2J Fuel pump wiring

[CSquared]

I have a very limited understand when it comes to wiring, so I sent the harness out and when I got it back ther was a green wire hanging by the ecu. I was told this was for the fuel pump and should be attached to a "switched ground". This is a paraphrased conversation I had about it:

Me: There is a green wire hanging out around the area of the ECU marked fuel that apparently needs to be connected to a power source. What would you recommend splicing this into on the ma70?

Them: This needs to go to a switched ground which will be used to turn the fuel pump on or off. note that the fuel pump will only run when the key in the on or start positions, so technically you could leave the switch on all the time, or just ground the wire. I recommend a switch.

Me: So from what I understand you are saying that I can just ground that wire straight to any chassis point and it would still operate correctly? I honestly have no idea what qualifies as a "Switched" ground. Would this be like a fuse or relay?

Them: The placement of the ground does not really matter. This is basically what I was saying before, run it to a switch, which basically meant run it to a ground that has a switch in the schematic so that it only works when the key is in the "RUN" and "START" positions.

So from my understanding I could just ground the wire to any ground point and it would operate under normal conditions? Normal conditions meaning only running when the ignition is "on" or "start". Reffering to the switch are they talking about an external switch (like a toggle switch) or would this be a type of ground that I am not familiar with? I'm running a turbo timer so I was thinking about splicing it to that ground because it only runs in "on" or start" but honestly I'm just confused at this point.

 

[Dirgle]

If you ground that wire the fuel pump will operate as normal. Turning on with the key, and off with the key. The reason they are mentioning a switched ground is as a safety precaution. Though it is not a very ideal solution. The 7M uses an RPM signal; to keep the fuel pump on, and the 2JZ uses a separate computer for the same task. So if you get into an accident the fuel pump will be switched off. Simply grounding the wire provides no means of shutting off the fuel pump in an accident, if you were say, unable to turn off the ignition.

 

[CSquared]

Gotcha. So basically you're saying that if I got into an accident and was unconscious or incapacitated the pump would keep running on my current setup as opposed to a MK4 where the pump would shut off on its own? I do intend to wire a toggle into the ground as a "please don't steal me" security measure but it doesn't seem like it would make a difference in that situation. Ha, that makes me feel safe.

Is there any way on this setup to account for something like that?

 

[Jeff Lange]

If you ground that wire the fuel pump will operate as normal. Turning on with the key, and off with the key. The reason they are mentioning a switched ground is as a safety precaution. Though it is not a very ideal solution. The 7M uses an RPM signal; to keep the fuel pump on, and the 2JZ uses a separate computer for the same task. So if you get into an accident the fuel pump will be switched off. Simply grounding the wire provides no means of shutting off the fuel pump in an accident, if you were say, unable to turn off the ignition.

Both the MK3 and MK4 use the main engine computer to control when the fuel pump is on. The "Fuel Control Computer" in the MK4 is a glorified relay, nothing more. It just combines the circuit opening relay and fuel pump control relay that the MK3 has into 1 box. There is no logic in it whatsoever. The ECU determines when the fuel pump is on.

What is turning your fuel pump on right now? Just the ignition switch?

Jeff

 

[Dirgle]

Yeah I would hate to have my fuel tank pumped into the street if I get into an accident. There are a few options available but I'm still doing some research on them. One way you could go is is the fuel computer provided by Aeromotive.

http://aeromotiveinc.com/products-p...nics/16306-billet-fuel-pump-speed-controller/

But it's a little pricey at $330.

The simplest option would be a tachometric relay. It's a simple relay that is activated when it detects a low voltage pulse, like a tach pulse. It's activation range is usually at around 150rpm. Unfortunately info is hard to come by on these. They seem more prevalent in Australia there they are used on their Automotive LPG systems. It also seems they were heavily used in 80-90 BMW, Mercedes, and Porsches. The best candidate would have been the BOSCH #0280230006 unfortunately this relay has been discontinued. The one I'm looking at now is the BOSCH #0280230001, I've heard it's similar but I'll be damned if I can find any documentation on it. Another nice thing about the BOSCH #0280230001 is Kaehler makes an OEM replacement for it. The KAE #13631276264, and the nice thing about it is it only costs around $25. But I'm still trying to find documentation about it. Once I can verify the specs I'll order one and try it on mine.

Both the MK3 and MK4 use the main engine computer to control when the fuel pump is on. The "Fuel Control Computer" in the MK4 is a glorified relay, nothing more. It just combines the circuit opening relay and fuel pump control relay that the MK3 has into 1 box. There is no logic in it whatsoever. The ECU determines when the fuel pump is on.

What is turning your fuel pump on right now? Just the ignition switch?

Jeff

I was wondering what it was like inside. Since I've never gotten my hands on one, and haven't seen a schematic for the inside, I wasn't sure.

 

[CSquared]

Yeah as far as I know the pump only turns on with the ignition but to be honest the only thing I've done with it since I bought the motor was pack it in a box and install it once I got it back. I do have to upgrade to the mk4 pump sometime in the near future and intend on doing the 12v mod. I apologize for my electrical ignorance.

Yeah 400 bucks is pricey. I guess if this car gets hit hard enough at this point to knock me out I may as well go with it.

 

[Dr Tweak]

We have found a much cheaper solution to this problem, a module that will turn the fuel pump off when the RPM signal from the igniter is lost. If you guys are interested let me know they are about $50.

-Doc

 

[Nihiliz]

Dr Tweak, just saved my life. i will be getting in contact with you soon bro.

 

[Silvermk2]

You can activate the fuel pump relay with the 2JZ ECU using a $1 transistor no need for something fancy.

 

[MrOizo]

You can activate the fuel pump relay with the 2JZ ECU using a $1 transistor no need for something fancy.

Do you have any more info on this? I am at the satge of sorting mine out and not having it on the COR for safety. Cheers.

 

[Silvermk2]

Do you have any more info on this? I am at the satge of sorting mine out and not having it on the COR for safety. Cheers.

I don't have my notes with me, but you use an NPN transistor with the B terminal connected to the 2JZ FPC terminal, C terminal to the ground side of the COR coil, and the E terminal is grounded to the chassis. The positive side of the COR coil goes to switched a 12V source. You should have a diode across the relay coil to prevent a current surge in the backwards direction. What this does is when the 2JZ ecu thinks the pump should be running it sends a 3-5V signal to the FC terminal. The transistor sees this and closes the circuit for the relay to ground. Mine has works flawlessly since day 1 and its built into my adapter harness. The total cost is under a buck and much more elegant than other solutions I've seen. HTH

 

[MrOizo]

Thanks for your reply!

I made a kit from Jaycar here in NZ (originally Australia) from a supplier called Silicon Chip ( i guess the magazine originates from the US continent some where.
http://www.jaycar.co.nz/productResults.asp?keywords=KC5434&keyform=KEYWORD&SUBMIT.x=0&SUBMIT.y=0
The intention was to have the signal from the ECU FPC pinout to be the input to the control module.

Had a play today and for some reason the output from the ECU on FPC pin was a lame 0.02v (i guess was nothing measurable). I measured from, IGN ON & START - Still nothing.

Any suggestions as to where i might be going wrong? I might have unpluged something in the engine bay that i have forgotten about but not sure yet. Check Engine Light goes on with key and switches COR (M-REL?) in engine bay.

Any advice is much appreciated -might end up with your trick in the next few days - cheers.

 

[MrOizo]

Oh - another thing that i was wondering - does DI (green wire) need anything done to it or is it fine being deleted?

Cheers.