Centurion Enzo 2007 Mercruiser 6.2L black scorpion ski engine fuel blockage

[sebady@gmail.com]

Hi there,

So a have picked up an old Centurion Enzo from 2007 with the Mercruiser 6.2L black scorpion ski engine.
The fuel has been drained from the tank to the fuel pump new fuel filter. Pick up has been disconnected from the tank and a temporary small fuel container is being used to confirm pump is priming when ignition is energized. The pump does prime and fuel does get sucked up, however once the pump stops priming the fuel drains form the line again over the space of 5 seconds.
So i checked the pressure relief valve on the fuel rail, no pressure, no fuel. Tried about 15 times of key on and off with the fuel rail valve open and pump priming, no fuel coming out the rail and the amount of fuel in the small fuel container not decreasing. I then removed the valve from the pick up with out any change in results. i am thinking that there is some bad fuel in the line from the pump to the fuel cooler or injectors. So i disconnected the cool fuel line off of the the second fuel pump and turn the key, nothing coming out.. bad pump, bad fuel pressure regulator?
Please let me know your thoughts.
Some back ground history, so far i am yet to have the engine running. i have hand cranked it and changed all oil and filter, all new plugs and batteries. The starter motor turns the engine but there is definitely a fuel starvation issue.

Model number - 3 - 0620293 U
serial Number - 1A090965
Number on the fuel pump is SAE J1171 MARINE

Thank you in advance for your ideas on how to get back on the water!

Seb

 

[Bt Doctur]

that setup uses 2 fuel pumps, a boost pump mounted at the fuel sep (low pressure) and a high pressure fuel pump in the cool fuel unit. There is a electrical line to combine both fuel pumps.

 

[sebady@gmail.com]

that setup uses 2 fuel pumps, a boost pump mounted at the fuel sep (low pressure) and a high pressure fuel pump in the cool fuel unit. There is a electrical line to combine both fuel pumps.

Thank for the quick reply, the pump is plugged in and when the ignition is turned and left on i am not getting a double tone sensor alarm every few minutes, so i believe the electrical side is good. Are you saying however that if one pump is running then the other should be too, priming i mean, at start up?

 

[alldodge]

Thank for the quick reply, the pump is plugged in and when the ignition is turned and left on i am not getting a double tone sensor alarm every few minutes, so i believe the electrical side is good. Are you saying however that if one pump is running then the other should be too, priming i mean, at start up?

Howdy Seb

As BT mentioned, you have two fuel pumps and they should both turn on when key is turned ON. They should both run for about 3 seconds and run again when the motor is cranked. The boost pump is above the fuel filter, and the cool fuel high pressure pump is under the motor mount on the port side. Look for a plastic box beside the oil pan, the cover comes off with snap clips (top and bottom) and lifts off.

On top the motor there are relays and fuses. Check the fuses next to the square relays to see if any have blown. When key is turned to ON the relays should click and pumps turn ON



See item 18 and 19 in link below. The plastic cap is removed and under it is a shrader valve. A fuel pressure gauge is attached here to measure pressure and you can also press in on the valve and bleed air out of the lin. Use a rag when doing this so not to spray gas all over and protect your eyes.

http://www.mercruiserparts.com/bam/subassembly/31790/15322/90

 

[sebady@gmail.com]

Howdy Dodge,
Thank you for your advice,
So , i have checked the fuses and they are good. i have installed a new fuel pick up and valve to the tank fuel line. New pressure regulator and new high pressure pump in the cool fuel box, so both fuel pumps are priming. . i now have fuel coming all the way to the fuel rail and air and fuel being released when i press on the shrader valve. Still no combustion though. I have checked the distrubuter and it looks ok. Starter just keeps cranking. All the water pipes are off and i can see that there is very very small amount of smoke being released when i turn it over. Total running hour on the engine is 100, it has been sitting for the last 5 years. What would you recommend next?
Cheers
Seb

 

[alldodge]

fuel coming all the way to the fuel rail and air and fuel being released when i press on the shrader valve.

If you getting AIR (this is an issue) and fuel then you need some more bleeding of the system. It should be all fuel and no air.

