1993 Mercruiser 4.3LX starting isue

Get a separate fuel tank. even a 5 gallon gas can, (plastic). put about 3 gallons in.

get some fuel line and put one end in in the gas can and connect the other to the fuel fitting before the fuel pump,

This make take some creativity.

I think your set up is now, Soft gas line from gas tank to water separator filter but you may have a hard line from the separator to the pump.

you need to come up with a way to connect the test soft line from the separate tank to the fuel pump. you may need some fitting to adapt it.

These fuel pumps produce no more than 7-8 psi of pressure MAX. so if he has a way to test the pressure of the output of the pump anything less than 5-6 psi would indicate either a bad pump or restriction before the pump.

then trying a external gas supply as suggested above will eliminate or confirm a restriction.

Oil pressure should be above the required amount to close the pressure switch within 2-3 cranks of the motor. I believe this is >5 psi. It could be higher I forget.

either way jump the switch out for testing purposes......

Also the power that runs the pump when cranking bypasses the oil pressure switch..............that power comes from the starter solenoid.

if there is a lack of power to the fuel pump when cranking then the solenoid would be suspect.

Confirm it is wired this way!!!!! if not it must be rewired this way...........

I think in the early '90's there may have been some that were not wired this way from the factory.

The schematic I posted in POST 7 shows the correct wiring.

Greg of Racine said:

So...not enough progress regarding resolution of my problems. Mechanic feels electric fuel pump is not supplying adequate fuel to carb. Supported by long crank-to-start time observation that fuel does not reach carb until after 25 seconds of cranking--coinciding with oil pressure build-up. Since timing was reset, no acceleration in forward gear beyond 1200 RPM. Carb has ben disassembled, inspected, cleaned and adjusted. Replaced rotor, distributor cap, coil, plugs and oil pressure switch. Mechanic feels something limiting fuel available to electric fuel pump. Perhaps a faulty check valve. Ever heard of blockage at fuel pick-up within fuel tank?

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Ayuh,... Has anybody checked the Contents of the fuel filter for water, 'n crud,..??

Like Jack says, hook up a remote tank to the fuel filter just before the fuel pump, 'n Try it,...