For those of you with Aftermarket Fuel Pumps and running out of gas at 1/4 tank!
10-04-11 | 07:41 PM
#1
For those of you with Aftermarket Fuel Pumps and running out of gas at 1/4 tank!
there seems to be another issue at hand. Please see Jeff's post # 9
I have a 255 walbro in my 03 GS300 and I can go all the way to empty with light on and keep going and fill up to full and run it back down to light on with no issues.
I also have a SARD Jet Pump Killer installed. This creates a venturi effect in order to put the side B gas into side A so the pump picks it up. Its designed for the higher flow of the aftermarket pump!
I have a 255 walbro in my 03 GS300 and I can go all the way to empty with light on and keep going and fill up to full and run it back down to light on with no issues.
I also have a SARD Jet Pump Killer installed. This creates a venturi effect in order to put the side B gas into side A so the pump picks it up. Its designed for the higher flow of the aftermarket pump!
Last edited by AMSMIKE; 10-05-11 at 09:56 AM.
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10-04-11 | 11:02 PM
#8
basically, when you run out of gas and it says 1/4 tank. How many gallons does the car pump until its full? This is very important.
please post the results!
10-05-11 | 03:46 AM
#9
AMSMIKE, I'm not trying to crap on your thread or anything. I'm just offering some insight into this issue. I've had several years of experimenting to test the theory lol.
This SARD jet pump doesn't quite fix the issue. You can drill out the stock jet unit and it will be similar to this sard jet. Even SRT builds the custom billet dual pump hanger and it has a large capacity one of these jet pump things intergrated into it. Still, that does not solve the 1/4 tank issue.
I don't have 100% positive proof on this, but this is my theory. The ECU or gauge cluster calculates the remaining fuel level via the float, MAF flow, and injector duty cycle. When you upgrade to bigger injectors it throws off this entire fuel tank calculation. Many of the GM ecu on Corvettes I've worked with and programmed do this to calculate fuel remaining in tank, so I don't see why the Lexus ECU does not do this. Inside the GM ecu, you can reprogram the parameters so that it will compensate for a larger fuel system. The Toyota ecu's are pretty locked down so this is not possible.
Those with the JDM Aristo GTE VVTi ecu may experience this to a lesser degree because those come stock with 440cc injectors while the USDM one comes with 280cc units.
I skewed the MAF voltage slightly in both directions on my FIC and tested through several tank of gas, and the point at where I run out of gas will change on the gauge! I've done this through several tank of gas and the point where it runs out of gas always changes as well. If I increase MAF voltage skew, but compensate for it in the injector duty cycle, the gauge will track more accurately down to the bottom line. If I keep the MAF at 0% skew, the car will run out of gas closer to the 1/4 mark. Also, if you have boost(especially on a bigger turbo) and drive the car hard all the time, it will run out of gas sooner than the 1/4. This is because a MAF clamp will hide the extra airflow from the ECU when it passes out of the ECU's reading range.
It's a really annoying issue that I've been facing for a while now. I think I may come up with a electronic solution for this when I have time in the future. I'll have to do some more testing, but I don't have so much time for that now days, but it is on my to do list lol
EDIT: Just some extra proof. When I've boosted cars on stock injectors, they never have this issue ever. Their fuel gauge will track perfectly to the bottom line EVERY single time. The fuel gauge will be off as soon as the injectors are upgraded to a bigger size. Just to keep things consistent, I even left the stock return-less fuel line and pump assembly in place. Did not change a single thing besides the injectors, and the 1/4 tank issue rear it's head right away. I've done this same test on 3 cars now with the same result every time.
Mike, I know you have a LS swap in your GS. Maybe once the stock MAF is out of the loop, it is possible that the ECU reads strictly from the float. In your case, the jet pump would of solved your problems.
This SARD jet pump doesn't quite fix the issue. You can drill out the stock jet unit and it will be similar to this sard jet. Even SRT builds the custom billet dual pump hanger and it has a large capacity one of these jet pump things intergrated into it. Still, that does not solve the 1/4 tank issue.
I don't have 100% positive proof on this, but this is my theory. The ECU or gauge cluster calculates the remaining fuel level via the float, MAF flow, and injector duty cycle. When you upgrade to bigger injectors it throws off this entire fuel tank calculation. Many of the GM ecu on Corvettes I've worked with and programmed do this to calculate fuel remaining in tank, so I don't see why the Lexus ECU does not do this. Inside the GM ecu, you can reprogram the parameters so that it will compensate for a larger fuel system. The Toyota ecu's are pretty locked down so this is not possible.