 

[sebady@gmail.com]

Hi Dodge,
So no more air coming out, just fuel. Now however i have noticed that the alternator is not turning. The serpentine belt is turning very slowly as it is slipping on the main fly wheel. So i am guessing this is reducing the compression. Do you have any experience with repairing alternator or should i just replace?
thanks
Seb

 

[alldodge]

Repairing is easy enough, and with bearing replacement will take a bit more. But with both I would replace the ALT. Search for Mercruiser 863077T and can find one around $80

Its not low compression, its bad bearings. Until the motor starts it has all to do with how strong the starter is

 

[sebady@gmail.com]

Thanks Dodge.
Found a well priced replacement Alternator. All set.
Interestingly enough, with no drive belt attached. The sound that the motor makes when started is the same regardless of the kill cord being in or out. I am guessing the kill cord interrupts the spark, so no spark either which way? Changing distributor and rotor next, unless you have any other ideas?

 

[alldodge]

The sound that the motor makes when started is the same regardless of the kill cord being in or out. I am guessing the kill cord interrupts the spark, so no spark either which way?

I would say your kill switch has been bypassed. The kill switch disconnects 12V to the motor (ECM and or coil). In pic below this is showing how to by pass, but the purple wire comes from the key switch to the kill switch then back to the gauges (purple wire)

 

[sebady@gmail.com]

Great Diagram Dogde, thank you.
Okay, so i now have things working like the should. with the kill switch off - the buzzer, the electric panel, gauges and fuel pumps are coming on and the engine is turning over ( but still not starting )
With the kill switch on - no electrics are turning on, no gauges. no buzzer, the pumps are not priming, but the engine sounds the same when turning over.
What fuel pressure should i be getting from the bleed valve on the fuel rail?

 

[alldodge]

Sounds like your kill switch is hooked up backwards. The motor should always turn over because it has no effect on it, but the kill switch should kill power to the gauges or buzzer.

Pressure should be 43 psi

 

[sebady@gmail.com]

Morning Dodge,
Okay, the kill switch is working as you have said that it should.
I have installed a new high pressure pump but i dont think that i am getting 42 PSI, is there a test kit you could recommend online?
The part in the manual (91-16850A5) is over 400 bucks!
thanks

 

[alldodge]

Just look up GM fuel pressure tester, or better yet go to your local autozone, O'Reilly or such and borrow one
http://www.tooldiscounter.com/ItemD...3cxYneoK2ewDZzHV9RBy8yUjLAEW1gxRoCgSoQAvD_BwE

 

[sebady@gmail.com]

Hi Dodge,
So, i am only getting 30PSI when the boost fuel pumps cycle on,this then drops down to 26PSI after priming and the pump cycles off. Only getting 30 PSI when trying to start. I have replaced with new the second stage boost pump. The first stage was working. i guess i need to replace the first stage also? In addition i got a spark test and i have spark on all 8 plugs.

 

[sebady@gmail.com]

Okay, so i removed the first pump in the fuel line and replaced it. ( i think the pump i installed is a high pressure pump not a priming pump ) I am now getting 90 PSI on the fuel rail and still not firing. So i guess all the injectors are blocked?

 

[alldodge]

Hi Dodge,
So, i am only getting 30PSI when the boost fuel pumps cycle on,this then drops down to 26PSI after priming and the pump cycles off. Only getting 30 PSI when trying to start. I have replaced with new the second stage boost pump. The first stage was working. i guess i need to replace the first stage also? In addition i got a spark test and i have spark on all 8 plugs.

Wish I would have seen this post sooner. So long as the boost pump was working at all (which it was) it would not cause what your seeing. Even a 30 psi the motor should run. Need to concentrate on spark and not so much on fuel right now.

Okay, so i removed the first pump in the fuel line and replaced it. ( i think the pump i installed is a high pressure pump not a priming pump ) I am now getting 90 PSI on the fuel rail and still not firing. So i guess all the injectors are blocked?

There is nothing wrong with the injectors, they are keeping fuel from leaking so that's good. Your reaching 90 psi because you have a high pressure pump (HPP) feeding another HPP so the regulator is not able to reduce the pressure toward the low side, because there no longer is a low side.

Reaching 90 psi may have also damaged the regulator