Cool Fuel Pump

joelger

Seaman
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Jul 29, 2021
Messages
60
This just keeps getting better and better. I repaired my seawater pump, put everything back together and the boat wont start.
Im working with a 2010 Mercruiser 8.2mag. Serial 1A351574.
I thought it must have something to do with the fuel system because i had to move the cool fuel pump out of the way to get to the seawater pump. After checking everything, i found a bad fuse. I replaced the fuse and tried to start it again. Still wouldnt start. Checked the fuse, it was blown again. Checked all the wires to the fuel pump and they all seem perfectly fine. I disconnected the lead to the cool fuel pump and turned the motor over. Obviously it didnt start. I checked the fuse and it was fine. Id didnt blow. I reconnected the lead to the cool fuel pump and turned the motor again, blew the fuse. I replaced the fuse once again and turned the ignition on but didnt try to start the motor, the fuse was fine. Cranked the engine again, fuse blew again.
Assumption....one of the motors in the CFP (cool fuel pump) is shorted. Removed both motors from the CFP and connected each to a power source off the boat and they both spun fine. Considered that i may have pulled too hard on the wires where they come from the CFP and possibly caused a short that way. I put the pumps back on the cap of the CFP and reconnected it to the electric for the boat. I cranked the motor and the fuse was fine.
So this now raises a bunch of other questions but i just put it all back together and when i cranked the motor, the fuse blew yet again.
Now im wondering if something else could be causing the fuse to blow once the system builds pressure. Then realized that isnt likely because the pressure line from the pump to the fuel rail wasnt connected when the fuse blew on the last test.
When i had the pumps out and powered them from a 12v source i should have put a fuse in the circuit to see if it blew the fuse out of the boat. (possibly drawing too much current?)
Is there any diagnostic i can do with the rinda software that might help me with this?

Thoughts?
 
Last edited:

joelger

Seaman
Joined
Jul 29, 2021
Messages
60
This just keeps getting better and better. I repaired my seawater pump, put everything back together and the boat wont start.
Im working with a 2010 Mercruiser 8.2mag. Serial 1A351574.
I thought it must have something to do with the fuel system because i had to move the cool fuel pump out of the way to get to the seawater pump. After checking everything, i found a bad fuse. I replaced the fuse and tried to start it again. Still wouldnt start. Checked the fuse, it was blown again. Checked all the wires to the fuel pump and they all seem perfectly fine. I disconnected the lead to the cool fuel pump and turned the motor over. Obviously it didnt start. I checked the fuse and it was fine. Id didnt blow. I reconnected the lead to the cool fuel pump and turned the motor again, blew the fuse. I replaced the fuse once again and turned the ignition on but didnt try to start the motor, the fuse was fine. Cranked the engine again, fuse blew again.
Assumption....one of the motors in the CFP (cool fuel pump) is shorted. Removed both motors from the CFP and connected each to a power source off the boat and they both spun fine. Considered that i may have pulled too hard on the wires where they come from the CFP and possibly caused a short that way. I put the pumps back on the cap of the CFP and reconnected it to the electric for the boat. I cranked the motor and the fuse was fine.
So this now raises a bunch of other questions but i just put it all back together and when i cranked the motor, the fuse blew yet again.
Now im wondering if something else could be causing the fuse to blow once the system builds pressure. Then realized that isnt likely because the pressure line from the pump to the fuel rail wasnt connected when the fuse blew on the last test.
When i had the pumps out and powered them from a 12v source i should have put a fuse in the circuit to see if it blew the fuse out of the boat. (possibly drawing too much current?)
Is there any diagnostic i can do with the rinda software that might help me with this?

Thoughts?
Also, anyone have any idea where the fuel pump relay is on this? Im reading that could be causing this as well
 

joelger

Seaman
Joined
Jul 29, 2021
Messages
60
Yet another update. I disconnected the batteries, disconnected the power leads to the CFP and with a fuse inline, applied power directly to the CFP. The pump ran and did not blow the fuse.
Fuel pump relay seems like the next logical place to look.
 

alldodge

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Mar 8, 2009
Messages
42,054
I'm unable to find the relays in the brake down
https://www.mercruiserparts.com/8-2l-mag-ec-base-model-1a350340-thru

There should be at least 3 square box type and will be close by the fuses.
Main power
Fuel pump
Start assist/slave relay

This is for a 555 ECM where you have PCM09 but the relays should be the same, maybe different color wires and different pins

The main power relay feeds all power to FP, PCM and Alternator. So that fuse would be 15 to 20 amp. The fuel pump will be smaller

555 relays.jpg
 

joelger

Seaman
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Jul 29, 2021
Messages
60
Do you think i am on the right track at this point. Meaning does the pump relay sound right?
 

alldodge

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If it's the FP fuse blowing then yes
What size fuse is blowing?

