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Old 09-30-2019, 03:19 AM   #1
Shahano
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LS3 BRZ Fuel Cut

My car is a sapped LS3 with cams. I have a DW300c fuel pump and I am having problems with the fuel system. When I get on and off the throttle aggressively, the fuel cuts when I get back on, however when I go WOT, the car will respond perfectly well and will not go lean at any point (meaning that my fuel pump isn't too small).

Has anyone had this problem? I checked with a number of tuners, and the problem is not coming from the tune, bust most likely from the fuel system.
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Old 09-30-2019, 06:27 AM   #2
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Awesome that you have a dry sump! Unfortunately it sounds like you did not adequately upgrade your fuel system. Does this happen even with a full tank of fuel? What do you do with the car? If it's just for the street you could try the radium dual hanger you asked me about otherwise a surge tank will be needed if you want fuel pressure 100% of the time with 2/3 of a tank or less of fuel. Holley Hydra mat would be a cheap solution that might work for you, I've heard good things about them.
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Old 09-30-2019, 07:13 AM   #3
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I use my car only for drift, so not really very high Gs going on in there.
Yes it still happens even with a full tank of fuel.
The weird thing is that under full throttle, the car is not going leaner, that's the only reason why I am hesitating to change for a larger fuel pump. @GrabTheWheel, I love your surge tank location and installation. I didn't know surge tanks could work without using a fuel cell.
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Old 09-30-2019, 08:14 AM   #4
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Quote:
Originally Posted by Shahano View Post
My car is a swapped LS3 with a cam. I have a DW300c fuel pump and I am having problems with the fuel system. When I get on and off the throttle aggressively, the fuel cuts when I get back on, however when I go WOT, the car will respond perfectly well and will not go lean at any point (meaning that my fuel pump isn't too small).

Has anyone had this problem? I checked with a number of tuners, and the problem is not coming from the tune, bust most likely from the fuel system.
When you say checked with some tuners, did they plug in and look at the tune while running? Because what you are describing is using two different fuel tables.
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Old 09-30-2019, 09:29 AM   #5
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Check your fuel pump installation. Your fuel setup is adequate for an NA LS3. I bet the fuel pump is not tight and is letting some fuel pressure to escape when itís going leaner. Had it happen the first time I replaced the fuel pump on the car. The fuel pump canister needs to close real tight and use as many O rings plus white spacer if you still have it as needed to make it happen.
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Old 09-30-2019, 09:31 AM   #6
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My LS3 swapped car has a DW300C and has no fueling issues other than not being able to go below 1/4 tank, but I am 98% sure that is due to my OEM FPR delete. I also made almost 500whp on it. I would double check to make sure you don't have a leak anywhere (double check the O-Rings on the pump it self), and possibly look at having the pump checked by DW.
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Old 09-30-2019, 09:37 AM   #7
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When you say checked with some tuners, did they plug in and look at the tune while running? Because what you are describing is using two different fuel tables.
We did a number of logs that were sent to the tuners for them to verify.

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My LS3 swapped car has a DW300C and has no fueling issues other than not being able to go below 1/4 tank, but I am 98% sure that is due to my OEM FPR delete. I also made almost 500whp on it. I would double check to make sure you don't have a leak anywhere (double check the O-Rings on the pump it self), and possibly look at having the pump checked by DW.
Taking the car to the mechanic this evening to check for all possible leaks. Will open up the whole assembly and see. We used all 3 o-rings that came with the pump as described in the instructions.
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Old 10-03-2019, 06:21 AM   #8
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Originally Posted by DustinS View Post
My LS3 swapped car has a DW300C and has no fueling issues other than not being able to go below 1/4 tank, but I am 98% sure that is due to my OEM FPR delete. I also made almost 500whp on it. I would double check to make sure you don't have a leak anywhere (double check the O-Rings on the pump it self), and possibly look at having the pump checked by DW.
Did you replace the fuel pump regulator with an aftermarket one? If yes, which one? @DustinS
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Old 10-03-2019, 10:01 AM   #9
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Did you replace the fuel pump regulator with an aftermarket one? If yes, which one? @DustinS
I replaced the Factory FPR in the fuel pump assembly with the VitViper FPR Blank and I am running and Aeromotive FPR in the engine bay.

I ran into an issue where my car straight runs out of gas at 1/4 on the gas gauge. I can put a gallon in and the car will run again for a bit. Seems my siphoning system was affected by the FPR blank. VitViper says they haven't heard of any other issues with it though. It's that or my MRS canbus device has the wrong calibration. I couldn't really get a solid answer and the guy that was working on the project at MRS is no longer working for them. So I am SOL
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Old 10-04-2019, 02:44 AM   #10
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I replaced the Factory FPR in the fuel pump assembly with the VitViper FPR Blank and I am running and Aeromotive FPR in the engine bay.

I ran into an issue where my car straight runs out of gas at 1/4 on the gas gauge. I can put a gallon in and the car will run again for a bit. Seems my siphoning system was affected by the FPR blank. VitViper says they haven't heard of any other issues with it though. It's that or my MRS canbus device has the wrong calibration. I couldn't really get a solid answer and the guy that was working on the project at MRS is no longer working for them. So I am SOL
@DustinS was there a benefit in running a different FPR than the stock one? What problems were you have with the stock one?
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Old 10-04-2019, 08:41 AM   #11
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@DustinS was there a benefit in running a different FPR than the stock one? What problems were you have with the stock one?
I did a custom Return system is the only reason I got rid of mine. Also let me set it up for a vacuum reference for boost later.
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Old 10-07-2019, 10:14 AM   #12
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Good news and bad news. The good news is we found the problem, bad news is we haven't yet found the solution.

So after installing a fuel pressure gauge, we realized that there is a problem somewhere with the electrical. When getting on and off the throttle, the pump stops receiving any power for a few seconds which is causing the cut in the throttle. We tried changing the relays, but that didn't make a difference.
Anyone had that before?
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Old 10-07-2019, 10:30 AM   #13
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UPDATE: Turns out the problem is from a faulty fuel pump control module (not sure what that means). Did you guys bypass it or is mine just bad and I should have it replaced?
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Old 10-07-2019, 11:01 AM   #14
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UPDATE: Turns out the problem is from a faulty fuel pump control module (not sure what that means). Did you guys bypass it or is mine just bad and I should have it replaced?
Bypass the factory pump controller if you aren't using Motec or Emtron (pretty sure those two are the only ones that use the factory pump module?). Pretty sure it's the grey and green wires going into it. Negative and Positive respectively. Just wire that to your ecu or a relay set-up preferably.
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