No Voltage to Fuel Pump

[Jackfrost]

Update... mechanic friend suggested to change the oil pressure sensor. Seems to have worked. 6 hours in and has started every time. Wow.
he said a bad sensor will stop the fuel pump from turning on.
Fingers crossed.

[prostar205]

I've been chasing a low fuel pressure issue for months now. I replaced my old Carter fuel pump with a new Mellenium pump ($800) and can only get 40-42 psi. Boat idles fine and runs to 3,000 rpm / 30 mph just fine but will not go past 3,000 rpm. Also, it is fouling plugs (6 of 8) in about 5 hours.

The boat doesn't throw any codes.

Here is what I've doing next.

1) replacing the 20 year old plug wires
2) checking the fuel pressure regulator on the fuel rail. Just found out about this one. Thought our boats only had 1 pressure regulator and that was on top of the fuel pump.
3) replacing the fuel pump with the old Carter that I still have since it still works

I'm open for any other suggestions.

[Cedaw]

This sounds stupid, but check for faulty main ground by using jumper cable from battery negative to engine block.


Sent from my iPhone using Tapatalk

[Jackfrost]

Wouldn't.t start today.
No power to fuel pump... again
3.3 ohms at fuel pump relay ground wire... pin 85
Alarm started to go off again.
"Check Engine"on dash too.

Any ideas?

[Jackfrost]

New low battery relay installed.
2 days of running. Computer has reset itself.
No more buzzer going off.

I still believe there is something wrong with the wiring. The boat now only very rarely drops power briefly while running.

Will keep checking.

[Jackfrost]

My low battery relay comes in 2 days.
There is a difference in voltages (as noted above) on pin 86 and 30 of the fuel pump relay. Any ideas?

[ValveCoverGasket]

Key, engine start or on position only intermittent power to fuel pump.

try back probing the signal line from the ECU at the relay - assuming its arranged as per a typical EFI controller the ECU would provide the ground signal to the relay coil.

if that stays grounded when it dies - or in those times youre testing and not seeing power at the pump, that would at least eliminate that as a path to follow.

otherwise checking the incoming power to the relay, and the connectivity between the relay and the pump connector itself.

[curver900]

you probably have to start wire tracing looking for the wire that is broken a plug that is corroded or slightly unplugged.. Looks like a good time to go through it all.. eliminate the easy stuff... parts are costly...

[Jackfrost]

Key, engine start or on position only intermittent power to fuel pump.
When it does energize the fuel pump the pressure is 5si and strong until it is not energized and engine dies.

[peytonvp]

What is the issue that you are currently having since replacing the regulator? Do you have adequate fuel pressure?

[peytonvp]

Peytonvp was your boat shutting off due to the fuel pump not pumping.

My boat would die due to no voltage to the fuel pumps which was because of a bad relay. The relay would only go out intermittently.

[Jackfrost]

Low Battery Alarm Relay Pin Organization:

85 Black (or on mine gray) comes from the MMDC. - alarm relay
30 Red stereo power
87A Red/Yellow Radio
87 Red Buzzer (+)
86 Red

[Jackfrost]

Found a schematic for the wiring harness.
Shows the 2 relays under the dash.
One is for low battery - the one with the buzzer - this must be why the previous owner unplugged it (it was always buzzing)
The second one is for the seat heater.

So I don't think this solves my problem... yet.
Ordered a new relay.
Will keep you informed.

[Jackfrost]

Still trying to figure out my engine not starting problem.
I.ve found 2 relays under the dash.
One was super corroded. It is closest to the buzzer.
What does this run?
Here are some pictures...
Question 2. Gray wire 85. Is it supposed to be ground?
Thanks

[Jackfrost]

Peytonvp was your boat shutting off due to the fuel pump not pumping.