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fuel pump not working when starting, ignition switch wiring?

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sailawaysg

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I have a 1989 454 that the electric fuel pump doesn't run when I try to start it, it will run when wired direct to battery. Fuel pump is new, oil pressure sensor is new. Fuel gauge used to work when that switch was turned on, now it doesn't. Could the ignition switch be suspect? I can't find a wiring diagram for it.
Thanks, I'm trying to get this engine running to haul out for coming hurricane!!!!
 
a 1989 454 would be a MarkIV block which would mean the electric fuel pump was a retrofit. It would normally be wired with an Oil Pressure Switch (not a sensor).

I'd say the switch could be the issue if you also DONT have spark...

I'll see if I can find the schematic for the factory wiring for using an electric fuel pump...
 
attached should be the engine wiring diagram from an early 2000 crusader using an electric fuel pump...
 

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makomark said:
a 1989 454 would be a MarkIV block which would mean the electric fuel pump was a retrofit. It would normally be wired with an Oil Pressure Switch (not a sensor).

I'd say the switch could be the issue if you also DONT have spark...

I'll see if I can find the schematic for the factory wiring for using an electric fuel pump...
Click to expand...
I have spark etc, just fuel pump not coming on...
 
The electric fuel pump circuit requires the following:

A N/O (normally open) low oil pressure switch that will do 2 things:

..... close the circuit and provide power to the fuel pump once engine oil pressure is achieved.
..... open the circuit and cut power to the fuel pump in the absence of oil pressure.

1..... During engine cranking, the oil pressure is not enough to close the N/O low oil pressure switch and activate the fuel pump.

2..... In order to power the electric fuel pump during cranking, we need what's called a "start-by-pass" circuit. This is generally triggered by the starter motor's "S" circuit.

3..... In order to prevent an electrical back-feed, you may see a relay in this circuit that would be excited by either the LOP S, and/or by the start-by-pass circuit.
 
RicardoMarine said:
The electric fuel pump circuit requires the following:

A N/O (normally open) low oil pressure switch that will do 2 things:

..... close the circuit and provide power to the fuel pump once engine oil pressure is achieved.
..... open the circuit and cut power to the fuel pump in the absence of oil pressure.

1..... During engine cranking, the oil pressure is not enough to close the N/O low oil pressure switch and activate the fuel pump.

2..... In order to power the electric fuel pump during cranking, we need what's called a "start-by-pass" circuit. This is generally triggered by the starter motor's "S" circuit.

3..... In order to prevent an electrical back-feed, you may see a relay in this circuit that would be excited by either the LOP S, and/or by the start-by-pass circuit.
Click to expand...
I replaced the 3 post switch but don't know what the other 2 are. Any help?
 

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  • boat switch3.jpg
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I'm getting 12v when cranking and the fuel pump is working but when the engine starts I lose 12v and the fuel pump stops. Would that indicate a bypass circuit issue like the 50amp relay/breaker located in the circuit? I have good oil pressure a new 4 psi oil sw.
 
assuming you are referring to +12VDC at the fuel pump, and it isn't there once the engine starts?

That suggests the supply side (with the engine running) isn't supplying current or you have the wrong oil pressure switch...
 
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