98SC

Hey guys, just finishing up my vvti 2j-gte into '98 SC300 swap and have a little fuel pump electrical problem.

The Aristo ecu seems to signal the stock SC fuel pump ecu to turn on during cranking but once the engine starts the fuel pump turns off I checked the voltage on the "fpc" pin which is the high/low voltage signal to the fuel pump controller and it's getting about +5v when cranking but drops to +1.6v after starting, both of these are with respect to body ground. I'm also using a new Denso tt fuel pump.

My questions are: Why the +1.6v for the low speed fuel pump signal from the Aristo ecu, from what I've read here it's supposed to be +2.5v?? Also, does anyone know what voltages a '98 SC300 fuel pump ecu operates at for high/low triggers? I checked part numbers and it appears to be the same as older SC300's... Hmm, is there an easily obtainable Toyota fuel pump ecu that is compatible with the Aristo engine ecu? I've heard mention of the '98 na Supra but nothing for for sure on that. I'm thinking one from a GS might also be a good bet.

On a side note I did the +12v wiring mod for the fuel pump and it got the car running nicely I just don't trust this mod for a daily driver because of the problem with the pump continuing to run after shutdown. I already had this happen once, not good.

Thanks for any help!

Phil

1sxyrxy

sounds like something my friend did on his v8 swap on his rx7. it would turn on but when you stop cranking the car would stop running. sounds like you have power for the ecu hooked up to only when cranking?. sorry, im really sick right now i didnt read your whole thread. i also thought it was 9v at low speeds and 12v at full throttle

98SC

Yeah, my first thought was that I screwed up the wiring and that the ecu didn't think the engine was running but now I don't believe that's it. For instance the Aristo ecu puts out a +5v signal to the fuel pump controller when cranking & once the engine starts it drops to about 1.6v, if it thought the engine wasn't running I would think it would drop all the way to 0v. Also, with the fuel pump +12v (hot wire) mod the car runs and drives great, I'm not even getting a CEL.

Anyone know what signal voltages the stock SC300 fuel pump controller is looking for? Thanks!

Phil

slappy96

Well written post. Refreshing.

I won't waste your time though. I can't answer the question. I have the same assumptions regarding (5.0V/2.5V) trigger with the pump looking for 9V/12V. I have also read (SC300TT username maybe?) that the 98NA Fuel ECU complies with the 2.5/5.0, but he told me I should just do the 12V mod because the ECU is a special order from Japan and hard to locate.

I am about to cross this bridge. Just got my engine in (see sig) and have a new denso TT pump. It's an Aristo harness merged with SC300 and obviously Aristo ECU. Hopefully we can put this issue to bed.

Coincidently, Dr. Tweak at phoenixtuning told me that there are several of these setups running fine with the SC300 Fuel Pump ECU. He didn't claim to be an expert on this, but it makes me wonder.

Good luck and I'll let you know.

98SC

Thanks for the replies. I think we are all in this to figure it out and create solid information for guys doing this swap in the future.

Before I started my swap it seemed there was a lot of info on it but now that I've actually done it I'm seeing little things like this fuel pump issue that are still unknowns.

Here's my latest, I did some research and found out that the 98 - 05 GS300/400 use the same part number Fuel Pump Controller (FPC) as the mkII Aristo. The number is 89570-30180. Just an FYI, the FPC from the '98 Supra na has a different part number.

Anyway, I have a GS300 FPC on order and I'll post the results after installing it. As of now I'm still unsure if my problem is from a wiring issue or from incompatibility between the Aristo ecu and the SC300 FPC and installing the correct FPC will answer that question. Another thing to keep in mind is that my swap is a vvti ge motor to a vvti gte motor. A lot of the swap info I've found for the SC's is for the non-vvti motor which has different wiring.