Maybe take each pump out again and measure the current draw
 

Fun Times

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At first thought of looking at the fuel pump wiring harness as seen below, I'd tend to want to lean towards an issue either with the fuel pump harness itself or in the working area of that harness...But since it seems to mostly happen while cranking the engine over?, Plus since you moved the pump housing out of the way, you may have done some damage to the Crankshaft Position wiring harness in which is in close enough proximity to touch the crank sensor wiring as it's mounted to the front cover under/behind the circulating water pump at the front of the engine...See item number 22,



1718233261583.png
 

Fun Times

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@Fun Times comment, doesn't the CPS work off 5V ?
Yep you're correct...Disregard as I missed this part of the post lost in thought. (e. I disconnected the lead to the cool fuel pump and turned the motor over. Obviously it didnt start. I checked the fuse and it was fine. Id didnt blow. I reconnected the lead to the cool fuel pump and turned the motor again, blew the fuse. I replaced the fuse once again and turned the ignition on but didnt try to start the motor, the fuse was fine. Cranked the engine again, fuse blew again.)
 

joelger

Seaman
Joined
Jul 29, 2021
Messages
60
If it's the FP fuse blowing then yes
What size fuse is blowing?

Maybe take each pump out again and measure the current draw
It is a 20amp fuse and thats the same fuse i used to test the motors when i powered them from an outside source.
 

alldodge

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20 amp seems a bit high for fuel pump but it is for 2 pumps. Are the other fuses smaller or larger?

Hey @dubs283 can you comment ?
 

joelger

Seaman
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Jul 29, 2021
Messages
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all of the fuses in that block are 20s. I figure it has to be for the fuel pump since it only blows when the pump is connected. I have tried pretty much everything i can think of and the only thing i can come up with is the relay. Most everything electrical is wired so it shouldnt be too difficult to located
 

alldodge

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That's the part that doesn't make since "IF" the MPR feeds everything and the FP's do draw a bit more then 10amp normally. I seem to remember a single fuel pump fuse is 7.5

Maybe try to run each pump with 5 amp fuse. Now if it does without pumping any fuel then it would increase under load
 

joelger

Seaman
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Jul 29, 2021
Messages
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In my post yesterday i indcated that the fuse would only blow when cranking the engine. That was not correct. The fuse would blow anytime it tried to run. (was powered by the relay)
Well, i took the pump apart a few more times. Everything worked fine until i reassembled the pump. Then the fuse would blow. I ended up taking the whole pump apart and removing the harness. I did find some dry rotting on the outside of the pump right where the wires meet the insulator. In any event i tried every combination possible. With one pump, with both pumps, with no pumps, nothing blew the fuse. When i put it all back together for the last time, I cleaned up the wires and the insulator where the wires go in to the pump. I put the whole thing back together and no blown fuse. I could hear the pumps kick on just as normal.
Boat still wont start. I removed the line between pump and injector and i wasnt getting any fuel out of the pump. Took it apart once again and found that with all of the in and out of the pumps, i damaged the seal on the bottom of the one pump. Cant by it separately as far as i can see so I made a seal out of automotive gasket material, put it all back together and finally the boat started.
I guess i need to replace the harness but i really would like to replace that seal. Anyone know where i might be able to find one?
 

alldodge

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BTW they do make a seal kit for the pump 892683A01 and looks like partsVu is cheapest place
 

joelger

Seaman
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Jul 29, 2021
Messages
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if that is the one that i found, it appears it is for an outboard. I found a cheap aftermarket pump that comes with a seal and ill try that for now.
 

alldodge

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Not to give you something else to thing about but .........

Could remove the 2 pump box and install the old cool fuel Gen 2 single pump
 
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