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Wires ripped off, what are they ?


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Okay 90 with 4.2 EFI. Loom runs into the cab with ECU behind seat. I have the main loom going forward into the engine. After about a foot 2 wire groups break out from the loom. One goes to the fuel pump. The other is red and black pair heading forwards. Unfortunately these ( red and black pair ) on mine caught the front prop and got slightly ( totally ) ripped out. So I have some red and black ends just under the drivers seat and about 60 cm of red and black wrapped round the prop. The question is where did the other end of that get ripped from ? The red looks live towards the ecu as it looks like it was earthing to the chassis judging by the black ends.

When I turn the key the starter motor spins but the fuel pump doesn't prime.

Where did these wires go and am I likely to have blown anything up ?

Help :(

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after lots of unwrapping of tape it turns out it was the old live and earth for the fuel pump. The live was disconnected but the earth was still used. New earth wired in a she lives once more.

Is the fuel pump supposed to go off on crank or do I need to wire something from the starter motor solenoid ?

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Is the fuel pump supposed to go off on crank or do I need to wire something from the starter motor solenoid ?

AFAIK the fuel pump on an EFI goes off after a few seconds - once it had pressurised the pipework, and then only runs 'on demand'?

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AFAIK the fuel pump on an EFI goes off after a few seconds - once it had pressurised the pipework, and then only runs 'on demand'?

A common misconception, it's not that clever.

I'm not sure if it actually bothers with a priming run, but until it sees the engine cranking over it won't run the pump. Likewise, if the engine stalls it will stop the pump after a second or two. Basically if the ECU isn't firing the injectors it doesn't run the pump up either. The old flappers the flap actually turned the fuel pump on as it opened, so no airflow = no pump run.

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A common misconception, it's not that clever.

I'm not sure if it actually bothers with a priming run, but until it sees the engine cranking over it won't run the pump. Likewise, if the engine stalls it will stop the pump after a second or two. Basically if the ECU isn't firing the injectors it doesn't run the pump up either. The old flappers the flap actually turned the fuel pump on as it opened, so no airflow = no pump run.

Yes - sorry, once the engine is running the pump appears to run constantly, giving a continual flow down the return pipe.

But in the case of my 3.9 hotwire there is a priming run when switching on the ignition; if the system is not already pressurised (from last time it ran).

TwoSheds

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But in the case of my 3.9 hotwire there is a priming run when switching on the ignition; if the system is not already pressurised (from last time it ran).

I suspect that's either on a timer or done by engine temperature as there's no fuel pressure sensing in the system.

<makes note to suggest CLT-based priming to MegaSquirt development team> :P

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I suspect that's either on a timer or done by engine temperature as there's no fuel pressure sensing in the system.

<makes note to suggest CLT-based priming to MegaSquirt development team> :P

Checked further into this. I was wrong again - note to self: Try not to let it become a habit!

The priming run appears to be timed (presumably by the ecu, or maybe a timer-relay) and happens every time the ignition is energised.

Sorry for the misdirection.

To cheer myself up after the above Great Cockup (OS grid reference. NY273333) I poured a couple of liters of water over the ignition system while the car was ticking over and it never missed a beat :)

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