Low power to fuel pump relay

[Wirewheels]

First time poster...

I was helping a friend with his boat today and we determined a dead fuel pump but connecting the old to the battery (nothing) and the new one to the battery - buzz buzz.
Now the trouble is there, when we turn the key there is only 1.5 volts going to the fuel pump relay and I think there should be 12.

This is a Volvo Penta 5.7 GSX (not sure of the year, but within 10 years old)

Can anyone point me to a diagram for this engine, or shed any light on what the issue could be? Thanks!

Brian

 

[Alpheus]

Re: Low power to fuel pump relay

Sounds like you got high resistance in that wire. Dig out the multimeter and start troubleshooting...

 

[Wirewheels]

Re: Low power to fuel pump relay

Sounds like you got high resistance in that wire. Dig out the multimeter and start troubleshooting...

Yeah, after 4 hours of that I figured it was time to ask the experts! Not having a wiring diagram is a real hindrance...

 

[rodbolt]

Re: Low power to fuel pump relay

about normal for key on engine off.
if its carbed relay hold voltage while running is tapped off the green/white wire on the altenator and if its EFI the ECU controls the ground path.
not knowing which you have nor where your placing your meter leads while testing,thats about all I can say.

 

[Don S]

Re: Low power to fuel pump relay

I can't even find a 5.7GSX listed, There is a 5.7GX, and a 5.7 GXl but no GSX models.
Other that what rodbolt mentions, that's about all the info there is. If it's a carbed engine, the pump will not run with the key on and the engine not running.

 

[Wirewheels]

Re: Low power to fuel pump relay

Sorry, I should have offered more info. It is a 5.7 GX carburetorated engine. The pump USED to go on (buzz) with the key "on" and engine not running, now nothing. There is 1.5 volts to the relay with the key on, none with the key off. I tested the pump straight off the battery and it is dead (not turning at all) and also tested the new pump straight off the battery and it spins nicely.

I wonder if the dying pump fried something in between the key and the relay? I've poked the wires where I could reach them but nothing obvious. Is there a fusable link, fuse, or ??? inline somewhere?

 

[Alpheus]

Re: Low power to fuel pump relay

Check the voltage while your turning the engine over...

 

[Wirewheels]

Re: Low power to fuel pump relay

I asked my friend to "just try turning starting the engine" - he jumped in the boat, turned the key and it fired right up! I am humbled to say "it works!" :redface: Guess I should have checked the simple and obvious first...

Thanks to all who helped!