort to keep a single reference of the options available as well as the proper application of those options out of the "general public" hands. There are plenty that know most if not all of this, but it would seem like most are looking to either profiteer from this information or keep others from using it themselves. Or, maybe it is just as simple as everyone just being too lazy to do the research and just wanting to copy someone else or "take a stab" at things without any real ability, knowledge, or engineering to make sure it is done "properly". I am not the type to horde information, and I HATE things being done improperly when, with a little more effort, things can be done the right way. A little background is needed in that all of the cars discussed (CTS/ATS/Camaro) share the same platform and engine combinations. Because of this, the factory fuel systems all share a large number of similar components, that being a dual-sump fuel tank (I will refer to the sides as "primary" for the side with the electrical pump and the "auxiliary" as the side without the electrical pump for the sake of this discussion), an electrical fuel pump module, a fuel sender module, a line or lineset that goes between the pump module and sender module, dual sump level sensors, a FPPM (Fuel Pump Power Module) or FSCM (Fuel System Control Module) which are programmable components to control fuel delivery, deadheaded fuel lines to the engine and then a HPFP (High-Pressure Fuel Pump) and the rails and injectors.
For this discussion, we will only focus on the fuel pump, sender, and line or line set and the components that are associated with them. First off the LTG system, as well as the CTS/ATS/Camaro v6 (LTG, LFX, LF3) systems are all what I will refer to as simple "siphon" based systems. I will from here out refer to this simplified system as "Config 1". It is comprised of an electrical fuel pump module that has a venturi feed (ie, it uses compressed fuel being flowed through a larger orifice to create a siphon effect to pull fuel through the larger orifice) to pull fuel from an opening at the bottom of the pump that has a one-way check valve in it. It also pulls fuel from a secondary feed tube via a siphon that is connected to the auxiliary sump via a line where the sender module is located. This sender module in this configuration is just another orifice sitting at the bottom of the sump with a one-way check valve that siphons fuel from this sump to the main pump. In this system, there is no fuel from the primary sump getting transferred to the auxiliary sump via the electrical pump module. This system generates the least amount of heat and noise.
The second system, which is used on the V8 engines as well as one of the larger twin-turbo V6 setups (LT1, LT4, LF4) is a system where the venturi-feed-based siphon is extended to the auxiliary sump as well. I will refer to this as "Config 2" for the rest of this discussion. This has the same components as the "Config 1" system, but there is now an additional "venturi-feed" line that goes from the primary electrical pump module to the sender module in the auxiliary sump. This extra "venturi-line" feeds a portion of the pressurized fuel to the auxiliary sumps sender module to allow it to pull more fuel through the sender module so that there is a greater supply of fuel for the larger electrical pump module. The electrical pump module also has a stub connection off the bottom that goes to a filter "sock" that allows a larger amount of fuel to be pulled from the bottom of the primary sump than is available via the small siphon hole that is still used in the bottom of the module. As can be imagined there is more noise and heat generated by this setup overall compared to "Config 1". The last component to be discussed is the Fuel Pump Module themselves as they are not just either a "Config 1" or "Config 2" setup, but they also have a built-in fuel pressure regulator. These regulators are the biggest difference between various pump modules outside of the configuration themselves. In doing my research it would seem that the fuel level senders are all pretty much the same with a few exceptions.
First off the Fuel senders are all the same either being a "Config 1" sender or a "Config 2" sender. The individual level sensors on the senders themselves are not available individually but are obviously compatible. There is only 1 part number available for either a "Config 1" or a "Config 2". The primary sump fuel level sensor is also the same across all platforms except for the ATS/ATS-V setup. For some reason that one has a different sensor part number associated with it. That is the only exception I have found which may be due to a different tank design for that vehicle. For 6th gen Camaros, all of the various models use the same fuel tank part number. The SS convertible originally had a different part number for the early years, but later was switched to the same part number as the rest and is backward compatible as replacements for those early-year vehicles. For ATS/CTS vehicles there is a whole host of part numbers depending on engine and drivetrain configuration. They all support the same parts as discussed.
