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+--- Thread: My IS300 story so far.... (/showthread.php?tid=7184)
My IS300 story so far.... - toxo - 21-07-2019
Fuel pump resistor.
What do I win?
My IS300 story so far.... - Dark Samurai - 21-07-2019
toxo Fuel pump resistor.
Exactly what my Dad said.
My IS300 story so far.... - jimxms - 21-07-2019
toxo Fuel pump resistor.
What do I win?
Man knows his stuff. They probably don't fail often enough for most people to know what they are :p
You win...errr...a fuel pump resistor!
My IS300 story so far.... - is300_dino - 21-07-2019
so what does that mean by disconnecting it? whats it likely to do/not do?
My IS300 story so far.... - toxo - 21-07-2019
Toyota like fitting them on a relay which means the ECU can optionally cut the fuel pump voltage down to 9V by passing the current through the resistor rather than directly to the pump. This makes the fuel pump run slower so they can fit a larger pump, and turn it up to full when it's required (i.e. when you floor it), but it'll still maintain fuel efficiency when cruising.
If you remove it you have to connect the 2 wires together otherwise when the ECU tries to knock your fuel pump down to 9V it will have 0V instead
My IS300 story so far.... - jimxms - 21-07-2019
toxo Toyota like fitting them on a relay which means the ECU can optionally cut the fuel pump voltage down to 9V by passing the current through the resistor rather than directly to the pump. This makes the fuel pump run slower so they can fit a larger pump, and turn it up to full when it's required (i.e. when you floor it), but it'll still maintain fuel efficiency when cruising.
If you remove it you have to connect the 2 wires together otherwise when the ECU tries to knock your fuel pump down to 9V it will have 0V instead
^ on the money.
The reason I removed mine was because my pump voltage was dropping to 7v when going through the resistor and my Walbro pump wasn't liking it very much.
I'm also trying to tackle an issue where my AFR's go 'randomly' rich when at idle. Now that I've got rid of the resistor my pump runs at a steady 13v and I think it looks like _maybe_ the pump is providing too much pressure for the car to compensate for..... which leads to the reason for me needing an OBD scanner which can read short term fuel trims.
My IS300 story so far.... - toxo - 21-07-2019
You're very rapidly moving into standalone ECU territory IMO!
My IS300 story so far.... - jimxms - 21-07-2019
toxo You're very rapidly moving into standalone ECU territory IMO!
Yeah tell me about it.
Here's the weird thing though.....
At idle my AFR's would 'randomly' flick between 13.0 or 14.7. I noticed this was happening when the noise/pitch of the fuel pump would change. So after a bit of reading I removed the fuel pump resistor which now means that the pump stays at a constant voltage.
This has now nailed my idle AFR's at an _almost_ constant 13.0 APART from when the radiator fans come on and the AFR jumps back up to 14.7.
My reasoning (which may well be wrong) is that the pump is providing too much pressure at idle and the ECU is having trouble backing off the fuel trims enough to compensate for it. However as soon as the radiator fans come on (or indeed I turn any high power draw devices on), the current to the pump drops slightly and the car is able to bring the AFR's back into check.
The only way for me to check this for certain though is to get an OBD tool to read the short term fuel trims and see if they are maxed out (-25 I think?) or install a fuel pressure meter to see how much pressure the pump is pushing through.
If this is indeed the problem I assume the solution would be to either put a permanent resistor on the fuel pump to drop the voltage a tad, or go standalone which will allow me to pull more fuel away at idle?
Or I could just close my eyes at idle and pretend my AFR's are OK. 13.0 isn't toooo terrible, and the idle is still fairly smooth at this. The only thing is I randomly get a CEL for "bank x running too rich" which doesnt put me in limp, but is annoying neverless
My IS300 story so far.... - jimxms - 22-07-2019
Annoyingly my radiator and lightweight pullies haven't arrived yet so I can only assume they are on some container ship sailing half way round the world.
But I cant wait any longer to get boosting again, so this weekend I think I'm going to put the new charger on the car and see if I can come close to hitting 1bar with my new setup.
My IS300 story so far.... - speedfreek - 22-07-2019
jimxms Annoyingly my radiator and lightweight pullies haven't arrived yet so I can only assume they are on some container ship sailing half way round the world.
But I cant wait any longer to get boosting again, so this weekend I think I'm going to put the new charger on the car and see if I can come close to hitting 1bar with my new setup.
Seriously mate, stop posting on this thread.
It makes me jealous and I don't like it :laugh: