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Old 09-29-2013, 09:26 PM   #1
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Default Where to source fuel pump signal?

So I'm working on a circuit, and need a signal from fuel pump to turn on a circuit via a relay.

I was thinking of the diagnostics box, the F/P pin. Will this work by just tapping into it and grounding it on the other side coil in the relay?
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Old 09-29-2013, 10:45 PM   #2
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Or use the fuel pump relay under the steering wheel. Look up the MS install threads for its location. What may I ask are you circuiting with fuel pump activity?
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Old 09-30-2013, 10:00 PM   #3
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Okay sweet! thanks mate.

I'm playing around with a dwell reducing circuit for Toyota COPs, using a 100W 0R47 resistor, in theory, it should reduce the voltage down to about 8-8.5volts therefore taking a bit longer to charge, it should be around the 5.3ms dwell time mark.

A problem I see is that if the ignition is sitting in accessory or on but the engine is not running, it could blow the coils since they're getting charged up and nowhere to dissipate.

If it works, I'll post up more details.
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Old 01-20-2014, 06:55 AM   #4
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Update:Been quite busy lately but finally finished off the loom and got it working. The resistor seems to been doing its job nicely supplying around 8.5 volts to the COPs.

I've ran them for about 100kms and not a misfire yet. The COPs feel just warm to touch and hasn't overheated yet.

Last time I ran COPs of the stock ECU, it misfired within the first 20kms. And completely failed after 150kms, overheated and burnt out.

I will report back in about a week or two after I've done some more mileage to see how they are performing.
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Old 01-20-2014, 12:31 PM   #5
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so what did you need the fuel pump for if you're playing with coils?
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Old 01-20-2014, 12:46 PM   #6
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To only supply power to the coils with the fuel pump (and engine) running?
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Old 01-24-2014, 07:02 PM   #7
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Oscar is correct, the fuel pump relay click over when the engine is cranked, and in so turns on the COPs circuit.

Without this, if the ignition was on but the car wasn't running, the COPs would be getting power which is supplied from the main fuse box in the engine bay. And the COPs would charge up, nowhere to dissipate and blow if left too long.
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