Now to utilize a "Config 2" pump setup in a vehicle that came with a "Config 1" pump setup originally, it is as simple as putting in the properly matched pump module, lineset, and sender module. I have seen a number of write-ups where LTG enthusiasts are installing the ZL1 pump module with the venturi feed capped off. There is no changing of the line set and no changing of the auxiliary sump sender module. This will result in the primary sump draining faster than the aux sump and there is a fuel imbalance. It will also cause the fuel in the primary sump to heat up faster due to the lack of balance of draw between the sumps. To make it clear you MUST use the proper sender and line set with the "Config 2" pumps otherwise, you WILL run into issues. One of the other big issues not being discussed is utilizing the proper pump for a given application. Given the wide variety of pumps that are available for either configuration, for everyone to just default to "drop a ZL1 in the tank" is not proper. Quite frankly it isn't even the "biggest" pump with the most headroom as the CTS-V pump has that configuration (ZL1 having 450kPa regulation vs CTS-V being 500kPa regulation).
Honestly, unless someone is planning to run full E85 and max out the LTG platform with a massive turbo there is little reason to run the ZL1 or CTS-V pumps given that there are plenty of options with lower flow and more than adequate pressure given that the LTG has a 400kPa regulator stock and almost all the other options offer more than that. Now, given the fact that at this point and time fuel pump modules themselves are pretty darn inexpensive (at least the GM OEM ones are), someone would argue that going to the biggest just makes sense given the amount of work involved, for the LTG platform there is a ton of considerations that go into the engine itself to even prepare for any power level, that this argument is just one of many to be considered. I figured I would give an overview of how the "Config 2" system connects up, since I am certain that is primarily the system most people with "Config 1" systems will upgrade to.
The "Config 2" upgrade is comprised of:
1) The Fuel Pump Module for the primary sump that is chosen for your needs
2) The venturi-based Fuel Sender Module for the auxiliary sump
3) The Lineset that connects the two
Part Numbers:
Fuel pump Module: Choose the one that best fits your application
Fuel Sender Module: 84873936
Lineset: 84203866
NOTE for ATS owners: Only the ATS will need to modify the fuel pump auxiliary "leg" that has the "sock" pickup attached to it. It will need to be shortened otherwise the pickup will keep the pump from going into the tank. You can use a razor to cut the line to where you feel it needs to be and then soften the line in boiling hot water. It can then be pushed onto the nipple like the original one. Once it is in place, wipe it dry and then use a heat gun to ensure it is shrunken back into place and will stay like the original.
** THIS DOES NOT APPLY TO THE CAMARO OR CTS VEHICLES. YOU DO NOT NEED TO MAKE ANY MODIFICATIONS FOR THE CAMARO OR CTS. **
To do the upgrade it is quite simple:
1) Drop the fuel tank (some will state that they prefer to cut a "trap door" to access the pump and sender, but in reality given the fact that both need to be replaced, it just makes sense to drop the tank. The question of structural integrity comes to mind in regards to cutting two trap doors (or worse yet, a giant single trap door). So I will only endorse actually pulling the tank to "do it right".
2) Remove the original sender from the auxiliary sump. It is the one with only an electrical connector attached to the top. Disconnect the electrical plug. Rotate the retaining collar to unlock the sender. Pull it up on the sender and disconnect the siphon-feed line. Once that is done it is out.
3) Remove the fuel pump module from the primary sump. Undo the electrical connector, the vent line and the feed line. Rotate the retaining collar to unlock the pump. Pull up on the pump module. Disconnect the vent connection from the top. Disconnect the siphon-feed line from the bottom of the pump. Lift the pump module out being careful not to mess with the fuel level sensor as you will be reusing it. Once the pump is out carefully pry back the few tangs holding the fuel level sensor and float to the side of the pump. Undo the electrical connection at the top of the pump, lift it off the pump, and set aside.