Those with the JDM Aristo GTE VVTi ecu may experience this to a lesser degree because those come stock with 440cc injectors while the USDM one comes with 280cc units.
I skewed the MAF voltage slightly in both directions on my FIC and tested through several tank of gas, and the point at where I run out of gas will change on the gauge! I've done this through several tank of gas and the point where it runs out of gas always changes as well. If I increase MAF voltage skew, but compensate for it in the injector duty cycle, the gauge will track more accurately down to the bottom line. If I keep the MAF at 0% skew, the car will run out of gas closer to the 1/4 mark. Also, if you have boost(especially on a bigger turbo) and drive the car hard all the time, it will run out of gas sooner than the 1/4. This is because a MAF clamp will hide the extra airflow from the ECU when it passes out of the ECU's reading range.
It's a really annoying issue that I've been facing for a while now. I think I may come up with a electronic solution for this when I have time in the future. I'll have to do some more testing, but I don't have so much time for that now days, but it is on my to do list lol
EDIT: Just some extra proof. When I've boosted cars on stock injectors, they never have this issue ever. Their fuel gauge will track perfectly to the bottom line EVERY single time. The fuel gauge will be off as soon as the injectors are upgraded to a bigger size. Just to keep things consistent, I even left the stock return-less fuel line and pump assembly in place. Did not change a single thing besides the injectors, and the 1/4 tank issue rear it's head right away. I've done this same test on 3 cars now with the same result every time.
Mike, I know you have a LS swap in your GS. Maybe once the stock MAF is out of the loop, it is possible that the ECU reads strictly from the float. In your case, the jet pump would of solved your problems.
Last edited by JeffTsai; 10-05-11 at 03:53 AM.
10-05-11 | 05:24 AM
#10
when you run out. how much gas goes to in Full and clicks off. I have seen others with issues and turned out it was the sending unit / float.
basically, when you run out of gas and it says 1/4 tank. How many gallons does the car pump until its full? This is very important.
please post the results!
basically, when you run out of gas and it says 1/4 tank. How many gallons does the car pump until its full? This is very important.
please post the results!
There's two 400's with swaps that I know an neither have the issue. Ones using the stock 400 pump an no SARD JPK, an the other is using the walbro 255 WITHOUT the SARD JPK. The three of us are on stock twins and I'm the only 300
10-05-11 | 06:10 AM
#11
Wicked, so you're also getting 19gal till empty right? Just that the gauge shows the 1/4 when you actually run out. That's my situation 19 gal when the gauge is at the 1/4, just wanted to see if everyone else is having the same thing going on. If that's the case with you and your friends 400's, then that can further confirm my theory above. Also, need to factor which ECU you guys are using.
10-05-11 | 08:00 AM
#12
Wicked, so you're also getting 19gal till empty right? Just that the gauge shows the 1/4 when you actually run out. That's my situation 19 gal when the gauge is at the 1/4, just wanted to see if everyone else is having the same thing going on. If that's the case with you and your friends 400's, then that can further confirm my theory above. Also, need to factor which ECU you guys are using.
but yea mine reads fine so far... least from what i can tell
10-05-11 | 09:45 AM
#14
AMSMIKE, I'm not trying to crap on your thread or anything. I'm just offering some insight into this issue. I've had several years of experimenting to test the theory lol.
This SARD jet pump doesn't quite fix the issue. You can drill out the stock jet unit and it will be similar to this sard jet. Even SRT builds the custom billet dual pump hanger and it has a large capacity one of these jet pump things intergrated into it. Still, that does not solve the 1/4 tank issue.
I don't have 100% positive proof on this, but this is my theory. The ECU or gauge cluster calculates the remaining fuel level via the float, MAF flow, and injector duty cycle. When you upgrade to bigger injectors it throws off this entire fuel tank calculation. Many of the GM ecu on Corvettes I've worked with and programmed do this to calculate fuel remaining in tank, so I don't see why the Lexus ECU does not do this. Inside the GM ecu, you can reprogram the parameters so that it will compensate for a larger fuel system. The Toyota ecu's are pretty locked down so this is not possible.
Those with the JDM Aristo GTE VVTi ecu may experience this to a lesser degree because those come stock with 440cc injectors while the USDM one comes with 280cc units.