Phil

slappy96

Good to point out the vvti aspect. Mine is in fact a non-vvti to non-vvti (all OBD I) setup.

booja

iTrader: (1)

pump running after shut down? if it does that maybe youre doing something wrong. i have a TT fuel pump in mine and the 12v mod done too. when the car turns off the pump turns off.

ive been driving around like this for over a year

98SC

The pump continued to run after shutdown once, which was one time too many for me to consider this mod as a permanent fix on a daily driver. You're right, it shouldn't do that but the 12v mod seems pretty hard to screw up, I mean it's just splicing two wires together.

I don't have the wiring diagrams in front of me but from memory the 12v mod connects the fuel pump directly to the +B (black/red) wire from the EFI main relay. So, anytime that relay is energized the pump will be running full bore. Is it possible that the extra load from the direct pump wiring could cause the relay to occasionally stick? (especially if it's already getting old?)

For what it's worth, I've read reports of a few others here having this same problem. Also, some of the mkiv Supra guys recommend against it after a few reports of melted fuel pumps, see link below:

http://www.mkivsupra.net/vbb/showthread.php?t=162745

Phil

98SC

I got the GS fuel pump controller and wired it in this weekend. It uses a different connector which I had to splice into the SC body harness. Also, it has an additional wire that is a dedicated ground for the fuel pump versus the original fuel pump controller which just has one ground that goes to the common body ground and fuel pump. Another thing I noticed on the pigtail connector was how much larger the stock GS +12V wire is compared to the SC's...

Anyway, it works great and the Aristo ECU is now controlling my fuel pump No more 12V mod to get my fuel pump running. So, for a swap using the vvti Aristo motor and ECU, the 2nd gen GS fuel pump controller (89570-30180) is needed unless you want to "hotwire" the pump and bypass the FPC and ECU.

Phil

BigGreen

iTrader: (2)

Nice work man, Thats the way to install the right way

slappy96

Now.....I guess it only remains for me to figure out how the Non-vvti side of the house works. I wonder if the GEN 1 GS Fuel ECU is the answer. Any inputs?

I am also going to give the no-mod shot at to see if any change is really necessary for non-vvti.

howat

Thank goodness slappy96 and I did not go with the vvti 2jzgte

Ali SC3

iTrader: (10)

the reason it works is because the sc300 ecu fuel pump ecu needs to see 12volts on high.
the new ecu you put in your car works on 5v high, which isnt even the amount the sc300 fuel pump ecu needs to see on low.

so the 12v mod is supplying the signal your fuel pump needs to see to operate properly, because the fuel pump ecu is not getting the right signal from your aristo ecu (confusing aint it).

so what you can do is 3 options:
run it bypassed always. the +12v that goes to the fuel pump ecu does not stay on when the key is removed. It simply doesn't , unless your car has a major problem. some people confuse priming for their pump being "on". My car has the pump on all the time if the key is in the on position. has never once stayed on when removing the key. some people report differently but I have never had a problem with it.

OR, you can do the bypass the right way, and get an automotive relay, and use the aristo signal thats supossed to go into the sc300 fuel pump ecu (the ones you didnt cut), and use that as a trigger to supply the 12v wire you did cut, to the other wire you cut going to the fuel pump ecu.
Using a relay is the proper fix, and conveniently, all the wires you need are right at the fuel pump ecu.

OR you can get a GS fuel pump ecu as stated above or one of the newer supra fuel pump ecus which run off 5v signal and wire it in. but this is not even a good idea for someone wanting to push anything above stock boost. why pay money to make it so your car can run lean in transition on an oem pump.

slappy96

He is using a TT denso. An oem pump, but maybe not in the frame of reference that you meant. Also, to follow up on my non-vvti setup. I just started my GTE swap after 1.5 years and it went absolutely perfect. I feel blessed, but the main point is that the sc fuel ecu works fine with my setup. See sig for details.

buckwheat

hey sorry to wake this fuel pump issue back up but i have done my swap and i am ready to see if the GS fpc works on the non vvti has anyone done that yet and if so dose anyone have a wiring diagram for it are the wires close to the same setup