[Diy_efi] '7747 trouble code list

[Programmer]

Exactly. John's nailed it.

When the FP relay driver circuit in the ECM fails, you'll get extended
cranking before the fuel pump fires up. The oil pressure switch will run the
FP standalone.

Lyndon

----- Original Message -----
From: <WEG1192 at aol.com>
To: <diy_efi at diy-efi.org>
Sent: Thursday, December 12, 2002 12:37 PM
Subject: Re: [Diy_efi] '7747 trouble code list


> In a message dated 12/12/2002 2:09:16 PM Eastern Standard Time, Ne14RoxCJ
writes:
>
> > The ECM will use the Fuel Pump Relay for pre-start pressurization (a few
seconds) and during cranking. After the engine starts, and builds oil
pressure the pump is powered through the pressure switch. I suppose
eliminating these components and powering the pump with a "hot in run"
curcuit would work, but the pump will run ANY time the key is on. Also, the
OP switch prevents the engine from running with less than ~5psi. I
> > consider it "cheap insurance" for my $$ engine.
>
> Not true. The engine will continue to run with no oil pressure due to the
fuel pump relay being continuously on as long as the ECM recieves reference
pulses from the distributor. The oil pressure switch is not a "low oil
pressure safety". It is simply a back up in case the fuel pump relay fails.
>
> The engine will still crank without the fuel pump relay, but cranking
times will be longer since it will take some time for oil pressure to build
and start the fuel pump.
>
> JW
> www.customefis.com
>
>
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