Mercruiser 1998 5.7L EFI Fuel Problem

Engine SN#0L082485

Fuel Pump Runs intermittently...

Had connection problem with Relay, which I resolved two weeks ago, but now the pumps on comes on intermittently when turning the ignition key on... I can verify that the relay picks up for the 2 seconds, then shuts back off, but the pump does not run. When the pump does run the engine fires up and runs perfectly normal. Once the enigne is running, I can hear the whining of the pump and everything is fine, though occasionally the pumps quits and the engine dies within a few seconds and it is back to whether or no the pumps kicks on again to pressurize the fuel system.

I had replaced the "cool fuel" system last August, so I cannot imagine it could be the pump, as this issue originally began last year and that didn't resolve it. The only that has changed is the correction of the bad connections within the relay connection socket. Since both the ignition relay and the fuel pump relay are the same, and I have repeatedly swapped them until determining the bad connection issue, I cannot imagine it is a bad contact inside the relay. I am intending later today to check the oil pressure switch for bad connection and to recheck a few things with my DVM and test light.

I have dealt with infant mortality on cars before and because parts are new doesn't mean there good, but I am hoping someone can provide a little insight prior to aid in verifying beyond reasonable doubt that I have to replace the pump again, same goes for the relay. As a side note, I do have the Seloc Manual and am planning to work through some of the troubleshooting guides to verify the senders/sensors. Also, when the pumps runs, the engine runs fine with no performace or other issues.

Re: Mercruiser 1998 5.7L EFI Fuel Problem

Assuming electric fuel pump, are you monitoring the voltage on the pump?

If the voltage is constant, you might have air in the system.

If the voltage is not constant, you may want to try, temporarily, bypassing the ground, then the + directly to the battery and then work your way backwards.

If this is not in the right direction, you may want to add a few more details.

Re: Mercruiser 1998 5.7L EFI Fuel Problem

Have not tried to monitor the voltage yet, but am planning to try that today, along with a jumper to by-pass the relay and forced power directly from the battery. Hoping this may tell me whether or not the pump is hanging up. The relay does click on from the ECM signal, but the pump doesn't consistenly kick on, with no existing fuel system pressure.

Also, the other observation I have made, is the alarm buzzer is signalling randomly, but it doesn't seem to correlate to whether or not the pump kicks on. Though the pump has not kicked on when the buzzer did not alarm. I am going to double check to make sure I have a good connection within the plug to the pump itself, as I discovered with the relay that the female connections had relaxed and were not putting adequate pressure onto the male stabs from the relay for good connection. At this point the problem seems to be somewhere between the relay and the pump, inclusive of the power path back to the battery.