Fuel pump upgrade & wiring 12v

[jdub]

Generally you want to size according to the circuit:

Gauge - Amps
14 - 15
12 - 20
10 - 30
8 - 40
6 - 65

Longer runs (> 100') or when the wire in a closed place where it can't dissipate heat well, you want to go up a size.

Here's a handy chart/calculator...you'll need to know the current draw for the Mk IV pump.
http://www.powerstream.com/Wire_Size.htm

It will tell you an acceptable drop for the size wire you use.

 

[isnms]

jdub - Do you know the size of the stock wiring for the fuel pump circuitry?

This site - http://www.roadraceengineering.com/fuelpumpflowrates.htm -
indicates the mkiv pump can draw up to 21amps.

edit: What points should I use for volt drop test? from battery to pump?

 

[jdub]

Pretty sure the stock wires are a 12GA.

This should be able to handle an upgraded pump, but is right at the limit.
Note that you get a 5.72% voltage drop (10' run) with 12GA vs a 3.59% drop with 10GA.

 

[isnms]

I just noticed one more thing. The stock fuel pump circuitry runs through the 15A EFI fuse :ugh:

 

[jdub]

There's no question what I would do then

 

[isnms]

put a penny in it?

 

[jdub]

LMAO! Yeah! That's a great idea!

 

[isnms]

I think I will be going with my option number one:

1. One keeps the low volt option
[thumb]http://i80.photobucket.com/albums/j187/isnms/Supra/fuelpumprelay.gif[/thumb][thumb]http://i80.photobucket.com/albums/j187/isnms/Supra/rewire_relays_fp.jpg[/thumb]​

That will leave me with only two questions:

• If the stock 0.7ohm resistor will drop to much voltage and make the mkiv pump bog down ?

• If the tccs switch point will correlate with the switch point demanded by current upgrades (I think it will) and future upgrades ?

 

[jdub]

Why not keep it a bit more simple:

- Run a dedicated 12V, 10GA wire (fused) to power the the circuit opening relay
- 10GA wire from circuit opening relay to FP relay
- Replace FP relay with 30 Amp Bosch 2 position relay
- 10GA wire from FP relay to FP
- 10GA wire from FP relay to resistor
- 10Ga wire from resistor to FP (splice into above)

 

[isnms]

That would mean getting two 10ga wires run to the pins 1 & 2 of the circuit opening relay on the back side of R/B No. 4 in the passenger side kick panel.

That's a tight fit I'd have to check into.

[thumb]http://www.cygnusx1.net/Supra/Library/TEWD/MK3/Main/Main_015.gif[/thumb]

edit: oh, and is the cir open relay rated for 20-30amps?

 

[jdub]

Just a thought
You should be able to do it...it would remove the EFI fuse from loop and solve any voltage drop issues. And, you keep the resistor for low FP ops.

 

[isnms]

Added a pretty convincing pro to the first post.

 

[Satan]

OMG my brain hurts... I have read this thread about 6 times and still end up lost, trying to make a good choice in method to go with :-/

So, here are 2 scenarios where we are looking to do the 12v mod:

1. 1JZ/Pre-89 (was N/A 5-speed) - Hooked up wiring according to Rick's wiring diagrams (http://web.archive.org/web/20051227170957/http://www.1jz-gte.us/) and connected the stock 7M FCU wire/signal to the 1JZ ECU's FCU signal. Pump will not come on w/key. Only when FP & B+ jumpered in diag box.

2. 2JZ/R154 in 91 turbo/auto - B1/Pin #4 (FP signal to diag) is grounded so that pump comes one when key is on.

Both cars have Walboro fuel pumps and batteries located in the hatch. We were 1st considering option #2 on the 1st page of this thread. We are not necessarily trying to further troubleshoot fix FP wiring, but looking to get most benefit of Walboro and know that we've done good/quality work with the rewire. I am working to do the mod on my 91/2JZ and send the wire/relay package to my friend so that he can install the same/same-way in his 89/1JZ. What do ya'll recommend (which bypasses the 15A fuse/bottleneck). Recommended parts list (ie. Bosch relay)?



Thanks again to all of you... so much great info in this thread!!

 

[Nick M]

OMG my brain hurts...

Well, put the ice cream down.

1. 1JZ/Pre-89 (was N/A 5-speed) - Hooked up wiring according to Rick's wiring diagrams (http://web.archive.org/web/20051227170957/http://www.1jz-gte.us/) and connected the stock 7M FCU wire/signal to the 1JZ ECU's FCU signal. Pump will not come on w/key. Only when FP & B+ jumpered in diag box.

Toyota doesn't run the pump without an airflow meter signal. Which is quite common. Many manufacturers run the pump for a couple of seconds to prime the system and make for easier starts. Notice they don't have hard starts when hot and are aged. That is one of my few gripes on Toyota.

2. 2JZ/R154 in 91 turbo/auto - B1/Pin #4 (FP signal to diag) is grounded so that pump comes one when key is on.

Better hope any fender bender isn't serious. When metal is crunched, short to ground and power happens quite easily. This is why they aren't wired that way, or have an inertia shut off switch that kills powwer if the car is hit.

 

[Satan]

Ice cream done, cold beer now ;-)

We were hoping to retain the Fuel/pump cut-off feature, but just does not seem to be working for us. Hence, "Let's do the 12v mod and try to incorporate that in there." I've been running mine like this for years (knowing the risks), but if possible to install the cut-off feature (at a reasonable cost) we're in... So, looking for the overall benefits of the 12v mod and also to have fuel cut-off which works like stock. I'm also looking at this thread http://www.supramania.com/forums/sh...ump-Computer-in-the-event-of-an-Crash-JDM-1JZ and am hoping to combine info and implement a solution soon.

Thanks,
E