I skewed the MAF voltage slightly in both directions on my FIC and tested through several tank of gas, and the point at where I run out of gas will change on the gauge! I've done this through several tank of gas and the point where it runs out of gas always changes as well. If I increase MAF voltage skew, but compensate for it in the injector duty cycle, the gauge will track more accurately down to the bottom line. If I keep the MAF at 0% skew, the car will run out of gas closer to the 1/4 mark. Also, if you have boost(especially on a bigger turbo) and drive the car hard all the time, it will run out of gas sooner than the 1/4. This is because a MAF clamp will hide the extra airflow from the ECU when it passes out of the ECU's reading range.
It's a really annoying issue that I've been facing for a while now. I think I may come up with a electronic solution for this when I have time in the future. I'll have to do some more testing, but I don't have so much time for that now days, but it is on my to do list lol
EDIT: Just some extra proof. When I've boosted cars on stock injectors, they never have this issue ever. Their fuel gauge will track perfectly to the bottom line EVERY single time. The fuel gauge will be off as soon as the injectors are upgraded to a bigger size. Just to keep things consistent, I even left the stock return-less fuel line and pump assembly in place. Did not change a single thing besides the injectors, and the 1/4 tank issue rear it's head right away. I've done this same test on 3 cars now with the same result every time.
Mike, I know you have a LS swap in your GS. Maybe once the stock MAF is out of the loop, it is possible that the ECU reads strictly from the float. In your case, the jet pump would of solved your problems.
This SARD jet pump doesn't quite fix the issue. You can drill out the stock jet unit and it will be similar to this sard jet. Even SRT builds the custom billet dual pump hanger and it has a large capacity one of these jet pump things intergrated into it. Still, that does not solve the 1/4 tank issue.
I don't have 100% positive proof on this, but this is my theory. The ECU or gauge cluster calculates the remaining fuel level via the float, MAF flow, and injector duty cycle. When you upgrade to bigger injectors it throws off this entire fuel tank calculation. Many of the GM ecu on Corvettes I've worked with and programmed do this to calculate fuel remaining in tank, so I don't see why the Lexus ECU does not do this. Inside the GM ecu, you can reprogram the parameters so that it will compensate for a larger fuel system. The Toyota ecu's are pretty locked down so this is not possible.
Those with the JDM Aristo GTE VVTi ecu may experience this to a lesser degree because those come stock with 440cc injectors while the USDM one comes with 280cc units.
I skewed the MAF voltage slightly in both directions on my FIC and tested through several tank of gas, and the point at where I run out of gas will change on the gauge! I've done this through several tank of gas and the point where it runs out of gas always changes as well. If I increase MAF voltage skew, but compensate for it in the injector duty cycle, the gauge will track more accurately down to the bottom line. If I keep the MAF at 0% skew, the car will run out of gas closer to the 1/4 mark. Also, if you have boost(especially on a bigger turbo) and drive the car hard all the time, it will run out of gas sooner than the 1/4. This is because a MAF clamp will hide the extra airflow from the ECU when it passes out of the ECU's reading range.
It's a really annoying issue that I've been facing for a while now. I think I may come up with a electronic solution for this when I have time in the future. I'll have to do some more testing, but I don't have so much time for that now days, but it is on my to do list lol
EDIT: Just some extra proof. When I've boosted cars on stock injectors, they never have this issue ever. Their fuel gauge will track perfectly to the bottom line EVERY single time. The fuel gauge will be off as soon as the injectors are upgraded to a bigger size. Just to keep things consistent, I even left the stock return-less fuel line and pump assembly in place. Did not change a single thing besides the injectors, and the 1/4 tank issue rear it's head right away. I've done this same test on 3 cars now with the same result every time.
Mike, I know you have a LS swap in your GS. Maybe once the stock MAF is out of the loop, it is possible that the ECU reads strictly from the float. In your case, the jet pump would of solved your problems.
Very interesting to see that the dual fuel hanger by swift didnt fix the issue. That certainly points to something else causing the 1/4 read when in fact the tank is empty! I was also looking into those units and I have been talking to Mo @ swift about them.
But as you know, LS swap and no factory maf or ecu and thats probably why I am having no issue at all. The cluster is reading from the float with no other calculation. So with that said, you are most likely spot on that the maf and ecu have a big part of it. Especially if you skew the maf percentage and see various results.
10-05-11 | 09:53 AM
#15
Wicked, so you're also getting 19gal till empty right? Just that the gauge shows the 1/4 when you actually run out. That's my situation 19 gal when the gauge is at the 1/4, just wanted to see if everyone else is having the same thing going on. If that's the case with you and your friends 400's, then that can further confirm my theory above. Also, need to factor which ECU you guys are using.