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post #1 of 4 (permalink) Old 04-08-2010, 09:40 PM Thread Starter
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fuel pressure

Does anyone know what the fuel pressure should be at the fuel filter of my 1990 F250 7.3 idi. I have about 3lbs. at idle. This seems low ?
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post #2 of 4 (permalink) Old 04-08-2010, 10:18 PM
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IIRC when you test the pressure/flow 4-7 PSI at the schrader valve is specs. 3 PSI might not be "bad" . You have to remember the IDI has a mechanical pump and it doesn't have to pressurize the fuel system- the IP does that.

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post #3 of 4 (permalink) Old 04-08-2010, 11:07 PM
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4-6 5-8 4-7

Depends on who you ask I guess, but I've never seen anything down to three.

Thing is, you never know exactly how precise your gauge is though.

I would try revving it and see what happens. If the pressure gets down to low at higher rpms it is bad for the transfer pump in the IP. A lift pump is much cheaper.

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post #4 of 4 (permalink) Old 04-09-2010, 04:01 PM
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The pressure is normally stated as 4-6 psi however there are absolute minimums......

Fuel: manual lift pump pressures.

Filter inlet min. ( lift pump to filter ) - 2.0 psi
Filter Outlet min. ( filter to injection pump ) - 1.0 psi
Most 6.9s-7.3s have at least 3 to 5 psi taken at the Schrader valve with core removed.

Volume is just as important, Specs are 1 pint in 30 seconds at 675rpms running or 1/3 pint after 10 seconds of cranking*** only, taken at the Schrader valve with the core removed.

*** FSS wire disconnected

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