MR2 Owners Club Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
ST215W full wiring, ECU and fuel system.
Has anyone removed fuel pump resistor? New high flow fuel pump does not support undervoltage.

Is ST215W fuel pressure controlled by ECU or conventional regulator? If fuel pump still provides full pressure and it won't lower when ECU is trying to lower pressure by resistor, does ECU make fault code or even worse - Whole system going into fault mode?

Has anyone done fuel pump change?

Thank you already!
 

·
Premium Member
Joined
·
12,047 Posts
The resistor doesn't lower the pressure. It just lowers the flow through the regulator. This is to prevent unnecessary heating of the fuel, and also to prevent the maximum flow from overloading the regulator.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
Thank you! So pressure or fault codes/limp mode won't be a problem.
But if resistor is made to lower flow, will original regulator be enough with AEM 340lph RE85 pump without resistor or do I have to go aftermarket fuel reg too? I'm planning to install FlexFuel system and run RE85, 95E10 and 98E5 fuels randomly. That is why I have to upgrade my pump in first place.
 

·
Registered
Joined
·
2,181 Posts
The fuel pump resistor lowers voltage to the fuel pump to slow the speed of the pump. Something like 12V vs 5V.
If your MR2 was originally NA then it won't have this system. If it was Turbo it will most likely.

If it's a Caldina then you can just bypass the resistor by joining the wires at the resistor. They are Blue w/Black. L = Blue in Japanese wiring diagrams.
69153
.

The ECU doesn't know what fuel pressure it is running, that is all mechanical.
You may need to upgrade the regulator for a pump with that much flow but I'm not sure. For what mods it seems you want to do you can't use the OEM ECU anyway.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #5 (Edited)
Okay, thank you. The eFlexFuel system is piggyback type, so you can use original ECU. Any good fuel reg suggestions?

Edit: Caldina wiring diagram shows Fuel Pressure Monitoring, that is why I thought ECU might be controlling Fuel Pressure.
IMG_20200214_051249.jpg
 

·
Registered
Joined
·
6 Posts
Discussion Starter #7 (Edited)
OK, thanks. I edited my last post and added picture of wiring diagram showing Fuel Pressure Monitor.

Does anyone know will stock fuel reg be enough? I tried Google and if "universal info" is correct, you "probably" won't have overflow overoverloading problems with factory regs. But that is universal, not vehicle specific info.


My car is daily driven for 100km/day so I'd like to know what to buy and what to consider when I start installing. That is why I'm gathering all this info.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #9
Thank you. My expertise is with older carburated xE7x series corollas so these EFI systems are a bit out of my comfort zone. Where do you get this information if I may ask? There aren't many sites that you find with Google that contain information about Caldinas
 

·
Registered
Joined
·
2,181 Posts
I have been doing extensive research on the SW20 and now the GEN4 3SGTE. Planning to do my own GEN4 swap in my MR2. I have already successfully created an engine wiring harness for one MR2 merging the original engine harness with the Caldina and planning to do another soon. I'm not quite in the financial position to do my own yet so helping mates.

I have found information all over the place and asking others but there is so much to cover it's too hard to give it all out in one post. Plus it's super confusing if you don't have things in front of you. Caldina wiring is only new to me, less than 1 year into it but the things you are asking about are the same for the MR2 so nothing special.

The Caldina wiring isn't too much different to a lot of late 80s and 90s Toyota so it's quite straight forward. To put it into the most simple terms, you have power, earth and signal to various sensors and switches and the ECU is programmed to deal with inputs and provide outputs. I am by no means a professional nor do I know how to tune ECUs or how they even run. I just know wiring for the SW20 MR2 and similar cars.

Working on some wiring information for a guy in Canada doing a simple 1991 JDM 3SGTE swap into 1992 JDM 3SGE powered SW20. Only 8-9 wires to adjust and the car will run and work mostly like OEM. Except you remove the Fuel Pump Resistor and Fuel Pump Resistor Relay as it's too hard to make it work as the 3SGE powered car never had it and it's part of the body harness. So doing what I suggest for your Caldina just like a lot of people do on the MR2 when the relay or resistor fails. Bypass the resistor or relay all together and run the pump at full speed the whole time. Your system is part of the engine harness but still works the same.
 
1 - 11 of 11 Posts
Top