Anyone want to walk me through a proper fuel pump ecu bypass?
03-01-17, 02:34 PM
#1
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Anyone want to walk me through a proper fuel pump ecu bypass?
My fuel pump ecu died, I'd like to do the bypass on my sc400 seems how I'm turboing it anyways, I want the fuel pump to cut on and off with the car or be ran to a switch. Please help, pictures and detailed explanation. Very new to Lexus world haha
03-01-17, 07:36 PM
#2
I am pretty sure this is documented on here, look thru the archives via a search I think you will find how to install a relay and use it to pick up the fuel pump with the ecu just like stock. It will just operate on full power which isn't a big deal most cars do.
03-02-17, 12:08 PM
#4
If your fuel ecu is dead in a pinch you can connect the input 12v to the fuel ecu to the output 12v wire to the pump. this bypasses fuel ecu and disables the safety functions for accidents though. I wouldn't do or recommend this at all.
If you want to put a switch or trigger off something, throw in a relay with the above as input and output, and on the trigger side run your switch or what you want to trigger off of. Still wouldn't do or recommend this at all.
Ideally you would have a working fuel pump ecu, and use its output to trigger the relay (keeping all the safety stuff). Then you could wire the power as above or use a new 12v line from the battery which is better. This is the "proper" way to do it. There is no "proper" way without the fuel ecu unless you have a standalone and are using one of the outputs to trigger the relay (as this retains some safety still).
In a modified turbocharged car on the streets I would never recommend bypassing the fuel ecu completely which disables the safety features, if you ever crash you are leaving it up to chance that you will be able to turn off the fuel pump which is not smart. Just get another used one that works or go standalone.
If you want to put a switch or trigger off something, throw in a relay with the above as input and output, and on the trigger side run your switch or what you want to trigger off of. Still wouldn't do or recommend this at all.
Ideally you would have a working fuel pump ecu, and use its output to trigger the relay (keeping all the safety stuff). Then you could wire the power as above or use a new 12v line from the battery which is better. This is the "proper" way to do it. There is no "proper" way without the fuel ecu unless you have a standalone and are using one of the outputs to trigger the relay (as this retains some safety still).
In a modified turbocharged car on the streets I would never recommend bypassing the fuel ecu completely which disables the safety features, if you ever crash you are leaving it up to chance that you will be able to turn off the fuel pump which is not smart. Just get another used one that works or go standalone.
Last edited by Ali SC3; 03-02-17 at 12:16 PM.
03-06-17, 02:09 AM
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If your fuel ecu is dead in a pinch you can connect the input 12v to the fuel ecu to the output 12v wire to the pump. this bypasses fuel ecu and disables the safety functions for accidents though. I wouldn't do or recommend this at all.
If you want to put a switch or trigger off something, throw in a relay with the above as input and output, and on the trigger side run your switch or what you want to trigger off of. Still wouldn't do or recommend this at all.
Ideally you would have a working fuel pump ecu, and use its output to trigger the relay (keeping all the safety stuff). Then you could wire the power as above or use a new 12v line from the battery which is better. This is the "proper" way to do it. There is no "proper" way without the fuel ecu unless you have a standalone and are using one of the outputs to trigger the relay (as this retains some safety still).
In a modified turbocharged car on the streets I would never recommend bypassing the fuel ecu completely which disables the safety features, if you ever crash you are leaving it up to chance that you will be able to turn off the fuel pump which is not smart. Just get another used one that works or go standalone.
If you want to put a switch or trigger off something, throw in a relay with the above as input and output, and on the trigger side run your switch or what you want to trigger off of. Still wouldn't do or recommend this at all.
Ideally you would have a working fuel pump ecu, and use its output to trigger the relay (keeping all the safety stuff). Then you could wire the power as above or use a new 12v line from the battery which is better. This is the "proper" way to do it. There is no "proper" way without the fuel ecu unless you have a standalone and are using one of the outputs to trigger the relay (as this retains some safety still).
In a modified turbocharged car on the streets I would never recommend bypassing the fuel ecu completely which disables the safety features, if you ever crash you are leaving it up to chance that you will be able to turn off the fuel pump which is not smart. Just get another used one that works or go standalone.
03-07-17, 02:50 PM
#6
generally when a sc400 doesn't start that means the fuel ecu, a coilpack or both could have gone bad (will usually run with 1 coilpack but down on power), or the ecu might have gone bad and need to be replaced or serviced.
Since you said sometimes it starts and sometimes it doesn't I would think the ecu is likely gone bad. You can open it up and take a look inside to see if the capacitors are leaking. its pretty common these days on these older vehicles to have the ecu going bad.
it doesn't matter if the connector on the fuel ecu is connected or not when you bypass, cause you are putting power straight to the pump when you cut and connect those 2 wires.
you can accomplish the same thing as a test by jumping b+ (12v battery) and fp (fuel pump) in the diagnostic connector with a paper clip but just as a test don't drive around relying on a paper clip.
Since you said sometimes it starts and sometimes it doesn't I would think the ecu is likely gone bad. You can open it up and take a look inside to see if the capacitors are leaking. its pretty common these days on these older vehicles to have the ecu going bad.
it doesn't matter if the connector on the fuel ecu is connected or not when you bypass, cause you are putting power straight to the pump when you cut and connect those 2 wires.
you can accomplish the same thing as a test by jumping b+ (12v battery) and fp (fuel pump) in the diagnostic connector with a paper clip but just as a test don't drive around relying on a paper clip.
03-07-17, 03:00 PM
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generally when a sc400 doesn't start that means the fuel ecu, a coilpack or both could have gone bad (will usually run with 1 coilpack but down on power), or the ecu might have gone bad and need to be replaced or serviced.
Since you said sometimes it starts and sometimes it doesn't I would think the ecu is likely gone bad. You can open it up and take a look inside to see if the capacitors are leaking. its pretty common these days on these older vehicles to have the ecu going bad.
it doesn't matter if the connector on the fuel ecu is connected or not when you bypass, cause you are putting power straight to the pump when you cut and connect those 2 wires.
you can accomplish the same thing as a test by jumping b+ (12v battery) and fp (fuel pump) in the diagnostic connector with a paper clip but just as a test don't drive around relying on a paper clip.
Since you said sometimes it starts and sometimes it doesn't I would think the ecu is likely gone bad. You can open it up and take a look inside to see if the capacitors are leaking. its pretty common these days on these older vehicles to have the ecu going bad.
it doesn't matter if the connector on the fuel ecu is connected or not when you bypass, cause you are putting power straight to the pump when you cut and connect those 2 wires.
you can accomplish the same thing as a test by jumping b+ (12v battery) and fp (fuel pump) in the diagnostic connector with a paper clip but just as a test don't drive around relying on a paper clip.
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03-07-17, 03:50 PM
#8
It sounds like the main ecu, but I can't say definitely. it could be a number of things but I would check the ecu first if it does run well when it runs.
the ecu's tend to get picky depending on the weather at first, then they will just die. if you smell lots of unburnt fuel when its running its even more likely the ecu.
the ecu's tend to get picky depending on the weather at first, then they will just die. if you smell lots of unburnt fuel when its running its even more likely the ecu.
03-07-17, 11:21 PM
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It sounds like the main ecu, but I can't say definitely. it could be a number of things but I would check the ecu first if it does run well when it runs.
the ecu's tend to get picky depending on the weather at first, then they will just die. if you smell lots of unburnt fuel when its running its even more likely the ecu.
the ecu's tend to get picky depending on the weather at first, then they will just die. if you smell lots of unburnt fuel when its running its even more likely the ecu.
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