4) Reach into the tank and remove the siphon-feed line that goes between the sumps.
5) Install the new line set. The sender side (auxiliary sump) is the one with the connections that are perpendicular to each other. The fuel pump side (primary sump) is the one with both connectors pointing at one another that have the corrugated flex lines attaching them.
6) Install the fuel sender in the auxiliary sump. Be sure to connect the lines to the appropriate nipple, as they will only connect one way. Make sure nothing is kinked or under pressure when you install the sender. Be sure to make sure the float is freely able to work up and down and the sender is oriented appropriately at the bottom of the tank. Install the new o-ring that is supplied with the sender. Install the retainer and rotate it into place to lock the sender in. Connect the electrical connector to the top of the sender.
7) Install the fuel level sensor you removed from the original fuel pump to the new pump module. Plug the electrical connector to the top of the module.
8) Install the new fuel pump module into the primary sump. Connect the two lines of the new line set to the two connections on the new pump module. Be sure that nothing is kinked or in any way going to be under heavy tension once the system is installed. Make sure the float will operate freely and does not hang up on anything. Be sure to plug in the vent line as well. Once it is in place and oriented properly, be sure to use the new o-ring supplied with the pump module. Reinstall the retainer and rotate it to lock the pump into place. Connect the fuel feed line and the vent line.
9) Reinstall the gas tank in the vehicle. Now, for the LTG, you are pretty much done. It utilizes a pre-programmed Fuel Pump Power Module that is programmed to deal with boost in connection with the ECM. For most other configurations that are turbocharged, I would imagine it is the same, primarily referring to the LF3/LF4 (in those cases the module is called the FSCM (Fuel System Control Module). Again, the only modifications that need to be made are for the ATS vehicles due to the different dimensions of their gas tanks. For the Camaro, the same gas tank is used throughout and for the CTS the dimensions are different for the various drivetrain options, but should not pose a problem. Here is the data I have collected. If there is an asterisk (*) next to a data item it is one I question because I have only validated from a single source. I have also NOT listed the horsepower potential of each pump as it would also be anecdotally derived from discussion, not actual calculation. There is a margin of error in all parts as well as a useable range for a given application and I will leave it to those who wish to use this information to determine what is best suited for their application.
Gen 5 ECM - Fuel System Data
Config 1 - Pump with bottom feed - single siphon line to aux sump
Config 2 - Pump with bottom feed with feed stub off pump to sock - venturi-feed line and siphon line to aux sump
Stock pumps and Information:
LTG - 400kPA (58psi) regulator - 185lph - Config 1
SS-LT1 - 400kPa (58psi) regulator - 255lph - Config 2
SS-Convertible - 400kPa (58psi) regulator - 230lph* - Config 1
LF3 V-Sport - 450kPa (65.2psi) regulator - 215lph - Config 1
LF4 V-Sport - 500kPa (72.5psi) regulator - 215lph - Config 2
ZL1 - 450kPa (65.2psi) regulator - 265lph - Config 2
CTS-V - 500kPa (72.5psi) regulator - 265lph - Config 2
Aftermarket OEM-Fit options:
DeatschWerks - Reuses the stock regulator - 440lph - Config 2 SKU: 9-442-C103-0902
DeatschWerks has released a drop-in pump replacement. It has its own controller that works with the factory PWM setup. It reuses the stock housing, and fuel filter "sock" and has its own upgraded wiring. Installation looks straightforward and can be used to upgrade ANY "Config 2" pump setup. It is not listed to be used on a "Config 1" pump setup and the installation instructions CLEARLY show a "Config 2" configuration. Given the capacity, it should ONLY be used on a "Config 2" setup. So, to clarify, if you have a "Config 1" setup and are looking to upgrade to the DeatschWerks 440lph setup you still NEED to buy all the parts to do a "Config 2" setup, including a Fuel Pump Module and the dual line set for it..
