07 Speed3 Fuel Pump Resistor

[Eatliftweld]

I'll make it quick.

Fuel pump was going out, I jumpered the relay as per the workshop manual, drove around like that for a little while, and either the pump finally died or the resistor fried (didn't know that yet). I replaced the fuel pump with an OEM Mazda pump, wired up, etc. No power to pump, no clicking of relay. I troubleshoot everything front to back, continuity test, resistance, etc. Everything is good until I got to the Fuel Pump Resistor (P/N L33X18831), it was reading 0.8 ohms versus the 0.32 it's supposed to read. I called the Mazda stealership in Atlanta, price is $178 for a new one and it would be 3-5 days to get to me.

Any way that I can avoid having to buy a new resistor? Build one? Safer method of jumping the Circuit Relay? Anything.

I need my car ASAP. I've got to get to work and do stuff.

[SSinstaller]

Connect the two wires that run to the resistor togeather. You'll run full battery voltage to the pump at all times, doesnt hurt anything, no need to ever buy a new resistor.

[Eatliftweld]

Originally Posted by SSinstaller Connect the two wires that run to the resistor togeather. You'll run full battery voltage to the pump at all times, doesnt hurt anything, no need to ever buy a new resistor.

Are there any issues that could be caused by doing that? Shorter fuel pump life? Anything? I tried jumping the two terminals at the connector, with the circuit relay in, and nothing different happened. Didn’t try with the jumper in, because it would’ve been pointless.


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[SSinstaller]

Originally Posted by Eatliftweld Are there any issues that could be caused by doing that? Shorter fuel pump life? Anything? I tried jumping the two terminals at the connector, with the circuit relay in, and nothing different happened. Didn’t try with the jumper in, because it would’ve been pointless. Sent from my iPhone using Tapatalk

The resistor just drops the voltage to the intank pump at idle. I removed mine years ago when I installed a kenny bell boost a pump.

My oem pump is still working fine.

[Eatliftweld]

Originally Posted by SSinstaller The resistor just drops the voltage to the intank pump at idle. I removed mine years ago when I installed a kenny bell boost a pump. My oem pump is still working fine.

I appreciate it. Unfortunately, after thorough diagnostics, pin 1H on the PCM is fried, so either a new PCM has to be installed or I’m splicing the wire from 1H into a switched 12V wire.


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[Vansquish]

You could also consider getting the PCM cloned by a company like this one: ECU Cloning | Replace Damaged ECU or ECM | My Auto Solutions Georgia

[Eatliftweld]

Originally Posted by Vansquish You could also consider getting the PCM cloned by a company like this one: ECU Cloning | Replace Damaged ECU or ECM | My Auto Solutions Georgia

I called them this afternoon and they said that they don’t have the capability to clone the MS3/MS6/CX7 ECM. So, not quite sure where to go from here.


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[SSinstaller]

I'd just trigger the relay with the ignition.

[Eatliftweld]

Originally Posted by SSinstaller I'd just trigger the relay with the ignition.

Probably going to run it to pin 1AW on the PCM. They seem to run parallel. See attached image.


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[SSinstaller]

Looking at that diagram pin (1H) will use a ground to trigger the fuel pump relay. You should be testing this wire for continuity to ground with the ignition on--not voltage.

At idle/very low load a ground on 1H will run the fuel pump at a reduced voltage through the resistor.

At higher loads a ground on pins 1H and 1AA runs the pump at full voltage (1AA trggers second relay bypassing the resistor).

Do not connect 12v to pin 1H.

[Eatliftweld]

Originally Posted by SSinstaller Looking at that diagram pin (1H) will use a ground to trigger the fuel pump relay. You should be testing this wire for continuity to ground with the ignition on--not voltage. At idle/very low load a ground on 1H will run the fuel pump at a reduced voltage through the resistor. At higher loads a ground on pins 1H and 1AA runs the pump at full voltage (1AA trggers second relay bypassing the resistor). Do not connect 12v to pin 1H.

How do you recommend wiring it? Just trying to get things “right” ASAP.


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[SSinstaller]

Originally Posted by Eatliftweld How do you recommend wiring it? Just trying to get things “right” ASAP. Sent from my iPhone using Tapatalk

It sounds like you need some more testing...

Can you trigger the fuel pump relay by grounding the pin in the check connector at the fusebox? If you can what voltage do you see at the fuel pump?

see attached diagrams.

[Eatliftweld]

Originally Posted by SSinstaller It sounds like you need some more testing... Can you trigger the fuel pump relay by grounding the pin in the check connector at the fusebox? If you can what voltage do you see at the fuel pump? see attached diagrams.

Where is the check connector? I’ll do that as soon as I get home and have a moment. Also, where did you find those wiring diagrams? I’ve searched and searched and couldn’t find them anywhere.


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[Jeff23spl]

how did you conclude the pcm was fried ? According to that diagram, it would put the relay coil to ground when activated. If you were looking for a +12v signal there, it won't work this way and you can't replace the PCM by a +12v either. Sending a solid 12v to 1AA or 1H would be a good way to fry the pcm.

When everything is fine and connected, you should see close to 0v at the PCM pins to close relays. And something like a 10-12v when the relay isn't triggered because positive voltage will pass thru the relay coil to the open circuit of the PCM.

If you disconnect the PCM and force a ground into 1H, you should have the pump to run at low voltage and is you add a second ground to 1AA, you would get the pump to full voltage. If this works fine but it don't with the PCM, you would know it is the pcm.

If this doesn't work, you need to figure out where in the power path, you have a problem...You can confirm to have 12v on both side of the resistor but it fall to very low on one side when you trigger just 1h. etc...

[SSinstaller]

The check connector is at the fuse box under the hood. The diagrams are from my alldata account at work.

[Eatliftweld]

Originally Posted by SSinstaller The check connector is at the fuse box under the hood. The diagrams are from my alldata account at work.

Is it labeled or anything? I guess I just haven’t seen it or looked for it hard enough. Or I was looking at the wrong thing.

Thanks for all the help, too.


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[SSinstaller]

Make sure you ground the correct pin...

[Eatliftweld]

Originally Posted by SSinstaller

Awesome. Hello yeah. I wish I had access to all that information, lol


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