5.0 merc fuel pump/sender

[jbenckert]

I have a 5.o mercruiser, 2000. Carb. It starts and after 20 seconds races then stalls. Starts right up and stalls again . someone said its probably the relay, another told me that its not the relay but the sending unit to the relay. another said I can bypass the sending unit. Whats your best guess.

 

[Haut Medoc]

Re: 5.0 merc fuel pump/sender

First of all, I would not bypass anything.....
The switches & relays have their purposes of protecting your engine or person from risk of explosion.....
I am not familiar with your specific set up, however some are equipped with a switch that will kill the fuel pump if you have low oil pressure...
If you have an electronic fuel pump, I would look for that relay.....
Again, there are those here who are far more knowlegeble on your specific set up than I am.....
Welcome to iboats, btw......​

 

[180shabah]

Re: 5.0 merc fuel pump/sender

What relay/ sending unit to relay ??

 

[jbenckert]

Re: 5.0 merc fuel pump/sender

I agree not to bypass but heres my question now. I know there is a relay and it works from the sending unit. I'll buy both just to get it done. Anyone know who to get in touch with for par numbers. Its a 2000, 5.o mercruiser with carb

 

[180shabah]

Re: 5.0 merc fuel pump/sender

Your fuel pump receives power from two different points.
1. the starter - so that the pump will run when trying to start
2. Oil pressure switch (no relay or sender) - so the pump will run as long as the engine is actually running.

Pull the wires off of the Oil pressure switch and clean the connections, test the switch, replace if it is bad.

This would be a good time to invest in a REAL mercruiser manual.

 

[180shabah]

Re: 5.0 merc fuel pump/sender

For part numbers take the serial number from your engine to your local dealer, or go to the Merc website.

 

[180shabah]

Re: 5.0 merc fuel pump/sender

Here is a drawing of the Merc wiring diagram. The fuel pump is #7, The oil pressure switch is #8

 

[Don S]

Re: 5.0 merc fuel pump/sender

I agree not to bypass but heres my question now. I know there is a relay and it works from the sending unit. I'll buy both just to get it done. Anyone know who to get in touch with for par numbers. Its a 2000, 5.o mercruiser with carb

There is no relay in that system. The oil pressure SWITCH is located on the port side of the engine just above the block oil filter boss on the block.
You can TEST the system by hooking the 2 wires going to that sender together. With the ign. switch in the run position, you should hear the pump run. Start the engine and verify the engine will keep running.

 

[jbenckert]

Re: 5.0 merc fuel pump/sender

thanks to all
JB