electric fuel pump problems

[Retsgtmoose]

I have a 2007 Mercury 40HP EFI and have problems starting it. I have reduced the problem to the electric fuel pump. I have checked the the fuses for the fuel pump/idle air control/fuel injector circuits and found that there is no power on either side of the 20amp fuse. can anyone tell me where this fuse gets its power. I would like to check that out before I go any further.

 

[alldodge]

Not an OB guy, but Merc uses the same wiring colors.
Battery - Red
After main engine breaker - Red/Purple
Red/purple to ignition fuse (normally 20A) to key switch
Key switch to Run circuit - Purple

 

[Faztbullet]

Power is off main power relay

 

[alldodge]

Check kill switch
After the key switch (turns power ON) it goes to the kill switch (man overboard) then to MPR fuse then MPR

 

[Retsgtmoose]

Not an OB guy, but Merc uses the same wiring colors.
Battery - Red
After main engine breaker - Red/Purple
Red/purple to ignition fuse (normally 20A) to key switch
Key switch to Run circuit - Purple

Thank you for your reply. This thing has turned into a Pandoras Box, I fix one thing and another pops up.

 

[Retsgtmoose]

Power is off main power relay

Thanks for your reply. I need to know if this relay is the one mounted at the rear end of the motor and the lowest of the three relays there.

 

[Retsgtmoose]

Check kill switch
After the key switch (turns power ON) it goes to the kill switch (man overboard) then to MPR fuse then MPR

Thanks for your reply. The kill switch was checked and I found it to be working.

 

[alldodge]

Where does power stop?
Is it before the key switch, after it, just where?

 

[Retsgtmoose]

Where does power stop?
Is it before the key switch, after it, just where?

As near as I can figure it stops at a relay at the rear of the motor. There are three stacked up back there and it appears to be the lower of the three.

 

[alldodge]

The MPR should have 12V on one side full time. If it does not, then its a fuse, a bad connection or broken wire.

The relays can be swapped with each other

 

[Retsgtmoose]

The MPR should have 12V on one side full time. If it does not, then its a fuse, a bad connection or broken wire.

The relays can be swapped with each other

Thanks I,ll have a look at that! The MPR is the lower relay?

 

[alldodge]

Don't know which one is which, but the MPR has to energize to supply power to others. It should be like this, but note this is for a Mercruiser but it should be the same just maybe different pins numbers

 

[Retsgtmoose]

Don't know which one is which, but the MPR has to energize to supply power to others. It should be like this, but note this is for a Mercruiser but it should be the same just maybe different pins numbers

View attachment 338140

Don't know which one is which, but the MPR has to energize to supply power to others. It should be like this, but note this is for a Mercruiser but it should be the same just maybe different pins numbers

View attachment 338140

 

[Retsgtmoose]

cleaned all the contacts and the thing started ( thank goodness) but I now think that I have to replace the water pump impeller. Thanks for all the very good advise that everyone gave me on this problem.