SC300 12v Fuel Mod w/ Pictures - FAQ
10-02-16, 07:58 PM
#286
Can we just continue to run the car by jumping the Fp & B+ on the diagnostic connector itself (for however long we wish to do so) instead of going through the process of removing the rear seat and splicing the green & red/black wire together. I mean is there a difference in the 2... Like for instance jumping it on the diagnostic block, does that cause the pump to run even if the key is tuned to Off position? I do have a Snap-On diagnostic hand held scanner and I realize that if I would ever need to use the connector I would have to do "ECM" route by removing the back seat, so this would just be temporary...
Another thing that concerns me is that Ive equipped this car with remote start for My wife (it earned me some good time points
) and if it would still work while the key is in the off position.
I just wanna make sure cause I did this and it worked, I could also hear the pump running even with the car running at idle, and my car is loud with dual straight pipe exhaust.
Another thing that concerns me is that Ive equipped this car with remote start for My wife (it earned me some good time points
) and if it would still work while the key is in the off position.I just wanna make sure cause I did this and it worked, I could also hear the pump running even with the car running at idle, and my car is loud with dual straight pipe exhaust.
06-11-19, 02:49 AM
#287
Driver School Candidate
Upping the pressure on an N/A 93 SC
So any one know if doing this mod and replacing the factory FPR would make a difference in power gain or drivability of my N/A sc300?, which I've fitted with a header, and a custom intake that uses the the LS400 MAF body (about 3" ID), The only reason I ask is my car breaks up a bit under load, or hesitates, a bit before the feeling of acceleration comes back when I give her the beans!
Mod Location:
The Fuel Pump ECU is located under the driver side rear qtr window.
Reason:
This mod is very easy - I did the mod because I was having Warm Start problems with my SC300, the car would start up then die (This would happen 10+ times in a row) This mod fixed my problem - everything works perfect now. This will also help when I go NA-T , I will have a step by step thread on that as well.
Vehicle Used:
This car is a 1992 SC300, Auto
Total Mod Time:
45 Mins
From MKIV.com
The Problem:
When modifications are made to the car to increase boost pressure and engine breathing ability, some owners have experienced detonation around 4000 rpm, as the 2nd turbo builds boost and comes on line. Usually, this detonation disappears above 5000 rpm. The problem is, the fuel pump is still in "low speed" mode around 4000 rpm's, but the performance modifications have increased fuel demand to the point of "outrunning" the low speed operation. By 5000 rpm, the fuel pump ECU has caught up and switches to high speed operation and all detonation disappears.
The Solution:
There is an easy way around this. You can wire a 12 volt signal directly to the fuel pump, effectively bypassing the fuel pump ECU so that the fuel pump is always in high speed operation. The TT Supra is one of only a few cars that has this dual mode of fuel pump operation, whereas most cars always have 12 volts to the fuel pump. This mod is completely safe. You are basically just turning your complicated fuel system into a basic, Camry style fuel system. You may shorten the life of your fuel pump from say 20 years down to 18 years, but nothing to worry about in the short term. I've personally had mine hooked up this way for over 2 years now without any troubles.
I hope this helps anyone looking to do the 12v fuel mod or starting issues.
Start with the rear seats.
Pull up on the front of the rear seats to remove the bottoms.
Rear seats removed
Remove the 3 bolts holding the rear back panel down. (12mm)
Rear seats removed
Remove 2 push tabs from the panel under the driver side qtr window.
The Fuel Pump ECU is located under the driver side rear qtr window.
Reason:
This mod is very easy - I did the mod because I was having Warm Start problems with my SC300, the car would start up then die (This would happen 10+ times in a row) This mod fixed my problem - everything works perfect now. This will also help when I go NA-T , I will have a step by step thread on that as well.
Vehicle Used:
This car is a 1992 SC300, Auto
Total Mod Time:
45 Mins
From MKIV.com
The Problem:
When modifications are made to the car to increase boost pressure and engine breathing ability, some owners have experienced detonation around 4000 rpm, as the 2nd turbo builds boost and comes on line. Usually, this detonation disappears above 5000 rpm. The problem is, the fuel pump is still in "low speed" mode around 4000 rpm's, but the performance modifications have increased fuel demand to the point of "outrunning" the low speed operation. By 5000 rpm, the fuel pump ECU has caught up and switches to high speed operation and all detonation disappears.
The Solution:
There is an easy way around this. You can wire a 12 volt signal directly to the fuel pump, effectively bypassing the fuel pump ECU so that the fuel pump is always in high speed operation. The TT Supra is one of only a few cars that has this dual mode of fuel pump operation, whereas most cars always have 12 volts to the fuel pump. This mod is completely safe. You are basically just turning your complicated fuel system into a basic, Camry style fuel system. You may shorten the life of your fuel pump from say 20 years down to 18 years, but nothing to worry about in the short term. I've personally had mine hooked up this way for over 2 years now without any troubles.
I hope this helps anyone looking to do the 12v fuel mod or starting issues.
Start with the rear seats.
Pull up on the front of the rear seats to remove the bottoms.
Rear seats removed
Remove the 3 bolts holding the rear back panel down. (12mm)
Rear seats removed
Remove 2 push tabs from the panel under the driver side qtr window.
01-24-21, 01:12 PM
#288
Fuel pump ecu relay mod
IMO, the way everyone is doing it here is not the best way to do it...
Not sure if I've said it before, but I will now, for sure...
The absolute best way to provide constant +12v power to the fuel pump and not have to worry about anything shorting out, or the fuel pump running indefinitely, is to run your own power wire directly from the battery, 10 or 8 gauge wire is sufficient. Run this to a relay that is near the pump... ground the relay, and use the existing power wire to the fuel pump to trigger the relay on and off, then run a new power wire from the relay to the pump itself (there is no need for much larger wire here, as it is very close to the pump anyways).
Been doing this for years on many different cars - it provides better voltage to the pump (due to larger diameter wiring and a direct run), and it also keeps the fuel pump running the same amount all the time, which is easier to tune in the long run.
The one problem many may run into here, however, is that the fuel pump may provide too much fuel at idle and lower rpm, causing the car to run rich because the fuel pressure regulator is not able to bleed off that much fuel (Especially when running an upgraded fuel pump). To fix this issue, the only real way is to run an aftermarket fuel pressure regulator...
Not sure if I've said it before, but I will now, for sure...
The absolute best way to provide constant +12v power to the fuel pump and not have to worry about anything shorting out, or the fuel pump running indefinitely, is to run your own power wire directly from the battery, 10 or 8 gauge wire is sufficient. Run this to a relay that is near the pump... ground the relay, and use the existing power wire to the fuel pump to trigger the relay on and off, then run a new power wire from the relay to the pump itself (there is no need for much larger wire here, as it is very close to the pump anyways).
Been doing this for years on many different cars - it provides better voltage to the pump (due to larger diameter wiring and a direct run), and it also keeps the fuel pump running the same amount all the time, which is easier to tune in the long run.
The one problem many may run into here, however, is that the fuel pump may provide too much fuel at idle and lower rpm, causing the car to run rich because the fuel pressure regulator is not able to bleed off that much fuel (Especially when running an upgraded fuel pump). To fix this issue, the only real way is to run an aftermarket fuel pressure regulator...
01-25-21, 08:37 AM
#290
01-25-21, 10:12 AM
#291
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